What is DrawFrame?

Prof.Dr. A.Kirecci
The drawframe contributes less than 5% to production costs of the yarn.However, its influence on quality, especially evenness, is all the greater for this.
Further, if the drawframe is not properly adjusted, there will also be effects on yarn strength and elongation. Secondly, a defect arising at the drawframe itself can exert an effect of significant proportions on the overall process.
High performance drawframes currently produce over 200 kg of sliver per hour at each delivery. Therefore, it should be noted that, very large quantities of poor quality sliver will be produced in a certain time before discovery of the defect.
There are two main reasons for the considerable influence of the drawframe on evenness. Firstly, within the sequence of machines in the cotton spinning mill, the drawframe is the definitive compensation point for eliminating errors.
Inadequacies in the product leaving the drawframe not only pass into the yarn, they are actually reinforced by drafting effects  following the drawframe.
The yarn is never better than the drawframe sliver.
'Autolevelling drawframe RSB-D 30
(Rieter) Drawframe SB-D



Auto Leveller Drawframe
Model RSB 851(Lakshmi)
Sophisticated Sliver
Guiding System


Breaker Drawframe

Tasks of the Drawframe

Equalising

One of the main tasks of the drawframe is improving evenness over short, medium and, especially, long terms.
Card slivers fed to the drawframe have a degree of unevenness that cannot be tolerated in practice.

II-Parallelizing

To obtain an optimal value for strength in the yarn characteristics, the fibers must be arranged parallel in the fiber strand. ,
The drawframe has the task of creating this parallel arrangement.
It fulfils this task by way of the draft, since every drafting step leads to straightening of the fibers.
The value of the draft must be adapted to the material, i.e. to several fiber parameters (here, mainly the staple length) and also
to:
1. the mass of the fibers;
2. the volume of the strand;
3. the degree of order (parallel disposition).

III-Blending

In addition to the equalizing effect, doubling also provides a degree of compensation of raw material variation, by blending.
This result is exploited in particular in the production of blended yarns comprising cotton/synthetic or synthetic/synthetic blends.
At the drawframe, metering of the individual components can be carried out very simply by selection of the number of slivers entering the machine.
For example, to obtain a 67:33 blend, four slivers of one component and two of the other are fed to the drawframe.

IV-Dust removal

Dust is steadily becoming a greater problem both in processing and for personnel involved. It is therefore significant to remove dust in every possible step in the process.
Dust removal can only be carried out where there is fiber/fiber fiber/metal friction, since dust particles adhere relatively strongly to the fibers.
A high performance drawframe with a sufficient number of suction point is a good dust-removing machine.

Operating Principle of the Drawframe

Four to eight card or drawframe slivers are fed to the drafting arrangement (3). A feed roller pair (2) is located above each can (1) to enable the feed step to be performed in a controlled manner without false drafts.

The feed roller pairs are carried in a creel frame or table and each is positively driven. The slivers runs into the drafting arrangement, subjected to a draft of 4 to 8 and leave it as a web lacking significant cohesion.
In order to avoid disintegration of the web, which would other wise be unavoidable at the high operating speeds currently in use, it is condensed into a sliver immediately after the drafting arrangement.

This sliver is then guided through a tube (4) via a passage (6) of the tube gear into a can (7), in which it must be laid in clean coils with optimal utilization of the space in the can.
To enable the can to take up as much material as possible, the sliver is compressed by passing it through calendaring or grooved railers (5).

Operating Devices

Creel (sliver feed)

In particular, the creel must be designed so that:
1. false drafts are avoided;
2. the machine stops upon occurrence of a sliver break;
3. sliver breaks can be dealt with easily, comfortably and safely.
For this purpose, it is necessary to provide a rotatable roller or roller pair above each can, one for each sliver.
A guiding device for leading the slivers into the drafting arrangement is also required. A table with rollers, or simply a line of rollers, can provide the required guidance.
Rollers alone are preferred in rapidly operating high-draft drawframes, since friction is lover when transport is effected by means of rolling than when it relies upon sliding.
The in-feed roller pairs also serve as electrical contact rollers for monitoring the sliver.
If a sliver breaks, the metal rollers come into contact when the insulating
sliver is no longer present between them, and the machine is stopped.
Normally, slivers may be fed in from up to eight cans per drawing head, and the cans may have diameters up to 1000 mm.

The drafting arrangement

The drafting arrangement is the heart of the drawframe and thus the part
which exerts the most decisive influence on quality. The requirements
placed on the drafting arrangement in general are correspondingly high:

1. simple, uncomplicated construction;
2. stable design with smooth running of the rollers (centricity);
3. a mode of operation giving a high-quality product even at high
running speeds;
4. high degree of flexibility. i.e. suitability for all raw materials, fiber
lengths, sliver hanks, etc..
5. optimal control over the movement of the fibers during the drafting operation;
6. high precision both of operation and adjustment;
7. rapid and simple adjustability of roller spacings and draft levels;
8. ease of maintenance and cleaning;
9. optimal ergonomic design.

