Textile Technology Spinning

DETERMINATION OF TRANSFER FUNCTION FOR OE – ROTOR SPINNING SYSTEM

2009-12-30T04:11:00.001-08:00

At present the significant direction of researches on the processes and systems of spinning technology is to find out a scientific method of dynamic simulation. This can be done by the application of the theory of random function. The principle lies on the conception of technological system as a stationary, linear dynamic system. The aim is to determine the modulus of the relative transfer function and subsequent technological analysis. The acts can be stated as to determine the influence of technological factors on the equalization effectiveness to a given spinning system and also to determine the conditions for improving the quality of the resulting linear fiber products (for example, sliver, roving, and yarn) from the point of view of mass irregularity.

It is necessary to point out that a procedure of dynamic simulation can solve the question of transformation through the spinning systems. The problem of transformation can also be solved with the help of determination of quadratic mass irregularity of short sections of the linear fiber products on the basis of autocorrelation function of mass irregularity.

Choice of the technological application of dynamic simulation

As an example of the method of dynamic simulation as well as process of determination of quadratic mass irregularity of short section of linear fiber product, we can discuss about the following technological applications.

- flat card with a drafting mechanism [ 1 ] – evaluation of the leveling effectiveness - a system of successive and combined doubling[2]- levelling effectiveness,

- the resulting quadratic unevenness, the technological causes of an increased levelling

effectiveness, the effect of replacement of spinning rotors with the increasing

frequency of revolution

- system of cyclic doubling [3] – the resulting quadratic unevenness, the influence of the collecting surface diameter of the rotor, requirements of the fiber flow taken over by the collecting surface

- the separating device of the OE- spinning system [4] – influence of the structure of the mass irregularity in the fiber flow

The main problem in the application of method of dynamic simulation is the process of determination of transfer function, subsequently modulus of relative transfer function. Relevant determination is possible with theoretical or experimental process. Dynamic model detailing transformation of mass irregularity comes from two basis aspects of a given technological problem. With these two basis aspects of the specified research problems, the following possibilities can be stated:

a) the quantities expressing the character of the characteristic property of a fiber product: these can be

- deterministic or

- random

b) the mechanical and physical action defining the character of the technological environment can be characterized as

- deterministic or

- random

In the dynamic model, the character of fiber product from point of view of mass of short sections of linear fiber product is random. The character of technological environment i.e., system of transformation is determined by the simplifying condition of processes.

Modulus of relative transfer function for OE – rotor spinning system

The concept of OE – rotor-spinning system as a dynamic system including the division into partial dynamic system is stated in [5]. An equation expressing the modulus of relative transfer function for system of cyclic doubling in spinning rotor process can be found in [5]. The main content of the present work is the presentation of results of experimental procedure for determination of the modulus of relative transfer function for OE – rotor-spinning system and the possibility of use of the apparatus Uster Tester 4 – SX is also explored. The spectrograms obtained from the above-mentioned apparatus may be directly used for determination of the modulus of relative transfer function for the given system. In principle, this acts about record harmonic components of mass irregularity depends on the wavelength. Instead of amplitude of the harmonic components, the quadratic mass irregularity (CV) of the harmonics components is plotted along the y-axis. This is directly proportion to the relative amplitude, so the modulus of the relative transfer function can be directly expressed as a ratio between the CV values of the corresponding harmonic components. It is important to obtain the CV values correctly in order to obtain correct values of the modulus, hence efficient application.

Results of experimental determination of the modulus of relative transfer function for the OE–rotor-spinning system are given below.

Interpretation of results and conclusion

The method of determination of the modulus of the relative transfer function for a given spinning system with the use of spectrograms obtained from the apparatus Uster Tester 4-SX makes it possible to obtain a function that characterizes transformation of the structural mass irregularity of the input fiber product (sliver) on the structural mass irregularity of the resulting or output fiber product (yarn). It offers a picture on the components of the OE-spinning system, which is important for preparation of sliver with optimal structural mass irregularity.

In the given example of OE-rotor-spinning system, it is known that there exits two very contradictory effects from point of view of mass irregularity, that is, the opening system highly increases the mass irregularity and the cyclic doubling reduces it. Globally,

the OE-rotor-spinning system is known as a system of very high draft (in the given example draft is P = 236) and that matches with the resulting modulus of the relative transfer function. It is evident, that with reference to the very high draft, given to an OE-rotor spinning system, thanks to the system of cyclic doubling, that decreases the mass irregularity!

A new philosophy, which uses the principle of dynamic simulation opens new directions of research for analysis of structural mass irregularity with a view to different consequential optimization of different spinning systems from the point of view of mass irregularity of the resulting fiber product.

P.Ursíny,R.K.Nag

Department of Textile Mechanical Technologies, Faculty of Textiles,
Technical University of Liberec, Hálkova 6, Liberec 1, 461 17, Czech Republic

Siro And Two-Fold Yarns

2009-12-26T07:20:00.001-08:00

Investigation was carried out on how the tensile and related properties of Siro yarns, spun from two separated rovings of different types of materials, were affected by the twist factor and draft. Comparison on Siro yarns and two-fold yarns of the same linear density and twist factor revealed that the former was better in tensile strength and related properties. The Siro yarns are believed to be able to bear extra tension during manufacturing processes such as weaving and knitting.

Keywords : yarn strength, evenness, imperfections, hairiness.

1. INTRODUCTION

In Siro spinning, two parallel fibre strands, separated at a distance, are drafted simultaneously in the drafting zone. After they emerge from the front roller nip, they converge to form a yarn by twisting. Previous researches"⁾ mostly focused on studying spinning geometry and yarn parameters for producing yarn from rovings of the same fibre type. There has been very limited information available regarding the use of rovings of two different kinds of materials on the Siro system. Thus, the present work was designed to carry out some spinning trials on attenuating two rovings of different fibre materials in the drafting zone and to investigate the capability of the resulting Siro yarn.

In staple yarns, twist is essential to hold the fibres together and to impart some degree of cohesiveness to the structure. Twist is a means by which a bundle of fibres is held together so that the ultimate structure is made capable of withstanding the stresses and strains generated in the next manufacturing steps. The role of twist in yarn is essential to manipulate the yarn properties. Thus, the influence of twist on the Siro spun yarn tensile strength was also included in the present work.

2. EXPERIMENTATION 2.1. Selection of materials

Wool, polyester and acrylic fibres were selected for the study. The characteristics of the fibres are shown in Table 1. All samples prepared for the present work were conditioned and tested under standard atmospheric conditions ( 20 + 2°C and 65 ±2 % relative humidity).

The Instruments for testing the fibre properties are listed in Table 2. The processing parameter used in drawing and roving are shown in Table 3. Table 4 gives the sequence of machinery used to produce the yarns.

2.2. Production of two-fold yarn

Comparison was made between Siro and two-fold yarns of the same linear density. A worsted twist factor of 2.2 [2600 (tpm x ^-qtex)] was adopted. This enabled the advantages of Siro yarn to be compared with those of two-fold yarn. Comparison was also made between the yarns of different linear density, to identify the effect of changes in draft on the properties of the two series of yarns.

Since the folded twist of the two-ply yarn should be equal to that of its corresponding Siro yarn, and the folded twist of a two-ply yarn is usually set at 70% of that of the single yarn, it is necessary to calculate the required twist that should be inserted into the single yarn by dividing the folded twist by 70%. Table 5 shows the required amount of twist inserted into the yarns.

3. RESULTS

The properties of the Siro and two-fold yarns are compared in Tables 6-9. 3.1. Comparison and•evaluation amongst Siro and two-fold yarns

Referring to Table 6, for pure wool worsted yarns, when the yarn linear density increased from 40 tex to 70 tex, the tenacity of the two-fold yarns increased from 7.8 to 8.3 cN/tex while that of the Siro yarns increased from 6.7 cN/tex at 40 tex, 8.5 at 60 tex to 8.7 at 70 tex. The Siro yarns, except for the 40 tex, were significantly stronger than the two-fold yarns, by 4.7% to 14.9% at twist factor 2.2. The breaking extension of Siro yarns was also significantly better than that of the two-fold yarns, by 60% to 73%. The evenness of the two-fold yarns was better than that of Siro yarns. At the twist factor of 2.2, Siro yarns were significantly less hairy than the two-fold yarns, by 10% to 18%.

For the wool/acrylic blended yarns, in referring to Table 7, the tenacity of two-fold yarns increased from 9.7 cN/tex at 40 tex, to 11.0 at 60 tex and 11.6 at 70 tex. Tenacity of the Siro yarns increased from 13.3 to 15.4 cN/tex. The Siro yarns were significantly stronger than the two-fold yarns, by 32% to 37%. The breaking extension of the Siro yarns was higher than that of two-fold yarns, by 56% to 125%. The evenness of the Siro yarns was better than that of two-fold yarns. The yarn evenness CV% of the two-fold yarn ranged from 15.8 at 40 tex to 13.1 at 70 tex while the evenness CV% of the Siro yarns decreased from 15.5 to 11.9 as the yarn linear density increased. The hairiness of the Siro yarn was lower than that of the twofold yarn, by 44% to 50%.

From Table 8, it can be seen that the tenacity of wool/polyester Siro yarn was higher than that of the two-fold yarn, by 6% to 23%. The tenacity of the two-fold yarns increased from 13.9 cN/tex at 40 tex, 14.9 at 60 tex to 15.8 at 70 tex. The tenacity of Siro yarns increased sharply from 14.8 to 19.5 cN/tex. The breaking extension of the Siro yarns was higher than that of the two-fold yarns, by 3% to 20%. The evenness of the Siro yarns was also better than that of the two-fold yarns. The evenness of the Siro yarns and two-fold yarns ranged from 17.6 at 40 tex to 12.6 at 70 tex and from 18.6 at 40 tex to 13.9 at 70 tex, respectively. The Siro yarns were significantly less hairy than the two-fold yarns, by from 30% to 41%.

For the synthetic (acrylic/polyester) fibre blended yarns (Table 9), the tenacity of the two-fold yarns increased sharply from 15.4 to 22.3 cN/tex as the linear density increased from 40 tex to 70 tex. The Siro yarn again exhibited better tensile strength, by 4% to 27%, compared to the two-fold yarns; it increased from 21.0 cN/tex at 40 tex, 22.5 at 60 tex to 23.2 at 70 tex. The breaking extension was generally higher for the Siro yarns. The evenness CV% of the Siro yarns decreased from 14.3 to 12.2, and that of the two-fold yarns decreased from 14.2 to 12.9, as the yarn linear density increased. The two-fold yarns were more hairy than the Siro yarns. The hairiness of the two-fold yarns increased from 11.6 to 12.0 and the hairiness of the Siro yarns increased from 6.8 to 6.9 as the linear density increased from 40 tex to 70 tex.

4. DISCUSSION

The present work focused on a comparison of the yarn properties of Siro yarns and two-fold yarns of equivalent yarn linear density. It was found that the Siro yarns were generally superior to the two-fold yarns in terms of yarn strength.

The breaking strength of the Siro yarn is higher than that of the two-fold yarns of equivalent linear density due to the particular Siro yarn structure - due to the fibres being more firmly bound within the yarn structure. The two twisted strands of the drafted fibres caused some surfaces fibres to be trapped into the Siro yarn so as to increase the inter-fibre cohesion in the yarn which can withstand higher breaking forces. In Siro spinning, the sense of twist is the same for both the single ends and the composite product. This gives a yarn that is somewhat more compact , with a firmer core, than the usual two-fold yarn with opposing singles and folding.

The better tenacity of Siro yarn could also be ascribed to the fact that the single strands have comparatively low twist which results in better and more even load sharing by the constituent fibres. In the process of yarn formation, fibres distribution is subjected to the twisting operation. The combination of varying numbers of fibres per cross section with varying forces binding these fibres together because of twist variation leads to varying tensile properties.

Another relevant factor with respect to the inferior yarn strength of two-fold yarns is the additional freedom of lateral movement permitted to the fibres. During extension of the yarn, the plies become grossly deformed r.nd the lateral displacement of fibres at different initial positions appear to follow a complex pattern. Fibres initially in the centre of the plies begin to move towards the central yarn axis. Fibres at greater initial radial positions in the plies simultaneously begin to gather around their own ply axis which is already moving independently towards the yarn axis.

The Siro yarns generally also performed better than the two-fold yarns in terms of evenness and degrees of imperfections. This is because the Siro yarn is produced by two strands of roving ; there would be a better parallel and straightening effect between the separated fibre strands during drafting. Since peripheral distribution of fibres during spinning is a combined effect governed to a large extent by the staple length, fibre cross-sectional resistance to twisting and other process parameters, it would not be possible to deduce the exact relationship of the combined fibre parameters and yarn unevenness. The poorer uniformity of the two-fold yarns may also be due to the greater number of production processes involved in producing two-fold yarns as compared to Siro yarns.

K.P.S. Cheng & C.H. Yuen

Institute of Textiles and Clothing, The Hong Kong Polytechnic University

CONTROL OF LAP AND CARD SLIVER EVENNESS AND CARD WEB NEPS WITH MECHANICAL VARIABLES AT SCUTCHER

2009-12-23T21:25:00.001-08:00

Different setting points of scutcher i.e. feed roller to krischner beater, krischner beater to stripping rail and grid bar gauges
were changed and their effect on lap evenness, card sliver evenness, and card sliver neps was observed. It was noted that feed
roller to krischner beater and krischner beater to stripping rail for evenness and all the setting points for sliver neps showed

highly significant differences in the mean values for different settings. Key words: lap evenness, scutcher settings, sliver evenness

INTRODUCTION

Cotton delivered by the opening machinery to the scutcher is well opened and usually arrives in the form of large tufts. Scutching is a process of cleaning by striking the cotton from a pair of rolls to a rapidly revolving beater after which it is formed into a continuous sheet of small tufts of cotton, held together by compression. The objectives of the scutching operation are: first, to continue the opening of the cotton even further than has already been done; second, to clean the cotton of more of the heavier dirt and undesirable short fibres; third, to form this cleaned cotton into a continuous sheet called a "Lap"; and fourth to make this lap as uniform as possible. The scutcher section may be classified as: feed unit, beater section, screen section and lap head. With improvements in trash extraction at earlier stages of processing, the extraction of trash at scutcher has been of less importance than making a uniform well textured lap. Khan (1972) found that regularity of sliver is dependent upon the uniformity of scutcher lap. Shrigley (1973) reported that incorrect setting of stripping rail is detrimental to lap regularity. Ratnam and Seshan (1987) mentioned that the short term variation in card sliver contributes 3.2% of the total, provided the sliver is regular. Variation introduced by cards together with the variation in blow room, a major part of this variation, can be attributed to blow room. Almashouley (1988), reported that inadequate settings and inadequate feedings are the sources of variation in weight per yard of lap. Alan and Alexander (1988) pointed out that processing of fibres tends to produce neps through a stress build up/sudden release mechanism which induced buckling along the fibre length. Ali (1998) reported that calender rolls pressure. kirschner beater gauges and kirschner beater speed mainly influenced the lap weight variation. He also recommended that CV of meter to meter lap weight be strictly controlled and maintained at level less than 2%. Anonymous (1999) recommended that distance between stripping rail and the kirschner beater should be 2mm. In case. distance between rail and beater is greater, this will badly influence flow of material and cause soft lap. Robert e at. (2000) observed that considerable amounts of short fibre content. created in production and processing, are removed

in the combing process. This study was undertaken to determine the effect of different setting points of scutcher on lap and card sliver evenness and card sliver neps.

MATERIALS AND METHODS

Lint cotton samples of Punjab American cotton variety MNH-93 were collected from the running material at M/S Nishat Mills Ltd., Faisalabad. The raw cotton samples were subjected to following physical tests:

Spinning Procedure: The samples were processed at Ohara
Hergath blow room line (Model 1988) with the following

changes at scutcher in blow room.

i. Feed roller to kirschner beater gauge: F1 =3 mm, F2=5 mm, F3= 7 mm

ii. Kirschner beater to stripping rail gauge: S,=2 mm.

S2=3 mm, S3=4 mm

iii. Kirschner beater grid bar gauge: G1=5 mm, G2= 7 mm,

G3= 9 mm

After every change at scuther, the samples from laps were collected and tested for the basic fibre characteristics along with the following lap quality evaluation tests:

Lap Evenness: This is yard to yard weight variation of lap and was determined by cutting it into one yard pieces then weighing each piece in grams on the weighing scale and in this way the coefficient of variation was calculated.

Sliver Evenness: Sliver evenness (U%) was determined on Uster Tester-llI according to the procedure supplied by the manufacturer, M/S Zellweger Ltd. (1995b). Uster Tester speed was set at 25 meter per minute for each test.

Card Web Neps: Neps were counted by AFIS-N according to the instructions laid down in its operational manual supplied by M/S Zellweger Ltd. (1992), Switzerland.

Three factor factorial completely randomized design was applied for testing differences among various quality characters evaluated in this study. Duncan's multiple range test was applied for individual comparison of means among various quality characteristics as suggested by Steel and Torrie (1980). The data were subjected to statistical manipulation on computer employing M-Stat computer programme designed by Freed (1992).

RESULTS AND DISCUSSION

Lap Evenness :The results pertaining to lap evenness are
shown in Table I. This Table shows that the effect of feed

roller to beater gauges, beater to stripping rail gauges and interaction F x S generate highly significant differences among mean values. The results in respect of SxG interaction also showed significant differences, while the effect of rest of gauge and interactions on lap evenness was non-significant.

The individual mean values of lap evenness recorded the best value as 0.80% at F2 followed by 0.87 and 0.93% for F3 and FI respectively while these gauges significantly differed in their mean values. Above results show that the setting F2 gives minimum lap. Similar views are given by Almashouley (1988), who reported that inadequate settings and inadequate feedings are the sources of variation in weight per yard of lap, while Ali (1998) reported that ealender rolls pressure, kirschner beater gauges and kirschner beater speed mainly influenced the lap weight variation. He also recommended that CV of meter to meter lap weight be strictly controlled and maintained at level less than 2%.

The comparison of individual means for beater to stripping rail gauges recorded the best value of 0.65% CV for SI followed by 0.85 and 1.10 % S2 and S3 respectively and recorded significant differences between the individual means. These results coincide with those of Anonymous (1999) which recommended that distance between stripping rail and the kirschner beater should be 2mm. In case, distance between rail and beater is greater, this will badly influence flow of material and cause soft lap. Likewise Shrigley (1973) reported that incorrect setting of stripping rail is detrimental to lap regularity. In case of grid bar gauges, the order for grid bar settings G3, G2 and G I was recorded as 0.85. 0.87 and 0.88 % respectively. These results indicated that the means of grid bar gauges recorded nonsignificant differences with respect to individual means. Sliver Evenness: The results pertaining to the sliver evenness are given in Table 2. This Table showed that the effect of feed roll to beater gauges, beater to stripping rail gauges and interaction F x S was highly significant. However, grid bar gauges and remaining interactioris were found to have non-significant effect. The individual mean values for sliver evenness between feed roller to beater gauges were recorded as 3.88, 4.12 and 4.28 % for F2, F3 and F1 respectively. Present results indicated significant differences among the individual means. These results are in line with those of Khan (1972) who found that regularity of sliver is dependent upon the uniformity of scutcher lap, while Ratnam and Seshan (1987) stated that the short term variation in card sliver contributed 3.2% of the total, provided the sliver is regular. Variation introduced by cards is in addition to the major variation caused in blow room. The comparison of individual mean values for beater to stripping rail gauges is shown in Table I. The best value of sliver evenness (3.31%) for SI was followed by S2 and S3 with respective means of 4.17 and 4.80%. These values showed significant differences among individual means indicating that the close gauge SI gave the best results for lap uniformity than for sliver uniformity, since the variation in lap leads to the variation in card sliver. These results get support from Merill (1960) who recommended that the stripping rail must be close enough to beater. Shrigley (1973) reported that incorrect setting of stripping rail is

detrimental to lap regularity. Khan (1972) found that regularity of sliver is dependent upon the uniformity of scutcher lap.

Comparison of individual means for grid bar gauges are shown in Table 2a. The individual mean values for grid bar gauges were 4.05, 4.10 and 4.13 % for G" G1 and G2 respectively, indicating that there was no effect of grid bar gauges on the regularity of card sliver.

Card Web Neps: The results pertaining to card web neps for different settings at scutcher in blow room are shown in Table 3. The results revealed that the effect of feed roller to beater gauges, beater to stripping rail gauges. grid bar gauges and interactions F x Sand S x G are highly significant, while interactions F x G and F x S x G differed significantly.

Duncan's multiple range test for comparison of individual means of card web neps for feed roller to beater gauges are shown in Table 1. The minimum web neps are recorded at F2 followed by F3 and F1 with their respective means as 80.17, 88.03 and 94.08 neps per gram. These results indicated that close gauge produced more fibre breakage and neps. Similar were the findings of Wegener (1980) who reported that neps originated from growth, harvesting, ginning, and processing and are often formed form fibre breakage. causing the fibre to coil itself, thus involving other fibres in its recoiling and producing entanglements. Similarly, Dever et at (1988) observed that neps are formed by increased aggressive cleaning. However. Alon and Alexander (1978) pointed out that processing of fibres tends to produce neps through a stress build up/sudden release mechanism which induces buckling along the fibre length.

The comparison of individual means for beater to stripping rail, gauges generated the minimum number of neps for SI followed by S2 and S3 as 69.69,88.94 and 103.65 neps per gram respectively. However, the individual means significantly differed from each other. These findings are supported by Shrigley (1973) who found that the stripping rail setting is the most important, since a setting that is too wide may permit the cotton to pass around with the beater instead of being discharged, thereby creating neps and flocking, whereas Steadman (1997) reported that neps seldom appear in boil, but every processing stage has the potential to be susceptible to fibre aggregation. When properly managed, both carding and combing can remove more neps than generated.

In case of grid bar gauges, the minimum number of neps was recorded at G3 followed by G2 and G I with their respective mean values as 85.11, 87.36 and 89.81 neps per gram. indicating significant differences between the individual means. More opening of grid bars generates more cleaning and less neps. Sheikh (1997) reported that an increase in seed, trash particles in cotton is associated with higher nep content. Herbert et at (1986) observed that three types of neps are present in cotton: i) entanglement with seed coat fragment, ii) entanglement with trash, and iii) non-fibrous material entanglement, while Harrison and Barge/on (1986) observed that neps are important in determining the quality of final product of cotton fabrics. Fibre characteristics and processing conditions are two factors that affect the nep formation.

Conclusion: The study showed that too wide stripping rail

setting with the beater may permit the cotton to pass round and round with the beater instead of being discharged which damages the fibres and generates neps, thus the rail must be close enough for proper functioning.

Magnetic Ring-Spinning Revolutionizing the Tradition

2009-12-23T21:13:00.001-08:00

In today’s spinning technology, at least 4 types of spinning systems are commercially available. These are the traditional ring spinning, rotor spinning, airjet spinning and friction spinning. Among them, ring spinning stands alone in providing high quality yarn suitable for any type of textile end product. Other more recent systems enjoy much higher production speed than traditional ring spinning, but yarn quality restricts their use to only narrow ranges of textile products. The primary technological limitation of ring spinning lies in the speed of the ring-traveler system. The traveler is a C-shaped thin piece of metal that is used for a limited period of time, disposed, and replaced on frequent basis. Three specific issues must be addressed to overcome this limitation:

· the dependence of the yarn linear speed (or delivery speed) on the rotational speed of the traveler

· the continuous need to stabilize yarn tension during spinning and the dependence of this stability on the traveler speed

· the impact of traveler speed on fiber behavior in the spinning triangle

Research to date has only provided about a 15% improvement in traveler speed without affecting the traveler/ring contact thermal load capacity. Ring spinning is still at a production rate disadvantage of 15 to 20 times in comparison with other spinning systems. Therefore, the challenging issue is how to break the traditional paradigm of ring spinning and revolutionize its principle in such a way that very high speed can be achieved without sacrificing the traditional quality of ring spun yarns.

Our design approach is to totally eliminate the traveler from the ring spinning system and replacing it with a magnetically suspended lightweight annular disc that rotates in a carefully pre-defined magnetic field (See Figure below). By creating a non-touching environment of the rotating element for ring spinning this system provides a super high spinning rotation without the limitations of the current traveler system.

Finite element system simulation

We are simulating the magnetic system using a magnetic finite element package. The magnetic field strength distribution on different system components shows the supporting forces exerted on the rotor part (See Figure below).

Our first estimate is that these forces are 25 N in the radial direction and 15 N in the axial direction. We are seeking more axial stiffness of the rotor.

Contributing Graduate Students: Gangumalla Yamshi Reddy, Jayendra S. Dabahde (Auburn).

Industry Interactions: 2 [Unifi, Velcro] Academic non-NTC Interactions: 2

Project Web Address: http://www.eng.auburn.edu/~fhady/magnetic-report.htm

Faissal Abdel-Hady, a Research Assistant Professor of Textile Engineering at Auburn since 1998 and an Assistant Professor of Mechanical Engineering at Ain Shams (Egypt), earned a B.S in 1975 and M. S. in 1981 there and a Ph.D. in 1988 at Ecole Nationale Superieure des Mines de Saint Etienne (France), all in mechanical engineering. Faissal then was a manager in industrial software for Hicon France. His research interests include thermal analysis. stress simulation, automatic control and mechatronics, mechanical components, CAD/CAM for filament wound structures, dynamic signal processing and software development.

S00-AE06, F01 -AE02*, S01 -AE32 fhady@eng.auburn.edu

(334)-844-5471 http://www.eng.auburn.edu/~fhady

By replacing the traveler in ring spinning
with a disc that rotates in a magnetic field,
we hope to maintain
the high quality of ring spun yarn,
but at much higher speeds.

EFFECT OF BLENDING RATIOS AND TECHNIQUES ON THE QUALITY PARAMETERS OF 30'S POLYESTER/COTTON YARN

2009-12-23T20:52:00.001-08:00

The present study was conducted to determine the impact of polyester/cotton ratio on the quality characteristics of yarn. The quality characters depend upon the ratio of polyester and cotton in the blend and also on the blending technique adopted during fibre production to yarn spinning. The quality characters such as single yarn strength, yarn elongation and rupture per kilometer of yarn were directly proportional to the ratio of polyester with cotton in the blend. Draw frame blending produced better quality yarn as compared to blow room blending, lap former blending and simplex blending.

Keywords: blending techniques; cotton/polyester ratio

INTRODUCTION

The cotton has a loin's share in the economy of Pakistan. It provides raw material for our leading industrial sector. The growing world population needs and ever-changing fashions have changed the consumer trends. Now they demand great versatility, wide variety, higher standards and precision in fabrics, which are scarce in cotton products due to fibre to fibre variation, pest attack and uncontrollable environmental conditions. Therefore, the natural fibres are blended with synthetic fibres, such as cotton with polyester. The ratio of natural and synthetic fibres in the blend is of prime importance due to its multiple uses, economical and environmental conditions. Blending of natural and synthetic fibres is still carried out in sliver form on the draw frame (Klein, 1987). This provides the best blend in the longitudinal direction. Nawaz et al. (1999) reported that there is a gradual decline in yarn strength as the share of polyester fibres decreases in the blend. Li and Van (1990) reported that fibre properties had a significant effect on yarn strength. Anandjiwal and Goswami (1999) investigated that the blending of dissimilar fibres leads to their non-uniform distribution throughout the yarn cross-section, which in turn leads to preferential migration depending on both fibre properties and mechanism of certain spinning processes. The present study was conducted in order to find out the impact of polyester/cotton ratio on the quality characteristics of yarn and also to find out the optimal blending stage that produced excellent quality yarn.

MATERIALS AND METHODS

The present study on the comparison of different blending techniques of cotton and polyester at different stages during fibre to yarn spinning was carried out at the Kohinoor Textile Mills Ltd., Faisalabad and in the Department of Fibre Technology, University of Agriculture, Faisalabad during 1999-2000. Lint cotton samples of MNH-93 were taken from the mills, with

average values of fibre properties as fibre length 27.07 mm, fibre length uniformity ratio 48.58%. fibre bundle strength 90.81 thousand lb/irr', fibre fineness 4.52 ug/in, fibre maturity 82.53% and trash contents! 0.20%, while polyester fibre having the quality characteristics as fibre length 38 mm, fibre denier 1.2, colour/luster semidull, moisture regain 5%, elongation 18.30%, tenacity 7.04 glden and crimps per inch 13. 10, was used in the study.

The blendings of polyester and cotton were carried out in ratios i.e. RI (65:35) and R2 (52:48) at various stages i.e. blow room (TI), lap former (T2), draw frame (T3) and simplex frame (T4). The yarn thus prepared was tested for evaluation of following characteristics:

Tensile Properties of Single Yarn: The tensile properties viz. single yarn strength, elongation and rupture per kilometer, were calculated with Uster Tensorapid. The procedure adopted is that of ASTM Committee (1997). The data were analysed statistically using completely randomised design and Duncan's new multiple range test, as suggested by Steel and Torrie (1984).

RESULTS AND DISCUSSION

Single Yarn Strength: The statistical analysis of single yarn strength at 30' (P/C) blend is shown in Table I(a) which shows that the effect of different blending ratios and blending techniques during fibre to yarn spinning were highly significant, while the interaction between RxT on single yarn strength was non-significant.

The Table I(b) shows that the mean values of single yarn strength for 30' (P/C) yarn were observed as 412.45, 398.61, 422.03 and 387.38 g for TI, T2, T3 and T4 respectively. The best single yarn strength was noted in case of blending technique at draw frame while the lowest value was observed for simplex frame.

For blending ratio, RI (65:35 PlC) produced yarn of the best single yarn strength while the lowest value was in case of R2 (52:48 PlC) yarn. The results showed that more the percentage of polyester fibres, more would be the single yam strength and vice versa. Similar views were expressed by Nawaz et al. (1999) who reported a gradual decline in yam strength due to a reduction in polyester fibres in the blend.

Booth (1983) reported that several factors tended to influence the single yarn strength. He further reported that fineness of fibre affected several properties of the yarn and therefore, influenced the behaviour and properties of resultant yarn and fabrics. Hamid (1987) noted that the single yarn strength gradually diminished with a progressive increase in yarn number.

Yarn Elongation: The statistical analysis of yam

elongation at 30' (PlC) blend is shown in Table l(a) which showed that the effect of different blending ratios and blending techniques during fibre to yam spinning was highly significant while the RxT interaction on yam elongation value was significant.

The Table I(b) shows that the mean values of yam elongation for 30' (PlC) yam were observed as 8.04, 7.87, 8.08 and 7.71% for rt, T2, T3 and T4 respectively. The best yarn elongation was noted in case of blending at draw frame while the lowest value was observed for simplex frame. These findings were identical to those of Klien (1987) who found that blending of natural and synthetic fibres is still carried out in sliver form on the draw frame . This provides the best blend in the longitudinal direction. Regarding blending ratios, RI (65:35 PlC) produced yarn of best elongation while the lowest was obtained in case of R2 (52:48 PlC). These, results showed that the higher the percentage of polyester fibres, more would be the yarn elongation and vice versa. Elongation is a key factor (Sheikh, 1991). He further opined that the yarn elasticity and elongation were also very important in yarn spinning processes. Yarn with low elasticity i.e. Iow elongation tended to break more frequently in weaving. However, Zhu and Ethridge (1997) claimed that increase in elongation would reduce the hairiness of yarn.

Rupture per Kilometer of Yarn: The statistical analysis of rupture per kilometer at 30' (PlC) blend is shown in Table I(a) which indicates that the effect of different blending ratios and blending techniques during fibre to yarn spinning was highly significant while the RxT interaction on rupture per kilometer of yarn was nonsignificant.

