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 norms1,2. 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. Ramachandralus has studied the influence of the air-jet nozzle
on the various ring yarn properties. Ramachandralus 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