Influences on the draft

In all types of drafting arrangement, the factors that affect the draft are as follows.
Factors dependent upon the fiber material
1. mass of fiber in the strand cross-section;
2. degree of order of the fibers;
3. shape of the cross section of the fiber strand;
4. compactness of the fiber stand;
5. adhesion between the fibers dependent upon surface structure,
6. crimp,
7. fiber length,
8. twist in the fiber strand;
9. compression of the strand;
10. evenness of distribution of fiber lengths (staple form) .
Influences on the draft
Factors dependent upon the drafting arrangement:
1. diameter of the rollers;
2. hardness of the top rollers;
3. pressure exerted by the top rollers;
4. surface characteristics of the top rollers
5. fluting of the bottom rollers;
6. type and form of fiber guiding devices, such as pressure rods, pin
bars, aprons, condenser etc.;
7. clamping distances (roller settings);
8. level of draft;
9. distribution of draft between the various drafting stages.
Elements of drafting arrangements
a)Bottom roller
Bottom rollers are made of steel and are mounted in roller stands or in the frame by means of needle, roller or ball bearings. They are positively driven from the main gear transmission.
In order to improve their ability to carry the fibers along, they are formed with flutes of one of the following types,
> axial flutes (a),
> knurled fluting (b),
> inclined flutes (spiral flutes) (c).

Elements of drafting arrangements
a)Bottom roller
Knurled fluting is used on rollers receiving aprons, to improve transfer of drive to the aprons.
Other rollers have axial or, increasingly, spiral fluting. The latter gives quieter running and more even clamping of the fibers compared with axial fluting.
Rolling of the top rollers on spiral flutes takes place in a more even manner and with less jerking.
The diameter of the bottom rollers can lie in the range 20 - 90 mm, but normally diameters between 25 and 50 mm are used.
A drafting arrangement includes three to six such rollers. In long machines (e.g. ring spinning machines) the bottom rollers are made up by screwing together short lengths.
Distances between the rollers of the drafting arrangement are usually adjustable and can then be adapted to the fiber lengths.

a) Top rollers
The top rollers are not positively driven. They can be either one-piece rollers (spinning preparation machines) or twin rollers (roving frames, ring spinning machines).
Ball bearings are used almost exclusively in the roller mountings.
The thick coating forming the roller surface is made of synthetic rubber.
An important characteristic of this coating is its hardness.
Soft coats surround the fiber strand to a greater extent than harder ones and thus guide the fibers better.

Top roller pressure
To clamp the fibers, the top rollers must be forced at high pressure towards
the bottom rollers. This pressure be generated by:
>loading by means of dead weights (now obsolete)
>spring weighting (the most usual form)
>hydraulic systems (hardly used)
>pneumatic weighting (the Rieter company)
>magnetic weighting (the Saco Lowell company).
Forms of drafting arrangement
Processing is carried out almost exclusively in two drafting zones. In extreme cases the break drafts lie between 1.05 and 2.5, but usually they are between 1.25 and 1.8. Extreme total drafts lie between 3.5 and 12
but the normal total draft lies between 4 and 8.
In many modern drawframes the draft is no longer adjusted by exchanging gear wheels but by simple setting of variator or stepping drives. The adjustment may be continuous or discrete steps.
Modern drawframes are more flexible in terms of the raw material they can process, and setting operations have been simplified 3-over-4 roller drafting arrangements
The characteristic feature of this arrangement is engagement of the middle pressure roller with two bottom rollers. The two bottom rollers are carried in a common cradle and are not adjustable relative to each other. The basic concept can be improved by the inclusion of a pressure bar in the main drafting field.

This type of arrangement is now found mainly in the combing room,
but also still to some extent on drawframes, for example in the Marzoli and Vouk machines.

3-over-3 roller drafting arrangemenTs with pressure bars
This form was first developed by Platt in the 1960s and is still in use today
in fact, the pressure bar arrangement is probably the most widely used
form of drafting arrangement for drawframes.
The starting point in the development of this design is the realization that
the drafting arrangement runs more smoothly the larger its rollers.

3-over-3 roller drafting arrangements with pressure bars
This applies especially to the front rollers. The effect is due not simply to
stability; for a given circumferential speed, larger rollers can be operated at
lower speeds of revolution. However, enlarging the rollers simultaneously
increases the nip spacings.
Accordingly, in the main drafting zone, a special guide system is needed,
at least for short fibers; this is the guide rail or pressure bar. It can operate
from below or from above. Similar arrangements have been or are built by
Rieter, Schubert & Salzer and Toyoda.
4-over-3 roller drafting arrangements with pressure bars
Strictly speaking, this is also a 3-roller, pressure bar drafting arrangement,
but a fourth roller with somewhat lower loading is added to the delivery
roller to act as a guide.
This leads the web in a curve round the grooved roller directly into the
delivery trumpet, thereby facilitating the formation of the sliver.
The top rollers are uniform in
diameter and are large in order to
keep the strain imposed on them
low.