Table I(b) shows that the mean values of rupture per kilometer for 30' (PlC) yarn were observed as 21.07, 20.48, 21.52 and 20.01 gltex for TI, T2, T3 and T4 respectively. The best rupture per kilometer of yarn was noted in case of blending technique at draw frame, while the lowest value was observed for simplex frame. These findings were similar to those of Klein (1987) who found that with evidently different raw materials (e.g. blends of natural and synthetic fibres), the blending at blow room was often unsatisfactory owing to uncontrolled extraction of flocks and the danger of subsequent de-blending.

As to the blending ratio, RI (65:35 PlC) produced yam of the best rupture per kilometer while the lowest was in case of R2 (52:48 PlC) yarn. The results showed that higher the percentage of polyester fibres, the more would be the rupture per kilometer of yam and vice versa. The properties of raw material seemed to directly influence the yam properties as reported by Li and Yan (1990) who remarked that fibre properties had a significant effect on yarn strength. However, Anandjiwal and Goswami (1999) investigated the blending of dissimilar fibres, leading to their disuniform distribution throughout the yam cross-section, which in turn led to preferential migration depending on both fibre properties and mechanism of certain spinning processes.

Conclusion: The study reveals that the quality characters such as single yarn strength, yarn elongation and rupture per kilometer of yarn were directly proportional to the ratio of polyester with cotton in the blend. However, draw frame blending produced better quality yarn as compared to blow room blending, lap former blending and simplex blending.

Shahid Saleem Shad^l, Asim Mumtaz¹ &. Iqbal Javed²
Departments of Fibre Technology' and Math. & Stat.", University of Agriculture, Faislabad

The raw materials | The textile fibres

2009-12-22T16:33:00.001-08:00

As known, the range of the textile fibres available on the market is at present rather extended. It includes in fact both natural and man-made fibres, which last were created about 100 years ago to the end of making up for the increased demand deriving both from the progressive improvement in the living standard and from the considerable growth of world population.

The natural fibres are divided, according to their origin, into animal (silk, wool, etc.) and vegetable (cotton, flax jute, etc.) fibres. Man-made fibres are divided into artificial (mostly originating from cellulose) and synthetic (from synthesis products) fibres.

In 1998 the world production of textile fibres amounted to over 47 million tons, which means a (potential) per capita consumption of about 8 kilos per year.

After the severe downturn of the world economy in the years 1992-93, in 1994 there was a recovery in textile production and consumption which went on, even if not at such a bright pace, also in the subsequent two years.

While cotton production depends substantially on the climatic conditions of the major producer countries and is therefore subject to heavy fluctuations (even up to 10%), the wool production is by now more or less stable since several years.

On the contrary the production of synthetic fibres, which in 1993 exceeded for the first time that of cotton, continued to grow, even if at a lower rate, in the following years to the extent that the synthetic fibre production exceeds nowadays that of the other fibres altogether.

Finally, as far as the production of artificial fibres is concerned, this is since some years slowly but steadily decreasing and accounts at present for only 4,6% of the global world fibre production.

Cotton | A millenary history

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All varieties of cotton (botanical name ″Gossypium″) grew originally in the desert zones of both the old and the new world. The cotton fibre was used probably at the end of the stone age in both hemispheres, to manufacture strings and maybe also fishing nets.

The time at which the real cotton growing started is not known, but from the remnants found at Cuzco (Peru) it was deduced that cotton spinning and dyeing date back to at least 2500 years ago; the excavations carried out in the village of Mohen Daro (Pakistan) gave evidence that cotton spinning and weaving were known already in 3000 B.C. Other archaeological finds prove that the Aztecs in Mexico and the Olmecs in central America, beside the Incas and their ancestors in the Andes produced cotton fabrics with very nice and complex designs which date back to over 2000 years ago.

The word ″cotton″ comes from the Arabic ″Katun″ which means plant of the conquered lands, with reference to the invasion of India by Alexander the Great in 327 BC. Several cotton fabrics still today bear the names of Asiatic and European towns, as well as of sea harbours situated along the cotton sea routes to Europe. Thus e.g. the term ″satin″ originates from the Arab name of the Chinese town Tseutung (Canton, today), the very popular ″denim″ from the French town Nimes, the name ″poplin″ from the papal city of Avignon and the name ″lisle″ from the French town Lille.

The cotton plant, as it originates from the desert, needs much sunlight and a warm climate; consequently it cannot be grown in Western Europe, except for Greece and Spain.

Production and consumption

The major cotton producing countries are at present China, the United States (the renowned ″cotton belt″ where the celebrated ″U.S. Upland″ cotton is being produced embracing several States: Texas, California, Mississippi, Louisiana, Alabama, Arizona and New Mexico), followed by CIS, India and Pakistan. According to a recent report of I.C.A.C. (International Cotton Advisory Committee), the world production of raw cotton in the harvest 1998-99 is estimated at around 18,3 million tons, recording a drop against previous years, while world consumption is predicted to remain at about 19,3 million tons (a rather stabile value).

The main exporting countries of raw cotton are the USA and the CIS (in the first place the state of Uzbekistan, followed by Turkmenistan and Tajikistan).

Cotton is mostly imported by those countries which, although having no possibility to grow it, have within their borders a more or less well developed textile industry. Typical countries are Italy, which in the biennium 1998-99 imported 355.000 tons of cotton, Germany (135.000 tons) and Portugal (174.000 tons). Russia too is a big cotton importer.

The major raw cotton producer countries (1997-1998 harvest)

In the Far East, the major raw cotton importer countries are Japan (278,000 tons, again in the year 1998-99), South Korea (275,000 tons), Thailand (315,000 tons) and Indonesia (386,000 tons). Even China imported about 400.000 tons of cotton.

These figures correspond in most cases to the consumption volumes.

The cotton plant | Fibre characteristics

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In ancient times the cotton plant was a perennial big shrub which bore fruits at all seasons; in time and after careful selections, almost in every country it has become a more or less branched out plant which is sown every year, grows and crops in 5 to 6 months.

The blooming takes place eight weeks after sowing, after few days the white and yellow flowers fall, leaving the boll which contains the seeds, around which the fibre fluff develops. In the subsequent weeks the capsule boll grows up to the size of a hen egg and bursts, releasing the white and bright cotton fibre which will continue to ripen until the harvesting time.

The cotton fluffs are picked either mechanically or manually and brought to the ginning room, where special machines called ″gins″ complete the separation of the fibres from the seed. The fibre mass is tightly compressed into bales, hence the term ″raw cotton″ used for this fibre. At this point the seeds are separated from the shorter cotton fibrils named ″linters″, which are used for the production of valuable artificial fibres, as we shall see later on.

From the botanical point of view, there are four basic species of cotton: Gossypium arboreum, herbaceum, hirsutum and barbadense. The first two species yield short staple, the third medium staple and the fourth long and extralong staple cottons (the term ″staple″ identifies the fibre length). In this connection we have to remind the prestigious varieties called ELS (extra-long staple), which are grown in relatively small quantities in Egypt, Sudan, Israel, USA and Peru. The staple length is one of the most decisive characteristics of the cotton fibre because the longer the staple length, the finer the spinnable yarn count. According to the official American standards, the staple lengths are divided into four ranges:

- below 0.99" : short staple

- 0.99" to 1.10": medium staple - 1.11 " to 1.26": long staple

- over 1.26": extra-long staple.

Fibre characteristics

The cotton fibre is characterised by the presence of a cavity in its interior, named ″lumen″. The quality assessment of the cotton fibres is based on following characteristics:

· staple length

· cross-section size, usually called fineness

· linear mass

The spinnability of a fibre, i.e. the finest yarn count attainable in spinning, depends on the length and on the fineness, while the yarn tenacity is related to the strength of the individual fibres as well as to the number of fibres in the yarn cross-section, which has to range between 90 and 120.

The fibre fineness is defined by the American standard ASTM D 123-85 and D 1448-84 as the weighted average linear mass expressed in micrograms per inch, but also in millitex µg/cm. For many years these values were assessed with a gravimetric test method, by weighing measured fibre lengths. For commercial purposes, the linear mass is assessed today more rapidly through special micronaire testing (or similar) instruments.

Besides fineness, a very important fibre property is the maturity degree, which is the ratio between the lumen length and the thickness of the fibre wall.

In fact there is a correlation between fibre maturity, linear mass and micronaire test readings, which is expressed by following values:

- micronaire lower than 3.0 = very fine; maturity degree 0.70-0.80 = immature

- micronaire from 3.0 to 3.9 = fine; maturity degree 0.80-0.85 = maturity below average - micronaire from 4.0 to 4.9 = medium fineness; maturity degree 0.85-0.95 = ripe

- micronaire from 5.0 to 5.9 = coarse fineness; maturity degree 0.95-1.00 = maturity

above average

- micronaire 6.0 and higher = very coarse fineness; maturity degree 1.00 and higher = very ripe

The fibre strength is, like fineness, the property which most affects the yarn characteristics: in fact the two properties are closely connected one another. Owing to the enormous difference in the values of these characteristics among the various fibres, cotton strength is measured with a so-called Pressley tester a flat fibre bundle composed by 500 to 1500 fibres.

For the assessment of fibre quality, also following factors are significant:

- colour: white, slightly spotted, spotted, slightly coloured, yellow stained, slightly grey, grey. The spinner requires anyway colour evenness.

- purity: contents of foreign matters. In fact another requirement of the spinner is the presence of a limited quantity of trash (coarse dusts).

- fibre preparatory process: this corresponds to the ginning process, which is a decisive factor for fibre softness, for uniform and open condition of the tufts and for the persistence of fibre entanglements, called ″neps.

Maturity degree of the cotton fibre— Relationship between lumen width and fibre wall thickness

The typical cotton characteristics all together as colour, foreign matter contents, kind of preparation as well as length and strength contribute to determine the ″grade″ and consequently the commercial value of the fibre, which in the trade is usually referred to as ″good middling″, ″strict middling″, ″middling″, ″low middling″, ″strict good ordinary″ or ″good ordinary″.

Cotton | The quality tests

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In cotton spinning the cost of the raw material is equal to 50% of the total processing cost.

It is therefore essential that the cotton type selection is based on a wide knowledge of the fibre properties and on the end-item to be produced.

In the last decade the so-called testing lines, which were initially used only by cotton producers and exporters, have been steadily developed and improved, so that they have now been adopted also by the spinning mills; these are driven in this direction by the need to control the quality of the various fibre sources and the reliability of the suppliers, moreover they are attracted by the effective advantages offered by these integrated testing systems, which ensure a closed loop control of fibre characteristics, yarn quality and production process and are focused on the spinning mill's profit. The initials HVI (High Volume Instruments), now well known to all cotton dealers, stand for the kind of instruments which compose the cotton testing lines. These lines offer several advantages:

- measurement of the main characteristics on a cotton fibre bundle: span length as measure of the fibre length, length uniformity, strength, elongation, micronaire as a fineness measure, colour and reflectance, foreign matter (trash) contents. The spinners have asked to add also the SFC (Short Fibre Contents) value which, as already mentioned, has a great impact on the quality of carded yarns. In fact short fibres increase yarn breakages while reducing the yarn tenacity and regularity. The combing process removes the short fibres and originates a quality yarn, but at the expense of a larger quantity of wastes. At least one manufacturer of HVI systems has already the software suited to provide the SFC value from the fibrogram produced by the HVI system. Although the standard error is still about 2%, this procedure allows to identify cotton batches which went through an excessive beating or drying or were too intensively cleaned in the ginning machine.

- possibility of testing up to 180 specimen/h and of checking each single bale. - attainment of reliable test results.

The American cotton growers, under the guidance of USDA (U.S. Department of Agriculture), are making considerable efforts to improve the quality and to reduce the damages caused to the fibre by mechanical picking and ginning. Therefore they were first to equip themselves with these HVI instruments, so that they are in a position to deliver controlled cotton bales with every information which can help the spinner to plan in the best way his production through:

- cotton bale management

- raw material optimisation

- process optimisation with consequent cost reduction.

By bale management we mean the ideal selection of the cotton bales to obtain acceptable technical and economic performance during their processing as well as consistent yarn quality.

By raw material optimisation we mean the result of following operations:

- consistent blending with the support of bales management;

- selection of fibre characteristics according to the requirements of the end-product and based on yarn structure;

- purchase of the most convenient raw material suited to meet the requirements of the end-product.

The process optimisation, on the other hand, depends on following factors:

- selection of the best setting for the drafting rolls;

- optimisation of the processing speeds through comparative trials.

What is Cotton stickiness ?

2009-12-22T16:30:00.001-08:00

The thorn in the side of the cotton producers and particularly of the spinners, is the notorious honeydew. This term defines the dreadful stickiness of cotton fibres due to the contamination by two terrible insects: the cotton aphid and the white fly, which last is widely spread in case of long dry spells. The researchers have intensified their efforts to control the reproduction of these insects in the last years, during which this infestation increasingly expanded. This spreading of the phenomenon is demonstrated by the result of a survey carried out by ITMF (International Textile Manufacturers' Federation) with 201 spinning mills in 22 countries all over the world about raw cotton contamination: a good 27% of the answers reported as serious the problem of cotton stickiness originated by honeydew, and Sudan was leading the high-risk countries.

Trials are under way to identify the honeydew-affected cotton batches through:

- the analysis of the sugary substances in the honeydew, which cause the cotton stickiness;

- the development of tests on the spot in order to detect the presence of sticky cotton types.

Specific treatments to neutralise cotton stickiness due to honeydew were also studied. Already in 1988 J. Gutnecht explained the results of stickiness tests carried out by ″Minicard″ method to show the influence of the relative humidity in the spinning room on the potential stickiness of a wide range of sticky cotton types and on various blends of sticky and non-sticky materials. At the same time he presented a new thermal method, simpler and less expensive than the Mini-card test, which results correlate pretty well with the Minicard System.

To remove stickiness from cotton fibres, various systems have been used:

- spraying of chemical substances on the fibres, which however causes some problems in subsequent processing

- passage of cotton bales or of a web of opened fibres through high frequency ovens.

In the past years a project was presented by R. Demuth to eliminate the cotton stickiness caused by honeydew. The project consisted in two phases: washing of the fibre with water and detergent with subsequent mild drying followed by thorough drying of cotton in a microwave tunnel, so that the adhesive substances become brittle and are reduced to powder. These systems however are not sufficiently cost-effective, so that there is a trend to dispose of the sticky cotton by mixing it in small percentages with the regular cotton.

The cotton stock exchange

2009-12-22T16:29:00.001-08:00

The major stock exchanges for cotton trading are situated in New York, Bremen and Tokyo. The cotton price is subject to broad fluctuations, which quite often are due to the seasonal and climatic trend.

Obviously the positive operating results of a spinning mill depend also on a careful and ″lucky″ purchase of the raw material. In this regard we would remind the practice of the purchase option of a ″future″, according to which during the validity of the option the buyer has right, but not the obligation, to turn the option into a ″cotton future″. In practice futures are contracts for the purchase or sale of goods to be delivered at long-term, but at a price established at the time of entering into the contract. There are two possible types of option:

- CALL, : in this case the buyer has the right to convert the option into a long-term

″future″”

- PUT: in this case the buyer has the right to turn the option into a short-term ″future″.

In New York since 1870 the NYCE® (New York Cotton Exchange) take place, which is the world’s leading market for the sale and purchase of cotton futures and options. It is a non-profit-making organisation which assists all segments of the cotton industry by providing the financial means needed for risk management.

Polyamide fibres

2009-12-22T08:22:00.003-08:00

Polyamide fibres were the first synthetic fibres to appear on the market. They were produced for the first time in USA in 1938, as a result of the research which Wallace H. Carothers had started already a decade before with the objective of preparing through synthesis polymers with a structure similar to that of cellulose and silk. The way followed by Carothers was directed at achieving, as an intermediate material for fibre production, a polymer of hexamethylene diamine adipate (salt N) resulting from the reaction between hexamethylene diamine and adipic acid.

This end-product was called nylon 6.6, because its two components have 6 carbon atoms each. However, in the same year 1938, Paul Schlack, taking advantage of the error of judgement of Carothers who claimed that caprolactam could not polymerise to form polyamides, succeeded in obtaining all the same a nylon - this time named nylon 6, being made up only of one product with 8 carbon atoms — without infringing the American patents. In the following years, his discovery was extensively exploited in Germany, where the product was called Perlon. Nylon 6.6 and 6 were later produced, under licence or through patent acquisition, also in other European countries, Italy included.

The polyamide fibre was rightly regarded as the "wonder" fibre by virtue of its countless end-uses: stockings and pantyhoses, swimwear, ladies' underwear, corsetry, linings, umbrellas, outerwear, raincoats and floorcoverings. Nylon is also used for several technical applications: tyre cords, conveyor belts, filters, fishing nets, cordage, parachutes, safety belts, inflatable boats and other sport articles.

More recently, this fibre has been further developed to originate continuous filament yarns composed of very fine filaments (abt. 1 dtex) as flat yarns, false-twist textured and air-jet textured yarns, which are used in the production of a new generation of high performance fabrics which meet not only quality and fashion requirements, but also take into account the physiological properties needed by clothing (snowsuits).

This yarn has good dimensional stability to washing, impermeability to water and to air, permeability to steam, good heat transfer, silky and soft handle, good dye yield; all these factors contribute to make this material particularly suited to sport and leisure wear.

The polyamide family includes also other types of nylon: : nylon 4 and 11.

More and more important is becoming the category of polyamide-imides, known also as
aramid fibres. Of relatively recent development, these high-tech fibres, which resist

highest temperatures and even flame and have excellent resistance to chemicals, are suited to technical and industrial uses.

A specialty fibre with optimal comfort properties belongs to the new category of the polyoxamide fibres. This fibre, which is produced in Italy, is particularly suitable for 20- 50% blends with wool, angora, cashmere, alpaca, cotton, viscose staple and synthetics, thus resulting ideal for knitwear.

For dyeing nylon 6.6. usually acid and disperse dyes are preferred, although many other dyestuff classes can be used. Dyestuffs suitable for nylon 6 are disperse and microdisperse, acid, mordant acid, premetallized, synthetic (on the fibre) dyes. The overall world output of polyamide fibres in 1998 was about 4.0 million tons (about 16% of the total production of synthetic fibres altogether).

What is Wool ? | Production and consumption

2009-12-22T08:22:00.001-08:00

Wool, as all animal hair both coarse and fine, falls under the class of natural fibres and more precisely under the class of animal fibres from hair bulbs. Although the term ″wool″ is commonly associated also with the name of the animals which supply the relevant pile as for instance Angora wool, this term wool stands only for the hair of the domestic sheep (Ovis aies L.) of various breeds.

Archaeologists affirm that sheep existed already when the man appeared on the earth, and it is almost beyond any doubt that wool was one of the first textile fibres available for spinning and weaving. Archaeological finds on the Zagros mountains, at the border between Iran and Iraq, prove that sheep were tamed already 9000 years BC. For a long time, sheep and their products were the main source of wealth and the best medium of exchange. In this connection we remind that the Latin word ″pecunia″ (money) derives from the word″pecus″ (sheep) and that the first coins portrayed this animal.

Wool characteristics depend on following factors:

- method used to obtain the fleece:

virgin wool = wool obtained by shearing the living animal;

plucked wool = wool obtained by chemical treatment of skins of slaughtered sheep - sheep age or sex:

lamb’s wool = first wool sheared from a lamb less than one year old;

ewe’s wool = wool obtained by subsequent shearing;

ram’s wool

- breed:

merino = wool with fineness ≤ 24,5 µ;

cross-bred wool = wool with fineness between 24,5 and 32,5 µ;

coarse wool = wool with fineness > 32,5 µ.

- wool state:

greasy wool, containing the original substances of just shorn wool, i.e. yolk and suint; fleece washed wool, obtained by making the living sheep pass through water; machine scoured wool, in which the grease is to a great extent removed; carbonized wool, that is wool treated with acids and heated to eliminate the contents of vegetable substances; wool tops, that is regular combed silvers composed of parallel long fibres from which all original impurities have been removed, intended for worsted spinning and for high quality products.

Production and consumption

It is estimated that sheep living on earth are today about 1 billion, of which 14% in China, 13% in Australia, 5% in the CIS and 5% in New Zealand. In the last years the production has progressively decreased. For the 1998-99 season a production of 2,4 million tons of raw wool (equal to 1,4 million tons of scoured wool) is expected. According to IWS estimates, the major producing countries of greasy wool in same season 1998-99 are: Australia (681,000 tons), the People’s Republic of China (302,000 t), New Zealand (256,000 tons), CIS (139,000 tons), Uruguay (63,000 t), Argentina (70,000 tons), Turkey (73,000 t), Great Britain (55,000 tons), South Africa (60,000 tons).

Production percentages for the different breeds are: merino 41 %, crossbred 25%, others 34%; 80% of the merino wool is supplied by Australia ad South Africa.

The main producing countries of greasy wool (1997-98)

Animal Fibres

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The so-called luxury fibres are produced by several different animals: rabbit, mohair goat, cashmere goat, camel, llama (alpaca, vicuna, guanaco) and cattle (yak and musk ox). In recent years a crossbreed, called Cashgora, was obtained by mating the angora he-goat with a wild she-goat. This name was acknowledged by the International Wool Textile organisation (IWTO) only in 1988, but the new wool variety aroused immediately the interest of many Italian spinning mills.

Luxury fibres gad their golden age at the beginning of the 80's; from the middle of the decade, various political and economic factors caused a general recession and a market stagnation. Italian spinners proved however to be real masters in the use of these fibres and especially in constantly creating new blends, making the most of the peculiarities of the woollen preparation and spinning machines "made in Italy".

Hereunder we give some information about the various types of luxury fibres:

- Angora rabbit: the yearly production of about 6,000-7,000 tons takes place mostly in China. The rabbits are clipped up to 4 times a year, thus producing about 250 grams of fibre each. The main market outlets are Japan and Italy. One of the latest developments is a process to produce unfelting angora yarn for handknitting.

- Mohair goat: These animals are bred in South Africa, Texas and Turkey, and it is precisely to the Turkish town of Angora, Ankara today, that they owe their name. The word ″mohair″ which identifies in trade their wool stems from the ancient Arabic word ″Mukhayar″, which means ″glossy goat hair cloth″. In fact the fibre has a rich silken aspect, but has a considerable strength. It is available in relatively large quantities - world production is about 13,000 tons - and is used in both apparel and furnishing. Each goat yields about 4 kg of hair per year. The finest hair coming from goatlings - 24- 25 g - is called kid-mohair. The main consuming countries of this fibre are Japan (25%), Europe and North America. The promotion of this fibre is co-ordinated by the International Mohair Association, which also created a quality trademark.

- Cashmere goat: these animals live in the plains of Central Asia, where climate is ice-cold in winter and hot in summer; just to protect them from cold, their skin gets covered by a thick and soft down (under-fleece down), which is plucked before summer. Each goat yields only 200 g of fibre per year, consequently the total production does not exceed 7,500 tons/year.

- Camel: camel hair is obtained mostly from the camel living in East and central Asia. The main outlet market for this fine, soft and golden fibre is America, where it is used for both woven and knitted fabrics, whereas in Europe it is used mostly for knitwear, especially in men’s garments. Each animal yields about 5 kg of fibre per year. Particularly valuable is the “baby-hair” type. The world production is about 3,000 tons/year.

- Alpaca: these are humpless animals of the camel family living in the Andean regions at heights up to 5,000 m. They are sheared only once every two years and each animal yields from 2 to 4 kg of fleece. This breed produces hair in 14 different natural colours, which is used in knitting and hand knitting yarns in the classic blends alpaca/wool, alpaca/wool/acrylic, alpaca/mohair/wool/acrylic. The alpaca production is about 6,000 tons/year.

- Yak: it is a long-haired ruminant living in Tibet at an altitude of 5,000 m. Its hair is considered as an acceptable alternative to cashmere. It is not produced in commercial quantities and, until 1980, the whole yak hair was exported to Europe and to the United States. At present the Chinese have developed a technology of their own and use directly most of this raw material.

- Musk ox: the underfleece of the musk ox is called “the Arctic’s Golden Fleece” and is probably the rarest and most expensive animal fibre in the world. Declared a protected species in the 30s, the musk ox has been saved from extinction and is today living in herds in North Quebec and in Alaska. Every spring, the animal looses its extremely valuable underfleece, known as ″quiviut″.

Silk | History, Production and consumption

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Silk is one of the most precious textile fibres of animal origin, obtained from the flossy filament ejected by the silk worm of the butterfly Bombyx mori.

According to tradition, silk was discovered by a young Chinese empress, Hai Ling Shi, in 2640 BC. She noticed in her garden, on the branch of a mulberry tree, a small white cocoon, and brought it into the imperial palace to examine it more closely. Casually she dropped it into hot water and noted that a thin filament began to unwind. The court weaver was asked to do experiments with the new filmy fibre which kept unwinding as the empress pulled it; his trials resulted then in the weaving of the first silk dress.

Silk processing aims at obtaining from cocoons a yarn as uniform as possible. It should be pointed out that it is the only continuous filament existing in nature. Raw silk consists by 60-70% of fibroin ( a white coloured protein), by 20-22% of sericin and, for the rest, of gummy substances, minerals and dyestuffs.

Before the pupa changes into a butterfly, cocoons are submitted to a first selection to eliminate the faulty ones and remove their outer layer (floss silk); then they are kept 16- 18 hours in drying ovens to cause the pupa's death and to eliminate moisture which would jeopardize their preservation.

The next operation is the cocoon sieving aimed at removing the residual floss silk, which may however be used together with other types of waste: imperfect cocoons, flock silk, filoselle, broken silk in schappe spinning.

A second sorting is then carried out to divide the cocoons into three size categories, which will be reeled separately because the smaller the filament diameter, the smaller the corresponding cocoon. After softening by immersion in warm water to facilitate the filament extraction, the cocoons are brushed to find the tail end of the filament and to remove from them the top layer of hair (flock silk). Once the tail ends are found, the cocoons are unwound until reeling begins to take place without difficulty. Degumming is followed by filament reeling, which produces a yarn composed of several filaments depending on the required yarn diameter. Once the yarn is twisted, it is wound with helical angle on reels, which are generally contained in special boxes which are closed and heated to enable yarn drying. The dried yarn is packed into skeins and put on the market under the denomination of raw or ecru silk.

Production and consumption

During the past 30 years, the world production of raw silk has steadily grown; this was however associated with a deep change of the production structure in terms of producing countries. In fact in 1970, with a silk world production amounting to abt. 40.000 tons, Japan accounted for the highest share with more than 50% (20,500 tons), followed by China (10,200), Soviet Union (3,000), South Korea (2,850), India (2,250). At that time, Italy still ranked among the producing countries with 310 tons.

On the contrary, today, the estimates of the International Silk Association show a global production of abt. 100,000 tons, where China is the leading producer with 70,000 tons (70%), whereas in Japan the production declined sharply to abt. 4,000 tons (4%). India, with 13,000 t, has therefore overtaken Japan and is now in second position, followed by CIS, Brazil and North Korea.

Among the "other" countries, let us mention Thailand, Turkey, South Korea, Vietnam, Indonesia and Paraguay.

Italy continues to rank among the leading importing countries of raw silk, which is converted, thanks to the skill of its domestic silk industry and to the high-tech Italian machines, into ply and schappe yarns, also blended with other fibres, into silk and bourette fabrics, scarfs, foulards and ties, which have made the Italian design renowned all over the world.

The main silk producing countries (1996)

Polyester fibres

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While pursueing the studies and the research works begun but left unfinished by Carothers, the British chemist John Rex Whinfeld with the co-operation of his young assistant James J.Dickson invented a method to produce polyester fibres from terephtalic acid and ethylene glycol, and applied for a patent on July 29, 1941.

This new polymer was suited to produce extremely fine, soft and strong filament yarns, but it was only in 1949, after the second world war, that a pilot plant for the production of polyester fibres was put on stream in England. The commercial production started both in USA and in England in 1953.

Polyester is the most common synthetic fibre and is marked by a high growth rate. At present polyester production (filament yarn + staple) accounts for 60% of the total production of synthetic fibres.

In 1998 polyester world production amounted in fact to 16 million tons (9 million tons filament yarn and 7 million tons staple).

Up to 1975, polyester was produced on ethylene glycol (EG) and dimethyl terephtalate (DMT) basis; later also a second method based on terephtalic acid (TPA) was used. Also the discovery of polyester marked a new milestone in the industrial revolution, because this fibre has deeply changed the textile industry, imposing itself for its great versatility. Either pure or in blend with cotton and wool, it gave rise to new types of clothing and furnishing fabrics with interesting easy-care properties.

A further advantage was provided by the development of inherently flame-resistant polyester types, which allowed its wide application in products where fire resistance is a must: furnishing and in particular curtainings, industrial textiles and protective clothing. These special fibres, which resist or slow down flame propagation, retain an agreable textile handle.

Polyester has excellent properties: dimensional stability, high tenacity, good resistance to light and weathering. Beside having increasing success in woollen, worsted and cotton-type apparel fabrics, polyester fabrics find wide application in household textiles and in nonwovens.

Polypropylene fibres

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Polypropylene fibres belong to the polyolefin fibre group. They were the result of the research work and of the discovery of isotactic polypropylene by Giulio Natta who, in 1963, together with K.Ziegler, was awarded the Nobel prize for chemistry. The term "isotactic", which summarizes a concept of molecular structure) is best explained by the stamp issued in Sweden in 1988, which symbolizes the close link between the order given for the molecule aggregation - the spider, admirable architect of nature - and a spinneret which - like the spider — extrudes thin filaments from a melt of ordered macromolecules.

The world production of polypropylene fibres amounted in 1998 to over 2 million tons. Polypropylene fibres have following peculiar properties:

- very low specific weight - high tenacity

- high resistance to acids and caustic soda

- high rubbing resistance

- minimal thermal conductivity, low soiling thanks to low electrostatic charges and to water-repellency.

On the other hand, just because of this last property, polypropylene fibres are difficult to dye and therefore are supplied already dyed by the producer (dope dyed fibre) in very nice colours. Research works and studies aim in fact at developing dyeable types and finer filaments, according to the general trend.

Polypropylene is the most used fibre in baby diapers and adult pads, because the so-called coverstock does not absorb liquids, but spreads them to the underlying fluff, thus ensuring that the skin remains dry.

Textiles for technical uses

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Technical textiles have some characteristics in common with traditional fabrics, but also other specific and different characteristics.

The elements which should be taken into consideration to identify this sector are:

· the raw materials

· the technologies

· the products and the end-uses.

Raw materials

Raw materials for the production of technical textiles are virtually all fibres, with preponderance of man-made fibres.

Technical textiles are still nowadays composed largely by traditional fibres, entirely similar to the raw materials of traditional textiles.

Innovative fibres are going however to be created even more in the future; these fibres have new and special features unobtainable in nature, aimed also at attaining performances which often conflict with each other (e.g. tenacity and softness, durability and degradability after use) which cannot be obtained with traditional fibres.

These high performance fibres (HP fibres) have however a cost considerably higher than traditional fibres.

Their cost is in fact closely related to the exceptional performances imparted by them, consequently their use has to be weighed depending on the real requirements of the single end-use.

Production technologies

Many of the technologies used for technical textiles are the same as for traditional textiles, from spinning to weaving until making-up, with some adjustments and modifications.

In some cases, however, specific technologies are used, which find exclusively application in technical textiles: f.i. nonwoven production, three-dimensional weaving, braiding, composite formation.

In this regard we point out that nonwovens overlap to a wide extent technical textiles: in fact nonwovens are largely applied in technical textiles, of which they have an important share.

Products and applications

Textiles for technical uses are products which are assessed on the basis of a series of factors which are the same used for assessing traditional textiles, but refer to a different hierarchy of values in terms of importance and of priority.

In reality we are facing two different worlds which however have some overlapping areas and some zones of common interest:

· they use the same kind of raw materials

· they use the same processes, and often the same machines

· they involve the same kind of operators

· in many cases the producers of technical textiles come, more or less directly, from traditional textile enterprises

· many enterprises have in their production both technical and traditional items technical products too have to comply with high aesthetical requirements, while traditional products must have well defined technical performances.