5-over-4 roller drafting arrangements

In this arrangement five pneumatically loaded pressure rollers rest on two large (90 mm) and two small (28 mm), non-adjustable bottom rollers.
The pressure rollers are suspended from two yokes. They have diameters of 39 mm, although the three middle rollers may be replaced by rollers of 28 mm diameter depending upon the circumstances.
5-over-4 roller drafting arrangements
Drafting is carried out in Field B (breakdraft) and in Field A (main draft). The nip spacing can be read from a scale and can be adjusted to suit the fiber length by simple radial shifting of rollers 2 and 4.
In the main drafting field, a pressure bar ensures firm guidance, especially for short fibers. The drafting arrangement is aligned on a curve; this permits proper guidance of the web material flow from the vertical into the horizontal. The curved disposition makes the system easy to service.

Suction systems for the drafting arrangement
One of the tasks of the drawframe is dust removal. Release of dust occurs almost exclusively in the drafting arrangement and this should be totally enclosed so that dust does not pass into the surrounding atmosphere.
The dust-laden air must be extracted by suction.
Each roller of the arrangement has an associated cleaning device so that fly and fibers tending to adhere to the rollers can also be carried away.

The air drawn away is passed via tubes directly into the exhaust ducts of the air—conditioning system, or to filters within the machine.
The filtered air should preferably be returned to the exhaust ducting, but can also be blown out into the atmosphere of the room.

Condensing
Downstream from the trumpet, the sliver runs between two calender rollers which are pressed towards each other.
This condensing of the sliver enables more material to be fitted into the cans.
Several manufacturers replace the fluted or smooth cylindrical calender rollers with grooved or stepped rollers.
Since these latter rollers do not permit the fibers to escape laterally, a still better condensing effect is achieved.
In this way, the total filled weight of the can may be increased by up to 20%.
Grooved or stepped rollers can be used simultaneously as measuring devices for autolevelling systems.
Coiling
As already described for the card, two rotational movements are required for cycloidally coiling of the sliver.
Modern high—performance drawframes are usually fitted with automatic can changers.
These reduce the burden an the personnel, enabling more machines to be allocated to one person reduce the necessity for attendance of the operative at the machine, and (the chief effect) also increase efficiency.

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Drawframe autoleveler – cotton yarn quality

Technological Study of Auto-Leveller at Draw Frame on Cotton Yarn Quality
Nasir Mahmood, Nisar Ahmed Jamil and Sh. Shoaib Ahmad
Department of Fiber Technology, University of Agriculture, Faisalabad, Pakistan
Abstract: The purpose of present research was to analyze the effect of draft, sliver hank and delivery speed on the quality of cotton yarn using different auto-leveller system at draw frame. Drawing is considered to be the key process in the whole set-up of yarn formation as all efficiency and quality of subsequent process depends upon the behavior of the sliver formed at drawing stage. In present research it is elaborated that during drawing, three factors are more important i.e. break draft, delivery speed and sliver hank. The best quality of yarn is obtained by controlling these factors. Rieter RSBD-35 is better in performance as compared to Trutzschler HSR-1000 which is efficient and modem auto-levelli^ng g system with high speed servo drive motor at Rieter draw frame. The overall results show that moderate break draft, D2 (1.3), delivery speed S2 (700 yards/min) and sliver hank H2 (60 grain/yards) produced the better results.
Key words: Ring spinning, draw frame, Autolevellors, mechanical variables

On auto-leveler draw frame Tongue and Grove rollers, pneumatic transducers and other devices are used for online monitoring of sliver weight. Infect, auto-leveller at high-speed drawing frame helped a lot in producing regularities in sliver by detecting the variations at feeding point and by synchronization in quick control of weight per yard of the material. Efficiency of the control varies with auto-leveller model and technology. The auto-leveller at drawframe act on open control loop principle. According to this principle, the thickness of the arriving sliver is measured with a groove and tonge roller. The measured values are stored until the measured sliver reaches the drafting porn' t in^. the main^. drafting area. At this moment the amount of draft size is changed by highly dynamic servo derive motor. This can even balance the smallest deviations.
One of the main tasks of the draw frame is to improve evenness over short, medium and long terms. Card sliver fed to the draw frame have a degree of unevenness that can not be tolerated in practice and slivers from the comber contain the infamous piecing these must be obscured. It should be noted however that short wave sliver evenness is not as sometimes assumed, the sole criterion for evaluating the performance of draw frame. It is true that unevenness over short length can be noticeably reduced by narrow settings of the drafting arrangement. But this is often associated with deterioration in others quality parameters of yam. Drafting is an indispensable stage in^. yam formation and plays a critical role in yarn quality. Each drafting process from carding to spinning introduces its irregularities to the product and these irregularities degrade the final textile product.
Earlier research focused that in comparison of Rieter draw frame with other draw frames reveals that the Rieter always show the better results for yam lea strength. While Douglas^[21noted that modem high-speed machinery has resulted in over all quality improvement. Haque^['l reported that drawframe with autoleveller gave the best value of yam count as compared to without autoleveller drawframe. Jamil and Mahmood^[41 concluded that increase in break draft setting at ring spinning beyond certain limit, reduce the strength and increase the evenness and neps. Siddique^[51 concluded that delivery speed has significant effect on yam count.
Subramaniam and Mohamee concluded that both strength and evenness decreases as the break draft increased. Nawaz et cti.^[71 stated that count lea strength product value largely dependent upon the yam lea strength. Ching and Sue reported that in the initial drafting zone, the drafting process straighten the fibre crimps and hooks and improves the yam quality. Klein^{. [91} stated that short fibre has greater in^. fluence on yam strength. Arshadm stated that count lea strength decreases with the addition of short fibres and moderate speed produced the lowest value of short fibres. At this age of competition, it has become necessary to produce an internationally accepted standard quality yarn and this can be achieved only by applying modern techniques during processing of cotton. The present study was proposed to in^. vestigate the effect of auto-levelling and different mechanical variables viz. break draft, delivery speed and sliver hank on drawing sliver and ultimate yarn

quality processed at Rieter RSBD-35 and Trutzschler HSR-1000 draw frames.
MATERIALS AND METHODS
The present study was carried out initially in the Department of Fibre Technology, University of Agriculture, Faisalabad and was conducted at Sargodha Spinning Mills Faisalabad during the year 2005.
Yarn count: Yam count was determined through digital Auto Sorter-III linked with computer system, which gives direct reading. A lea of 120 yards was fed to the computer to determine English count according to its operational manual recommended by AST1VVI, the yarn count was noted from its automatic digital display.
Yarn lea strength: Pendulum type lea strength tester was used to find the lea strength in pounds. The lea of 120 yards was fed to the instrument according to the method recommended by ASTM''''.
Count lea strength product: Count and lea strength product was determined by multiplying the actual count value with respective breaking load of yam lea of 120 yards according to British Standards. CL SP = Yarn Count X Yarn Lea Strength.
Analysis of data: The data obtain^. ed was analyzed statistically using four-factor factorial in CRD, while Duncan's Multiple Range Test was applied for in^. dividual comparisons of means as suggested by Faqir on M-stat computer statistical program devised by Freed'''.
RESULTS AND DISCUSSION
Yarn count: The results indicate that the effect of break draft is non-significant, where as the effect of delivery speed and sliver hank is highly significant on yarn count. In case of interactions first and second-degree order interactions remained non-significant.
Comparison of individual means in^. respect, to machine and model type shows that both machines have non-significant difference with each other (Table 1). The values for yarn count are noted as 10.142 at M, followed by 10.143 at M2 (Table 1 a).
Duncan's Multiple Range Tests in the case of different break drafts the highest value for yam count is be recorded at D, followed by D, and D₃ with mean values as 10.147, 10.138 and 10.142, respectively. The results indicate that the effect of break draft is non- significant. The results also show that variation in count 10' is very small and count is course and such count show very small variations upon the data.
In case of delivery speed the means obtain for yam count are 10.289, 10.139 and 10.00 at S_i, S, and S,, respectively. DMRT for comparison of in^. dividual means show that in case of delivery speed of drawframe, the highest yam count 10.28 is found at S_i followed by S, and S, as 10.139 and 10.00. It indicates that the delivery speed affects the yarn count. These findings are in accordance with that of Siddique stated that delivery speed has significant effect on yam count. Similarly Douglas reported that yarn count, strength, irregularity and imperfections are influenced by raw material, type and machine settings. While Rehman^[151 found that actual value of yam count spun from cotton or any other fiber, generally differ from nominal value.
In case of sliver hank the means obtain' ed are 10.192, 10.139 and 10.096 at H,, H, and H₃, respectively. All these values differ significantly from each other. These values clearly in^. dicate that by in^. creasing the weight of sliver the yarn count decreases.
Yarn lea strength: The results in^. dicate that the effect of break draft is significant, where as the effect of sliver hank and delivery speed is highly significant at