As for traditional textiles, also in the case of technical textiles there is a close link between the economical situation and the consumption volumes, but it differs according to the sector.

For instance, the trend of the transport sector conditions considerably the consumption of textiles for automotive applications (air bags, safety belts, panels and seat covers), just as the trend of avionics conditions the consumption of composites.

In other cases, on the contrary, technical textiles are anyway expanding, e.g. in the sectors related to ecology, health and wellbeing. Here trends remain even under difficult economic situations: in fact some values have become for certain reasons irremissible. The following tables show the fibre consumption for technical textiles in the major countries, the percentages of used fibers, the processes employed, the products and the market shares of each type of technical textile.

Spinning systems using Italian machinery

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Technologies for cotton spinning

The spinning systems

The Italian textile machinery industry can offer a complete range of machines for the spinning of cotton and of man-made fibre in cotton staple length.

Chart 1 shows the spinning systems which are used for converting the fibre into yarn.

Chart 1 - Spinning systems using Italian machinery

The insertion of electronic systems for controlling the various movements, as well as the use of pneumatic and hydraulic devices and of data processing systems permitted not only to enhance performances, but also to obtain flexibility in spinning and the on-line control of product quality consistency.

The installation of automation systems on board the machine and the linkages among the various machines enable to reduce the attendance by the operator.

Besides we point out that the personnel in charge has taken up mainly a function of supervision and of control, while dropping progressively the heaviest and most exacting tasks.

Spinning preparation

The laying out of a spinning preparatory line shall take following targets into account:

· minimization of the residual impurities in the fibres

· most intensive mixing of the fibres

· lowest discard of good fibres

· maximum flexibility

This is in fact a continuous process, from the fibre bale up to the card sliver contained in the cans, which later on are carried to the drawing frames.

The factor which became of the utmost importance is the flexibility of the process, which permits blends of up to 4 different types of fibre in percentages ranging from 2% to 98%.

Automated systems for material handling

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The automated systems have been installed in the spinning mill whenever the price/performance ratio was profitable. Automatic can changing devices on cards and drawing frames have become standard, as well as the automated doffing systems on roving frames and on spinning frames.

As to the linkages between the various machines and to the material handling, following systems gained ground:

· linkage between lap winder and combing machine, for lap transport

· transport system for the roving bobbin with bobbin change by six or three units. An overhead trolley removes the bobbins produced by the roving frame, in a number corresponding to a sixth of the machine spindles and conveys them to an overhead store-room situated in front of the spinning frame. With same system the empty tubes are removed from the spinning frame and brought to the roving frame.

· robotized systems for unloading the bobbins from the open-end spinning machines and from the winders and their loading on pin trolleys or on pallets. These last, as soon as full of cones, are wrapped with a polyethylene sheet , weighed and labelled. These equipments can be placed at the end of the machine or in fixed positions fed by a bobbin transport system.

Environment technology in Textile Spinning

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Air conditioning, waste recovery, dusty air control, noise abatement, are all essential conditions to optimize product quality and working environment.

The air-conditioning plants for textile mills are based on cooling through evaporation and
have as their target to keep temperature and relative humidity constant in the various

production departments. These two parameters are essential for a successful running of the machines in all departments.

The air in the various departments is changed 20-30 times per hour, using suitable fans. The air is filtered, cooled and humidified and conveyed back to the working rooms. The plants have generally modular structure and are adjusted to the requirements of the single department.

Cotton processing causes the emission of large quantities of dust.

The machines are maintained clean through suction systems integrated in the machines, as in the case of cards and drawing frames.

On roving frames and spinning machines cleaning systems running on trolleys along the machines (travelling cleaners) are used which, through appropriate air blowing and suction phases keep machines and floor clean.

A particularly important role is played by the filtering systems, which are suited to the kind of dust originating in the different departments.

The spinning mills are also provided with waste recovery systems, which separate the single types of waste depending on the machines originating them, as they can be reused in different forms.

Carding | Wool spinning

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For wool worsted spinning, cards with rotating drums covered with needled clothing are used. The card has the task of cleaning, parallelizing and laying the fibres in form of a web (Fig. 9). The fibre feeding is at present completely automated.

The cards are equipped with computerized control systems which monitor each processing phase. The result of the process is entrusted to precise micrometric adjustments of the various machine members and this is the more important, the more valuable are the fibres to processed.

In these cases cards with up to 12 carding points are used, which ensure a mild and progressive opening and parallelizing action.

At the delivery from the machines, the web is taken-up in form of sliver which is made thinner by passing through a draft unit with pinned discs for a guided control of the fibres.

To increase production at same speed, the working width have been increased up to 3500 mm.

In this draft unit also autolevelling systems are installed.

Combing | Wool Spinning

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This operation characterizes the processing of longer and finer wool for the production of valuable yarns.

Combing produces wool slivers (tops) of 20-30 g/m, which are made up in bobbins or cans, which contents is successively pressed into bumps.

The aim of this operation is to eliminate the shorter fibres and at the same time to parallelize and to clean the fibre bundle.

The combing line envisages several passages.

Pre-combing

Pre-combing lines generally consist of three intersecting passages which enable to parallelize the fibres, so as to comb the fibres with minimum discarding of long fibres. When processing wool and long-stapled man-made fibres, pin drafters are used which have combs placed between the feed and delivery rollers to control the fibres during the drawing operation.

The combs are driven by chains or by rotating cams and the drawing frames can be fed by cans or by bobbins. The delivery units are automated both for can and bobbin delivery.

The drive systems use motors with frequency controlled speed (inverter), which permit to change the working speed according to the kind of processed fibres.

The drawing frame has at its delivery automatic devices for sliver threading, so as to facilitate sliver piecing in case of sliver breaking.

The geometry of the comb system is of primary importance, especially the distance between the points at which the comb quits the sliver and the nipping point of the delivery rollers, in particular when processing wool types containing high percentage of short fibres.

In the latest machines, the axis of the feed and delivery sides are driven by separate motors with electronic control of the speed and consequently of the change of draft ratios. These drawing frames can be equipped also with on-line control systems to ensure sliver regularity. The drawing frames with electrically driven axis enable to apply new self-adjustment systems, since the speed of the feed and delivery rollers are controlled and can modify the draft ratio depending on the electronic impulses coming from mechanical feelers which measure the mass of the input sliver.

The system includes also a memory which considers the time needed by the sliver coming from the feeler to reach the draft zone. These electronic systems have replaced complex mechanical systems.

Rectilinear combing machine The purpose of this machine is:

· To eliminate shorter fibres

· To obtain a sliver with a fibrous diagram showing fibres with a higher average length

· To clean the sliver

· To further parallelize the fibres.

This process is carried out with the single-headed, intermittent working. rectilinear combing machine (Fig. 10).

A fibre tuft is torn out of the feed sliver by a gripper system. The heads of the fibres are cleaned by a rotating comb and the fibre tuft is then gripped by a pair of detaching rollers. At this stage the rectilinear comb lowers itself and combs the back ends of the fibres. The tufts are then overlapped and taken up in form of sliver. A crimping device imparts consistency to the sliver, before its laying into a can. The working speed reaches 260 strokes/min, the feeding charge is up to 500 g/m and the delivered slivers weigh 23- 35 g/m.

The machine is provided with a suction system which removes impurities and collects the discarded short fibres, which are used within further processes.

Post-combing

The combing machine is followed by three passages of intersecting gill-box which, through the usual doubling and drawing actions, impart regularity to the sliver. A contribution in this direction is also given by the autolevelling system applied on one of the three intersecting passages. This operation is extremely important, as this is the last passage in which a change can be brought about to obtain a regular yarn.

In fact the following passages - the finisher drawing frame or the roving frame or the spinning machine - have only the function of thinning the count.

The pre-combing and post-combing stages can rely, in case of big production lots, on automated systems, although not neglecting the technological requirements which are essential for a good yarn quality:

· Doubling of the slivers

· Alternate combing of the top end and of the bottom end to eliminate fiber hooks.

Considerable are the economies in material handling (-30%) and in the occupied floor space (60%).

Wool Spinning | Worsted system

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Wool top preparation

Wool is received in bales and has to be scoured to eliminate all foreign substances. Prior to scouring, wool is prepared in a plant including a bale-breaker and an opener (Fig. 8). The bale-breaker has an opening and evening cylinder running at variable speed as well as a stripping roll. The opener has a step structure without watertight elements, so that wool can reach the scouring bowls thanks to the simple action of the beating cylinders. To prepare blends of various types of wool ensuring an optimal price/performance ratio, prior to scouring a blending system is used.

The line is composed of a heavy-duty bale-breaker, of a drum beater which cleans and opens up the greasy wool (raw wool). A system of conveyor belts transfers the wool to a set of storage bins with a capacity of 10 tons each. In this way it is possible to form layers of different types of wool.

From these bins the wool is automatically conveyed to the feeder of the scouring line. After passing through a step cleaner, the scoured and dried wool is pneumatically conveyed to into storage bins having a capacity of 7 tons. Wool is taken out from these bins and transported to the feeding hoppers of the cards by means of mechanical systems. The technological cycle from the wool bale to top is described in Chart 4.

Opening - blending - oiling

For the processing of small lots (100 to 1000 kg of fine and delicate fibres), a monobloc line is used; this carries out all following working stages:

· bale-breaking

· mixing of different components

· fibre opening and intimate blending

· dust exhaustion

· batching oil spraying (fibre is oiled to facilitate subsequent processing stages)

· proper baling for the semifinished product.

Combed ring spinning

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To obtain finer yarns, besides using longer fibres (30-38 mm) of smaller diameter, the sliver is submitted to a combing operation, which has a dual purpose:

· to eliminate the shorter fibres

· to further parallelise and clean the longer fibres.

Before combing, the sliver must be prepared with a passage of pre-combing drawing frame, followed by a lap winder, which has the task of assembling a certain number of slivers (24 or 36) in form of a roll (lap) suitable for feeding regularly the combing machine.

The lap winder is equipped with automatic systems for lap weighing and with differential pressure systems during lap formation, so as to reduce felting even at high production speeds.

The combing machine (Fig. 7) in which, through an intermittent movement, some fibre tufts are picked up, made to pass through two combs (a circular comb for combing the top ends of the tufts and a straight comb for the back ends), separates the short fibres according to the fibre diagram to be obtained. This operation causes also a reduction in the neps, the fibre entanglements which cause later on broken ends in the spinning machine and irregularities in the yarn.

The new models of combing machines are equipped with automatic lap feeding devices. Besides, systems have been developed for the automatic lap transport from the lap winder to the combing machines. After combing, the cycle continues with a drawing frame passage, the roving frame, the spinning frame, the winder and, if necessary, yarn doubling, twisting and finishing (see chapter 3.3).

Open-end spinning

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This is a spinning system in which the spinning frame is fed by the drawing frame sliver and builds up directly the cones, omitting the roving frame passage and in many cases the cone winding.

The fibres composing the sliver are drawn and individually separated by an opening roller and are conveyed into a rotor which regroups them and imparts the twist to the yarn.

The rotor speed has now reached 130.000 rpm, which enables to the machines a considerable production.

The system has however a technical limit: in fact as not all fibres are positioned parallel to the yarn axis, the yarn has a lower tenacity. Moreover a certain number of fibres per cross-section is necessary, therefore it is not possible to spin counts finer than Ne 32-36. The produced yarn is of optimal quality and is used also to produce knitwear and plush fabrics, besides household textiles and denim.

The open-end spinning frame, thanks to its particular configuration (feeding through slivers, take-up on cones) has enabled a complete production automation through following units:

· automatic can-changing

· piecing of the fed sliver

· piecing of the broken yarns and automatic rotor cleaning

· change of the full cones and feed of the tubes

· production of metered cones

· control of yarn regularity

· centralized control of all machine functions.

The production data of the spinning machine can be displayed on a video terminal or printed for each spinning position or for each section or each shift. The possibility of producing low twist yarns and of spinning successfully polyester, acrylic and viscose fibres, both pure and blended, make this machines highly flexible.

Carded ring spinning

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Carded ring spinning is employed for coarser yarns (up to Ne 40) and makes use of less valuable cotton types in terms of fibre length, diameter and cleaning degree.

After one or two drawing frame passages, the sliver coming from the cards is laid into cans which feed the roving frame (Fig. 5). This machine has the purpose of reducing through draft the weight of the sliver, forming a roving which receives a certain twist by a flyer system. This roving is wound onto bobbins suited to feed the ring frame.

The roving frame can be equipped with a manual doffing, in which case the bobbins are positioned on trolleys and carried to the spinning room.

Alternatively the roving frames offer, now quite frequently, automatic linkage systems between the roving frame and the spinning frames. The bobbins are laid by this system on a storage line in front of the spinning frame.

The machine is equipped with automatic cleaning and suction systems of the broken rovings. The next machine is the ring spinning frame (Fig. 6). The roving coming from the bobbin of the roving frame is drawn up to 50 times. Fibres up to 60 mm length can be processed.

The drawn and parallel fibres coming out of the draft unit are imparted a twist through the ring-traveller system.

Special systems have been worked out, which at the delivery of the draft unit improve the control on the fibres and prevent the edge fibres from moving with their ends outwards, which would cause a certain hairiness to the yarn as well as a loss of tenacity. These developments offer following advantages:

· improve yarn quality and reduce hairiness, with ensuing advantages in the subsequent singeing and sizing operations

· increase yarn tenacity while leaving twist unvaried, or increase production, as it is possible to confer a lower twist while leaving tenacity unchanged.

The yarn thus obtained has the final dimensions and, through the fibre twist, attains the desired tenacity according also to the fibres used.

The yarn is wound on bobbins weighing about 50 to 100 grams. Bobbin removal from the ringframe is at present generally carried out by automatic doffing devices, as also the loading of the empty tubes, ready to be wound.

The bobbins can be discharged into containers which feed the following machines: the winders. The spinning frame can be also linked through automatic conveyor systems to the winders, a machine which we shall examine more in detail in the chapter concerning yarn finishing.

The spinning frame can produce a wide range of counts and handle both up to 60 mm long cotton and man-made fibres, with a wide range of ring diameters, depending on the count being processed. Spindle speed can attain up to 25.000 rpm. The spindle can be operated either by tangential drive through a single belt for each side of the machine, or by tangential drive divided into sections of 48 spindles each and a single shaft along the machine.

At the moment the single motor systems are too expensive, even if they have inferior energy consumption and are less noisy.

Flat card and cotton drawing frames

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This machine is intended to clean and parallelise the fibres and to produce a card sliver in which fibres are regularly distributed (Fig. 4).

The card carries out also a cleaning action. The careful study of the clothings and of the air passages permitted to increase further the productivity of these machines.

An industrial production of 50-60 kg/h has become to-day a quite usual reference. This result has been attained by further developing following features:

· the feeding of a batting of constant count, well opened and sufficiently cleaned

· a more intensive opening and cleaning action, by the licker-in, with an effective waste removal

· the improvement of the suction system

· the automatic control of the sliver regularity and quality, in terms of neps.

The cotton drawing frames

The purpose of this machine is to parallelise the fibres by doubling and drawing several slivers.

In order to produce a sliver with maximum regularity, automatic adjustment systems are used for reducing short-, medium- and long-term variations in the sliver weight. In fact sensors are used to measure the variations in sliver weight, and the consequent necessary corrections are applied by varying the draft, that is the speed of the delivery rollers as compared to the feed rollers.

Depending on the envisaged end-product, one or two drawing frame passages can be made. This processing stage is extremely important for the regularity of the end-product, as the following machines (the roving frame and the spinning frame, both ring and rotor frame) cannot correct any more the weight irregularities of the roving and of the yarn.

BLOWROOM | Opening and cleaning

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Spinning preparation begins with the bale plucker (Fig. 1).

This machine has been fundamental in improving quality, as it enables to remove from the feeding bales, which number can be up to 100, very small tufts of material.

This fact is the ideal prerequisite for a good blending in the subsequent passages.

The plucking carriage can handle cotton and man-made fibres with up to 60 mm staple length.

The subsequent opening and blending line must be studied and adjusted according to the kind of cotton, to its degree of impurity and to the quality to be obtained.

The search after blends of different qualities of cotton is of utmost importance to optimize the quality/cost ratio.

The mixer (Fig. 2) plays therefore a fundamental role to produce a homogeneous fibre mixture which can lead to an optimal regularity in terms of tenacity and of count of the end-product and consequently to reduce yarn breakages on the following machines.

The automatic mixer can have up to eight cells , with standard delivery or with joint cleaning unit.

The material, reduced to small tufts, is delivered to the horizontal opener and to the dust separator.

In case of blending of two different fibres, two weighing hopper feeders can enter into the line, in order to achieve an intimate blend of the two fibres (Fig. 3).

The fibres are conveyed by a power-driven fan into the feeding channel of the feed chute positioned above the cards.

Each card is equipped with its own feed chute. In some cases a horizontal opener is used, equipped with dust suction hood before the feed chutes.

A regular feeding of the material to the upper rooms of the feed chutes and a constant weight of the delivery material guarantee the excellent count regularity of the card sliver. In the opening line, machines have been included which detect foreign substances among the cotton fibres, as heavy matters, synthetic material, etc. and eliminate them through local suction systems.

The spinning preparation phases are summarized in Chart 2.

(*) Number and type of opening and picking machines depend greatly on the quality degree and on the impurity contents of cotton

Elastomeric fibres

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These fibres are derived from an elastomer containing at least 85% of segmented polyurethane. The fibre, when stretched under tensile force until three times its initial length, recovers rapidly this length as soon as tension is removed.

This fibre was launched in 1959 by an American producer, who is still their major producer in the world. Its use became however widespread only some years ago when the stretch comfort became a must, so that, at a certain moment, available capacities were no longer sufficient to cover the market demand, and expansions and new plants had to be provided. Some new producers were also attracted by this promising market outlet.

Concerning this leading fibre, it has to be taken in mind that the yarn, although looking like a single continuous filament yarn, is actually composed of a bundle of thin filaments joined together. Main end-uses are: stockings and panty-hoses, tubular knit fabrics for ladies' underwear and sportswear, warp knit fabrics for ladies' lingerie and swimwear, warp knit fabrics for corsetry and sundry applications.

The elastomeric yarn is used in different percentages, depending on type of fabric and on its end-use; even only 2% is sufficient to improve the quality of the product by imparting liveliness, drape and better recovery properties. The yarn has the same dyeability and processing characteristics as a synthetic fibre and can be integrated, in the nude state, into many textile structures. It can however be covered with another yarn

or with another fibre. The covering can be either single or double; alternatively it is possible to produce stretch core yarns which, during weaving or knitting, are doubled with non-elastic yarns, thus obtaining fabrics of greater value, more comfortable and with better wear properties.

A third alternative is interlacing: an anelastic multifilament yarn is caused to pass through an air jet together with the strained elastomeric yarn. As a result of an air jet, the yarns get interlaced and the elastomeric yarn gets partially covered.

Microfibres

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Concerning filament yarns, two were the most recent and striking developments: their application in textiles for automotives and the microfibres, that is yarns composed by filaments with a count finer than 1 dtex, hence fine than silk, for use in clothing. Microfilament yarns are offered in following versions: flat, untwisted, twisted, false-twist textured, false-twist textured and hard twisted, crepe and air-textured. Microfibres have obtained with polyester amazing results in terms of filament fineness: 0,4 dtex. These yarns established themselves on the market of the silk-like products and in part replaced previous types which too had been designed to imitate silk. These are polyester yarns woven into fabrics which were treated batchwise or continuously with a decorticating finishing process also on Italian machinery, to impart a soft feel and a silky look to the fabric.

It is also worth to mention, that microfibres and in particular polyester microfibres, accomplish the task of satisfying "fashion + function" requirements. In fact from the aesthetic point of view the outstanding filament fineness translates into fabrics with absolutely innovative drape and handle, which are very often obtained through an emery grinding process carried out once again on Italian machines. As regards comfort, microfibres allow to manufacture fabrics with a density of up to 30,000 filaments/sq.cm., which are absolutely waterproof and yet breathable thanks to their permeability to body moisture.

Microfibres are offered also in staple form in 0.85 dtex by several producers both for short staple spinning on ring or open-end machines, and for long staple spinning. A special version for nonwovens is also available. Developments in the fibre sector continue unceasingly all over the world. Nylon and polyester producers bring out fibres with special cross-sections which differ from the basic sections, i.e. round, multilobal and triangular sections. A separate sector is that of the hollow fibres: recently a polyester hollow fibre with round cross-section has been produced for underwear of tracksuits. This is the finest polyester hollow fibre so far produced, which has outstanding heat insulation properties. The researchers of the U.S. laboratory where it was developed claim that undershirts made of this thermal fibre are 23% warmer than currently available products. Moreover these fibres can be dyed at lower temperature and can also include a percentage of elastomeric fibre (see below) to impart stretch properties, a result which was almost impossible to obtain before.

Acrylic fibres

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Acrylic fibres were officially developed in 1948 by the same American producer who launched nylon. It was marketed two years later, but in the 50s this fibre was produced also in Europe by several companies and was characterised by a rapid boom which in 1975, barely 25 years after its invention, got it to equal wool world consumption. This success is closely related to the development of flat and circular knitting machines, which can produce considerable quantities of knitted fabrics.

In 1998 the world production of acrylics was 2.5 million tons (10% of the world total of synthetic fibres).

The name acrylics identifies the fibres made of pure polyacrylonitrile or of its co-polymers containing at least 85% in weight of acrylic nitrile. On the contrary the name modacrylics identifies the fibres produced from polymers containing at least 35% (but less than 85%) in weight of acrylic nitrile. The latter fibres have excellent flame-retardant properties and, through this characteristic, they integrate the polyester fibre range.

Acrylic fibres are offered as tow, staple and top. Quite economical are the spun- or producer-dyed types, which now account for a substantial share of the total production. The use of dyed fibres allows a lower processing cost (from fibre to dyed yarn) compared to the conventional cycle composed of raw yarn spinning and of hank, cone or piece dyeing, moreover it enables to obtain a superior quality in terms of appearance and properties of the yarn. Also dyeing evenness and shade uniformity among different lots are better. By mixing 2 to 4 basic colours with the raw fibre, a wide range of melange colours can be also obtained.

The end-uses which emphasize the characteristics of the acrylic fibre are:

- all knitted items: outerwear and underwear, hosiery, hand knitting yarns (advantages: high bulkiness, stitch clarity, unshrinkability, easy washability without any felting, quick drying, high comfort);

- fabrics, furnishing velvets, carpets (advantages: item's long duration, low soiling, easy

cleaning, good resilience of the pile which therefore does not get crushed);

- awnings (advantages: excellent resistance to sunlight, weathering and mildew);

- imitation furs (so-called ecological furs) and pile fabrics for clothing linings (advantages:

lightweight, softness and easy-care properties).

In 1991 microfibres were developed also in the acrylics sector with the launch in Italy and almost at the same time in Germany of staple fibres 0.8 dtex which were immediately well accepted by the spinning mills. The yarns produced have a very soft, but firm handle, a silky lustre as demanded by the knitwear market, optimal bulkiness and roundness and, therefore, a high covering power and high thermal insulation even with lightweight fabrics.

Synthetic fibres

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Synthetic fibres originate from non-fibrous products which become textile raw materials thanks to "synthesis" operations, hence their name. In chemistry, by the term synthesis is meant an operation by which, starting from simple substances, more complex substances are obtained. Thus synthetic fibres are the result of the combination of a great many chemical units, which are assembled to form long chains, the polymers, which are then converted into fibres by the spinning operation. The polymer is transformed by orientating the macromolecules in the formation process of the filament, which is the basic element of the following phases: drawing, production of continuous filament yarn or of staple fibre and, if necessary, texturing. By this last process, the filaments composing the continuos yarn are crimped to make the yarn bulkier.

Polymerisation is the basic requisite for fibre chemistry, as shown by the fact that the prefix of several product names is "poly": polyamide, polyester, polyacrilonitrile, etc.

The world production of synthetic fibres has by now surpassed that of cotton; in 1998 it amounted to more than 25 million tons, compared to a little more than 18 million tons of cotton. Growth has been considerable over the last 30 years: suffice it to say that the output was 4,8 million tons in 1970, 10,6 million tons in 1980 and 16,0 million tons in 1990.

It is noteworthy that the synthetic fibre production, which until some years ago was concentrated especially in the United States, Western Europe and Japan, has progressively extended to other countries. Suffice it to say that, whereas in 1990 45% of the production still came from those three areas, in 1998 their market share shrunk to 31 %, and this trend is likely to go on.

As regards Italy, the total synthetic fibre production reached in 1998 abt. 600,000 tons, which is equivalent to about 20% of total EU production and to 2.4% of world production.

The main producing countries of synthetic fibres (1998)

Artificial fibres

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As already mentioned in the introduction, the increase in world population (from 3 billions in 1960 to over 6 billions in the year 2000) and its growing needs made it necessary to integrate the production of natural fibres with those of man-made fibres ; these last expanded altogether at higher rates than natural fibres.

Moreover this fact permitted to countries lacking in natural raw materials to develop an important textile industry and to extend their application field (just think of the countless blending possibilities of natural with man-made fibres).

The exact product definition of artificial fibres (quite often referred to as ″cellulosics″) originates from the fact that they originate from a raw material which, though fibrous in nature, cannot be used directly by the textile industry and is therefore properly ″reclaimed″ through technical processes or ″expedients″.

Silk is the queen fibre that served as a model for the development of artificial silk, which took place at the turn of the 19^th century thanks to the invention of Count Hilaire de Chardonnet who applied for the first patent covering a ″textile material similar to silk″. Silk was also the model for the chemist Max Fremery who, in co-operation with the engineer Johannes Urban, succeeded in 1891 in dissolving cotton's natural cellulose in cuprammonium and thus obtained a filament for electric bulbs with better performances and much longer life than the filament used until then. Later on, having realized that by stretching the filament they could obtain a much finer yarn suitable for the textile sector, they started the production of viscose.

The artificial silk by the cuprammonium process was successively produced and bore the trademark Bemberg. The raw material of the Bemberg yarn are the linters, which are filaments of pure cellulose covering the cotton seeds and which are used in the production of some rayon types.

At the same time a process was developed, by which cellulose was converted to the liquid state through a solution of diluted caustic soda. This principle was successively named ″viscose process″.

Viscose too has a natural origin as it is derived from the cellulose of trees, which are specially grown for this purpose. It takes 22 years to a tree (generally pine tree) to reach the inner structure and the maturity which are decisive for the future quality of viscose. 100 years after the discovery of viscose, its production, in particular filament yarn production, remains still rather complex and time-consuming; in fact 30 days are necessary to obtain viscose from the cellulose sheet.

With the advent and development of synthetic fibres, the production curve of the artificial fibres have gradually levelled out, so that already in 1970 they were surpassed by synthetics. In fact in 1970 3.6 million tons of artificial fibres were produced, compared to 4.8 of synthetics. In 1998 the output of artificial fibres amounted to 2.8 million tons against 25 million tons of synthetics; therefore artificial fibres account today for less than

10% of the total production of man-made fibres. The Italian production of artificial fibres in 1998 amounted to about 30,000 tons; our country does not produce viscose staple.

As a matter of fact, in the last few years there has been a certain revival of the interest in viscose, especially as a filament yarn, which application fields extended from the traditional and highly appreciated linings to apparel and furnishings. However the viscose producers proceeded cautiously in new investments to cope with the increased demand, since these plants often use old technologies and have to tackle serious environmental problems. On the other hand, as regards staple fibre, new processes have been developed. They are solvent processes : one for Tencel viscose fibre produced in the U.S.A. by an English company, and the other for Lyocell fibres produced in Austria by a process in which cellulose is dissolved in N-methyl-morpholine oxide (NMMO) and water.

Well established is the high wet module viscose fibre, known as modal fibre, which is often used in blend with other fibres. A 1.0 dtex micro-version of this type of staple has been recently introduced. On the market there are also types of flame resistant viscose staple, which can be used in blend with other fibres to provide textile items with fireproof properties. We also wish to mention the extra-bright silky acetate and triacetate yarns derived from cellulose acetate. After spinning, also acetate can be subjected to the regular textile operations, as twisting, texturing, warping and sizing.

Bast fibres | Flax – Ramie - Jute

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The main bast or stem fibres, which are fibres containing fibrous bundles in their inner bark, are: flax, jute, hemp, ramie and kenaf. We shall here limit us to some short hints at flax, ramie and jute, which are currently the three most widely used bast fibres.

Flax

Flax is a herbaceous plant (Linum usitatissimum) of the Linaceae family, which is grown to obtain the most valuable vegetable fibre. It is part of the so-called bast fibres, as from their inner bark, called liber, fibrous bundles are extracted which, properly treated, are converted into fibres. As to the processing of flax, we refer to the chapter 4 'Bast fibre spinning technologies", which illustrates two different spinning systems: wet and dry spinning.

The linen fabric is characterised by a considerable moisture absorption, therefore linen items are particularly comfortable. Linen is employed for the manufacture of high-class fabrics for top quality household linen, apparel and also decoration fabrics.

In these last years the linen world production has gradually declined. In 1996, in Western Europe about 21,000 tons of flax yarns and 16,000 tons of linen fabrics were produced. Italy ranks first in terms of production of both flax yarns (6,800 tons) and of linen fabrics (9,100 tons), followed by Ireland, Belgium and France.

Ramie

Ramie is a bark or stem fibre, which use in fabric production dates back to ancient times; in the ancient Egypt, it was used as early as in 500 BC. At present it is mostly grown in China in form of white ramie; its production totals about 100,000 tons/year.

The ramie plant is a species of the Urticaceae family and resembles the flax plant; in fact it grows up to 2 metres height and to a diameter of 1-2 cm ; the fibres are distributed on a cortical layer situated just underneath the outer bark and are glued together by gummy and gelatinous substances.

Unlike other bast fibres (flax and hemp), ramie is not retted, because of the low corruptibility to micro-organisms of the organic substances glueing the fibres together, and because of the risk of fibre fermentation during retting, with ensuing tenacity loss.

Owing to its whiteness and silky lustre, ramie is the most beautiful cellulosic fibre. Its tenacity and the possibility of converting it into single fibres enable to produce fine counts, while its resistance to wear and to excess of moisture (rot) makes ramie fabrics extremely weather resistant.

Unlike flax, ramie does not show any tenacity loss in wet state. Its length can vary from 60 to 250 mm and its diameter from 10 to 100 µ: as such, it is the longest and broadest vegetable fibre. Its chemical resistance is better than that of other bast fibres; it reacts properly to bleach, which yields light, extremely pure colours and pearly shades.

Jute

Jute is obtained from the bark of some trees of the Tiliaceae family which live in Asia and in Africa and is grown mainly in Bangladesh. It is mostly used for weaving primary and secondary carpet backings and packaging materials.

Italian textile machinery industry

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The italian textile machinery industry, today: characteristics, raw materials, technologies.

The textile machinery industry requires conspicuous research investments, in-depth know-how, long experience in textiles, mechanics and electronics, so that there are not many countries capable of ensuring a textile production of technological high level.

Italy is one of the 3 leading producer countries in the world and the technological level of its production is considered, even by its competitor countries, as up to the highest standards.

The value of the Italian production of textile machines in 1998 amounted to 3,7 billion dollars, 65% of which exported to more than 100 countries.

The Italian export of textile machines can be divided as follows:

25% spinning machines 20% weaving machines 25% knitting and hosiery machines

21 % finishing machines

8% dry cleaning and laundry machines

1 % other machines

Europe (48%) is the main export area, followed by Asia (22%), North America (17%), South America (8%) and Africa (5%).

Export of Italian textile machinery

A complete production line

The Italian offer of textile machinery is characterised by an extremely wide and complete range, which includes:

· spinning preparatory and spinning machines

· twisting, winding and reeling machines

· weaving preparatory and weaving machines

· hosiery machines

· dyeing, printing and finishing machines

· machines for the making-up industry

· machines for textile maintenance

The Italian textile machines can process any kind of fibre, both natural (cotton, wool, silk, etc.) and man-made fibres, thus meeting adequately any requirement by the textile industry.

The reasons of a success

The Italian companies manufacturing textile machines and accessories are over 350 and employ 26.000 people.

They are generally situated in areas of age-old textile tradition, where a synergetic exchange of experiences with the end-users offers a big stimulus to the improvement of the machinery.

These areas are situated in the North and Centre of Italy: at Biella, Como, north of Milan, Prato and Vicenza.

Thanks to the high number of manufacturers, almost any type of machine can be supplied by more than one manufacturer, so that the customer can easily find the type of machine which is better suited to his own requirements.

As however a process of industrial integration is under way also in our sector, the number of companies active in this field seems to be doomed to a slow but progressive reduction.

The main characteristics of the Italian textile machines which ensured their success worldwide are:

· extremely advanced technological level

· versatility and flexibility

· excellent quality/price ratio

· reliability.

Moreover the Italian manufacturers are continuously intensifying their research on the issues of industrial safety and environment in order to propose solutions which are more and more abreast of the times.

What is ACIMIT

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ACIMIT, the Italian Association of Textile Machinery Producers, groups together at present 251 Italian producers of textile machines and accessories, whose production accounts for 85% of the whole production of Italian textile machines, and 19 associated members (consortia, technical institutes, technical magazines, engineering and trading companies, research centres).

The purposes of the Association

The main purpose of the Association (which is a non-profit-making body) is the promotion of the Italian textile machinery industry and the support of its activities, especially abroad, through the most innovative means.

In order to promote in particular the knowledge of the Italian textile machinery worldwide (that is to inform about “who is making what”),ACIMIT can offer any kind of information on the activity of their member companies, thus ensuring to the image of the Italian textile machinery sector the widest diffusion (through exhibitions, publications, technological seminars).

Another important activity of ACIMIT is to inform their member companies about the commercial, financial and technical problems which can be met with on the various markets, thus making their access easier.

The ACIMIT Foundation

Beside these activities, ACIMIT felt the necessity of promoting an additional range of initiatives regarding economical and professional training issues, which however can be better dealt with by a Foundation: this was the reason of constituting the ACIMIT Foundation in 1997.

Among the most significant activities started by the Foundation during the first three years of activity, worth mentioning are the publication of 4 economic researches on the textile machinery sector and a significant activity of professional training in favour of Italian and foreign students (which involved the implementation of technology courses in Italy, the publication of school text-books and the awarding of scholarships).

The ACIMIT service company

With a view to build up an organisation which could be better up to the new requirements of the enterprises and to the provisions newly established for the associations, ACIMIT constituted on January 1 st, 1999 the service company ACIMIT Servizi srl.

The subject-matter of the new company is to provide services for the promotion, organisation and advertising of exhibitions and shows in Italy and abroad, as well as administrative outsourcing services for the companies intending to displace abroad their tasks and activities.

Fiber (Fibre) Processing

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Cotton fiber quality determines the type of yarn and fabric that can be produced. Parameters such as fiber length, strength, and micronaire can be

measured precisely and accurately with high volume instruments (HVI). These instruments, as well as the operating procedures associated with them, are well described and standardized. HVI data are used all over the world by the textile industry in buying

cotton and in managing the mixes in the textile mills. Important, though not yet completely standardized, are measurement, characterization, and quality control standards for lint contaminants. In this chapter, we focus on one specific type of contaminant, cotton lint stickiness.

Effect of Stickiness on Productivity and Yarn Quality

Cotton stickiness caused by excess sugars on the lint, from the plant itself or from insects, is a very serious problem for the textile industry—cotton growers, ginners, and spinners (Hequet et al. 2000, Watson 2000). During the transformation process from fiber to yarn of sticky cottons—opening, carding, drawing, roving, and spinning—the machinery is contaminated to different degrees depending on the processes involved and the location within the machines. This affects processing efficiency as well as the quality of the products.

Stickiness is caused primarily by sugar deposits produced either by the cotton plant itself (physiological sugars) or feeding insects (entomological sugars) (Hendrix et al. 1995). Insects have been documented

as the most common source of contamination in some studies (Sisman and Schenek 1984). The analysis of honeydew from cotton aphids (Aphis gossypii Glover) and sweetpotato whiteflies (Bemisia tabaci (Gennadius) strain B (= Bemisia argentifolii Bellows and Perring)) has shown that aphid honeydew contains around

38.3 percent melezitose plus 1.1 percent trehalulose, while whitefly honeydew contains 43.8 percent trehalulose plus 16.8 percent melezitose under the conditions described by Hendrix et al. (1992). Relative percentages may differ depending on environmental

or feeding conditions. Sucrose is virtually the only sugar in the phloem sap of cotton plants (Hendrix et al. 1992). The insects produce trehalulose and melezitose by isomerization and polymerization of sucrose. Neither of these sugars is produced by the cotton plant (Hendrix 1999); therefore, their presence on cotton lint demonstrates honeydew contamination. Furthermore, Miller et al. (1994) demonstrated that stickiness is related to the type of sugars present on the lint. The authors showed that trehalulose and sucrose, both disaccharides, were the stickiest sugars when added to clean cotton while melezitose (trisaccharide), glucose, and fructose (both monosaccharides) were relatively nonsticky.

Investigations have been conducted to elucidate the factors affecting the behavior of cotton contaminated with stickiness. In textile mills, the method mainly used to reduce the effects of stickiness is blending sticky cotton with nonsticky cotton (Perkins 1984, Hequet et al. 2000).

Gutknecht et al. (1986) reported that stickiness caused by honeydew depends on the relative humidity in which the contaminated cotton is processed. Relative humidity is a function of both water content and temperature of the air. Frydrych et al. (1993) reported that stickiness measured with the thermodetector is dependent on relative humidity. Price (1988) noticed that sticky cotton (with 1.2 percent reducing sugar content) when stored in high relative humidity (70

°F, 80 percent relative humidity) gave more problems during processing than the same sticky cotton stored at low relative humidity (75 °F, 55 percent relative

humidity). However, at low relative humidity the fibers are more rigid, which will increase the friction forces creating static electricity (Morton and Heade 1993). Therefore, milling machinery will require more energy to draw the lint.

Stickiness has also been reported to cause a buildup of residues on the textile machinery, which may result in irregularities or excessive yarn breakage (Hector and Hodkinson 1989). When processing low to moderately contaminated cotton blends, residues will slowly build up. This translates into a decrease in productivity and quality forcing the spinner to increase the cleaning schedule.

Perkins (1983) reported that the cause of the severe stickiness of some 1977 California San Joaquin Valley cottons was probably whitefly honeydew. The

stickiness was most severe in the picking, carding, and roving processes, with frequent interruptions in

production at carding and roving because of ends down and roll lapping. Storage of the cotton for more than 8 months did not relieve the stickiness. Processing the cotton through a tandem card eliminated the sticking problem at carding, but did not relieve the problem at roving enough to prevent production failures.

Fonteneau-Tamine et al. (2001a), studying 26 bales of Sudanese sticky cotton, reported that textile machinery performances decreased when sticky cottons were processed. At more than 50 sticky spots detected with the high speed stickiness detector (H2SD) and relative humidity between 45 and 50 percent during opening and carding, carding is not possible. In addition, stickiness reduces significantly the productivity well below the 50-H2SD-spot limit. As shown in table 1, the roving frame appeared to be the most sensitive

of all the machineries involved in the fiber-to-yarn transformation.

Fonteneau-Tamine et al. (2001b) reported on the same lot of Sudanese cottons that cotton stickiness not only affects productivity but also the quality of the end products. Although a clear decrease in productivity was noted for both the carding and draw-frame operations, it did not translate into a measurable decrease in sliver quality. It is only from the roving frame onward that there is a stickiness-induced decrease in regularity. The coeffient of variation (as a percentage: CV%) of the roving mass is slightly higher, thus increasing the irregularity of the yarn on the ring spinning frame. When considering actual spinning, the quality of ring-spun yarn is more susceptible to stickiness than that of rotor-spun yarn. As shown in the table 2, the regularity. imperfections, and tensile properties clearly highlight this difference between the two processes. The CV% of mass, number of thin places, number of thick places, and number of neps in the ring-spun yarn increases significantly with the number of H2SD sticky points. The tensile properties of the ring-spun yarn decrease

as stickiness increases. By contrast, most of the quality characteristics of the rotor spun yarn are unaffected by cotton stickiness.

Hequet et al. (2000) obtained very similar results. They examined the threshold level of stickiness for acceptable performances of both ring and rotor

spinning, in terms of productivity and quality of the yarn produced. In the short term, between 0 and 11 sticky spots (average H2SD count of sticky spot in the

cotton mixes) the stickiness contamination does not appear to influence the productivity for either ring- or rotor-spun yarns, but it clearly does above this 11-spot threshold. Nevertheless, a slight but significant negative effect on the ring-spun yarn quality has been detected even at the very low levels of stickiness tested. No negative effect has been noticed on the quality of the rotor-spun yarn. In the long term, however, it appears that some insect sugars are slowly contaminating the equipment. This accumulation of sugars may reduce both productivity and yarn quality in the long term.

Stickiness may cause a buildup of residues on the textile machinery, which may result in irregularities or excessive yarn breakage. When the cotton is very sticky it cannot be processed through the card;

however, with low to moderate stickiness levels, yarn can generally be produced. Hequet and Abidi (2002) studied the origin of the residues collected on the textile equipment after processing of sticky cotton blends with low to moderate levels of contamination. They worked with mixes having a very moderate level of stickiness in order to see, over time, a slow residue buildup on the textile equipment. This way of doing

the spinning test is more representative of the industrial practice. Indeed, a spinner will not run a very, or even moderately, sticky blend. He will rather mix the sticky cotton in such a way that no short-term effect will be noticed. Nevertheless, in the long term, residues build up and translate into a slow decrease in productivity and quality, forcing the spinner to increase the cleaning schedule.

Twelve commercial bales contaminated with insect honeydew were selected based on their insect sugar (trehalulose and melezitose) content and their stickiness as measured with the high speed stickiness detector. In addition, five nonsticky bales from one module were purchased for mixing with the contaminated cotton so that alternative stickiness levels in the mixes could be obtained.

Preliminary tests were run on ring spinning before testing the mixes. Thirty pounds of lint from each bale was carded and drawn. If noticeable problems occurred at the draw frame, the process was stopped. If not, the drawing slivers were transformed into roving. If noticeable problems occurred at the roving frame, the process was stopped. If not, the roving was transformed into yarn at the ring-spinning frame. If noticeable problems occurred at the ring-spinning frame, the process was stopped. If not, 100 pounds of

lint was processed for the large-scale test. If noticeable problems occurred at any step of the process, the cotton was mixed with 50 percent nonsticky cotton and the process was repeated. Using this procedure led to the execution of 17 large-scale tests.

High performance liquid chromatography (HPLC) tests were then performed on card slivers, flat wastes, draw frame residues, and the sticky deposits collected at the end of each test on the rotor-spinning and ring-spinning frames. These tests quantify the amount of each sugar, expressed as a percentage of total sugars present. In addition, H2SD measurements were made on card slivers.

After each spinning test was completed, the opening line and the card were purged by processing a noncontaminated cotton, then all the equipment was washed with wet fabrics and thoroughly dried.

From the 12 contaminated and the 5 nonsticky bales, 17 mixes were evaluated in both ring and open-end spinning. As expected, H2SD readings on the mixes

indicated slight to moderate stickiness (from 2.0 to 15.7 sticky spots). During the processing of the 17 mixes, sticky deposits were noticed on the textile equipment as shown in figures 1 to 3.

Figure 4 shows average HPLC results obtained on the 17 mixes for the fiber, the flat waste, and the residues collected on the draw frame and the drawing zone of the ring spinning frame. In this chart the HPLC results are normalized, the base being the HPLC results on the fiber. It shows that trehalulose content is always higher in the residues collected than on the original fiber while the other sugars are not. The same behavior was

observed in rotor spinning (figure 5). Among the sugars identified in contaminated cotton, only trehalulose exhibits higher concentration in the residues.

Figures 6-10 show the nonlinear relationship between trehalulose on the fibers and trehalulose on the residues for some selected locations on the textile equipment. These figures show that during the processing of the mixes having trehalulose content above 5 percent of the total sugars, trehalulose content has a clear tendency

to increase in the residues collected. Consequently, the authors decided to investigate the sugars' properties in order to understand why trehalulose content increases in the residues while the other sugars do not. The

thermal properties of the five sugars identified on the contaminated fiber and on the residues collected on

the textile equipment were investigated. Differential scanning calorimetry was chosen to study the thermal properties of the following dehydrated sugars: fructose, glucose, trehalulose, sucrose, and melezitose. The differential scanning calorimetry profiles were recorded between 25 °C and 250 °C. Among the selected sugars, trehalulose has the lowest melting point (48 °C), as shown in table 3. It begins to melt immediately when the temperature starts rising. The other sugars remain stable when the temperature rises until it reaches 116 °C (melting point of fructose). Therefore, any increase in the temperature of the textile processing equipment will first affect trehalulose, causing it to either stick on the mechanical parts or become the precursor of nep formation. Figure 11 shows one example of a sticky nep collected from the yarn produced in this study.

Sugars belong to the carbohydrate class. They are hydrophilic because of several hydroxyl groups (—OH), which interact with water molecules, allowing many hydrogen bonds to be established. Therefore, several authors (Gutknecht et al. 1986, Price 1988, Frydrych et al. 1993) investigated the relationship between stickiness and relative humidity. It was generally reported that contaminated cottons are less sticky at low relative humidity than at high relative humidity. Therefore, the hygroscopic properties of the five sugars identified on the contaminated fiber were investigated. The quantity of water adsorbed

on each sugar was evaluated at 65±2 percent relative humidity and 21±1 °C. Figure 12 shows the percentage weight gain during the first 12 hours of hydration.

No sugar exhibited any significant variation within this time period except trehalulose, which picks up about 12 percent moisture; this corresponds to two molecules of water per molecule of trehalulose. Then, the weight gain of the sugar samples continued to be recorded until the plateaus were reached. Trehalulose continued to pick up moisture, while fructose began to pick up moisture after 12 hours of exposure to the

laboratory conditions (figure 13). The hydration kinetic was very fast for trehalulose, with the equilibrium being reached after 80 hours, but slow for fructose, with the plateau being reached only after 500 hours. The total amount of weight gain corresponds to three molecules of water per molecule of trehalulose and three molecules of water per molecule of fructose.

If we assume that trehalulose accumulates more on the spinning equipment than other sugars because of its hygroscopicity, then fructose should accumulate in a similar way, but this is not the case. Indeed, the

HPLC tests performed on the residues collected on the

Figure 5. High performance liquid chromatography results on the 17 mixes for fiber, flat waste, and residues collected on the draw frame and the rotor spinning frame. The HPLC averages are normalized, the base being the results on the fiber. A: card flat; B: draw frame, drafting zone; I: rotor spinning frame, face plate; J: rotor spinning frame, feed table; K: rotor spinning frame, rotor groove; L: rotor spinning frame, rotor housing; M: rotor spinning frame, rotor ledge; N: dust test (Hequet and Abidi 2002).

Figure 6. Relationship between the trehalulose content on the fiber of the 17 mixes and the trehalulose content on the residues collected from the front rubber rolls of the ring spinning frame. The trehalulose content is expressed as a percentage of the total sugars (y = 14.62Ln(x) — 2.47; R² = 0.702). The straight line is the equality line (Hequet and Abidi 2002).

textile equipment do not show any increase in fructose content, even if fructose content was high on some mixes. On the 17 mixes tested, the fructose content, expressed as a percentage of the fiber weight, ranges from 0.012 to 0.101 percent, which corresponds to 10.6 to 33.6 percent when expressed in percentage

of the total sugars identified. Thus, the fact that trehalulose is highly hygroscopic does not alone explain why this sugar has the tendency to accumulate more on the textile equipment than other sugars. The combination of high hygroscopicity and low melting point of trehalulose renders it stickier than the other sugars, allowing its higher concentration on the textile equipment.

The combination of high hygroscopicity and low melting point could explain the higher concentration of trehalulose in the residues collected on the textile equipment than on the original fiber. This research demonstrated that, among the sugars involved in cotton stickiness, trehalulose was probably the cause of the worst problems in processing. Thus, the effect of trehalulose throughout the spinning process was investigated for both conventional and compact ring spinning.

Hequet and Abidi (in press) processed 12 mixes, obtained by mixing sticky cotton with nonsticky cottons, through a short-staple spinning line. In addition to the trehalulose content (determined by HPLC), H2SD readings were obtained. The twelve mixes ranged from 0.013 percent to 0.204 percent of the fiber weight in trehalulose content and from 2.5 to 26.4 H2SD sticky spots. Among the mixes, some had high H2SD readings and low trehalulose content while others had high H2SD readings and high trehalulose content.

For this set of cottons, there was no correlation between H2SD readings and trehalulose content. Previous work done on 150 bales showed the same lack of correlation, especially in the low-to-moderate H2SD stickiness range. There was a marked evolution of the H2SD readings along the processing line and a strong interaction with the type of contaminant (aphid honeydew vs. sweetpotato whitefly honeydew), while there was only a slight evolution of the trehalulose content. It seems that some sticky spots, depending on the sugar composition, are broken into smaller particles in the opening line.

The mixes with high H2SD readings and low trehalulose content (aphid honeydew contamination) had no more ends down than mixes with low H2SD readings. Mixes with high H2SD readings and high trehalulose content (whitefly honeydew contamination) had excessive ends down or could not be processed. Cotton stickiness had a significant detrimental effect on both yarn evenness and yarn hairiness, even for the moderate levels of stickiness tested, but had no effect on yarn tenacity and CSP (count strength product).

In conclusion, stickiness affects productivity of the ring and rotor spinning processes and yarn quality. The origin of the honeydew contamination seems to affect the processability of sticky cottons. For a

given level of stickiness, as measured by the H2SD, cottons contaminated with whitefly honeydew are more problematic to run in the spinning mill than cottons contaminated with aphid honeydew.

Effect of Storage on Stickiness

Storage of cotton has been reported to either reduce or remove the incidence of stickiness. In other instances authors reported little to no effect of cotton storage

on stickiness. Perkins (1986) reported that whitefly honeydew contaminated cotton samples were still sticky after 2 years of storage, while other sticky cotton samples with high physiological sugar contents were much less sticky after only 4 months of storage. Frydrych et al. (1993) reported that some spinners store sticky cottons with the hope that the natural decomposition of the sugars present on the lint will reduce stickiness. The authors concluded that, on the range of cottons contaminated with insect honeydew tested and after storage for more than 2 years under various relative humidity and temperature conditions, there was no significant change in cotton stickiness measured using the thermodetector.

It seems that stickiness from high level of physiological sugars may disappear after several months of storage because of biotic activities on the lint, while stickiness from insect honeydew will not. This could be due to the inability of most of the microorganisms to metabolize some insect sugars.

Effect of Mill Conditions

In past publications, it has been suggested that
machinery speeds, settings, roll pressures, and

humidity levels are likely to influence processing problems, namely roll lapping, caused by sticky cotton. In fact, many have provided data that show dry (low-humidity) conditions in processing areas of a textile mill will allow for the adequate processing of sticky contaminated cottons (Reynolds et. al. 1983,

Perkins 1983, Gutknecht 1988, Price 1988). However, Backe (1996a) has suggested that (in addition to low humidity) bale bloom time, crush roll pressure, waste extraction, and cleaning cycles, either by themselves or in combination, can aid in alleviating the processing problems associated with sticky cotton.

Gutknecht (1988) has shown that the potential for stickiness increases for sticky contaminated cotton as the relative humidity of the surrounding atmosphere increases. Chellamani and Kanthimathinathan (1997) have reported that processing cottons known to be contaminated with stickiness at a relative humidity of 50 percent or lower will reduce the processing

problems associated with these cottons. Backe (1996a) states that a relative humidity of less than 42 percent in the blowroom, carding, and drawing processes was helpful in processing sticky cotton. In addition, he indicates that success was met by allowing the bales to bloom in a fairly dry atmosphere for 48 hours prior to processing. Bringing the humidity surrounding

the sticky contaminated cotton during processing to low levels dehydrates the sugars present on the sticky contaminated cottons. Hughes et. al. (1994)

demonstrated that dehydrating the cotton to low levels of moisture drives off water until the sugar of the sticky contamination changes to a crystalline structure, which is not sticky. These researchers suggest that this effect seems to occur somewhere between 4.5 and 5.0 percent moisture content.

In processing sticky cotton, it was suggested by Backe (1996a) that relieving the crush roll pressure at the card will help in reducing the roll lapping on the crush rolls. However, Perkins (1993) warned that

removing the crush roll pressure or increasing the gap between the crush rolls will allow large trash particles to remain in the stock, which could adversely affect yarn quality. Further, removing crush roll pressure

to alleviate carding difficulties with sticky cotton will only act to transfer the problem downstream to drawing, roving, combing, and spinning. At these

processes, roll lapping is a result of the sticky point on the cotton fiber attaching to the rollers in the drafting zone and subsequently collecting fiber passing through the zone. Known methods of minimizing this effect

are increasing the cleaning cycle of drafting rolls or treating the rolls with iodine to coat the rolls. Coating the rolls with iodine keeps the sticky point from adhering to the rollers and creating a roll lap (R. Insley, 2001, personal communication).

Use of Additives

Since the 1980's, there have been many reports on the use of additives to process sticky cotton. Some

success was demonstrated with nonionic combinations of hydrocarbon plus surfactant (Perkins 1983, 1984). However, Perkins (1971) warns that cationic additives will not be completely removed downstream in textile processing and will result in reduced scouring and dyeing efficiency. Chun and Brushwood (1998) have shown that treating cotton with water plus ammonia or urea at a 30 percent moisture content during storage for 15 days drastically reduced sugar content and stickiness without adverse affect on fiber properties. A practical application of these findings has not been developed.

Backe (1996b) reported on the use of a new additive, Gintex, for processing sticky cottons. This product

is a nonoil- and nonsilicon-based product that is said to reduce fiber-to-machine friction so that fiber and foreign matter move freely without static electricity. In 1995, Backe (1996b) reported that several mills used this additive to process sticky cottons from the 1995 West Texas crop, Uzbekistan crop, and the crop from Francophone Africa with good success. Some of the positives of processing with this additive were said to be less dust, improved cleaning efficiency, increased yam tensile properties, and improved mass evenness in addition to alleviating sticky cotton processing difficulties. Typically the additive is applied at the bale feeding (top feeder or hopper) stage of processing at the textile mill. Treating cottons with additives may be

feasible if the user is willing to incur the additional cost for not only the additive but also the hardware to apply it.

E.F. Hequet, N. Abidi, M.D. Watson, and D.D. McAllister

Willow Mat Machine | Working Principal

2009-12-21T05:47:00.001-08:00

Willow Mat Machine consists mainly of three basic machines i.e., Feed System, Step Cleaner and High Speed Condensor. The Control panel is provided to regulate the feed and the number of passages the material has to pass in Step Cleaner.

The Condensor and Step Cleaner motors are direct on motors for which Push Button Switches are provided and the Feed Table motor is controlled by a Timer. The Step Cleaner is provided on the delivery side with a damper system, which when open, shall allow the material to be sucked by Condensor and the same is dropped in the Step Cleaner again for repeated operation.

The damper in close position will allow the material to either drop on the ground through a Delivery Funnel or can be connected to a Condensor placed on a bin. There are three basic timings for which timers are provided and these Timers can be individually set for required settings. The first Timer is to control the Feed Table which will allow the material to be delivered to the step cleaner which is called Feeding Timer. The second Timer will allow the material to rotate into the Step Cleaner which is called Cleaning Timer. The third Timer is for emptying, which will allow the material to either drop down to the ground or can be delivered to subsequent machine.

The Feed timer and the cleaning timer are adjusted depending on the type of material to be processed. If it is dirty material such as Blow Room waste, then the feed is restricted, and the cleaning timer is increased for better cleaning. But in case of flat strips, the cleaning timer can be reduced, as the material fed is comparatively cleaner. The production of the Willow Mat will depend upon the quality of the material to be fed into the Willow Mat. In case there is higher lint, the production will be more and in case of lower lint, the production will be less. Production of 80 to 100 kg/hr for Blow room droppings and Licker in waste and 300 to 400 kg/hr for Flat strip can be expected from the Willow Mat.

Henna Tex

5/12, Manish Ind. Estate, Navghar, Vasai (E.), Dist: Thane - 401 2 10, INDIA. Tel/Fax: +91 – 0250 – 2321522/+91 – 9820083040 Email: hennatex@mtnl.net.in Website: www.hennatex.com

Adoption Of Ring Spinning In Lancashire, 1880-1913

2009-12-20T20:54:00.001-08:00

TIMOTHY LEUNIG

This paper returns to the long-running debate concerning the slow adoption of ring spinning in Lancashire. It uses new data on the location of firms within Lancashire to more accurately analyse the causes of Lancashire’s continuing preference for the mule. It shows that the primary determinants of spindle type were not the supply side factors of transport costs and technical inter-relatedness, but instead were demand side factors, notably the high level of demand for fine yarn, and the sizeable yarn export trade. The paper also resolves two smaller puzzles, the atypicality of Oldham’s investment patterns, and Lancashire’s lack of interest in paper tube rings.

The paper proceeds as follows. The first section contains a brief summary of the industry’s rise and fall, along with a survey of the literature on the slow adoption of ring spinning. The next section shows analytically that the standard divide into vertically integrated and vertically specialised firms is insufficient, and instead proposes a three way division into vertically integrated firms, vertically specialised spinners located near to weaving firms, and vertically specialised firms with no weavers close by. Section three confirms empirically that all three types of firm existed in substantial numbers. The fourth section shows that vertically specialised spinners located close to weavers adopted rings as often as vertically integrated firms, and these

groups adopted rings four times as often as vertically specialised firms without weavers close by. This allows us to compare the relative merits of the two supply side factors, transport costs and technical inter-relatedness. The final substantive section demonstrates that the division of the industry proposed in the paper, the size of the sectors, and their propensity to adopt rings are in line with both observed investment behaviour and the total stock of spindles in Lancashire. It shows that although the supply side factors mattered, they were less important than the demand side issues in determining the number of rings and mules in Lancashire.

THE INDUSTRY AND THE LITERATURE

Although Britain grows no cotton, the spinning and weaving of imported raw cotton proved central to Britain’s development as an industrial nation. The rise and decline of the industry is well known, and is summarised in figure 1.

Cotton’s centrality to British industrialisation is reflected in the literature, with all writers from W.W. Rostow to N.F.R. Crafts and C. Knick Harley perceiving cotton to be the most important element in the British industrialisation process.¹ But the decline of cotton has not prompted such unity. In particular there remains a dispute as to whether the Lancashire cotton industry should have behaved differently in the ‘glory years’ prior to 1914. A number of issues have been raised, including the question of technology. Why was Britain so much slower at adopting new technology, such as the ring spindle and automatic (Draper) looms? Was the atomised structure of the industry, with a large number of relatively small, vertically specialised firms, part of the problem?

Before we survey the literature looking at the Lancashire’s slow adoption of ring spinning, it may be helpful to offer a short explanation of cotton processing. The industry has two main sectors, spinning and weaving. The spinning sector transforms raw cotton into yarn or thread, which can then be woven or knitted into cloth, or used for sewing or lace. Yarn is divided into ‘warp’ and ‘weft’ yarns; warp yarns are held in position during weaving, while weft yarns are interlaced between the warp yarns to make cloth. Warp yarns have to be stronger than weft, and are sometimes called twist yarns, reflecting the extra twist inserted during spinning to increase strength .² Once spun, warp yarns are ‘warped’, that is, rewound onto warping beams, each of which contains many parallel warp yarns. The weaving sector transforms yarn into cloth. A single package of weft yarn is placed in a weaving shuttle; that shuttle is then shot back and forth between the warp threads in order to make cloth. In so doing the weft fills the gaps between the warp yarns, and for that reason is sometimes called filling yarn. When the weaving shuttle runs out of yarn, the loom is stopped and the weaver places a new weft package in the shuttle. This process is manual on a power loom, and automatic on an automatic (Draper) loom. The ratio of warp to weft yarns varies according to the type of cloth: on average coarse cloth had 33 percent

more warp than weft.³ All yarns, warp and weft, are classified by count, which measures the fineness of the yarn. A high number indicates a finer yarn; a yarn of count n has n lengths of 840 yards per pound weight. In Britain counts of up to 40 were classified as coarse, counts of 40-80 as medium, and counts of over 80 as fine.⁴

Prior to the first world war there were two competing spinning technologies, mule spinning and ring spinning. In Britain mules were used for spinning all counts of yarn, but rings were rarely used for counts of over 40.⁵ At a technical level the two methods are fundamentally different. The mule spins intermittently, that is to say, it spins approximately five feet of yarn, and then winds that section of yarn onto the spindle before spinning the next five feet of yarn. The ring, in contrast, spins and winds in one action, and is thus able to spin continuously. The ring spindle produces more yarn per hour than the mule,⁶ but at a cost of treating the raw cotton more harshly, necessitating the use of a better grade of raw material for any given type of yarn. In Lancashire, and elsewhere, mule spindles were operated by relatively highly paid men, and ring spindles by relatively lowly paid women. Both methods produce yarn in relatively small packages, generally around six to eight inches tall, and no more than two inches across. Mule spun yarn can be lifted off of the machine as a package made up of nothing but yarn, whereas ring spun yarn is attached to a wooden bobbin, from which it cannot easily be removed. Mule spun weft yarn could be taken from the spindle and placed directly into a power loom shuttle, whereas ring spun weft yarn had to be rewound prior to weaving. Ring spun yarn was stronger than mule spun yarn, and was a prerequisite for using automatic looms. For these reasons we say that there are technical complementarities between weft mules and power looms, and between rings and automatic looms.7

Many early writers were in no doubt that Lancashire’s failure to adopt rings was a manifestation of ‘the conservatism of our captains of industry who have idolised the obsolescent techniques which have made the fortunes of their grandfathers.’⁸ Since the publication of Lars Sandberg’s pioneering work in 1969, no one believes that those firms who purchased mules were doing anything other than responding accurately to the costs that they faced. The question becomes whether the cost structure could have been altered so that rings were preferred more often.⁹

Sandberg argued that the industry was making a smooth transition towards ring spindles for all counts up to around 40, a little higher for warp, a little lower for weft, but that mules continued to be preferred for counts finer than 40s. In this story the continuation of a large mule sector had two causes, demand patterns and factor costs. The demand for supra-40 counts was high by international standards, and British costs were such that mules remained advantageous for those counts. In particular the relative cost of skilled mule labour to that of unskilled ring labour was low in Britain, so Lancashire employed mules for counts spun on rings in New England.

Sandberg also noted a further potential cost of adopting rings: a ring spinner may face higher transport costs. As mentioned, the mule produces packages consisting entirely of yarn, whereas the ring spins its yarn onto a heavy wooden bobbin from which it cannot be removed easily. The

spinner has two options when transporting the yarn. The first is for the bobbin to be transported with the yarn, and later returned for re-use. As the bobbin weighed twice the yarn spun onto it, this would imply a fivefold increase in transport costs.¹⁰ The alternative is to rewind the yarn into packages made up entirely of yarn, prior to shipping, but the cost of so doing was as high as the additional transport cost.¹¹ Lancashire’s industrial organisation system, with individual firms either spinning or weaving, made this potentially important. In contrast it did not matter in the U.S. where spinning and weaving were carried out by a single firm, on a single site. Within Lancashire the additional cost was lower for warp yarns, because they had to be rewound onto (relatively light) warping beams between spinning and weaving in any case. Ring spinners could warp their yarns prior to sending, rather than allowing the weaver to do the warping.