both machines. In case of interactions, all interactions regarding first and second order degree are proved to be non-significant. Duncan's multiple range tests for individual comparison of drawing machines is show that both machines have significant difference for yarn lea strength (Table 2). The best value for yam lea strength is obtained at M, as 243.433 pounds followed by M, with its mean value as 232.081 pounds (Table 2a) This indicates that Rieter drawframe improved the strength parameters of yarn. These findings are fully supported by Anonymous^[11 who stated that in comparison of Rieter drawframe with
other drawframe, Rieter drawframe always shows best results for lea strength yarn might be due to natural change, different organic factors, machine settings etc.
DMRT in the case of comparison of individual treatment means of yarn lea strength at different break drafts, the highest mean value for yam lea strength is found at D, followed by D₃ and D, as 238.404, 235.261 and 233.607 pounds, respectively. These values differ significantly with each other. Results also indicate that at too low and too high break draft the yam lea strength decreases. Higher and lower break draft produces more
short fibre. While moderate break draft produces minimum short fibres. On the basis of these results it can be inferred that yarn lea strength and short fibre are directly related i.e. sliver with more short fibre produce weaker yarn. In this regard Jamil et al.t⁴¹ stated that yam strength is significantly affected due to different level of break drafts.
In case of comparison of individual means for delivery speed the highest mean value obtained for yarn lea strength is recorded at S, as 243.474 followed by S, and S₃ with their respective values as 239.682 and 230.116 pound. It indicate that delivery speeds affect yarn lea strength. It is evident that too low and too high drawing frame speeds produce lower yam lea strength. This might be due to fact that too low and too high speeds produce minimum fibre growth and reduce lea strength. Similarly Siddiquet⁵¹ concluded that delivery speed of drawframe has highly significant effect on yarn strength and imperfections.
Comparison of individual means for yarn lea strength at different level of sliver hanks i.e. H,, H₂ and H₃. Results show that the highest values for yarn lea strength is obtained at H, as 241.753 pounds followed by H, and H, with their respective values as 238.874 and 232.644 pounds.
Count Lea Strength Product (CLSP): The results indicate that the effect of break draft is significant while the effect of sliver hank and delivery speed is highly significant. In case of interactions, all first and second order degree interactions remained non- significant.
The individual comparison for count lea strength product value with respect to machines model and type is incorporate in Table 3. The highest mean value for count lea strength product is obtained as 2470.38 hanks at M, followed by 2356.34 hanks at M₂.
(Table 3a) Maximum count lea strength product of M, is attributing to its higher lea strength as Douglas^[21 reported that modern drawframe are design for overall quality improvement.
DMRT in case of different break drafts the highest mean value of yarn count lea strength product is found at D, as 2432.333 hanks followed by D, and D, with mean values as 2418.785 and 2388.977 hanks, respectively. These values differ significantly from each other. Results also indicate that at too low and too high break draft count lea strength product decreases. Higher and lower break draft produces more short fibre as indicated in Table 3a. While moderate break draft produces minimum short fibres. On the basis of these results it can be inferred that count lea strength product and short fibre are directly related. While Klein^[91 stated that short fibre has greater influence on yam strength. Similarly previous researchers like Subramaniam and Mohamed^[61 found that moderate break draft produces highest count lea strength product value while very low and very high break drafts produce lower count lea strength product of yam.
In case of delivery speed the mean of count lea strength product is recorded at S, as 2431.93 hanks followed by S, and S₃ with mean values as 2507.389 and 2301.154 hanks, respectively. It is evident that these values significantly different from each other. This indicates that at optimum levels of speed maximum strength is achieved, while above and blow this level the strength decreases i.e. too low and too high drawing frame speed produce lower count lea strength product. This might be due to fact that too low and too high speeds produce minimum fibre growth and reduce count lea strength product. In this regards Arshadt^1°1 stated that count lea strength decreases with the addition of short fibres and moderate speed produced the lowest value of short fibres.
As regards to sliver hank the highest values for count lea strength product is obtained at H, as 2442.897 hanks followed by H, and H, with values mean as 2422.475 and 2374.723 hanks, respectively. These results show that count lea strength product increases by increasing sliver weight unto certain limit.
CONCLUSIONS
The present research elaborated that during drawing, three factors are more important i.e. break draft, delivery speed and sliver hank. The best quality of yam is obtained by controlling these factors. It is also concluded that Rieter RSBD-35 is better in performance as compared to Trutzschler HSR-1000 which is efficient and modern autolevelling system with high speed servo drive motor at Rieter draw frame.
The overall results show that moderate break draft, D2 (1.3), delivery speed S2 (700 yards/min) and sliver hank H2 (60 grain/yards) produced the better results.

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THE DRAWFRAME

The drawframe contributes less than 5% to production costs of the yarn. However, its influence on quality, especially evenness, is all the greater for this. Further, if the drawframe is not properly adjusted, there will also be effects on yarn strength and elongation. Secondly, a defect arising at the drawframe itself can exert an effect of significant proportions on the overall process.
High performance drawframes currently produce over 200 kg of sliver per hour at each delivery. Therefore, it should be noted that, very large quantities of poor quality sliver will be produced in a certain time before discovery of the defect. There are two main reasons for the considerable influence of the drawframe on evenness.
Firstly, within the sequence of machines in the cotton spinning mill, the drawframe is the definitive compensation point for eliminating errors. Inadequacies in the product leaving the drawframe not only pass into the yarn, they are actually reinforced by drafting effects following the drawframe. The yarn is never better than the drawframe sliver.