As well as the cost differences in labour, raw cotton and transport; Sandberg noted other potential factors influencing technological choice. The difference in capital cost in purchasing rings and mules, and the cost of fuel and lubricants proved small in both Lancashire and New England. ¹² Unions were unimportant in Lancashire, and marginal in New England. In both cases male mule spinners were more likely to be unionised than were female ring spinners, but the Lancashire mule spinners’ union was less likely to be obstructive. Finally Sandberg noted the technical complementarity between ring spindles and automatic looms. Since the latter were rare in Britain, Sandberg argued that technological inter-dependence could be ignored. The advantages and disadvantages of rings and mules are summarised in table one.

Following several empirical corrections to Sandberg’s work, William Lazonick agrees that British managers were responding accurately to the costs that they faced.¹³ He shows, however, that Sandberg overestimated the labour cost advantage and underestimated the transport cost premium. According to Sandberg the labour cost advantage outweighed the transport cost premium by a factor of five, making transport costs a secondary factor in his analysis.¹⁴ In contrast, Lazonick finds that the labour cost saving on rings was less than 25 percent greater than the transport cost premium.¹⁵ Given that there was a reasonable chance that the bobbin – an expensive item – would not be returned, Lazonick argues that the savings from using rings were insufficient to lead firms to install them unless the spinner was vertically integrated with the weaver.¹⁶ These cost estimates, along with the extensive size of the vertically specialised sector leads him to conclude that ‘The primary constraint on the introduction of ring spinning in Lancashire was the cost of shipping ring yarn.’ ¹⁷

Lazonick buttressed his finding that Lancashire’s industrial structure slowed the rate of ring adoption in two ways. First, he argued that not only would vertical integration overcome the transport cost constraint, but was also essential if corporate capitalist firms were to introduce ring spinning and automatic looms in a co-ordinated fashion.¹⁸ In this story it is incorrect to dismiss the idea of technological inter-relatedness between ring and automatic loom simply because so few British firms adopted automatic looms prior to the first world war. On the contrary, this fact serves to emphasise the need for co-ordinated technological change in the industry. Lazonick showed that those ring spindles that existed in Britain were concentrated in the vertically integrated sector of the industry,¹⁹ especially for weft yarn.²⁰ Observed investment behaviour thus implies that specialised firms faced a constraint not faced by their integrated rivals. Finally,

Lazonick also made use of a detailed case study of one of the Lancashire cotton towns, Oldham. ‘With its standard count of 32, large limited liability companies, and a high growth rate, the Oldham district was very favourable terrain for investment in ring spinning. Yet in the decade prior to World War 1, 75 percent of Oldham’s added capacity took the form of mules.’²¹ Lazonick argues that Oldham ‘puts the burden of proof on those who reject a “bias in favor of mules” on the part of Lancashire’s cotton mill managers’, ²² although Sandberg held that ‘Oldham was atypical in its response to ring spinning ... its relevance to an industry-wide study is limited.’²³

Gary R. Saxonhouse and Gavin Wright use the records that survive for six of the eight textile machinery makers to cast doubt on the link between rings and vertical integration. They note that Japan’s vertically specialised industry used rings, whilst the integrated industries of Russia and Canada continued to make sizeable mule purchases.²⁴ They also note that had Lancashire’s vertically specialised spinners been constrained from adopting rings by the transport costs of moving wooden bobbins, they could have used paper-tube ring machines.²⁵ These machines were manufactured in Lancashire, and enabled the yarn to be spun onto paper tubes instead of wooden bobbins. The very low rate of paper tube adoption leads them to conclude that transport costs cannot have been a constraint for Lancashire cotton spinners. Lazonick notes that Saxonhouse and Wright’s claims for paper tubes do not address the second part of his critique of the industry, that the inter-relatedness between ring and automatic loom implies that these machines will be taken up more readily when investment decisions are co-ordinated.²⁶

Saxonhouse and Wright show that the Indian and Russian industries, which ordered both rings and mules, did not use mules for higher counts than rings. This leads them to argue that ‘the rationalisation of the British preference for mule-spinning in terms of the composition of demand

for British goods is similarly unsustainable.’²⁷ They conclude instead that the main determinant of technological choice at the country level stems from the mules’ more gentle treatment of the raw cotton. Those industries that needed to or chose to economise on cotton, including India, Russia and Lancashire opted for the mule, ‘a machine whose forte was getting the most out of low-quality cotton’,²⁸ while others with plentiful supplies of reasonable cotton, such as Brazil and the US, relied on the ring.

CO-LOCATION: AN ALTERNATIVE WAY TO ELIMINATE
TRANSPORT COSTS

Our re-interpretation of the determinants of technological choice starts from the observation that, excluding paper tubes, to which we return later, there are theoretically three, rather than two, ways in which ring-spinning firms can eliminate the transport cost premium on moving their yarn to the weaver. The first is to rewind the yarn from the bobbin into packages made up entirely of yarn. The literature is unanimous that such rewinding was prohibitively costly. The second, as Lazonick has argued, is for spinning firms to be vertically integrated with weaving firms, so that spinning and weaving are carried out on the same site. The third way, advanced here, is for independent spinners and weavers to be located close together. Avoiding transport costs does not require that the spinner and weaver are co-owned, merely that they are co-located.

It follows that the division of the industry into the vertically integrated and vertically specialised sectors is insufficient. Instead we should sub-divide the vertically specialised sector into two parts: vertically co-located firms, and vertically isolated firms. A vertically co-located spinning firm is defined as one with enough weaving capacity nearby to allow them to be sure that they could sell their yarn to local weavers. Further, that market must be thick enough to avoid hold-up problems: local weavers must not be able to exploit the spinner’s dependence on the local market. In other words the spinner must have both sufficient looms and, independently, those looms must be owned by a sufficient number of weaving firms. In contrast, a vertically isolated firm is defined as one that does not have substantial weaving capacity close by. Note that this

does not imply that the firm is geographically isolated in any absolute sense, simply that it is isolated from firms at next stage in the production process. Indeed, as we shall see, many vertically isolated firms were located in Oldham, a town of many spinners, but few weavers.

Since all firms were located in south-east Lancashire, an area about twenty miles square, we take as given that all three groups of firms faced broadly the same raw materials and labour costs, had the same access to information and were able to purchase new machinery on the same terms. Further, the technical complementarity between weft mules and power looms applied to all

firms. There are, however, two important potential constraints that vary by group. Vertically integrated firms face neither a transport cost constraint nor a problem of introducing rings and automatic looms in a co-ordinated manner. Vertically specialised but co-located firms also escape the problem of transport costs, but do face the co-ordination constraint, while vertically isolated firms face both transport cost and co-ordination constraints. In effect we have three equations and two unknowns. By contrasting the behaviour of integrated and co-located firms we can discover whether co-located firms’ inability simultaneously to introduce rings and automatic looms was a constraint on ring adoption. Similarly, by comparing the rate of ring adoption between vertically co-located and vertically isolated firms, we can test whether transport costs were a constraint. We use constraint to mean a factor that affected ring adoption rates, as opposed to simply being an additional cost that was more than covered by other offsetting cost reductions.

THE EXISTENCE OF CO-LOCATED FIRMS

We begin by demonstrating the existence of the vertically co-located sector. In his original analysis Sandberg assumed that all firms in the Lancashire cotton industry were vertically specialised and vertically isolated, with spinners located 30 miles from weavers. ²⁹ Broadly speaking spinners were to be found in the south, and weavers in the north. Lazonick noted that some Lancashire firms were vertically integrated, but, using the same source, retained the assumption that all vertically specialised spinners were vertically isolated, and located 30 miles

from weavers.³⁰ We use a new source, the British Government’s 1906 Enquiry into Earnings and Hours, to show that of the coarse yarn that was spun and woven into cloth in Lancashire, 33 percent was produced by vertically specialised, co-located spinners. A further 36 percent of yarn came from vertically integrated firms, while only 31 percent had to be drawn from firms that were vertically specialised and geographically isolated.

In 1906 the Board of Trade sent out 2329 detailed earnings and hours schedules to firms in the cotton industry, of which 967,or 41.5 percent, were returned .³¹ The Board found the sample representative, citing compatibility with the earlier 1904 Factory and Workshop Returns, and concluding that ‘the returns for each of the different industries included may be regarded as covering a sufficiently large proportion of the work people employed to yield sound statistical results.’³² Their report on cotton runs to 324 pages of statistics. For our purposes what is most important is that the regional breakdown of spinners and weavers within Lancashire is accurate. Three pieces of evidence suggest that this criterion is met. First, working from Worrall’s Directory, Mike Williams and D.A. Farnie calculate that the southern (spinning) towns contained 78.5 percent of the industry’s spindles in 1903. Using the 1906 Enquiry, we calculate that these towns contained 81.0 percent of all spindles.³³ Again using Worrall’s Directory, Farnie also finds that the weaving district contained 66.4 percent of all looms, while the 1906 Enquiry gives a figure of 64.9 percent.³⁴ In both cases the figures are very close indeed, making it clear that the overall distribution of spindles and looms between spinning and weaving areas is broadly accurate in the 1906 Enquiry. Comparing the 1906 Enquiry figures for Oldham to those provided by Lazonick reinforces this impression of accuracy. Lazonick states that, in 1907, Oldham

accounted for 25 to 30 percent of spinning capacity, contained about 40 percent of Lancashire’s sub-40 mule spindles, well over one-third of Lancashire’s total sub-40 capacity, and that, in the decade prior to 1914, 75 percent of Oldham’s new spindles were mules. According to the 1906 Enquiry the equivalent four figures are 31 percent, 41 percent, 34 percent and 82 percent. ³⁵

Again, in each case the 1906 Enquiry figures are close to those from an independent source. Finally, our confidence is enhanced by the clarity of the results. Those areas found to have sufficient weavers to allow us to define their spinners as co-located do so by a considerable margin. The 1906 Enquiry would need to contain errors of considerable magnitude to reverse the findings. As well as offering a reliable regional breakdown, the 1906 Enquiry has one important advantage over other sources: it distinguishes between coarse, medium and fine spinning. As noted above, rings were only used for coarse yarn in Britain, so we are able to limit our analysis to those spinners who would have been deciding between rings and mules.

The 1906 Enquiry gives job and district specific information on 10,010 mule spinners, 4,001 ring spinners and 72,134 weavers. ³⁶ By converting employment data into output data, we can assess how much yarn was spun and woven in each of twelve districts. The 1906 Enquiry sub-divides weavers in each district by the number of looms tended. This makes it trivially easy to calculate the number of looms of any one area: this measure of weaving capacity is given in table two. 37

The 1906 Enquiry sub-divides spinners in each district into ring spinners, coarse mule spinners, medium mule spinners and fine mule spinners. Ring and mule spinners tended different numbers of spindles, and each category of spindle had different levels of productivity. We therefore convert first from employment to actual spindle numbers, and then from actual spindle numbers to ‘effective’ spindle numbers, which are corrected for the different level of productivity per spindle. The full details are given in the appendix. Effective spindles are taken as a proxy for output, and reported in table three.

We now have, by district, the number of effective spindles – a close proxy for yarn output; and the number of looms – a close proxy for weaving capacity. We know that, for Lancashire as a whole, yarn output and weaving capacity must be equal, taking into account that some yarn was exported, and some was not woven but used instead for hosiery, lace and elastic webbing. ³⁸ To allow ready comparison of yarn output and weaving capacity in each area, we multiply the number of looms by the spindle to loom ratio, 72:1. This allows us to express both yarn output and weaving capacity in effective spindle terms. The results are given in table four.

Notes: Coarse is defined as sub-40 yarns. All figures are in thousand effective spindles,

figures do not sum owing to rounding. For division between integrated and co-located firms, see text.

Sources: Cols 2 & 3: table 2; col. 4: table 1; col. 5 is the minimum of col. 2 and col. 3.

Those districts where weaving capacity exceeded total spinning output are termed ‘co-located’ districts: all coarse spinners in these areas could have sold all of their yarn to weavers in their districts. Given that weaving firms were on average 30 percent smaller than spinning firms, there would also have been sufficient weaving firms to prevent spinners being faced with hold-up problems.³⁹ Although it is straightforward to classify all spinners in these districts as co-located, it does not follow that all spinners in all other areas were vertically isolated. Some areas, such as Ashton and Stockport had sizeable weaving sectors in absolute terms, while others, such as Manchester, were close to being self sufficient in weaving. In these areas many coarse spinners could have been confident that they could have their yarn woven locally. The one exception that stands out is Oldham, where spinning output exceeded weaving capacity by a factor of 23:1. Oldham spinners were indeed vertically isolated.

Of course, the overall figure for yarn that could be woven locally includes yarn that was spun and woven by integrated firms. We know that integrated firms accounted for 23.6 percent of industry output in 1907, and that they were concentrated in the coarse goods sector. ⁴⁰ We therefore assume that 80 percent of their output – rather than the 60 percent figure for the industry as a whole – was coarse. This implies that the yarn that could be woven locally was made up of 4.1m spindles-worth of yarn from vertically integrated firms, with the remainder, 3.7m spindles-worth of yarn, being produced by vertically specialised, co-located firms. This gives three sectors broadly equal in size, with integrated firms accounting for 36 percent, co-located firms for 33 percent and isolated firms for 31 percent of coarse yarn production.

Since we define a vertically co-located district as one in which spinners did not face a transport cost constraint, we need to show that weaving firms in such districts were located in the immediate vicinity of spinners, rather than simply in the same district. An unpublished thesis by James Cotton on the town of Blackburn allows us to do this. Cotton lists 132 mills in operation in Blackburn in 1919, stating whether they were vertically specialised spinners, weavers or integrated spinner-weavers at that date. Of these, he is able to exactly locate 118 of these mills: 8 spinners, 104 weavers and 6 integrated firms. He plots these on a large-scale map (six inches to one mile), from which we can measure precisely the distance between spinning and weaving mills.

As table five shows, every vertically specialised spinning firm in Blackburn had more than 20 weaving mills within half a mile. We are correspondingly confident that these spinners are correctly characterised as co-located.⁴¹ Although we do not have evidence of this calibre for other towns, Cotton demonstrates that proximity to canals, rivers and major roads explains three quarters of mill locations in Blackburn.⁴² This strongly suggests that that clustering pattern of mills in Blackburn will be replicated in other cotton towns.

INVESTMENT BEHAVIOUR BY FIRM TYPE: WHAT CONSTRAINED
RING ADOPTION?

Having established the existence of three sectors, we now test whether the sectors differed in their rates of ring adoption. We do this by comparing how frequently firms in each group chose rings over mules between 1880 and 1906/7. 1880 is the year in which the ring first became available, 1906/7 are chosen for data availability. Since all rings in place in 1906/7 were installed

after 1880, comparing the stock of rings in 1906/7 with total spindle purchases between 1880 and 1906/7 tells us how often manufacturers picked rings over mules. Spindle purchases can be divided into two types: additional spindles for new mills and extensions, and replacement spindles. The number of additional spindles is the change in sector size between 1880 and 1906. The number of replacement spindles is a little harder to assess. We know that ‘English mules were built to last’ ,⁴³ and needed replacing only after fifty years.⁴⁴ This means that mules installed between 1830 and 1856 would have needed replacing between 1880 and 1906. Since the automatic mule was introduced in 1830 all mules in place in 1856 must have been installed between 1830 and 1856, and would have needed replacing between 1880 and 1906. We therefore use the stock of spindles in 1856 as our estimate of the number of spindles replaced between 1880 and 1906.

The behaviour of integrated firms has been extensively studied, and the necessary data is readily available. Farnie uses the Returns of the Factory Inspectors to calculate the number of spindles in integrated firms in both 1856 and 1880.⁴⁵ Work by Sandberg on the Census of Production and by Lazonick on Worrall’s Directory give the number of rings and mules in integrated firms in 1907.⁴⁶ This gives us sufficient information to assess the frequency with which integrated firms picked rings over mules.

Although data that explicitly distinguishes between firms that are vertically specialised but co-located and those that are both vertically specialised and isolated is not generally available, town specific data is reasonably available, at least for the post 1880 period. We now know that spinners in Oldham can be characterised as vertically isolated – only 4 percent of their yarn could have been woven locally – so we use the behaviour of Oldham spinners to assess the behaviour of vertically isolated firms. Similarly, we know that all spinners in the northern towns of Accrington, Blackburn, Burnley, Preston and Rochdale were all able to have their yarn woven

locally, so we use data for these towns to measure the behaviour of vertically co-located firms.⁴⁷ Data on the number of spindles in 1880 and 1906 are taken from Farnie’s work; the proportion that were rings in 1906 is given by the 1906 Enquiry.⁴⁸ We do not have town specific data prior to 1880, so we assume Farnie’s Lancashire wide figure for the proportion of spindles in all specialised firms in 1880 that were installed prior to 1856 holds for firms in both areas.⁴⁹

Notes: Co-located districts comprise the Accrington, Blackburn, Burnley, Rochdale and

Preston 1906 Enquiry districts. Figures do not sum owing to rounding.

Sources:

Rows 2 & 3: Integrated firms: 1906: Sandberg, “American Rings,” p. 29, Lazonick “Rings and Mules,” p. 394; 1880: Farnie, English Cotton Industry, p. 317; Co-located districts: Williams and Farnie, Cotton Mills, p. 46; Oldham: Farnie “Emergence,” p. 42. Aggregate spindle numbers are converted to m.e.s. using the ring to mule ratios in table 2.

Row 4: Row 2 minus row 3

Row 5: Farnie, English Cotton Industry, p. 317.

Row 6: Row 4 plus row 5

Row 7: Integrated firms: In the absence of data, we note the standard view that integrated

firms were more heavily concentrated in the coarser section, and assume that 80 percent of m.e.s. were devoted to sub-40 production. Co-located districts and Oldham: table 2.

Row 8: Integrated firms: Sandberg, “American Rings,” p. 29, Lazonick “Rings and

Mules,” p. 394; Co-located districts and Oldham firms, table 2.

Row 9: Row 7 minus row 8

The result from table six is unambiguous: rings were the clear majority choice for both vertically integrated and co-located firms, whereas mules were the clear majority choice for vertically isolated firms. We must note one reservation. The data for ‘firms in co-located districts’ and ‘Oldham’ cover all firms, that is, vertically integrated as well as vertically specialised firms. Since there was little weaving capacity in Oldham the data cannot contain many integrated firms, so the figure is a reliable indicator of the choices of vertically specialised firms in Oldham. In contrast we estimated earlier that just over half of the effective spindles in co-located areas were in fact in integrated firms, adding a strong converging bias to our result. That said, as the results for integrated firms and co-located district firms are close, it follows that vertically specialised co-located firms were choosing rings over mules about as often as were vertically integrated firms.⁵⁰ Notwithstanding the limitations of the data, the overall result that the choices of co-located firms were similar to those of integrated firms, and substantially different to those of isolated firms seems to be established by a sufficient margin to be considered sound.

We now know which constraints were binding. We noted that vertically isolated firms faced transport costs that was not faced by vertically co-located firms. As vertically isolated firms were only one quarter as likely to pick rings as were vertically co-located firms, we can conclude that Lazonick is right that transport costs did act as a constraint on the adoption of ring spinning. It is worth noting, however, that this constraint, far from affecting all vertically specialised firms, only affected those specialised firms located in areas with few weavers close by. Proving both the existence and limited nature of this constraint allows us to resolve Sandberg and Lazonick’s disagreement over Oldham. Lazonick is right to argue that transport costs did constrain the

adoption of ring spinning in Oldham. But as this paper shows, Oldham was almost unique within Lancashire in having such a high ratio of yarn output to weaving capacity. Lazonick is not right, therefore, to think that ‘the Oldham district was very favorable terrain for investment in ring spinning’⁵¹, instead Sandberg was correct to argue that ‘Oldham was atypical in its response to ring spinning ... its relevance to an industry-wide study is limited.’⁵²

We also noted that the difference between integrated and vertically co-located firms was that the former were able to introduce rings and automatic looms in a co-ordinated manner whereas the latter were not. We found the investment behaviour of the two groups to be similar, so we know that vertical specialisation was not per se an obstacle to ring adoption. Vertically specialised firms’ inability to co-ordinate the introduction of these two machines did not retard the adoption of ring spinning. This result should be unsurprising: automatic looms were the exception even in integrated firms.⁵³

The finding that integrated and co-located firms had similar ring adoption rates throws doubt on Lazonick’s claim that rings were used for weft in integrated but not specialised mills. ⁵⁴ If both groups had the same rate of ring adoption, it seems likely that either both or neither group used rings for weft. In fact the technical complementarity between mules and power looms seems to have been such that neither group used rings for weft to any extent. Instead, firms in both groups shifted well-functioning warp mules over to the production of weft yarn, and used new ring spindles to produce warp yarn. Three pieces of evidence support this claim. First, both integrated and co-located firms had more mules than rings in total, making it possible that rings were limited to one side of the production process. Second, and more importantly, both groups continued to purchase new mule spindles. Nor were their purchases trivial: table six shows that the two groups purchased 1.8 and 1.1 million coarse mule spindles in the quarter century after

the ring’s introduction. This indicates that they perceived mule spindles to have a clear continuing role in the production process.

Third, Worrall’s Directory provides direct evidence that integrated firms rarely used rings to produce weft prior to the invention of the automatic loom.⁵⁵ Worrall lists 272 integrated firms, with 188 firms specifying spindle type. Of these 188, 13 used only rings, 86 used only mules and 89 used both types. This does not mean that 13 firms used rings for weft, because many integrated firms produced only part of their yarn, purchasing the remainder in the market.⁵⁶ Of the 13 ring only firms, four state explicitly that they produced only warp yarn, presumably purchasing weft from outside suppliers, while four state that their rings were used for warp and weft, and five give no details. Of these five, three have low spindle to loom ratios similar to those firms known to purchase weft yarn, while two have high spindle to loom ratios, suggesting that they were producing their own weft yarn.⁵⁷ Our best guess, therefore, is that six of the 188 integrated firms used only rings for weft.

In addition, some firms using both rings and mules may have used rings for weft as well as warp. Without knowing the warp to weft ratio of each firm’s cloth, we cannot be certain. We can say, however, that if British cloth output had the same distribution of warp to weft ratios as the 677 coarse cloths sampled by the US Tariff Board, then the distribution of rings to mules in the Worrall sample would imply that ten integrated firms used both rings and mules to produce

weft.58

It appears, therefore, that rings were used for weft by no more than 10 percent of the 188 integrated firms whose machinery choices are recorded. This figure overstates the percentage of weft that was spun on rings, as the majority of these firms were using both mules and rings for weft production. Since integrated firms account for under a quarter of the total industry,59 and that we know that rings for weft were very much the exception in vertically specialised firms, it seems unlikely that more than 2 percent of Lancashire’s total weft was spun on rings. The cost of rewinding ring weft yarn into shuttle ready packages – a stage not necessary when using mules – appears to have been sufficiently high that the use of weft rings and power looms was exceptional, whether or not the firm was integrated. Since even integrated firms adopted automatic looms only very slowly, the use of rings for weft was, if not unheard of, at least unusual in this period.

This finding would explain the relatively sparse references to ring weft in standard contemporary texts. Sandberg laments that James Winterbottom, writing in 1907, ‘neglected to include ring weft’, in his discussion of the suitable raw cotton lengths for differing counts of yarn. ⁶⁰ Winterbottom’s ‘neglect’ is much easier to comprehend if rings for weft were an unusual choice. Similarly J.E. Holme, writing in 1887, states that ‘the ring has made great progress in the cotton industry for warp yarns; but it has not yet brought any great advantage for weft yarns.’⁶¹ Even as late as 1921 William Taggart argued that ‘Weft yarns are not so easily produced on the ring system as on the mule.’⁶² Like Winterbottom, he gives details of suitable twist factors for mule warp, mule weft and ring warp, but not for ring weft .63

The finding that rings for weft were exceptional even for integrated firms allows us to better understand the sense in which transport costs acted as a constraint on vertically isolated firms in Oldham. It is clear that the issue is not, after all, the transport of ring weft on heavy wooden bobbins: even integrated firms did not use rings for weft. The difference between ring usage in

integrated and co-located firms on the one hand, and vertically isolated firms on the other, relates to the spinning of warp yarns, not weft yarns. Ring warp yarns did not, of course, have to be shipped on heavy wooden bobbins, as the spinner could warp the yarn prior to sending it to the weaver. Warping beams were not, however, weightless. A standard 36-inch warping beam weighed in the region of 30 to 521/2 pounds in 1900.⁶⁴ That beam would have held between 91 and 248 pounds of yarn, depending on the type of cloth to be made.⁶⁵ Given that the beam had to be returned, the transport cost of shipping ring warp on a beam would exceed that of shipping mule warp in yarn packages by between 24 and 115 percent, depending on the exact weight of the beam and the fineness of the yarn. These figures are dramatically smaller than the five-fold increase in transport costs for ring weft. That a smaller increase in transport costs should act as a constraint on ring adoption fits well with the conclusions from Saxonhouse and Wright’s machinery data, namely that the choice between rings and mules was much more finely balanced than had previously been realised.⁶⁶ In that context a much smaller transport cost increment would be sufficient to reduce the take-up of ring spinning. The finding that ring warp but not ring weft was moved from spinner to weaver would explain why contemporaries noted spinners complaining that warping beams and skips were not returned from the weavers, but did not hear them make the same complaint about bobbins.⁶⁷

The relatively small size of the transport cost premium on warp yarn explains Oldham’s lack of interest in paper tube rings. Notwithstanding that transport costs acted as a constraint, the absolute reduction in transport costs that could be gained by using paper tubes for warp yarn was small. This means that paper tubes would only have needed a small drawback to outweigh the benefits they offered in terms of lower transport costs. It appears, in fact, that paper tubes had a number of disadvantages. One of the few contemporary authors to mention paper tube rings, Melvin Copeland, noted that ‘paper tubes are used instead of wooden bobbins in some ring

spinning mills, but the bobbins yield better results’. ⁶⁸ Mule spun warp also retained an advantage over paper tube ring warp because mule warp packages contained more yarn than ring warp packages, in that both have approximately the same total volume, but the latter contains a hollow paper tube at its core. ⁶⁹ This means that mule cops would not have to be changed as frequently when being wound onto warping beams, lowering costs to the warper. It is also worth noting that Lancashire was not alone in ignoring paper tubes. Japan, the other internationally successful industry with vertically specialised spinners, did not adopt paper tubes even though they were large users of ring spindles .⁷⁰ That neither Lancashire nor Japan adopted paper tubes suggests that they were not a good solution to the problem of transport costs.

ACCOUNTING FOR RINGS

It has long been clear that the lower transport costs associated with mule spun yarn ensured that yarn spun for export was effectively reserved for mule spinning. Similarly we already knew that the mule was much the better machine for all counts above the low 40s. This paper has shown that the technical complementarity between mule and power loom ensured that almost all weft yarn was spun by mules. Further, we have shown that transport costs affected specialised firms in Oldham, and, to a lesser extent, the neighbouring districts of southern Lancashire, obliging them to use mules for coarse warp. In contrast firms with weaving capacity nearby (whether integrated or co-located) were able to use rings to produce sub-40 warp yarn. We will now show that this analysis is compatible with both the overall gross investment pattern of the industry between the invention of the ring in 1880 and 1907, and with the total stock of spindles in that year.

Gross investment figures can be drawn from the 1907 Census and from Saxonhouse and Wright.⁷¹ Table seven compares these investment figures with those predicted by our sectoral breakdown and sector specific estimates of ring adoption rates. As can be seen, the predicted and actual investment figures are very similar, with the model overpredicting the adoption of rings by less than 2 percent of total investment.

Notes: Co-located firms includes integrated firms. Figures do not sum owing to

rounding.

Sources: Row 2: Saxonhouse and Wright, “New Evidence,” p. 511; Row 3 & 4: col. 2,

Sector sizes from table 4 row 16 and 17 respectively, multiplied by investment rates from table 6; cols. 3 & 4 from table 6. Row 6: Saxonhouse and Wright, “New Evidence,” and 1907 Census, see text.

As well as assessing our results by dividing the industry by firm type, we can also divide the industry by product type. We noted that rings would have been used only occasionally when producing yarn to be exported, weft yarn, warp yarn produced by isolated firms, as well as supra40 warp yarn produced by integrated and co-located firms. In contrast, without any constraints to their take-up, and given the possibility of shifting well functioning mules from warp to weft

production, we would expect all sub-40 warp yarns produced by non-isolated firms to be spun on rings. Since we know the relative size of these sectors in 1906, we can allocate rings and mules to these sectors as predicted above; table eight compares the results with the observed stock of spindles in 1907.

Notes: Co-located firms includes integrated firms. Figures do not sum owing to

rounding.

Sources:

Row 2: col. 3: 1907 Census, includes yarn for lace, hosiery and elastic webbing, see text.

Row 3: col. 3, table 3; col. 4 & 5, Saxonhouse and Wright, “New Evidence,” p. 511.

Row 4: col. 3, 1912 Tariff Board Report, see text; col. 4, Worrall Directory, see text.

Row 5: col. 2, 1912 Tariff Board Report, see text.

Row 6: col. 3, table 4, row 17, col. 4 & 5, table 6, col. 4.

Row 7: col. 3, table 4, row 16.

Row 8: sum rows 2 to 7

Row 9: UK Census of Production 1907, p. 293

It is clear that our predicted patterns of behaviour are a good explanator of the stock of rings and mules in Britain. This gives us confidence that the overall breakdown of the industry presented here, and our assessment of the incentives and constraints faced by each sector, are correctly characterised.

CONCLUSIONS

This paper has shown that many of the previous ideas used to explain the slow take-up of rings in Lancashire are incomplete. We are now, however, in a position to be clear about the reasons for Lancashire’s continued and positive preference for the mule. The principal reason was Lancashire’s greater emphasis on fine cottons. Lazonick records that 42 percent of Lancashire’s yarn was of counts finer than 40, the 1906 Enquiry data gives a figure of 44 percent, while Saxonhouse and Wright’s data suggests that 53 percent of new machinery were for counts of over 40.⁷² In contrast only 8 percent of yarn in the United States was of such counts.⁷³ Although it was technically possible to spin these higher counts on rings, contemporary literature is unanimous that the mule was the better machine. There is a second demand side factor that favoured mule spinning: the large demand for yarn exports, both to be woven abroad, and to be made into lace and knit goods elsewhere in Britain. The mule’s ability to produce lightweight packages consisting entirely of yarn made it well suited to this sizeable market niche. As table eight shows, these two demand side factors together ensured that a little over half of Lancashire’s yarn would be spun on mules.

Supply side factors, as well as demand side factors, mattered too. That rings were adopted at all shows that the unit labour cost saving gained by replacing male mule spinners with female ring spinners outweighed the extra cost of buying the slightly better raw cotton needed for ring spindles. But very few firms, integrated or otherwise, used rings for weft. Ring weft, unlike mule weft, had to be rewound to make it shuttle ready. In this case the labour cost saving was insufficient to outweigh the combination of the raw cotton and rewinding premiums. There is a sense, then, in which wage moderation on the part of mule spinners was sufficient to keep mule spinning as the method of choice for weft production, but insufficient to prevent ring spinning becoming important in warp production. Second, the additional transport cost of moving ring warp was sufficient to make the decision between ring and mule at best marginal for those firms

that needed to move their yarn any distance to the weaver. This factor was, however, relatively unimportant: even had the transport cost premium been eliminated altogether, the figures in table eight show that Lancashire’s spinners would have used just 3.5 million fewer mule spindles, that is, an eight percent fall in the total stock of mule spindles.

APPENDIX

CONVERTING EMPLOYMENT FIGURES INTO EFFECTIVE SPINDLE FIGURES. CONVERTING EMPLOYMENT FIGURES INTO ACTUAL SPINDLE FIGURES.

RING SPINNING

The number of spindles is calculated by multiplying employment data by the number of spindles per operative. The numbers of spindles per operative are derived by dividing data on weekly earnings by the Universal Wage List, which gives the rate paid per spindle tended. We use Saxonhouse and Wright’s data on the count distribution of rings to average the count specific spindleage numbers.