Tasks of the Drawframe

(Equalising)
One of the main tasks of the drawframe is improving evenness over short, medium and, especially, long terms. Card slivers fed to the drawframe have a degree of unevenness that cannot be tolerated in practice.
II-Parallelizing
To obtain an optimal value for strength in the yarn characteristics, the fibers must be arranged parallel in the fiber strand. , The drawframe has the task of creating this parallel arrangement. It fulfils this task by way of the draft, since every drafting step leads to straightening of the fibers.
II-Parallelizing The value of the draft must be adapted to the material, i.e. to several fiber parameters (here, mainly the staple length) and also to:
1.         the mass of the fibers;
2.         the volume of the strand;
3. the degree of order (parallel disposition).
III-Blending In addition to the equalizing effect, doubling also provides a degree of compensation of raw material variation, by blending. This result is exploited in particular in the production of blended yarns comprising cotton/synthetic or synthetic/synthetic blends.
III-Blending At the drawframe, metering of the individual components can be carried out very simply by selection of the number of slivers entering the machine. For example, to obtain a 67:33 blend, four slivers of one component and two of the other are fed to the drawframe.
IV-Dust removal Dust is steadily becoming a greater problem both in processing and for personnel involved. It is therefore significant to remove dust in every possible step in the process. Dust removal can only be carried out where there is fiber/fiber fiber/metal friction, since dust particles adhere relatively strongly to the fibers. A high performance drawframe with a sufficient number of suction point is a good dust-removing machine.

Operating Principle of the Drawframe

  Four to eight card or drawframe slivers are fed to the drafting arrangement (3). A feed roller pair (2) is located above each can (1) to enable the feed step to be performed in a controlled manner without false drafts.
The feed roller pairs are carried in a creel frame or table and each is positively driven. The slivers runs into the drafting arrangement, subjected to a draft of 4 to 8 and leave it as a web lacking significant cohesion. In order to avoid disintegration of the web, which would other wise be unavoidable at the high operating speeds currently in use, it is condensed into a sliver immediately after the drafting arrangement.
This sliver is then guided through a tube (4) via a passage (6) of the tube gear into a can (7), in which it must be laid in clean coils with optimal utilization of the space in the can. To enable the can to take up as much material as possible, the sliver is compressed by passing it through calendaring or groovedrailers (5).

Operating Devices
Creel (sliver feed)
In particular, the creel must be designed so that:
1.           false drafts are avoided;
2.           the machine stops upon occurrence of a sliver break;
3.        sliver breaks can be dealt with easily, comfortably and safely.
Creel (sliver feed)
For this purpose, it is necessary to provide a rotatable roller or roller
pair above each can, one for each sliver.
A guiding device for leading the slivers into the drafting arrangement is
also required.
A table with rollers, or simply a line of rollers, can provide the required
guidance.
Rollers alone are preferred in rapidly operating high-draft drawframes,
since friction is lover when transport is effected by means of rolling
than when it relies upon sliding.
Creel (sliver feed)
The in-feed roller pairs also serve as electrical contact rollers for
monitoring the sliver.
If a sliver breaks, the metal rollers come into contact when the insulating
sliver is no longer present between them, and the machine is stopped.
Normally, slivers may be fed in from up to eight cans per drawing head,
and the cans may have diameters up to 1000 mm.
The drafting arrangement
The drafting arrangement is the heart of the drawframe and thus the part
which exerts the most decisive influence on quality. The requirements
placed on the drafting arrangement in general are correspondingly high:
1.                simple, uncomplicated construction;
2.                stable design with smooth running of the rollers (centricity);
3.                a mode of operation giving a high-quality product even at high
running speeds;
4.                high degree of flexibility. i.e. suitability for all raw materials, fiber
lengths, sliver hanks, etc..
5.                optimal control over the movement of the fibers during the drafting
operation;
6.                high precision both of operation and adjustment;
7.                rapid and simple adjustability of roller spacings and draft levels;
8.                ease of maintenance and cleaning;
9.               optimal ergonomic design.
Influences on the draft
In all types of drafting arrangement, the factors that affect the draft
are as follows.
Factors dependent upon the fiber material
1.                mass of fiber in the strand cross-section;
2.                degree of order of the fibers;
3.                shape of the cross section of the fiber strand;
4.                compactness of the fiber stand;
5.                adhesion between the fibers dependent upon surface structure,
6.                crimp,
7.                fiber length,
8.                twist in the fiber strand;
9.                compression of the strand;
10.            evenness of distribution of fiber lengths (staple form) .
Influences on the draft
Factors dependent upon the drafting arrangement:
1.           diameter of the rollers;
2.           hardness of the top rollers;
3.           pressure exerted by the top rollers;
4.           surface characteristics of the top rollers
5.         fluting of the bottom rollers;
6.           type and form of fiber guiding devices, such as pressure rods, pin
bars, aprons, condenser etc.;
7.           clamping distances (roller settings);
8.           level of draft;
9. distribution of draft between the various drafting stages.
Elements of drafting arrangements
a)Bottom roller
Bottom rollers are made of steel and are mounted in roller stands or in the frame by means of needle, roller or ball bearings. They are positively driven from the main gear transmission.
In order to improve their ability to carry the fibers along, they are formed with flutes of one of the following types,
> axial flutes (a),
> knurled fluting (b),
> inclined flutes (spiral flutes) (c).