Sources: Col 2: 1906 Enquiry, p. 30.

Col 3: Jewkes and Gray, Wages, p. 121.

Col 5: Saxonhouse and Wright, “New Evidence,” p. 511, sub-divided pro-rata where necessary

Notes: Col 4 equals col. 2 divided by col. 3.

The average is the average of column 4, weighted by column 5.

MULE SPINNING

John Jewkes and E.M. Gray give the number of spindles on typical new mules in Oldham and Bolton at ten yearly intervals.⁷⁴ We use the figures for new mules installed in 1886-7 as a proxy for all mules in place in 1906. Mules lasted some 50 years,⁷⁵ and the mule sector was growing relatively slowly in this period,⁷⁶ so an average age of twenty years seems reasonable. In any case the growth in spindles per mule was only around 1 percent per year,⁷⁷ so mis-estimating the average machinery age will yield only a small mis-estimation of the capital to labour ratio. We weight the figures for Oldham and Bolton (1044 and 936 respectively) by the ratio of mule spinners in each town as given in the 1906 Enquiry (3165 and 1806),⁷⁸ remembering that each spinner tended two machines.⁷⁹ This tells us that each mule spinner and his team tended 2046 mule spindles.

Spindles: rings: Jewkes and Gray, Wages, p. 121, Saxonhouse and Wright, “New Evidence,” p. 511; mules: Jewkes and Gray, Wages, p. 205.

CONVERTING ACTUAL SPINDLE DATA INTO EFFECTIVE SPINDLE DATA

Different types of spindle produced different amounts of yarn per hour. Following the literature, we use one coarse mule spindle as our numeraire spindle, and covert other spindles into coarse mule equivalent spindles, which we term effective spindles. For sub-40 counts ‘effective spindles’ are exactly analogous to ‘mule equivalent spindles’. More generally the definition of an effective spindle is one that produces an equivalent length of yarn per hour, so data for effective spindles is a proxy for yarn output.

For ring spinning, we use the standard assumption that the output of one ring spindle was equal to that of 1.45 coarse mule spindles. ⁸⁰ For mule spinning Jewkes and Gray give count-specific information on the time taken to complete three cycles of the mule, the traditional way of measuring mule speeds. We use the Saxonhouse and Wright installation data to construct a weighted average for sub-40 counts, and in the absence of further data, we use linear weights for averaging data for finer yarns.

Silk REELING | RE-REELING TECHNIQUES

2009-12-18T08:26:00.001-08:00

Silk Reeling is simply the unwinding of filaments from a group of cocoons in hot water bath on to a reel.

There are two methods of reeling a) Direct Reeling method on standard reels and b) Indirect method which includes preliminary reeling on small sized reels and transferring the reeled silk directly from the reels to standard sized reels on re-reeling machines.

Before reeling, cocoons have to pass various stages and production of quality silk depends upon various factors:

Purchase of Cocoons :

Selection of cocoons must be done carefully as any carelessness is this respect would spell serious losses to the reeling enterprise. Selective purchase of cocoons in an open market is extremely difficult, and becomes imperfect particularly in the absence of determined standards of quality for cocoons, and standard methods of testing for classifying cocoons into quality grades.

Cocoons should not be too flossy. Floss merely adds to the weight of cocoons when yielding silk for reeling. Cocoons should have well-rounded and firm ends and must not have too pronounced points. Well pointed ends are easy to detect because of their shape; thin ends can be detected by the lighter shade of colour at the end which when pressed yields readily, when floss is peeled off the cocoons, the surface must be fine grained and not deeply wrinkled.

Transporting Techniques :

The selected cocoons must be transported safely in perforated bamboo baskets or in loosely packed plastic crates, and must be transported during the cool hours. Packing the cocoons tightly and transporting them in the hot sun must always be avoided.

COCOON STIFLING & PRESERVATION

COCOON STIFLING:

Cocoons in their fresh condition with the pupae alive in them cannot be stored for a long time as the living pupae are soon transformed into moths. They are useless for reeling raw silk because the continuity of the bave in them is broken. Reeling cocoons, therefore, have to be subjected to a process of stifling with the object of killing the pupae inside without in anyway interfering with the structure of the silk shell around it. Cocoons can be stifled

by several methods but the popular methods in reeling industry are sun drying, steam stifling and hot air conditioning.

PRESERVATION:

Storage of cocoons is an important problem especially when the stiled cocoons have to be stored for a very long period. Complete desiccation of cocoons is a fairly satisfactory solution to the problem but even fully desiccated cocoons are liable to mould damage if the storage room is kept dry.

The other source of damage to cocoons in storage comes from the beetle pest, Dermestes lardarius. The following measures have to be followed for preservation of cocoons.

· Complete desiccation of cocoons before storing should be ensured.

· All care should be taken to see that the relative humidity in the store room does not rise above 70%.

· The store room must have good ventilation.

· Cocoons should be given regular and frequent turnings during the period
of storage and on no account should they be allowed to become damp.

· When fumigants are used care should be taken to keep the doors and windows open until all the traces of fumigants are removed

REELING & RE-REELING TECHNIQUES

Silk Reeling is simply the unwinding of filaments from a group of cocoons in hot water bath on to a reel.

Systems of Reeling

There are two systems of reeling cocoons :

( i ) Floating System

( ii ) Sunken System

Floating System of Reeling

In floating system, the cocoons are cooked only to the extent the shell becomes wet, but is still impervious to water, so that they float in water when the cooked cocoons are put into the reeling basin. Floating system is associated with

1. Reeling of cooked cocoons which float in reeling basin.

2. High speed reeling.

3. High basin temperature.

4. Less number of reeling ends.

Sunken System of Reeling

In this system, the cooked cocoons sink in water at the time of reeling. In this system, not only the shell is cooked but in the process, the cocoon also gets filled with water inside to the extent of 97 to 98%, with the result, the cocoon becomes heavy and sinks in the reeling water. This system of reeling is associated with :

1. Reeling of cooked cocoons which sink under water in reeling basin.

2. Slow speed reeling.

3. Low basin temperature reeling.

4. Large number of reeling ends.

This system is suitable for superior quality cocoons like bivoltine. RE – REELING

Re – reeling is done to transfer the raw silk into standard sized hanks. The grant reeling helps in finding of broken ends of the thread and also its knotting. In grant reeling the hank is divided into several parts which can be kept separately by means of lacing. The ratio of the bevels determine the width of the diamond. For finer denier silk, more number of teeth have to be used. Re – reeling speed is almost double the reeling speed. So one end re-reeling will be enough to take the input of two end reeling. 13/24 bevel combination will produce 13 diamonds.

SKEINING

The standard size hanks from the swift are carefully examined for defects if any,it is laced and folded upon itself to form a skein with the help of skeining machine. The weight of the skeins varies from 50 g. to more that 100 g.

The skeins of raw silk are then made into books and bales are marketed later.

DIFFERENT SILK REELING DEVICES WITH ECONOMICS Reeling Devices:

There are three distinct reeling devices in mulberry sector namely

(a) Charka : It is a crude system of reeling. It is a simple hand driven device consists of a large cooking cum reeling pan where boiling water is kept.

(b)Cottage Basin System : It is improved over charka. It consists of separate cooking and reeling basin, where temperature is at boiling point only in the cooking basin, but reeling basin temperature is hardly 40 C.

(c) Multiend Basin System : It is a further improved version over the Cottage Basin and it is power driven. Boilers are installed and steam is used for cooking and reeling purpose and also for cocoon stifling in the special steam chambers.

BYE – PRODUCTS USES

During the process of mulberry silk reeling, the different qualities of mulberry silk waste obtained as bye-products:

a) Waste from cocoons:Floss or Blaze, Spelaia (Italian) or Keba (Japan) Discarded cocoons, pierced, double, stained etc.,

Floss or Blaze: Floss silk or blaze also known as borra is the first part of the bave extruded by the worm for the frame work of the cocoon. Most of it is removed from the cocoons during their collection and rest while sorting. This can be used for noil spinning.

Discarded cocoons : This includes all cocoons found to be unreelable during sorting like :

Double Cocoons: which are jointly formed by the combination of two worms in the same shell and which due to the the interlocking of the continuous filaments cannot be reeled alongwith good cocoons. These cocoons are also employed for reeling ‘dupion silk’

Inferior Cocoons:The improperly built cocoons and those deformed in shape and also melted cocoons and other cocoons which become unfit for reeling due to some reason or the other.

b) Reeling waste :It may be filature, Cottage basin or charka silk waste

c) Winding waste: Re-reeling, winding or throwster’s waste, Weaving waste (Hard waste)

Suessen | Compact Spinning System

2009-12-18T05:52:00.001-08:00

Market oriented solutions by Suessen

The purpose of a genuine compact spinning process is to arrange the fibres in a completely parallel and close position before twist is imparted. This is the most important criterion for perfect compact yarn. The eliminated spinning triangle is a by-product of this concept. This close and parallel arrangement of fibres immediately before twist is imparted is responsible for the characteristic advantages of compact yarn. Suessen is a pioneer in the compact spinning technology, a world-wide technological leader and a highly successful supplier of compact spinning systems. Since the ITMA 1999 in Paris, Suessen has sold more than 2.8 million EliTe^®Compact Spindles and is, therefore, the most successful company offering compact spinning systems, as well as technology leader of the market. Over 10% of these compact spindles have been successfully equipped with the EliTwist^®Technology.

EliTwist® Two-Ply Compact Yarn directly from Ring Spinning Machine

EliTwist^® has successfully further improved the excellent textile and physical characteristics of compact yarn. The extremely cost-effective application of this spinning process on existing ring spinning frames with the EliTe^®CompactSet further emphasises the high flexibility of the EliTe^®Process. EliTwist^® can be retrofitted to all spindles of EliTe^®CompactSet and Fiomax E already installed. EliTe^®CompactSet with EliTwist^®CompactSet can be used on many types of ring spinning frames. The structure of these EliTwist^®Yarns provides new approaches for the production of core-yarns and other special yarns. The Core-Yarn Device developed by Suessen for this purpose allows to spin core-yarns with perfect covering effect by feeding the filament into the centre of the twisting triangle.

Depending on the fibre material, even the smallest yarn twist coefficients are possible. As a rule, the optimum twist coefficient of EliTwist^®Yarns is between the twist coefficient of a single yarn and the ply-twist coefficient of a conventional S/Z two-ply yarn.Splicing of EliTwist^®Yarns is technically possible and has been solved by all manufacturers of winding machines.

EliTe®CompactSet V5 - Compact Spinning System for any application

The EliTe^®CompactSet V5 compact spinning system is designed to meet even the most challenging demands that high-end spinning mills make on a compact spinning system:

Optimum and sustained yarn quality.

e• High consistency of all yarn parameters.

e• Minimal variation between spinning positions.

e• No restrictions in regard to raw material.

e• Easy handling.

e• Universal application.

e• Can be installed on almost all machine types.

e• Many optional features.

Optional applications in compact spinning:

EliTwist^® - production of two-ply yarns directly on your ring spinning machine with compact spinning technology.

EliCoreTwist^® - production of two-ply core yarns directly on your ring spinning machine with compact spinning technology.*

Truetzschler comber proves successful in practice

The introduction of the new Truetzschler comber TCO 1 in Munich last year came certainly as surprise to many. Behind the scene, however, this involved long-term preparations. Marzoli comber specialists developed this machine in close cooperation with the Truetzschler Development Department.

The development goal was a nip rate of 500/minute, which is 25% higher than that of the Marzoli machines on the market at that time. And the first practical results show that this goal has been achieved. All the users mention that they are surprised about the smooth and quiet operation of the Truetzschler comber TCO 1. This is not only perceivable, but also measurable. The vibration level of the new comber TCO 1 at 500 nips/min. is only half that of older Marzoli machines at 400 nips/min. The low noise emission is the result of a number of new machine elements and drive solutions.

Thus, the frame has been newly designed. The dynamic stress during operation was simulated with special software. This made it possible to gear the design of the frame components precisely to the stress variations. The resulting combination of cast-iron and steel elements ensures minimum vibrations.

The nipper jaws have also been newly designed. At a nip rate of 500, they must swing forward and backward more than 8 times per second. Thus, it is important to have a very light-weight design, without impairing stability. The solution is found in the application of three special metal alloys. The actual nipper jaws are made of magnesium and aluminium alloy, the side parts of high-strength aluminium, and the jaws of

precision-ground steel. It goes without saying that these nipper jaws can safely handle today’s regular batt weight of up to 80 g/m. Of course other successful Truetzschler solutions were adapted as well. Hence, the top rolls of the drafting system and the delivery rolls of the comber are individually controllable, pneumatically loaded - same as on Truetzschler draw frames. As is customary with Truetzschler, operation takes place via a large-size colour touch-screen. Meanwhile, Truetzschler combers are operating in spinning mills in eight countries. The applications range from Ne 30 at a nip rate of 480, to Ne 100 at a nip rate of 360. The quality expectations of the users have been met everywhere. Comparisons with existing combers were throughout positive.*

RING AND COMPACT SPINNING SYSTEMS | EFFECT ON WOVEN FABRIC

2009-12-18T05:35:00.001-08:00

TECHNOLOGICAL STUDY OF RING AND COMPACT SPINNING SYSTEMS
FOR THE MANUFACTURING OF SLUB FANCY YARN UNDER MULTIPLE
SLUB VARIATIONS AND ITS EFFECT ON WOVEN FABRIC

Textile technologies are continuously evolving with the objects both of increasing productivity and reducing processing costs, and of creating new products or variants of existing ones. Fashion, in the widest sense of the word mean fulfillment of consumer demands, through the ages constitutes a fundamental and conditional element for the whole textile industry. Fancy yarns present deliberate, decorative continuous or programmed effects of colour and/or form; they are used to create some variation in the aesthetic appearance of a fabric. The drafting process is deliberately interrupted through the effect yarn device to produce slubs in the final yarn. The present research study was aimed to evaluate the quality characteristics of slub fancy yarn by changing slub length, inter slub distance, slub thickness and twist multiplier (T.M) at ring and compact spinning systems.

Keywords: Compact and ring spinning, slub fancy yarn, fabric

INTRODUCTION

Fancy yarn is a textile yarn with virtually unlimited pattern designs. Fancy yarns present deliberate, decorative continuous or programmed effect of Coloures and are used to create some variations in the aesthetic appearance of a fabric or garment. Fancy yarns differ from the normal construction of single and folded yarns by way of deliberately produced irregularities in its construction. These irregularities relate to an increased input of one or more of its components, or to the inclusion of periodic effects, such as knops, loops, curls, slubs, or the like. Some of the effects which could be produced using the ring spinning system are slub, loop, gimp, boucle, spiral, corkscrew, eccentric, button etc. The fundamental features of all these effects are the variations in delivery speed. These yarns are used in modern fabric to produce a natural, rustic and attractive character of the product. Slub yarn is a kind of fancy yarn, whose slub appearance is gained by the variation of the yarn linear density during the spinning process and because of its special appearance, has been widely used in a variety of garments.

There are numerous technologies that can be used to create fancy yarns. Some of these technologies include machinery such as hollow-spindle machinery, chenille machines, ring-spinning and rotor-spinning frames, folding/cabling machinery, and specialized machines. Ring spinning is still regarded as the “standard spinning method” against which all other yarn production systems and compared (Gong and Wright, 2002). Count and twist have considerable influence on yarn hairiness. Yarn hairiness bears a

close correlation with irregularity, with coarser regions having more hairiness than finer portions. The yarn from thick band is found to be more hairy. In the slub fancy yarn slub portions have more hairiness than base yarn because of higher number of fibres in cross-section.

In compact spinning, a condensing zone is introduced after normal drafting zone. As a result, the strand width becomes closer to yarn diameter and the size of spinning triangle is considerably reduced. Fibres get fully integrated into yarn and projecting fibres are markedly reduced. In normal yarns projecting fibres do not fully contribute to yarn strength. When these fibres are fully integrated into yarn as in compact spinning their contribution to yarn strength and elongation improves. This is the reason for the increase in strength and elongation of yarn in compact spinning. The basic principle of producing slub fancy yarn is based on roller drafting system. The drafting process is deliberately interrupted to produce thick places at random intervals in the final yarn (Lawrence, 2003). The high performance drive is designed with a specific amsler-device in customized combination with a new high-voltage servo motor regulator which is forced to run with extreme high frequencies of slubs per minute. The thick place in the yarn is followed immediately by a thin place, rather than by a simple return to the basic yarn count being spun. This, in turn, creates a weak place in the yarn. The slub effects of the amsler system are specially constructed to ensure that no thin spots develop after the slub. It is necessary to adjust the slub length to avoid basic yarn twist exceeding critical twist. Increased length of the slub leads to the increased twists of the basic yarn. Twists in every section of the

slub yarn are in inversely proportion to the square of the linear density of the corresponding section. In this concern the present research study was planed to examine how multiple process variables such as slub length, inter slub distance, slub thickness, yarn count and twist multiplier affect the fancy yarn properties.

MATERIALS AND METHODS

This present research study was initiated in the Department of Fibre Technology, University of Agriculture Faisalabad, and mainly conducted at Crescent Bahuman Ltd., Hafizabad during the year 2008. The complete description of the material used and the methods applied to test the quality characteristics of spun yarn and fabric are described here under.

Material used

Lint sample of cotton variety MNH-93 were collected from the running stock of the mills. All the yarn samples prepared were subjected to the following characteristics by using standard techniques and the data was recorded for statistical interpretation.

Yarn count

The yarn count was estimated through “Skein Method”, according to ASTM standard (1997a) with the help of Uster auto sorter.

Yarn lea strength

Yarn lea strength was also determined by “skein Method” recommended by ASTM Committee (1997a) according to standard method by using pendulum type lea strength tester.

Counts lea strength product value (CLSP)

Count Lea Strength Product value was calculated by multiplying average count with respective average lea strength value of yarn.

Yarn evenness (U %)

Yarn evenness (U %) was determined by Uster Evenness Tester-IV (UT-4), the procedure for testing was derived from ASTM Standards (1997a).

Weaving process

The yarn samples were then used in the weft of the fabric on a power loom. Samples were wound on bobbins by using a winder to use in weft direction. Warp was kept constant for all fabric samples. Warp and weft count was; 9^s. The woven fabric was evaluated for the tensile parameters of the fabrics.

Tensile strength of fabric

The Testeron Electronic Tensile Tester STE-1000 was used for the tensile strength testing. The method was adopted as mentioned in ASTM (1997b).

Analysis of data

The data thus obtained have been analysed statistically by applying analysis of variance technique, while DMR test was applied for individual comparisons as suggested by Faqir (2004) using M-Stat micro computer package devised by Freed (1992).

RESULTS AND DISCUSSION Yarn count

The statistical analyses of data regarding yarn count indicate significant difference in the mean values of yarn count due to different twist multipliers (T). Whereas, non-significant differences were recorded for spinning system (S), slub length (L), inter slub distance (D), slub thickness (W) and all the remaining interactions.

The individual comparison of mean values of yarn count for spinning systems S1 and S2 presented in Table 1 show that both the values have non-significant difference with each other. The closest value was

obtained for compact ring spinning machine (S2) as 9.24^s while the mean value for conventional ring spinning machine (S1) is 9.25^s. Non-significant results indicate that both machines preformed equally better for yarn count. These results get support from the work of Saleem (2003) who observed that yarn count was not significantly changed by using modified and conventional ring spinning machines.

The comparison of individual means for slub length
revealed that effect of slub length on yarn count was

non-significant. The highest value of yarn count 9.27^s is noted for L1 (50mm) followed by 9.24^s and 9.23^s for L2 (60mm) and L3 (70mm) respectively. The individual comparison of mean values of yarn count for inter slub distance D1, D2 and D3 presented in table 1, show that the values were non-significant with each other. The closest value was obtained for inter slub distance D1 (170mm) as 9.23^s followed by 9.25^s and 9.25^s for D2 (200mm) and D3 (230mm) respectively. The individual mean values of yarn count for slub thickness W1, W2 and W3 are 9.25^s, 9.25^s and 9.24^s respectively, which have non-significant differences from one another.

The individual mean values of yarn count for twist multipliers T1, T2 and T3 were observed as 9.41^s, 9.22^s and 9.11^s respectively, which had significant differences from one another. Likewise, Jamil et al. (1998) reported that break draft affected significantly the yarn count as well as significant differences were found for yarn count due to twist multiplier. Whereas, Sharma et al. (1987) concluded that a slight variation in actual count obtained with different twists because as twist increases yarn becomes more compact.

Yarn lea strength

The statistical analysis of variance pertaining to yarn lea strength show highly significant effects due to spinning system (S), slub length (L), inter slub distance (D) and twist multiplier (T). While non-significant effects were obtained for slub thickness (W) and all the remaining interactions.

The individual comparison of mean values regarding yarn lea strength for different spinning systems S1 and S2 given in Table 2 shows that both the values have significant difference. The stronger yarn was obtained

at compact ring spinning machine (S2), with lea strength 257.28 Pounds followed by conventional machine (S1) as 252.23 pounds. Which endorse the views of Stalder (2000) who observed that compact yarns display significantly better strength and elongation values and also display better CV percentage . This leap in quality is so great that even with reduced twist, the condensed yarns displayed better values than normally twisted conventional yarns. Similarly, Ahmad (2004) investigated that in compact yarn less twist is possible without any loss of strength

and further stated that other than yarn hairiness, yarn parameters such as strength, elongation, imperfections and uniformity are also better than ring spun yarn.

As regarded to slub length (L) results revealed that highest value of yarn lea strength 258.32 Pounds was recorded for L1 (50mm) followed by 254.65 and 251.28 Pounds for L2 (60mm) and L3 (70mm) respectively. The results indicate that slub length has significant effect on yarn lea strength. The values have significant difference with one another and results are fully supported by Ajmal (2005) who explained that slub length significantly affects the yarn count, lea strength and single end strength. However, the variation of slub thickness produced a non significant effect on most of the yarn properties. Likewise, Testore and Minero (1988) reported that parameters influencing the characteristics and appearance of slub yarn are metric count, average number of slubs per meter, average distance between consecutive slubs and slub length and there is a significant correlation between the yarn count and final twist.

The individual comparison of mean values presented in Table 2, regarding yarn lea strength for inter slub distance D1, D2 and D3 show that the values have significant difference with respect to one another. The best value for yarn lea strength was obtained under D3 (230mm) as 258.39 Pounds followed by D2 (200mm) and D1 (170mm) with their respective mean values as 255.04 and 250.81 pounds. These results get full support from the findings of Pouresfandiari (2003) who reported that the parameters influencing the characteristics and appearance of fancy yarns were the yarn count and the average distance between two consecutive effects.

The individual mean values of yarn lea strength for slub thickness W1, W2 and W3 were obtained as 255.24, 254.69 and 254.31 lbs respectively, which have non-significant differences from one another.

The comparison of individual means concerning to yarn lea strength due to twist multiplier (T) presented in Table 2. The highest value of Yarn lea Strength 261.68 Pounds is recorded for T3 (5.2) followed by 255.66 and 246.90 Pounds for T2 (4.9) and T1 (4.6) respectively. The results have significant difference with respect to one another. It indicates that as the twist multiplier

increases the value of lea strength also increased. These results were fully supported by Klein (1998) who stated that strength of a thread increased with increasing twist because of increased inter fibre friction with in the yarn. Selection of a twist level below maximum strength is appropriate because higher strengths were mostly unnecessary, cause the handle of the end-product to become too hard and reduce productivity. Similarly, Almashouley (1988) narrated that strength of cotton yarn varies with twist. Up to a certain point additional twist causes an increase in strength; however, beyond that point added twist causes a decrease in strength.

Yarn evenness (U %)

The statistical analysis of variance of yarn evenness indicates that the effect of spinning system (S), slub thickness (W) and twist multiplier (T) upon yarn evenness were highly significant. While non significant effects were also recorded for slub length (L), inter slub distance (D) and all possible remaining interactions. The Comparison of individual means of yarn evenness due to spinning systems S1 and S2 presented in Table 3 show that both these values differ significantly with

mm) as 16.53 percent followed by D2 (200 mm) and D3 (230 mm) with their mean values 16.50 and 16.49 percent respectively. Lord et al. (1998) reported that quality of a textile yarn is judged in the past by its evenness. The lack of evenness is caused by mechanical defects in the machine used to make the yarn.

The comparison of individual means concerning to yarn evenness percentage due to slub thickness is presented in Table 3. The values obtained of yarn evenness percentage were 16.37, 16.51 and 16.64 percent for slub thickness W1 (1.6), W2 (2.00) and W3 (2.4) respectively. The results show significant difference from one another. These results were fully supported by Testore and Minero (1988) who reported that parameters influencing the characteristics and appearance of slub yarn were metric count, average number of slubs per meter, ratio of maximum to minimum diameter of yarn, average distance between consecutive slubs and slub length. Sheikh (1994) mentioned that yarn irregularity was a measure of cross-sectional variation in the yarn and closely associated with imperfections in the yarn. As regard to the twist multiplier results reveal that the highest value

each other. The highest value of yarn unevenness was obtained at conventional machine (S1) as 16.66 percent followed by the modified machine (S2) as 16.35 percent. These results were fully supported by Frey (2000) who stated that the compact yarn was found 15 to 20 percent higher in strength at 3 percent less twist and with 20 percent higher elongation, better U percentage and lower imperfection values. Similarly, Smekal (2001) stated that the technique improves the structure of the yarn, as the edge fibres are incorporated, leading to reduced hairiness, a higher yarn strength, and improved yarn evenness with fewer faults. The individual comparison of mean values, regarding yarn evenness for slub length (L) shows that the highest value of yarn unevenness was obtained at L2 (60 mm) as 16.55 percent followed by L3 (70 mm) and L1 (50 mm) with their mean values 16.49 and 16.48 percent respectively and show non significant effect on yarn evenness. In case of inter slub distance the values show non significant difference from one another. The highest value was obtained at D1 (170

of yarn unevenness 16.63 percent is recorded for T3 (5.2) followed by 16.50 and 16.39 percent for T2 (4.9) and T1 (4.6) respectively, which shows significant effect on yarn evenness. Present results are in line with Sharma et al. (1987) who stated that strength parameters and elongation increases with twist level. The yarn unevenness increases with twist. Yonghua and Yan (1990) reported that there are many aspects of yarn quality, among them unevenness is very important because it is closely correlated with fabric appearance.

Weft wise tensile strength

The statistical analysis of data regarding weft wise tensile strength of fabric indicates that the effect of spinning system (S) and twist multipliers (T) is highly significant. While non-significant effects were recorded for slub length (L), inter slub distance (D), slub thickness (W) and all the remaining interactions.

The mean values of weft wise tensile strength of fabric for different spinning system S1 and S2 presented in

strength was obtained at modified compact spinning machine (S2) as 136.45 lbs followed by conventional ring spinning machine (S1) as 133.58 lbs. As the stronger yarn is produced on S2 so its weft wise tensile strength is also high as compare to S1. The results were fully correlated with Artz (1998) who stated that compact yarns always display higher yarn strength and elongation at a breaking length above the fibre staple length. A significant increase in fabric strength can be achieved only through a proportional increase in yarn strength. The product quality of the fabric in terms of strength is therefore, increased by using compact spinning.

The comparison of individual mean values relating to weft wise tensile strength of fabric at different levels of slub length (L) show that the difference in the mean values of slub length are non significant from one another. The maximum value is observed at slub length L1 (50 mm) as 135.17 lbs followed by L2 (60 mm) and L3 (70 mm) with their respective mean values as 134.99 and 134.89 lbs. Therefore decrease of the weft wise tensile strength is found due to increase of slub length. As regard to inter slub distance results clarifying that the best value of fabric weft wise tensile strength is obtained for D2 (200 mm) 135.18 lbs followed by 135.00 lbs and 134.81 lbs for D3 (230 mm) and D1 (170 mm) respectively. The results show non significant differences between these values. The comparison of individual means concerning to weft wise tensile strength due to slub thickness is represented by Table 4. The values obtained for slub thickness W1_, W2 and W3 are 135.18 lbs, 135.09 lbs and 134.84 lbs respectively which have non significant difference from one another.

The individual comparison of mean values for weft wise tensile strength under twist multiplier (T) shows that all these values were significant with one another. The best value is observed at T3 (5.2) as 138.52 lbs followed by T2 (4.9) and T1 (4.6) with mean values 135.33 lbs and 131.20 lbs respectively. These results were consistent with the research work of Iqbal (2005) who concluded that twist multiplier significantly affected

tensile properties of the slub yarn and resultant fabric are improved by increasing twist multiplier. Yarn imperfections increase at higher slub length and population. However variation of thickness produced a non significant effect on most of the yarn and fabric properties. Likewise, Booth (1996) described that the variable that a technologist include in the tensile strength of the fabric are raw material characteristics, yarn structure (count, irregularity, twist factor, doubling etc) and fabric structure (settings, crimps percentage and weave). Whereas, Arora (2002) stated that high twist and high fibril cohesion increase the stability of spun yarn, giving longer yarn breakage time and twist increases the strength of the yarn by creating lateral forces which prevent the fibers in the yarn from slipping over one another also stated that under low stress the mechanical behavior of the fabrics is primarily determined by the structure and have significant effect on tensile behavior.

Nasir Mahmood^'*, M. Arshad², M. Iftikhar^' and Tahir Mahmood^'

^'Department of Fibre Technology, University of Agriculture, Faisalabad
²Department of Irrigation and Drainage, University of Agriculture, Faisalabad
*Corresponding author’s e-mail: nasirmahmood23uaf@yahoo.com

Textile Industry in Bangladesh

2009-12-17T04:49:00.001-08:00

The Current Position of the Textile Industry in Bangladesh

Textiles have been an extremely important part of Bangladesh's economy for a very long time for a number of reasons. The textile industry is concerned with meeting the demand for clothing, which is a basic necessity of life. It is an industry that is more labor intensive than any other in Bangladesh, and thus plays a critical role in providing employment for people. Currently, the textile industry accounts for 45% of all industrial employment in the country and contributes 5% of the total national income.

Today, the textile industry of Bangladesh can be divided into the three main categories: the public sector, handloom sector, and the organized private sector. Each of these sectors has its advantages and disadvantages. Currently, the organized private sector dominates, and is also expanding at the fastest rate.

Public Sector

The public sector is that portion of the industry controlled by organizations that are part of the government. The factories in the public sector enjoy certain privileges such as government funding. However, in Bangladesh, factories in the public sector are not well supervised. There are frequent changes in officers, and many of these officials do not have a personal interest in the factory for which they are responsible. In addition, the equipment in this sector is not well maintained, as much of the money allocated for this purpose is not spent as planned, but is wasted through corruption and poor accounting.

Handloom Sector

The rural group of textile producers includes operators of handlooms and a number of organizations which employ rural women, such as BRAC, or the Bangladesh Rural Advancement Committee. The Handloom industry provides employment for a large segment of the population of Bangladesh. The industry also supplies a large portion of the fabric required by the local market. Factories in this sector are usually well looked after by the owners and are quite productive, considering the equipment available. However, the inferiority of their machinery, mostly due to their narrow width, means that the fabric production is slow, and usually falls short of the quality needed for export.

Private Sector

The most productive of the three categories is the private sector. This, as the term suggests, is made up of those factories owned by companies or entrepreneurs. Since the owners of such factories are directly affected by their performance, they take an active part in planning, decision making, and management. Most of these factories also have machinery that is superior to those in the two other sectors because the owners are well aware of the connection between their equipment and their profits.

Future Challenge

In future, some of the international policies regarding the export of textiles and garments will change, which may present the Bangladeshi textile industry the greatest challenges it has had to face so far. There is much speculation at present about the situation of the RMG (Ready Made Garment) exporters in the post-MFA (Multi-Fiber Arrangements) period, when the World Trade Organization, or WTO, instead of GATT (General Agreement on Tariff and Trade) will control the sector. Under the WTO all quotas will be removed, resulting in a free market worldwide.