Elements of drafting arrangements
a)Bottom roller
Knurled fluting is used on rollers receiving aprons, to improve transfer
of drive to the aprons.
Other rollers have axial or, increasingly, spiral fluting. The latter gives
quieter running and more even clamping of the fibers compared with
axial fluting.
Rolling of the top rollers on spiral flutes takes place in a more even
manner and with less jerking.
Elements of drafting arrangements
a)Bottom roller
The diameter of the bottom rollers can lie in the range 20 - 90 mm, but
normally diameters between 25 and 50 mm are used.
A drafting arrangement includes three to six such rollers. In long machines
(e.g. ring spinning machines) the bottom rollers are made up by screwing
together short lengths.
Distances between the rollers of the drafting arrangement are usually
adjustable and can then be adapted to the fiber lengths.
Elements of drafting arrangements
a) Top rollers
The top rollers are not positively driven. They can be either one-piece rollers
(spinning preparation machines) or twin rollers (roving frames, ring spinning
machines).
Ball bearings are used almost exclusively in the roller mountings.
The thick coating forming the roller surface is made of synthetic rubber.
An important characteristic of this coating is its hardness.
Soft coats surround the fiber strand to a greater extent than harder ones and thus
guide the fibers better.

Top roller pressure
To clamp the fibers, the top rollers must be forced at high pressure towards
the bottom rollers. This pressure be generated by:
>loading by means of dead weights (now obsolete)
>spring weighting (the most usual form)
>hydraulic systems (hardly used)
>pneumatic weighting (the Rieter company)
>magnetic weighting (the Saco Lowell company).
Forms of drafting arrangement
Processing is carried out almost exclusively in two drafting zones. In
extreme cases the break drafts lie between 1.05 and 2.5, but usually they
are between 1.25 and 1.8. Extreme total drafts lie between 3.5 and 12
but the normal total draft lies between 4 and 8.
In many modern drawframes the draft is no longer adjusted by
exchanging gear wheels but by simple setting of variator or stepping
drives. The adjustment may be continuous or discrete steps.
Modern drawframes are more flexible in terms of the raw material they
can process, and setting operations have been simplified
3-over-4 roller drafting arrangements
The characteristic feature of this arrangement is engagement of the middle
pressure roller with two bottom rollers. The two bottom rollers are carried in
a common cradle and are not adjustable relative to each other. The basic
concept can be improved by the inclusion of a pressure bar in the main
drafting field.

3-over-4 roller drafting arrangements
This type of arrangement is now found mainly in the combing room,
but also still to some extent on drawframes, for example in the
Marzoli and Vouk machines.

3-over-3 roller drafting arrangemen s with pressure bars
This form was first developed by Platt in the 1960s and is still in use today
in fact, the pressure bar arrangement is probably the most widely used
form of drafting arrangement for drawframes.
The starting point in the development of this design is the realization that
the drafting arrangement runs more smoothly the larger its rollers.

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3-over-3 roller drafting arrangements with pressure bars
This applies especially to the front rollers. The effect is due not simply to
stability; for a given circumferential speed, larger rollers can be operated at
lower speeds of revolution. However, enlarging the rollers simultaneously
increases the nip spacings.
Accordingly, in the main drafting zone, a special guide system is needed,
at least for short fibers; this is the guide rail or pressure bar. It can operate
from below or from above. Similar arrangements have been or are built by
Rieter, Schubert & Salzer and Toyoda.
4-over-3 roller drafting arrangements with pressure bars
Strictly speaking, this is also a 3-roller, pressure bar drafting arrangement,
but a fourth roller with somewhat lower loading is added to the delivery
roller to act as a guide.
This leads the web in a curve round the grooved roller directly into the
delivery trumpet, thereby facilitating the formation of the sliver.
The top rollers are uniform in
diameter and are large in order to
keep the strain imposed on them
low.

5-over-4 roller drafting arrangements
In       this          arrangement       five
pneumatically loaded pressure
rollers rest on two large (90 mm)
and two small (28 mm), non-
adjustable bottom rollers.
The       pressure       rollers        are
suspended from two yokes. They
have diameters of 39 mm,
although the three middle rollers
may be replaced by rollers of 28
mm diameter depending upon the
circumstances.

5-over-4 roller drafting arrangements
Drafting is carried out in Field B
(breakdraft) and in Field A (main draft).
The nip spacing can be read from a scale
and can be adjusted to suit the fiber
length by simple radial shifting of rollers 2
and 4.
In the main drafting field, a pressure bar
ensures firm guidance, especially for
short fibers.
The drafting arrangement is aligned on a
curve; this permits proper guidance of the
web material flow from the vertical into
the horizontal. The curved disposition
makes the system easy to service.

Suction systems for the drafting arrangement
One of the tasks of the drawframe is dust removal. Release of dust
occurs almost exclusively in the drafting arrangement and this should be
totally enclosed so that dust does not pass into the surrounding
atmosphere.
The dust-laden air must be
extracted by suction.
Each roller of the arrangement has
an associated cleaning device so
that fly and fibers tending to
adhere to the rollers can also be
carried away.

The air drawn away is passed via tubes directly into the exhaust
ducts of the air—conditioning system, or to filters within the machine.
The filtered air should preferably be returned to the exhaust ducting,
but can also be blown out into the atmosphere of the room.