Bangladesh's garment and textile manufacturers will have to face steep competition from countries such as India, Pakistan, China, and Thailand, from whom the country now imports fabric to meet the demands of its RMG sector. When the WTO free market is established, all these countries will be able to expand their RMG exports, now limited by quotas. As a result, these countries will be able to utilize more of their locally produced yarn and fabrics internally, resulting in the rise of prices for these in the export market, putting pressure on the industries of countries such as Bangladesh.

Technical Overview

Number of units:

There are two units:

1. Local unit

2. Export unit.

Machines Used:

a) Blow room:

1. RIETER UNIFLOC A11

Suction velocity: 14 m/min.

2. RIETER UNIFLEX B60

With 6 chambers and suit fit are given.

b) Carding room:

1. Carding machine: RIETER C-51

Production rate: 60 kg/hour.

2. Breaker drawing Machine: RIETER SB-D10 Capacity: 700 m/min.

c) Simplex Machine:

TOYOTA FL100

Flyer revolution: 1050 rpm

Delivery Speed: 21.9 m/min

d) Ring Frame:

JINGWEI

Japan.

e) Auto Conner:

Specification: Type: RM, 12 bar, 61 A, 50 Hz Made in: Germany

f) Yarn Conditioning Plant:

Specification: Capacity: 1200 Kg/hr

Country of origin: India.

Sources of bale:

Bales used by the industry are imported from Holland, Russia, USA.

Power:

As the power source gas generators are used. No. of gas generators: 4

Capacity: 950kw each.

3 shift duty.

No co-generation is implemented.

Humidity:

The humidity maintained at various parts of the factory are as follows. Blow room and carding room: 54% to 55%

Ring room: 55% to 56%

Total Production of the factory:

The total production of the factory is about 1050 Kg/day. The efficiency of various processes are:

Carding : 96% to 97%

Drawing : 85%

Ring : 94% to 95%

Finishing : 82%

Air Conditioning Plant:

Not much information regarding this plant was obtained. No chillers are used here.

Quality Control Management:

Here in this industry the Quality Control is managed in every step of the production process. The speciality of its management is that in every stage of production every lot is being checked. Even in case of purchasing bales of cotton every bale is being checked.

Description of different Processes: BLOW ROOM:

There are four machines for blending, opening, and cleaning.

UNIFLOC:

· The compressed mass of raw fiber is removed from the bales.

· Fine particles of metals are detected in the metal detector.

· Opening is necessary to lessen hard lumps of fiber & disentangle them

· Blending is necessary so as to obtain uniformity of the fiber.

UNICLEAN:

· Removes trash such as dirt, leaves, burs & any remaining seeds

· Prepare the fiber for spinning into yarn

UNIMIX:

· Fibers of different staple length are mixed here.

· Mixing is mainly done to reduce the cost.

· Fibers come in six lanes then mixed by betting.

UNIFLEX:

· Fine betting is done

· Waste product are separated

· Waste id not used but sold

CARDING:

· Initial process of arranging the fiber in a parallel fashion is known as carding, and is done on a carding machine.

· The lap is passed through a beater section and drawn on a rapidly revolving cylinder covered with very fine hooks or wire brushes.

· A moving belt of wire brushes slowly moves concentrically above this cylinder.

· As the cylinder rotates, the cotton is pulled by the cylinder through the small gap under the brushes.

· The teasing action removes the remaining trash, disentan-gles the fibers, and arranges them in a relatively parallel manner in the form of a thin web.

· This web is drawn through a funnel-shaped device that molds it into a round rope like mass called card sliver.

CARDED PROCESS: BREAKER DRAWING:

· Combines several slivers

· Eliminates irregularities that would cause too much variations if slivers were put through singly.

· Slivers passed through several pairs of rollers, each advanced set of rollers, revolves at a progressively faster speed.

· This action pulls the staple lengthwise over each other, thereby produces longer & thinner slivers.

FINISHER DRAWING (auto leveling):

To measure the sliver thickness variations and then continuously to alter the draft accordingly so that more draft is applied to thick places, and less to thin places with the result that the sliver delivery is less irregular than it otherwise would have been.

Besides an improvement in production appearance, it also contribute to,

· Better productive efficiency

· Fewer end-breakage in subsequent processes

· Less waste, and

· Constant process conditions.

SIMPLEX:

· After several drawing operations the fiber passes through simplex and the output is roving.

· Slight twist is given.

· The diameter is reduced.

· Gain some tensile strength.

RING FRAME:

Roving is fed in ring frame and the output is yarn.

AUTO CONER:

· The yarns are further winded on cone from the ring frame.

· Only the good quality product passes.

HEAT SETTING:

· To make the twist permanent steam is passed through the yarn.

· Moisture is absorbed in the yarn.

· During dyeing more uniform performance is achieved.

· The steam is supplied from yarn conditioning plant.

PACKING:

Finally the yarn is ready to export or weaving.

COMBED PROCESS:

Combed process is different by two additional process, those are

· Unilap

· Comber

UNILAP:

After carding the sliver is turned into lap form in unilap machine.

COMBING:

· Combed sliver produces a smoother & more even yarn.

· Short fiber called noils are combed out & completely separated from longer fibers.

· Operations eliminates as much as 25% of the original card sliver, thus almost ¹/4 of the raw cotton becomes waste.

· Produces consumer’s goods with better quality.

· Long staple yarns produces stronger, smoother, more serviceable fabrics.

Textile humidification

2009-12-16T23:16:00.001-08:00

Increasing profits with environmental control

By maintaining a level of 65-75% relative humidity (%rH) in textile manufacturing facilities static build-up can be reduced, regain improved, yarn breakage minimised and dust, fly and lint suppressed.

This will dramatically improve quality and maintain consistent product weight thus maximising profits.

Textile humidification will:

· Improve regain

· Maintain yarn strength

· Reduce static build-up

· Maintain product__ weight

· Reduce fly and micro dust

· Provide free cooling

We have over 25 years experience in helping the textile industry across the globe solve dry air problems. As specialists in humidification, we offer a wide selection of low energy and close control humidifiers for all textile applications.

Textile humidification

Why humidify in the textile industry?

Humidity control in the textile industry is essential in order to maintain product quality and reduce imperfections. A dry environment in textile manufacturing and storage facilities can have many serious implications:

Regain

Dry air causes lower regain and this contributes to poor quality and lower productivity. By humidifying the materials are kept at optimum regain

and are less prone to breakage heating and friction effects, they handle better, have fewer imperfections, are more uniform and feel better.

Static electrification

Dry materials create more friction and are more prone to static electrification. Higher humidity reduces static

problems and makes materials more manageable increasing machine speeds.

Yarn strength

Yarns with low moisture content are weaker, thinner, more brittle and less elastic.

Fabric shrinkage

Low humidity causes fabric shrinkage. Maintained humidity permits greater reliability in cutting and fitting during garment creation and contributes to the maintenance of specification where dimensions are important, such as in the carpet industry.

Product weight

Textile weights are standardised at 60%rH and 20°C (68°F). Maintaining humidity will ensure low product weights don’t lead to lowered profits.

Dust

Humidification reduces fly and micro-dust, providing a healthier and more comfortable working environment.

Cooling

A cold-water spray humidification system can provide an evaporative cooling effect of up to 12°C (54°F). This makes the environment more comfortable to work in and improves staff productivity.

Why JS Humidifiers?

JS Humidifiers offers a comprehensive service of humidifier system design, installation and maintenance. Our range includes spray, steam and evaporative humidifiers and with over 25 years experience in textile humidification we are ideally place to advise you on which type will be most suitable for your specific application.

Electrospinning - Molten Polypropylene in Vacuum

2009-12-16T23:00:00.001-08:00

Very fine polypropylene (PP) fibers were made from molten PP in vacuum using an electrospinning process. Under the influence of a modest external electric field, a droplet of PP melt was pulled out, trailed by a jet that became thin and soon broke. When the electric field strength was increased, a steady charged jet flew toward a collector. Jets solidified to form fibers either in flight or after reaching the collector. The semi-angle of the Taylor cone from which the jet emerged was about 37.5 ± 2 ^o. The diameters of the fibers ranged from 300 nanometers to 30 microns. Scanning electron micrographs showed a variety of fiber morphologies, including coils indicating that the charged jet developed an electrically driven bending instability.

INTRODUCTION

The electrospinning process utilizes an electrostatic force to destabilize a surface of a polymer liquid droplet, creating a charged jet that elongates and solidifies to form an electrospun fiber. (Doshi, et al. 1993; and Doshi, 1994). Electrospinning provides an attractive and relatively easy route to produce nanofibers and thicker fibers. Advantages over the conventional spinning of fine fibers, such as a conjugated spinning method, include a simple apparatus, a compact spinning station, a wide range of materials that can be used and, best of all, its capability of producing fibers with very small diameters.

The diameter of electrospun fibers are typically in the range of tens to a few hundreds of nanometers for solution electrospinning and in the range of hundreds of nanometer to a few micrometers for fibers electrospun from molten polymers. (Doshi, et al. 1993; Doshi, 1994; Chun, 1995; Koombhongse, 2001; and Rangkupan, 2002). For comparison, the diameters of conventional textile fibers made by typical spinning processes are about 10 to 20 micrometers or more. The diameter of electrospun fibers is one to two orders of magnitude smaller than that of conventional fibers. Because of its smaller diameter, an electrospun fiber has a higher specific surface area than a conventional textile fiber. This feature is attractive to many applications that require a high surface area or high specific surface area. Figure 1 shows a plot of a specific surface area as a function of fiber diameter, assuming that the fiber has a circular cross section and a density of 1 gram per cm³. The arrow indicates a typical range of diameter for electrospun fibers.

Figure 1 Specific surface area as a fucntion of fiber diameter. Circular cross sections and a density of 1 g/cm³ were assumed. Arrow indicates the typical range of diameters of fibers electrospun from polymer solutions and melts.

Several applications for electrospun fibers are under development including filtration of

submicron particles in separation industries, artificial blood vessels, sutures, wound dressings, controlled drug released and tissue engineering scaffolds for biomedical applications, controlling application of pesticides in agriculture, protective clothing against chemical warfare agents, nanotube construction, optical sensors, nanofiber solar cells, nanocomposites, and contruction of solar sails (Koombhongse, 2001; Rangkupan, 2002; Liu, et al. 2002; Schreuder-Gibson, et al. 2002; Wang, et al. 2002; Lennhoff, et al. 2002; and Whithe, et al. 2002).

With few exceptions, (Chun, 1995; and Larrando, et al. 1981) studies of the electrospinning process and the applications for electrospun nanofibers were made by electrospinning a polymer solution. It is presently more difficult to electrospin fiber from a polymer melt than from a polymer solution because of the higher viscosity and lower electrical conductivity of molten polymers (Rangkupan, 2002). Moreover, the diameter of a melt-electrospun fiber, which can be in the range of tens of micron, is much larger than the diameter of a solutionelectropun fiber, making fibers with a range of diameters that is achieved with conventional apparatus.

Melt–electrospinning eliminates the cost associated with the removal and recovery of the solvents, and any health risks associated with solvents. Melt-electrospinning complements the solution-electrospinning for polymers which are difficult to dissolve. It is clear that further study about the melt-electrospinning process, from both scientific and engineering standpoints can produce valuable information.

The objectives for this study were to produce sub-micron fibers from molten polypropylene and to prove the concept of producing a very fine fiber in space using electrospinning process. A vacuum system simulates a space environment, and takes advantage of the much higher electrical break down strength of a vacuum compared to air. This enables us to obtain higher electric fields which exerts larger electrical forces on the fluid jet.

MATERIALS AND EXPERIMENTAL SET UP

Material

Polypropylene (PP) used in this study was obtained from Aldrich and used as received. The molecular weight was 190,000 with a melt flow index (MI) of 35 g per10 min, at 200^°C and 10 kg. Load (Sigma-Aldrich).

Experimental apparatus

Figure 2 shows a schematic diagram of a typical appartus used in this study. PP pellets were loaded into a spinneret, typically a copper cup with a 1.5 mm hole on the side, and melted with a radiant heater at the temperature about 250 to 300°C. Charges were supplied by a copper wire connected to the spinneret. The wire was connected to either a positive or negative high voltage power supply outside a vacuum chamber through an electrical feed-through. The high voltage power supply used was a dual polarity high voltage power supply model D-ES30PN/M692 by Gamma High Voltage Research. The input voltages were read from analog voltage meters on the power supply. A collector plate, made of an aluminum sheet was placed 20 to 150 mm away from the spinneret and maintained at a high electrical potential. The electric field strength between the spinneret and the collector was varied from 100 to 3000 kV/m.

The behavior of a charged jet during the electrospinning process was followed by a video camera, connected to a 12.5-75 mm zoom lens, with and without a 2X close up lens. An observation window was located at the front panel of a vacuum chamber. Multiple halogen lamps were positioned inside the vacuum chamber at strategic locations to illuminate the jet.

Electrical current carried by the molten jet was monitored by a nanoampere meter, which was maintained at the potential of the spinneret. A similar nanoampere meter maintained at the potential of the collector, measured the current flowing to the collector. This arrangement of two ampmeters monitored the jet current and provided an indication of leakage currents if they were present.

RESULTS AND DISCUSSION.

The electrospinning process of molten polymers can be divided into 3 steps: initiation of the charged jet, elongation of the jet, and solidification of the jet.

Initiation of a molten charged jet in vacuum

When the external electric field was applied to a molten hemispherical droplet, excess charges, such as mobile ions from impurities, with the polarity of the electrode, migrate to the surface of the droplet of molten polymer. A repulsive force, from the Coulombic interactions between the ions, tends to increase the surface area, while the surface tension tends to minimize the surface area. At a sufficiently high field, the surface tension was overwhelmed by Coulombic interaction and the surface area grew by deformation of the shape of the droplet from hemispherical to conical.

A further increase in the electric field strength caused the droplet to deform more, creating a cone with a sharper tip. At the critical field strength, at which the electrical forces equal the surface tension, the droplet assumed the shape of the Taylor cone. Above the critical field strength, the electrical forces overcame both surface tension and the viscous forces within the melt, a tiny droplet of molten polymer was pulled out of the tip of the cone. The droplet was trailed by a jet that became thin and often broke. When the electric field strength was again increased, a steady charged jet formed and flew toward the collector. Multiple charged jets were created occasionally at high field strength. At a melt temperature of 250°C, the critical electric field strength was about 200-400 kV/m, and a steady charged jet was formed above this field strength.

The mobile charges in the melts were believed to come from small concentrations of ionic impurities, from sources such as monomer residues, other chemicals used during a post-polymerization step, contamination during handling of polymer and moisture uptake. Charges may also come from other charging mechanisms, such as an ion transfer between an electrode and the melt, and by ionization of residual gases in the vacuum chamber (Cross, 1987).

Figure 4 shows the initiation of a charged jet of molten PP electrospun at 300^°C, in an electric field of 200 kV/m. After the electric field was applied for about 60 seconds, a droplet of molten polymer hanging from the orifice started to deform from a semi-spherical to an elongated droplet. After the critical shape was formed at t = 0 s, ejection of the charged jet occurred at t = 0.20 s. The steady charged jet was formed at about t = 2 s. For comparison, for a sessile droplet of an aqueous solution of 6% poly(ethylene oxide) electrospun in an electric field of 146 kV/m, the critical shape formed at t= 0.77 s and charged jet ejection occurred at t = 0.83 s.

(Koombhongse, 2001). The times involved in the critical shape formation and steady charged jet ejection in the melt were considerably longer than those in the solution. The longer time is associated with a slower charge migration rate in polymer melts, a lower charge concentration at the surface and a higher surface tension in the melt.

From figure 4, at t= 0 s., the semi-angle of the cone at the critical point observed from the experiment, áEXP, was about 37.5 ± 2^o. This value

was closer to the prediction of a semi-angle of the cone at the critical point by Yarin, áY, at 33.5^ï than the prediction of a semi-angle of the Taylor cone, áT, at 49.9^ï (Yarin, et al. 2001; and Taylor, 1964). Because the exact moment at which the theoretical equilibrium condition was satisfied was difficult to pinpoint from visual observation, the point at which the Taylor cone was formed was determined by analyzing numerous video images.

Elongation of a molten charged jet in vacuum

The Coulombic repulsion among surface charges on the jet is the dominant force that causes the segment of the jet to elongate, and to eventually cause a bending instability. As the jet segment elongates, its diameter decreases. The elongation of the jet continue as long as the electrical forces can overcome the surface tension and viscoelastic forces, even the presence of the bending instability.

Experimental observations showed that after a charged jet of molten polymer was ejected from the droplet, the jet often flew toward a collector as a straight jet without developing any bending instability. Occasionally, the jet coiled and oscillated back and forth in a motion resembling the faster electrically-driven bending instability observed in a solution electrospinning. Images from an ordinary video camera, recorded

at 30 frames per second, were unable to resolved the jet path in detail, and use of a high frame rate camera was also unrewarding because of constraints imposed by the vacuum chamber.

Scanning electron microscope images of fibers electrospun in vacuum showed coils indicated that the molten charged jet developed the electrically-driven bending instability. Rangkupan reported the formation of an electrically-driven bending instability of a molten chargedjet of poly(å-caprolactone) electrospun in air (Rangkupan, 2002). The behavior of a molten charged jet in vacuum was expected to be similar to the behavior of a molten charged jet electrospun in air, since the electrospinning process in vacuum and in air were essentially identical, with the main difference lying in the solidification of the charged jets. Also the viscous forces of the air were small since the velocity was low.

Solidification of a charged jet of molten polymers

Solidification of the charged jet is often the termination step of the electrospinning process. After a molten charged jet solidifies into a strong fiber, elongation can no longer occur. The solidification process in solution electrospinning takes place via evaporation of solvent. The solidification of the fibers in the melt electrospinning process, however, takes place through a radiation of thermal energy from the jet to its cooler surroundings.

In a vacuum, heat dissipation of molten charged jet took place in two stages. The first stage occurred as soon as the jet emerged from the spinneret and flew toward the collector. Heat was removed mainly through the radiation process. Any thermal energy remaining after the jet reached the collector was removed by conduction to the collector.

Diameter of electrospun fibers

Fibers electrospun from molten polymers were often collected in a small area. When the electrospinning was done in an axisymmetric electric field, such as the field in a point and plate geometry, a fiber mat was collected into a small circular area that grew larger with time. The center of the mat was near the point at which a line perpendicular to the collector projected to the spinneret. When the electric field was not symmetric, the shape of collected fiber mats deviated from a circular shape and was difficult to predict.

The diameter of electrospun

polypropylene fibers was in the range of 300 nm to 30 gm. The fiber diameter tended to decrease as processing temperature increased, as the distance between the spinneret and collector increased, and as the electric field strength increased. The diameter of fiber segments had large variation along the length of the fiber, often showing multi-modal histograms of fiber diameter. The term ‘fiber segment’ was used because different segments of a long single fiber were photographed in the same image. The diameter variation of the fiber segment was affected by: (i) the mass flow rate of the molten polymer to the site where the jet ejection occurred was lower than the fiber formation rate, thereby

starving the segment and reducing its diameter, (ii) the elongation of each segments of the charged jet was not uniform, (iii) charge density in the fiber was not uniform, (iv) different segments of the charged jet solidified at different rate, and (v) a fluctuation in electrical field strength caused by corona discharge or other reasons which could be controlled .

Morphology of electrospun fibers

The morphology of electrospun fibers was examined using scanning electron microscopy and optical microscopy. Figure 5 shows an image of regular PP fibers electrospun in vacuum. The fibers were fully solidified before they were collected and had a smooth texture. Figure 6 shows PP nanofiber, with a diameter of about 300 nanometers, wrapped around a bigger electrospun PP fiber, which had a diameter in the range of a very fine textile fiber.

Figure 7 shows a SEM image of a PP ribbon with instability waves on the ribbon. The ribbon was collected before the wave could grow and stretch out to form a flat ribbon. Figure 8 shows a spring-like morphology in a fiber running from top to bottom in the middle, which is an indication of the occurrence of an electrically-driven bending instability in the electrospinning of a jet of molten polypropylene. Other morphologies observed included coiled and bent fibers. Depending on the path of the collected fibers and the details of the bending instability, different segments of the same fiber could exhibit different morphologies.

SUMMARY

Polypropylene was successfully

electrospun into fine fibers with a diameters in the range of 300 nm to 30 gm with a large fiber diameter variation. Several fiber morphologies were found. Morphological evidence also indicated that a molten charged jet underwent the electrically-driven bending instability after it was ejected from the spinneret. The observed semi-angle of the cone at the critical point was about 37.5 ± 2^o compared to a 33.5^° predicted by Yarin and 49.9^° predicted by Taylor.

ACKNOWLEDGEMENT

This work was part of the first author’s Ph.D. thesis and was done at the Maurice Morton Institute of Polymer Science, University of Akron, Akron, Oh, USA with a partial scholarship support from the Royal Thai Government.

Ratthapol RANGKUPAN¹ and Darrell H. RENEKER²

¹Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok,
Thailand
²Maurice Morton Institute of Polymer Science, University of Akron, Akron, OH, USA

THE MINIMUM TWIST OF COHESION OF RING AND COMPACT SPUN YARNS

2009-12-16T20:58:00.001-08:00

AN INVESTIGATION ON THE MINIMUM TWIST OF COHESION
OF RING AND COMPACT SPUN YARNS

The major factors required for determining the optimum twist to be given to a yarn are the count of the yarn and the desired level of twist multiplier. These are the factors that are taken into account in the mill. But one of the other important parameters for determining the optimum twist to be inserted is the fibre cohesion, which is always neglected.

The minimum twist of cohesion, in twist per meter (tpm) is inversely proportional to the square root of the number of fibres in the cross section of the roving. The minimum twist of cohesion increases with micronaire index and decreases with fiber length at constant roving weight.

The compact spinning system[1], which was developed and is an improvement over ring spinning, has created much scientific and commercial interest over the last few years. The reason for better strength in this spinning system has been due to better fibre cohesion[2]. It was Barella( 1960 ) and his colleagues who did pioneering work on minimum twist of cohesion in rovings and yarns produced from wool and cotton[4]. Studies were also conducted for worsted yarns [3] For several years Barella’s concept was not utilized but now it plays a very important role in compact spinning, in view of its usefulness.

This work is concerned with the study of minimum twist of cohesion of various types of yarns differing in structure which differ in their structure and form.

2. Materials and methods

The yarn samples were subjected to various chemical treatments such as scouring , mercerizing, bleaching and dyeing, following usual methods. The yarn samples were conditioned at the standard atmosphere with relative humidity of 65+ 2% and at a temperature of 27+ 2 ⁰C for 48 hours. Various chemical treatments such as scouring, mercerization, bleaching and dyeing, were given to the yarns. Both ring as well as compact spun yarn samples were used for the study.

2.2.1 Determination of minimum twist of cohesion of yarns

An instrument based on Barella’s technique was designed and fabricated. The instrument consisted of upper and lower jaws, and a specimen length of 25cm was fixed and the tension was kept at 0.1 gm/tex. Instead of following Barella’s method of determining minimum twist of cohesion, a departure was made. The minimum twist of cohesion (MTC) is given by the expression

MTC = Number of turns present in the yarn – Number of turns removed from the yarn x 100

Number of turns present in the yarn

The mean of 20 tests was considered.

2.3 Results and discussion

2.3.1 Effect of chemical treatments on MTC

From Figure 1 it can be seen that generally all the chemical treatments have led to a significant drop in the minimum twist of cohesion thus showing consolidation in yarns. From the graph it can be seen that the dyed fibers showed the best cohesion.

2.4.2 Effect of the type of fibre on MTC

The effect of different fibres on the minimum twist of cohesion is shown in Table 1. Among the yarns made of different fibres of the same count, viscose yarns show better cohesion, followed by polyester. The least cohesion is shown by cotton yarn.

2.4.3 Effect of blend composition on MTC

The effect of varying blend proportions on the MTC is shown is Table 2. The results show that in case of P/V blend, the blend proportion of 65:35 has better cohesion than the blend proportion of 75/25.This is due to the higher percentage of viscose content in the yarn. Viscose has higher fiber frictional value than polyester. In the case of P/C blend, the yarn having blend proportion of 75:25 has the greatest cohesion than the other proportions. This is because polyester content is maximum in this blend ratio and cotton content is minimum. Polyester has higher friction value than cotton fiber.

2.4.4 Variation of MTC in commercial samples

The comparison of MTC of yarns taken from various mills is shown in Table 3. Among the yarns of same count of 20s hosiery yarn, the yarn from mill G has the best cohesion. Among the yarns of 30s combed type, the yarn from mill A has the highest cohesion. This implies that in order to achieve the same cohesion in yarns, the same twist level and same fiber mixing should be used. Also it is possible to obtain high cohesion with lower twist per inch for a particular fiber type.

The comparison of MTC between carded, semi-combed and combed cottons is shown in Table 4. The results show that carded yarns have better cohesion than semi combed yarns. This is due to the draft given at carding (100 draft approximately) which reduces the trailing hook percentage. This in turn increases the compactness of the material by the increase of lateral pressure between the fibers.

2.4.6 Effect of different spinning methods on MTC

The comparison of MTC between ring and compact spun yarns is shown in Table 5. The results show that compact yarn showed better cohesion than ring yarn.

3. Conclusion

It is observed that scouring improves the cohesion of the yarn due to the removal of wax. The mercerization treatment further improves the cohesion over scoured materials. Bleaching exhibits further reduction in the minimum twist of cohesion. Reactive dyed yarns show better cohesion than those of previously treated yarns. Among yarns made of different fibers of the same count, viscose yarns show better cohesion. This is followed by polyester and the least cohesion is shown by cotton yarn. It is concluded that in a polyester/viscose blended yarn, the yarn having higher viscose content has the maximum cohesion. Similarly for polyester/cotton blended yarns, yarns having higher polyester content has better cohesion. It is also concluded that yarns of same cotton count from various mills have different cohesion values due to the variations in the fiber mixing. Also, the comparison between compact and ring spun yarns show that compact yarns have better cohesion. Finally, the comparison between carded, semi combed and combed yarns of the same count shows that there is a gradual decrease in cohesion from carded to combed yarns.

N.Gokarneshan¹ , N.Anbumani² , V.Subramaniam³

1 Department of Textile Technology, Kumaraguru College of Technology, Coimbatore – 641 006, Tamil Nadu, India.

2 Department of Textile Technology, PSG College of Technology, Coimbatore – 641 004, Tamil Nadu, India.

³ Formerly Department of Textile Technology, A.C.College of Technology, Anna University, Chennai – 600 025, Tamil Nadu, India.

Spinning | Latest Trends

2009-12-16T20:14:00.001-08:00

SPINNING – THE PRESENT SCENE

SPINNING
– THE OPTIONS

RING SPINNING

· The “standard” for judging yarn quality;

· Improvements in recent years: – higher traveler velocity,

– automatic doffing,

– longer machines

– link winding,

– splicing,

– smaller ring sizes

have interacted to yield cumulative benefits (potential spindle speed increase from 10,000 to 25,000);

THE FUTURE OF RING
SPINNING ??

· Longer machines (1488 spindles available)?

· High drafts?

· “Heavy roving” or “light weight sliver” feed?

· Higher traveller speed (or alternative)?

· Compact Spinning?

· Spindle ID# used with defect detection at winding?

RING SPINNING

RING AND TRAVELER
DEVELOPMENTS

A new spinning system to replace the ring system ?

PROBLEMS WITH HIGH DRAFTS?

“Hitherto the evaluation of drafting systems has been based only on yarn quality measurements such as appearance tests, Uster % and Spectrograph.

However these tests often fail to give
high correlation with the final fabric quality.”

Ring Spinning
– Compact Spinning

· A lot of interest in the system

(outside USA).

· Offers selective advantages of

– Compact yarn structure; – Reduced Hairiness;

– Higher tenacity;

– Lower Twist;

– Higher productivity

COMPACT SPINNING

Compared to conventional spinning compact yarns can be:

– Stronger

– Less hairy

– Spun with lower twist

– Softer

– Need less sizing

– Produce less fly in knitting, etc

^{________________________________________________________________________________________________________________________ 51}

COMPACT SPINNING

· Machinery costs 50 –100% greater than conventional?

· Yarn costs 10-20% higher than conventional?

· Problems with shorter fibers, “trash”, fiber adhesion, etc.

· Reduced hairs can impact spindle speed and potentially weaving costs?

· Are compact yarns needed for all markets?

ROTOR SPINNING

· Good for weaving and knitting;

· Longer frames being introduced - up to 320 positions;

· Smaller rotors used at higher speeds (150,000 revs/min);

· “Customers” prefer ring spun!

· In USA “upgrading” being carried out.

Twist in the rotor is a combination of:

· Real twist created by the rotation of the rotor;

· Temporary twist – due to the

interaction of the yarn and the navel

– The latter is further influenced by the fiber

properties (length, fineness, friction),

spinning speed, opening roller, etc.

Thus the twist measured inside the rotor can be more than double the twist in the final yarn

________________________________________________________________________________ 62

JET AND VORTEX
SPINNING

VORTEX SPINNING

· Problems of fiber waste 5-8%;

· System is still restricted to finer counts;

· Even though potentially capable of 100% cotton used mainly for blends;

· Major advantage of Jet and Vortex is low hairiness and less pilling.

· Problems of fabric appearance (use of high draft system) ?

SELF-TWIST SPINNING

Self Twist Spinning MACART S300

GILBOS Air Twist System

· Creates a yarns that looks like a multifold twisted yarn.

· Uses “detorque jets” to create S and Z alternating twist in filaments.

· These then self twist to form a coherent structure.

· No twist area reinforced by intermingling jet.

· Computer control of process

COMPOSITE YARNS

COMPOSITE SPINNING

· Staple (cotton or wool) + Filament (?)

· Filament can be:

– bonded to staple fiber (Bobtex?),

– wrapped with staple fiber (core spun),

– wrapped around staple fiber (wrap-spun {hollow-spindle})

· Good for “technical” uses - problems with aesthetics and cost.

FRICTION SPINNING

“Compact Spinning”
FEHRER DREF 3000

CENTRIFUGAL SPINNING

· Old idea currently arousing interest among machinery makers.

· Technique should yield properties almost identical to ring spun yarn.

· Automation an essential feature of the system.

THE FUTURE?

SPINNING MACHINES
(USA & Canada)

FUTURE DEVELOPMENTS

· Ring will continue to dominate.

· Rotor improvements –better utilization of present potential speeds.

· Vortex will increase – particularly with ongoing developments – and possible speed increases.

· Other systems – difficult to see justification for development costs.

NEW DEVELOPMENTS ?

· Who pays for development?

· High quality yarn is a given requirement!

· “New” supply chain is dominated by a few retailers and thus higher spinning costs (associated with new machinery and/or more expensive fiber) must be borne by spinner?

NEW MARKETS ?

· Technical yarns

· Medical applications

· Smart materials

· Niche markets

THANKYOU FOR YOUR ATTENTION

USTER® TESTER 5 | USTER® OM Sensor

2009-12-16T19:25:00.001-08:00

DIAMETER AND SHAPE – ADVANCED PREDICTION OF APPEARANCE

THE YARN INSPECTION SYSTEM

MORE BRILLIANCE – HIGHER MARKET VALUE

12% of problems in dyeing are caused by shape and density variation. Spinning methods, machine components and raw material directly impact those quality characteristics. The two-dimensional diameter measurement of the USTER^® OM SENSOR enables the determination of yarn roundness (shape) and consequently the controlling of the brilliance and lustre in a fabric. Exactly those characteristics can often be the reason for complaints about garments.

EXTENDED QUALITY CONTROL MAKES THE DIFFERENCES VISIBLE

A length of yarn is practically never completely round. A fact which has a decisive influence on the look of fabric. Optoelectronic measuring provides new possibilities for predicting the quality of yarns – to your advantage!