Condensing
Downstream from the trumpet, the sliver runs between two calender rollers which
are pressed towards each other.
This condensing of the sliver enables more material to be fitted into the cans.
Several manufacturers replace the fluted or smooth cylindrical calender rollers with
grooved or stepped rollers.
Since these latter rollers do not permit the fibers to escape laterally, a still better
condensing effect is achieved.
In this way, the total filled weight of the can may be increased by up to 20%.
Grooved or stepped rollers can be used simultaneously as measuring devices for
autolevelling systems.
Coiling
As already described for the card, two rotational movements are required
for cycloidally coiling of the sliver.
Modern high—performance drawframes are usually fitted with automatic
can changers.
These reduce the burden an the personnel, enabling more machines to
be allocated to one person reduce the necessity for attendance of the
operative at the machine, and (the chief effect) also increase efficiency.

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DRAWFRAME

TASKS OF DRAWFRAME
Through doubling the slivers are made even doubling results in homogenization(blending) through draft fibres get parallelised hooks created in the card are straightened through the suction ,intensive dust removal is achieved autoleveller maintains absolute sliver fineness
Quality of the drawframe sliver determines the yarn quality. Drawing is the final process of quality improvement in the spinning mill Drafting is the process of elongating a strand of fibres, with the intention of orienting the fibres in the direction of the strand and reducing its linear density.In a roller drafting system, the strand is passed throgh a series of sets of rollers, each successive set rotating at a surface velocity greater than that of the previous set. During drafting, the fibres must be moved relative to each other as uniformly as possible by overcoming the the cohesive friction.

Uniformity implies in this context that all fibres are controllably rearranged with a shift relative to each other equal to the degree of draft. In drawframe, the rollers are so rotated that their peripheral speed in the throughflow direction increases from roller pair to roller pair, then the drawing part of the fibres, i.e.the draft, takes place. Draft is defined as the ratio of the delivered length to the feed length or the ratio of the corresponding peripheral speeds.
Drawing apart of the fibres is effected by fibres being carried along with the roller surfaces. For this to occur, the fibres must move with the peripheral speed of hte rollers. This transfer of the roller speed to the fibres represents one of the problems of drafting operation. The transfer can be effected only by friction, but the fibre strand is fairly thick and only its outer layers have contact with the rollers, and furthermore various, non-constant forces act on the fibres. - . Roller drafting adds irregularities in the strand.

Lamb states that,though an irregularity causing mechanism does exist in drafting, drafting also actually reduced the strand irregularities by breaking down the fibre groups. Drafting is accompanied by doubling on the drawframe, this offsets the added irregularity. Variance(sliver out) = Variance(sliver in) + Variance(added by m/c) In Statistics , Variance is the square of standard deviation Two passages of drawing with eight ends creeled each time would produce a single sliver consisting of 64 ribbons of fibre in close contact with each other.In the ultimate product, each ribbon may be only a few fibres thick, and thus the materials of the input slivers are dispersed by the drawing process. The term doubling is also used to describe this aspect of drawing


Drafting arrangement is the heart of the drawframe. The drafting arrangement should be simple stable design with smooth running of rollers able to run at higher speeds and produce high quality product flexible i.e suitable to process different materials , fibre lenths and sliver hanks able to have good fibre control easy to adjust Roller drafting causes irregularities in the drafted strand since there is incomplete control of the motion of each individual fibre or fibre group.
The uniformity of the drafted strand is determined by draft ratio roller settings material characteristics pressure exerted by the top roller hardness of top roller fluting of the bottom rollers distribution of draft between the various drafting stages drafting is affected by the following rawmaterial factors no of fibres in the cross section fibre fineness degree of parellelisation of the fibres compactness of the fibre strand fibre cohesion which depends on surface structure crimp lubrication compression of the strand fibre length twist in the fibre distribution of fibre length 3-over-3 roller drafting arrangements with pressure bar is widely used in the modern drawframes Bigger front rollers are stable and operated at lower speeds of revolution, this necessitated pressure bar arrangement for better control of fibres. Some drawframes are with 4-over-3 drafting arrangement, but strictly speaking it behaves like a 3-over-3 drafting system except for the fact that fourth roller helps to guide the sliver directly into the delivery trumpet.

DRAFTING WAVE:
Floating fibres are subject to two sets of forces acting in opposite directions. The more number of fibres which are moving slowly because of the contact with the back rollers restrain the floating fibres from accelerating. The long fibres in contact with the front rollers tend to accelerate the floating fibres to the higher speed. As the floating fibres move away from the back roller, the restraining force by back roller held fibres reduces, and the front roller influence increases. At some balance point, a fibre accelerates suddenly from low to high speed. This balance point is compounded by the laws of friction, static friction being higher than dynamic friction.When one floating fibre accelerates, the neighbouring shor fibres suddenly feel one more element tending to accelrate them and one fewer trying to restrain them. Thus there may be an avalanche effect which results in drafting wave.

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