With a revolutionary two-dimensional measuring method, the USTER^® OM SENSOR for the USTER^® TESTER 5 defines the diameter and at the same time evaluates the surface structure, shape and density of yarn. These quality parameters are especially important for testing yarns which will be finished using state-of-the-art spinning processes, which are conditioned, or contain conducting fibers.

ACCEPTED – USTER^® STATISTICS

Differing dye behavior makes fabric and knitted fabric unuseable. The expected appearance of further produced goods will be predictable with the help of the new quality parameters.

Parameters which are recognized all over the world guarantee an optimal yarn trading process. An automatic assessment of the yarn quality can be done either by means of the USTER^® STATISTICS or own choice of limits.

TWIST MEASUREMENT IS REPLACEABLE

In the final dyeing process, any variation in the diameter of the processed yarn will make the produced fabric unuseable. Differences of more than 10% in the absolute yarn diameter (2DØ) will result in visible dyeing faults. The USTER^® TESTER 5 OM SENSOR and knowledge of the effective or relative mass allows controlling of the twist variations of the spinning machines.

OPTIMIZED QUALITY – INCREASED PROFITS

Loose fibers or loose fiber accumulations in the yarn strongly disturb the appearance of knitted goods. These faults are not detectable with a capacitive measurement. Only the unique USTER^® OM SENSOR can identify disturbing diameter variations (CV FS). Controlling of CV FS helps to prevent production of cloudy knitwear. A significant reduction of second quality.

USTER^® OM SENSOR – A MUST FOR COMPACT SPINNING

Compact yarns have a greater density (D) and a better variation in the fine structure (CV FS). The better fiber compactness makes compact yarn appear more even which is reflected in the diameter variation, an important quality parameter in yarn trading. With such a high visual evenness, the smallest increases or decreases in the mass of compact yarn are disturbing even though they seldom appear.

The variation of the number of fibers in the cross-section is similar for both, ring and compact yarns – the variation coefficients of the mass (CVm) stay at the same level.

USTER^® OM SENSOR WITH THE USTER^® TESTER 5

The simultaneous measurement of diameter variation, shape and density completes the controlling of yarn quality. This information is gained by optoelectronic measuring of the two-dimensional yarn diameter.

The Standard from Fiber to Fabric

USTER^® is the world’s leading supplier of total quality solutions from fiber to fabric. USTER^® standards and precise measurement provide unparalleled advantages for producing best quality at minimum cost.

USTER^® – Think Quality

Our commitment to state-of-the-art technology ensures the comfort and feel of the finished product – satisfying the demands of a sophisticated market. We help our customers to benefit from our applied knowledge and experience – to think quality, think USTER^®.

Broad Range of Products

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Optimal Service – Complete Satisfaction

Know-how transfer and instant help – we are where our customers are. A total of 200
certified service engineers worldwide grants fast and reliable technical support. Benefit
from local know-how transfer in your specific markets and enjoy our service à la carte.

USTER^® STATISTICS – The Textile Industry Standards

We set the standards for quality control in the global textile industry. With USTER^® 34!4)34)#3 we provide the benchmarks that are the basis for the trading of textile products at assured levels of quality across global markets.

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USTERIZED^® stands for “defined quality assured” within the textile chain. We invite selected customers to join the USTERIZED^® Member Program. More information at www.usterized.com.

USTER^® Worldwide

With three technology centers, six regional service centers and 50 representative offices around the world, USTER^® is always sure of delivering only the best to its customers. USTER^® – committed to excellence, committed to quality. And that will never change.

Twin Air-jet Nozzle System for Ring Spinning

2009-12-16T19:13:00.001-08:00

Design and Development of Twin Air-jet Nozzle System for Ring Spinning

The utility of the air-jet and ring combination has been known in the last decade, on its ability to reduce the yarn hairiness. However, it still offers enough scope for further work, with respect to its application in cotton spinning. In the recent past, it has been proved by the textile researchers that with the employment ofair -jet nozzle in ring spinning the yarn hairiness could be reduced. This paper examines the effect of employing twin air-jet nozzle in ring spinning. In this study an attempt has been made to combine the advantage ofair -jet spinning system, with conventional ring spinning system.

Two types of air -jet nozzle similar in all dimensions but differing in the direction of inclination of orifice, namely, ‘S’ nozzle and ‘Z’ nozzle and a suitable air chamber to house these two nozzles in tandem have been designed and fabricated. This twin air-jet nozzle assembly has been positioned in between the front roller nip and lappet hook without altering the spinning angle. The yarn emerging from the front roller nip has been guided to pass through the twin air-jet nozzle and subjected to the action ofopposing swirling air current created by air vortex inside the nozzles. Trials have been conducted in mill condition on 30's carded count on conventional ring spinning machine without and with twin air-jet nozzle under four different combinations of air pressure, ie, 0.25/0.25 bar, 0.25/0.50 bar, 0.50 /0.50 bar and 0.5/1.0 bar in the ‘S’ and ‘Z’ nozzles, respectively.

The yarn samples thus produced have been tested for their properties like tenacity, elongation, evenness, imperfections, hairiness, diameter and twist. From the results it has been observed that the introduction of twin air-jet nozzle system in ring spinning has lead to better compaction of yarn with improvement in yarn quality index, yarn tenacity and packing factor. The twin air-jet nozzle system under 0.25 / 0.50 bar pressure combination in the ‘S’ and ‘Z’ nozzles has produced the best results with 17.5% increased tenacity, 18.8 % improvement in Yarn Quality Index and 15% increased Packing Factor, when compared to regular ring spun yarn. This paper proves that the twin air-jet nozzle technology could be beneficially employed for the improvement of yarn quality by the spinning industry.

Keywords: Ring spinning; Yarn hairiness; Twin air-jet nozzle system

INTRODUCTION

The ability of the spinner to keep the hairiness down and in turn reduce the number of imperfections during winding is gaining much importance in this era of stringent quality norms^1,2. The fibres can be made to bind into the yarn structure by the use of methods like compact spinning where the spinning triangle is reduced or by the means of some external element like a pressure column or an air-jet nozzle that reduces the yarn hairiness. Research work on hairiness reduction using such methods has been going on for some time now. Kalyanaraman’s³ study shows that the hairiness in cotton yarn can be reduced by the use of a pressure column in between the lappet hook and front roller nip. Wang, et al⁴ studied the application of an air-jet nozzle in between the front roller nip and the lappet hook. They proved that there was considerable reduction in the hairiness index. This was explained by the tucking of fibres due to the swirling air current which resulted in loosening and tightening of the yarn structure. Ramachandralu^s has studied the influence of the air-jet nozzle

on the various ring yarn properties. Ramachandralu^s carried out research work using both ‘Z’ and ‘S’ type of nozzles and found that the Z nozzle performs better by producing yarns having higher tenacity and lower hairiness index of the yarn when subjected to the action of air vortex.

In this paper the application of both the type of nozzles fitted in tandem between the roller nip and lappet hook of ring frame is studied. This paper examines the effect of different combinations of pressures of air administered inside both the nozzles on the yarn quality aspects such as tensile properties, hairiness and packing factor.

This research work aims at

· design and development of twin air-jet nozzle system for ring spinning; and

· evaluating the influence of the twin air-jet nozzle on the quality of ring spun yarn under different air pressure combinations in the two nozzles.

RESEARCH METHODOLOGY

A cotton roving of 0.91 hank was produced in the usual manner and 30 s K yarn was produced with the following process parameters.

Design and Fabrication of the Twin Air-jet Nozzle

The material used for the manufacture of the nozzles was Brass. Two nozzles with the same dimensions but differing in the direction of the orifices were designed and fabricated. One nozzle was designed to produce air vortex with rotational direction opposite to that of mechanical twist ( S nozzle ) while the other was designed to produce air vortex with rotational direction same as that of mechanical twist ( Z nozzle ).

The two nozzles were housed in air jacket in tandem and this assembly was mounted in between the roller nip and the lappet hook in ring frame in a similar fashion like the N1 and N2 nozzles of air-jet spinning. Compressed air was administered inside both the nozzles through the air jackets and yarn samples were produced under four different air pressure combinations in ‘S’ and ‘Z’ nozzles as given in Table 1.

The yarn samples thus produced with and without the twin air-jet nozzle arrangement were tested for tenacity, elongation, evenness, imperfections, hairiness, diameter and twist.

RESULTS AND DISCUSSIONS

The results obtained in the present study on various properties of ring spun yarn with and without twin air-jet nozzle system are tabulated and analysed.

The physical properties of yarn, such as, count, twist, tenacity, elongation, unevenness, imperfections, hairiness, yarn diameter and yarn quality index of all the samples produced with and without using twin air-jet nozzle are shown in Table 2 and the comparison of results are depicted in the form of histograms in Figures 4-7.

It is observed from Table 2 that the employment of twin air-jet nozzle system contributes to the improvement of certain yarn quality parameters, such as, Tenacity and Yarn Quality Index. It could be noted that the system doesn't affect other quality aspects, such as, elongation and imperfections in general.

Effect of Twin Air-jet Nozzle System on Tensile Properties

It could be observed from Table 2 that except 0.50 bar-1.0 bar pressure combination in the ‘S’ and ‘Z’ nozzles, all other air pressure combinations have resulted in increased tenacity when compared to the parent yarn which was spun without twin air-jet nozzle arrangement. The percentage increase in tenacity over parent yarn pertaining to different air pressure combinations are shown in Table 3.

The increase in tenacity of yarn spun with twin air-jet nozzle could be explained as follows:

When the fibre strand leaves the front roller it is encountered with the action of the air vortex inside the ‘S’ nozzle. This air vortex, which is rotating in the direction opposite to that of the yarn twist, ie, ‘S’ direction and moving in the direction opposite to that of yarn flow will detwist the yarn and loosens its structure. When the yarn comes out of the ‘S’ nozzle and enters into the Z nozzle, it encounters with the air vortex which is rotating in the direction same as that of the yarn twist, ie, ‘Z’

direction, and moving in the direction opposite to that of yarn flow. Here, the loosened structure of the yarn undergoes re-twisting in the ‘Z’ direction and gets tightened. When the yarn comes out from the ‘Z’ nozzle it is further twisted and tightened by the mechanical twist inserted by the revolution of the traveller. This loosening and tightening up of the yarn structure results in the compaction of yarn, which is believed to contribute to increase in yarn strength.

It could be seen from Table 2 and Figure 4 that the air pressure combination of 0.25 bar-0.50 bar has produced the best result in tenacity showing 17.54% increase and 0.50 bar-1.0 bar combination has produced yarn with the lowest improvement in tenacity, ie, 2.91%. Hence, it could be taken that with the given nozzle design, 0.25 bar-0.50 bar combination is the most suitable one.

Regarding elongation it could be observed from Table 2 that the twin air-jet nozzle system doesn’t affect that property which is evident from the fact that the elongation percentage obtained at various air pressure combinations do not differ much with that of parent yarn spun without twin air-jet nozzle arrangement.

Effect of Twin Air-jet Nozzle System on Evenness

From Table 2 it could be seen that the twin air-jet nozzle system doesn’t seem to affect the evenness of yarn, as there is not much difference in the value of U% obtained for yarns spun under different air pressure combinations when compared to the parent yarn.

Effect of Twin Air-jet Nozzle System on Imperfections of Yarn

From Table 2 it could be noticed that there is not much difference in the values of various imperfections obtained for the yarns spun with different air pressure combinations when compared to the parent yarn.

Effect of Twin Air-jet Nozzle System on Yarn Quality Index

From Table 2 it could be observed that except 0.50 bar-1.0 bar air pressure combination, other combinations of air pressure have produced yarns with better YQI values. The percentage increase/decrease in YQI when compared with the parent yarn is given in Table 4 and Figure 5.

From Table 4 and Figure 5 it is evident that 0.25 bar- 0.50 bar air pressure combination has registered the highest YQI showing 18.8% increase over the parent yarn. This is due to the higher tenacity value obtained in case of 0.25 bar- 0.5% bar combination.

Effect of Twin Air-jet Nozzle System on Hairiness of Yarn

From Table 2 and Figure 6 it could be observed that 0.50 bar-1.0 bar pressure combination works well as far as hairiness reduction is concerned. It has accounted for in 15.8% reduction in hairiness. This could be due to the sweeping and binding action of the air vortex at 1 bar air pressure in the ‘Z’ nozzle as explained by Ramachandralu⁵. But under other air pressure combinations there is not much difference in hairiness values when compared to parent yarn.

Effect of Twin Air-jet Nozzle System on Compaction of Yarn

From Table 2 and Figure 7 it could be observed that the twin air-jet nozzle system results in producing yarns with reduced diameter which helps essentially in increasing the packing factor. The percentage increase in yarn packing factor obtained under different air pressure combinations is shown in Table 5 .

It could be observed from Table 5 that all the air pressure combinations have produced yarns with improved packing factor, which is a clear indication that the yarn undergoes compaction with twin air-jet nozzle arrangement.

It could be also observed from Table 5 that 0.25 bar- 0.50 bar combination has condensed the yarn to the maximum extent with 15.07% increase in packing factor.

With these values it could be confirmed that the compaction of the yarn samples produced with twin air-jet nozzle system has contributed to the increase in the tenacity of yarn as discussed earlier in this paper. This corroborates well with the findings of Ramachandralu⁵.

Effect of Twin Air-jet Nozzle System on Yarn Twist

From Table 2 it could be noticed that there is not much difference in the values of TPI obtained for the yarn spun with different air pressure combinations when compared to the parent yarn. Hence, it could be taken that the twin air-jet nozzle system does not affect the TPI of the yarn.

CONCLUSION

l In general twin air-jet nozzle arrangement is found to contribute to the improvement of Tenacity and Yarn Quality Index under different pressure combinations of air administered in the ‘S’ and ‘Z’ nozzles.

l In general it is found that the structure of yarn undergoes compaction exhibiting increase in Tenacity and Packing Factor with the twin air-jet nozzle system.

l In particular the twin air-jet nozzle arrangement is found to produce the best results with 0.25 bar-0.50 bar air pressure combination in ‘S’ and ‘Z’ nozzles showing 17.5% increase in yarn Tenacity and 18.75% improvement in Yarn Quality Index.

• In particular the air pressure combination of 0.25 bar0.50 bar in ‘S’ and ‘Z’ nozzles is found to condense the yarn to the maximum extent with 15% increase in Packing Factor.

ACKNOWLEDGEMENT

The authors thank the Management, Principal and Head of the Department of Textile Technology, PSG College of Technology for providing the facilities to carry out the research and the encouragement extended during the course of the research work.

The authors are grateful to the Management of The Lakshmi Mills Co Ltd for permitting to carry out the trials at their Palladam Unit and the Vice President Technical, General Manager and the Technical Officers for their technical and logistic support without which this research work would have been not completed successfully.

The authors thank Dr V Subramanian, Chair Professor Anna University, for the useful discussion on this study.

Prof K Ramachandralu, Non-member V Ramesh, Non-member

Cotton Gin | How it Works

2009-12-16T00:21:00.001-08:00

INTRODUCTION TO A COTTON GIN

Cotton fibers must be separated from the seed (ginned) before they can be used to manufacture textile goods. The first machine to gin cotton was the "Churka" gin. The "Churka" gin was most efficient when handling naked seeded varieties with loosely attached fibers. Early American settlers found that the fuzzy seeded varieties that yielded best in this country were difficult to gin on a roller gin. Consequently, the fiber was generally pulled from the seed (ginned) by hand until Eli Whitney patented his gin in 1794.

Whitney's gin used spikes on a hand-driven cylinder to remove fibers from the seed. The spikes pulled lint through slots that were too narrow for the seeds to pass. A revolving brush then removed the lint from the spikes. Whitney's gin could process as much cotton as 100 people could gin by hand. This invention enabled cotton growers to rapidly expand production, and marked the beginning of the modern cotton industry.

Henry Ogden Holmes received a patent in 1796 for an improved gin that used saws rather than spikes to remove the fibers from the seed. The saws were spaced on a shaft to provide openings that allowed the clean seed to drop out the bottom. Holmes' invention made ginning a continuous rather than a batch process, and greatly increased capacity. The basic principles developed by Whitney and Holmes are used in modern gin stands, but there have been many improvements.

When cotton was hand picked and carefully handled, the only machines needed in a ginning system were a gin stand, a baling press, and conveying equipment. Rougher hand harvesting methods and mechanical harvesters caused more moisture and foreign material (trash) to be mixed with the seed cotton. Thus, seed cotton cleaning and drying equipment and lint cleaners were developed to compensate for the trashier harvesting methods. Currently, about three-fourths of the U.S. crop is harvested with spindle pickers and one-fourth with mechanical strippers.

There is a major difference in the trash content of the spindle picked and stripper harvested seed cotton. On the average, about 2,200 pounds of stripped seed cotton containing about 800 pounds of trash are required for a 480-pound bale of lint. About 1,500 pounds of spindle picked seed cotton, containing about 120 pounds of trash would be required for a bale.

Storing Seed Cotton

Seed cotton can be safely stored in modules or trailers if its moisture content is kept at 12

percent or less. Wet cotton or cotton containing green plant material will heat during storage and quickly deteriorate. Cotton damaged in this manner produces low grades and poor quality seed. Fresh modules should be checked daily. If the temperature inside a seed cotton module exceeds 110°F, it should be ginned immediately to prevent further deterioration.

Modules of dry seed cotton should be carefully formed so water will run off the top and sides, placed on a well-drained site, and covered with good quality tarpaulins.

Cotton rope should be used to anchor the module coverings. Plastic twine should not be used to tie down covers since pieces of this material can get into the cotton and become a serious contamination problem at the textile mill.

Machinery in the Saw Ginning system

Quality preservation during ginning requires the proper selection and operation of each machine in a ginning system.

Automatic Feed Control

Gin machinery operates more efficiently when the cotton flow rate is constant. In early gins the flow rate was often erratic because of the variable work rate of the man operating the unloading system. The automatic feed con‑

trol was developed to solve this problem by providing an even flow of cotton to the gin's cleaning and drying system. A mechanical module feeder also performs a similar function and may be used to feed seed cotton directly from a module.

Green Boll Trap

The green boll trap is important for removing green bolls, rocks, and other heavy foreign matter from rough cotton. These large, heavy materials should be removed early in the ginning system to prevent damage to machinery and to preserve fiber quality. Green boll traps use sudden changes in flow direction and/or reduced air velocities to separate heavy foreign materials from seed cotton. A typical green boll trap is shown in Figure 1.

Driers

The most important factor in preserving quality during ginning is the fiber moisture content. At higher moistures, cotton fibers are stronger, but trash is harder to remove and cleaning machinery is less efficient. Consequently, selecting a ginning moisture content is a compromise between good trash removal and quality preservation. For most conditions, cotton should be ginned at 6 to 7 1/2 percent lint moisture.

The tower drier is the most widely used gin drier. Tower driers commonly have 16 to 24 shelves arranged so cotton must slow down while making turns through the machinery (Fig. 2). Heated air conveys the cotton through the shelves in 10 to 15 seconds. Practically all of the approximately 1,600 gins in the United States are equipped with at least one stage of seed cotton drying, and most ginning systems have two stages.

The temperature of the conveying air is regulated to control the amount of drying. To prevent fiber damage, the maximum temperature in the drying system should be kept below 350 °F. The temperature control sensor should be located near the entrance to the drier and a maximum temperature limit switch should be located between the burner and the mix point to keep the temperature below 350°F. If the temperature control sensor in your gin is located near the bottom of the drier, the reading may be 200-240 degrees lower than the temperature at the mixpoint.

Seed Cotton Cleaners

Seed cotton cleaners (cylinder cleaners) consist of six or seven revolving spiked cylinders that turn about 400 r.p.m. (Fig. 3). These cylinders convey the cotton over a series of grid rods or screens, agitate the cotton, and allow fine foreign materials such

as leaf trash and dirt to fall through openings for disposal. In many gins, two cleaners are

installed in parallel (split stream), with each one cleaning half the seed cotton.

Seed cotton cleaners break up large wads and generally get the cotton open and in good condition for additional cleaning and drying. Cylinder cleaners may also be used to remove seed cotton from the hot air line as it comes from the drier. They may be used in either a horizontal position or inclined at an angle of about 30 degrees (inclined cleaners).

Stick Machines

The stick machine (stick and green leaf machine) was developed to remove the extra foreign matter taken from the plant by mechanical harvesters (Fig. 4). Stick machines use the centrifugal force created by high-speed saw cylinders to sling off foreign material while the fiber is held by the saw.

Inside a stick machine, seed cotton is wiped onto the sling-off saw teeth by stationary wire brushes. Grid bars or stationary wire brushes are located around the saw cylinder to reduce the amount of seed cotton that is thrown off the cylinder. Some models have two sling-off cylinders while others use only one.

The seed cotton which is thrown off with the foreign matter is picked up by reclaimer saws and put back into the seed cotton stream. Reclaimer saw cylinders are similar to main sling-off cylinders, but usually run slower and have more grid bars. The foreign matter that is slung off the reclaimer feeds into the trash handling system.

Extractor-Feeders

The primary function of an extractor-feeder is to feed seed cotton uniformly to the gin stand at controllable rates (Fig. 5). Seed cotton cleaning is a secondary function. Feed rollers, located at the top of the extractor-feeder and directly under the distributor hopper, control the feed rate of seed cotton to the gin stand. These feed rollers are powered by variable-speed motors controlled manually or automatically by various interlocking systems with the gin stand.

Gin Stand

The gin stand consists of a set of saws rotating between ginning ribs (Fig. 6). The saw teeth pass between the ribs at the ginning point. Here the leading edge of the teeth is approximately parallel to the rib to pull the fibers from the seed rather than cutting them.

On traditional gin stands, cotton enters the stand through a huller front (Fig. 7). The saws grasp the cotton and draw it (in locks) through a widely spaced set of ribs known as "huller ribs". This causes hulls and sticks to fall out of the machine. The locks of cotton are drawn into the bottom of the roll box through the huller ribs.

Newer gin stand designs have eliminated the huller fronts, dropping the seed cotton directly into the roll box from the feeder apron (Fig. 8). This change increases stand capacity, but obviously eliminates the final stage of seed cotton cleaning.

The actual ginning process (separation of lint and seed) takes place in the roll box of

the gin stand. When all the long fibers are removed, the seeds slide down the face of the ginning rib between the saws and fall onto a conveyor under the stand. Lint is removed from the saw by a rotating brush or by an air blast. It is then conveyed to the next machine in the ginning system, usually a lint cleaner.

Saw-Type Lint Cleaner

In the lint cleaning process, a condenser removes the fiber from the conveying air stream and forms it into a batt (Fig. 9). The batt is introduced to the lint cleaner saw cylinder which normally rotates at approximately 1,000 revolutions per minute. The saws carry cotton over grid bars which, aided by centrifugal force, remove immature seeds (motes) and foreign matter. The cleaned lint is removed from the saw by a rotating brush which also provides air to convey it to the next machine.

Lint cleaners can improve the grade of cotton by removing foreign matter if the cotton has the necessary color and preparation characteristics. Lint cleaners may also blen'd light spotted cotton so that it becomes a white grade. But fiber length and several other important quality factors can be damaged by excessive lint cleaning, especially when the cotton is too dry.

For average machine-picked cotton, the first stage of lint cleaning will remove 20-30 pounds of lint and foreign matter from each bale. The second lint cleaner would be expected to

remove an additional 10-12 pounds and the third stage about 6 pounds.

Determining the number of lint cleaners that gives maximum bale value is a compromise between increased grade and reduced length, turnout, and other fiber quality factors important to textile manufacturers. The price differentials for grade and staple length have a great

influence on this decision. Under most circumstances, one or two saw-type lint cleaners will give the best economic returns. Consequently, ginning systems should be designed so that all saw-type lint cleaners after the first stage can be by-passed.

Bale Press

Cotton must be baled and packaged to protect it from contamination during transportation and storage. The U.S. cotton industry has adopted the universal density bale with a nominal density of 28 pounds per cubic foot. Universal density bales may be produced at a compress from modified flat bales, or they may be produced at the gin with a universal density (U-D) press. In 1990, approximately 85 percent of the U.S. crop was packaged in U-D bales at the gin.

Bale coverings and ties should meet the specifications developed by the Joint Cotton Industry Bale Packaging Committee. Detailed specifications are available from your county Agricultural Stabilization and Conservation Service office or from the National Cotton Council.

Moisture

Moisture is the most important single factor affecting fiber quality during ginning. When ginning at higher moisture contents, the average length of cotton fibers will be greater than if the same cotton was ginned at low moisture contents. However, trash is easier to remove from drier cotton. Consequently, determining a ginning moisture content is a compromise between

For spindle-picked cotton, the generally recommended machinery sequence is as follows (Fig. 10):

1. Rock and green-boll traps

2. Feed control

3. Tower drier

4. Cylinder cleaner

5. Stick machine good trash removal with some fiber length damage and length preservation with less lint cleaning.

The ideal ginning moisture content is 7 percent, but moistures between 6 and 7 1/2 percent are acceptable. Ginning at moistures outside this range can cause machinery operation and fiber quality problems.

6. Tower Drier

7. Cylinder cleaner

8. Impact cleaner (optional)

9. Extractor feeder

10. Gin Stand

11. Lint cleaner

12. Lint cleaner

13. Press

Machinery Systems Recommendations

Spindle-Picked System •

Machine-Stripped System

Since machine-stripped cotton that was not cleaned on the harvester contains 6 to 10 times as much foreign matter as machine-picked cotton, ginning systems in stripper areas need more cleaning equipment to maintain fiber quality. The following system of gin machinery (Fig. 11) is generally recommended for stripped cotton:

1. Green-boll trap

2. Air-line cleaner

3. Feed control

4. Tower drier

5. Cylinder cleaner Stick machine

6. Tower drier

7. Cylinder cleaner

8. Stick machine

9. Stick machine (The optional stick machine is recommended only for stripped cotton containing in excess of 32 percent foreign matter (lint turnout less than 22 percent).)

10. Extractor feeder

11. Gin stand

12. Lint cleaner

13. Lint cleaner

14. Press

These recommendations are the maximum amount of machinery that should be needed. Any machinery which is not necessary for the particular lot of cotton should be by passed. Driers, seed cotton cleaners, and lint cleaners should have bypass valves so they are not used unless they are needed.

Roller Gins

The first mechanical gin (Churka) was a roller gin consisting of two rollers (one metal, one hardwood) less than one inch in diameter, turned together by means of a hand crank. In 1840, Fones McCarthy invented a more efficient roller gin which consisted of a single leather ginning roller, a stationary knife, and a reciprocating knife which pulled the seed from the lint as the lint was held by the roller and stationary knife. Although the McCarthy gin was a major improvement over the Churka-type gin, machine vibration due to the reciprocating knife along with maintenance problems prohibited high ginning rates.

In the late 1950s and early 1960s, a rotary-knife roller gin was developed by the USDA Southwestern Cotton Ginning Research Laboratory, gin manufacturers, and private ginneries. The ginning roller and stationary knife were retained from the McCarthy gin while a rotary knife replaced the reciprocating knife, eliminating the lost time of the backstroke of the reciprocating knife and reducing the vibration. The rotary knife allowed increased ginning rates and is currently the only roller-type gin used in the United States. A typical rotary knife roller gin stand is shown in Figure 12.

Roller gins are used to preserve the quality of extra long staple (Pima) cottons grown in the western United States. Although only about 5 percent of the U.S. cotton crop is Pima, it is a highly valued specialty crop which demands a premium price. Roller gins are slow, averaging about 1 to 1.5 bales/hr/gin stand on good running cotton, compared to as much as 15 bales/hr/sawstand. Consequently, the cost of roller ginning is about 50 percent higher than saw ginning.

Since it is a very valuable product, the harvesting, seed cotton storage, and seed cotton conditioning of Pima cotton are criti cal. Seed cotton conditioning equipment in roller gins is similar to the type used in saw gins. Roller ginning systems normally include four or five seed cotton cleaners while a ginning system for machine picked upland cotton would normally include three or four seed cotton cleaners. Improper adjustment of seed cotton cleaning equipment causing

roping or recirculation of cotton can damage the quality of Pima cotton by stringing out and twisting the locks.

Tower dryers and hot-air cylinder cleaners are commonly used for seed cotton drying. Optimum fiber-moisture content for roller ginning is 5 to 6 percent. Drying fiber lower than 4 percent may result in static-electricity problems and fiber breakage. All United States roller-ginning plants have at least one stage of drying, 98 percent of the plants have at least two drying stages, and 59 percent have three drying stages. Drying temperatures should be monitored or automatically limited to no more than

300 °F because high drying temperatures damage fiber and waste energy.

The ginning roller is the most important and expensive component in the gin stand. Roller-covering material is made from 13 layers of plain-woven cotton fabric cemented together with a white rubber compound. The fabric lays on the bias so that neither the warp or fill yarn are parallel to the direction of cutting; this prevents the material from unraveling from the roller surface. The roller material mounts on to the roller core with the cut edges of the fabric layers serving as the ginning surface.

Rotary-knife roller gin stands separate fiber from seed by using the frictional forces between a moving roller and fixed stationary-knife surface. During normal ginning, the roller-to-fiber force is greater than the stationaryknife-to-fiber force; therefore, the fiber sticks to the roller surface and slips on the stationary knife surface. Cotton is ginned as fibers adhered to the roller surface slip under the stationary knife which holds the seed.

Each stroke of the rotary knife clears the stationary knife edge of accumulated seed cotton and ginned and partially-ginned seed. Partially ginned seed are either pulled back to the stationary knife and completely ginned or swept along with the seed and carryover and later reclaimed.

At the ginning point, seed cotton trash is separated with about 45 to 50 percent going with the lint and the remainder with the seed.

The carryover reclaimer removes unginned and partially ginned seed cotton and spindle twist from the seed flow and returns them to the distributor for ginning. The reclaimer usually cannot distinguish between seed cotton and spindle twist. Most of the spindle twists are returned and accumulate at the gin stand, resulting in reduced ginning efficiency and premature wear of the roller and rotary knife. Carryover percentage increases with feed rate but is typically less than 6 percent of the seed cotton fed.

Lint cleaning in roller gins is different from saw gins and varies among gins. Traditionally, the mill-type opener/air-jet lint cleaner combination was used to remove motes, broken seed, entanglements caused by the machine pickers, and pin trash not removed in seed cotton cleaning. But because if low capacity, many of the mill-type openers have been replaced by cylinder and revolving screen (impact) cleaners used in combination with air-jet cleaners. Currently, the most common lint-cleaning sequence is an incline, impact, and air-jet cleaners (Fig. 13); 35 percent of the plants have such

an arrangement.

U.S. DEPARTMENT OF AGRICULTURE
NATIONAL COTTON GINNERS ASSOCIATION

The National Cotton Ginners Association
Through The Support Of Its Member Associations

Arizona Cotton Ginners Association
California Cotton Ginners Association
Cooperative Ginners Association of Oklahoma
New Mexico Cotton Ginners Association
Oklahoma Cotton Ginners Association
Southeastern Cotton Ginners Association
Southern Cotton Ginners Association
Texas Cotton Ginners Association

Safety

Every employer has the responsibility of providing a safe working environment. Providing safe, comfortable working conditions is a good business investment when considering the costs of accidents and health problems. A general safety program should be developed for each gin, including the education of employees on unsafe conditions, practices, and behavior. Basic gin safety materials to create a gin safety program are available from your state/regional ginners association or from National

Cotton Ginners Association, P.O. Box 820285, Memphis, Tennessee 38182.

by W.D. Mayfield, National Program Leader, Cotton Mechanization and Ginning, Extension Service, USDA, Memphis, TN; R.V. Baker, S.E. Hughs, and W.S. Anthony, Research Leaders, respectively, USDA, ARS, Cotton Ginning Research Laboratories, Lubbock, TX; Mesilla Park, NM; Stoneville, MS