Research On Double S Curves Soft-drafting Technology

The most widely used drafting mechanism of the traditional ring spinning was long and short aprons drafting mechanism or double short aprons drafting mechanism.The large friction between the aprons in double short aprons drafting mechanism resulted in short life of aprons.Thus it was easy to produce fiber rubbing with the increase of service time,which affected the yarn quality.Compared with the double short aprons drafting mechanism,the long apron in the long and short aprons drafting mechanism had long working life.But its floating area was long and the elastic jaw of the long and short aprons drafting device had poor control of the floating fiber,which increased the distribution range of the speed points of floating fiber and the instability of yarn quality.In the Double S curves soft-drafting technology("Double S soft drafting"for short,similar ly hereinafter),the drafting area of the traditional double aprons was modified,and the fiber strips was controlled by the S-shaped plates,curve pipes and lattice aprons.The distribution of the friction field in the main drafting zone was fully extended to the front jaw,which was conducive to the promotion of yarn evenness.Based on the existing Double S soft drafting device,the systematic experimental analysis and the preliminary theoretical research were carried out for the Double S soft drafting in this paper.Firstly,the periodic testing of double S soft drafting and ring spinning with long and short aprons drafting mechanism was carried out for yarn evenness,yarn faults and yarn hairiness.Combining with the"Independent-Sample T-test"statistical method,the difference of yarn quality between the double S soft drafting and ring spinning was determined and the quality characteristics of the yarn spun by double S soft drafting was analyzed.Secondly,through the analysis of test data and drafting principle,the existing problems of double S soft drafting was found and the optimized improvements and suggestions were proposed,which laid the foundation for the industrialization applications of the new spinning technology.For this purpose,this paper focused on the following aspects:(1)Comparison of periodic testing results.In this paper,three kinds of yarns(T65/JC3532~S/JC60/T40 32~S/JC60/T40 30~S)were spun by double S soft drafting and ring spinning technologies.The yarn evenness,frequent yarn faults and yarn hairiness were tested by USTER Tester,and the"Independent-Samples T-test"method was used to analyze the significance of difference between the test data of double S soft drafting and ring spinning.The results show ed:The yarn evenness of the yarn spun by double S soft drafting was better than that of the yarn spun by ring spinning,especially in the kind of yarn composed of JC60/T40 30~S spun by double S soft drafting,which was signif icantly better than the yarn spun by ring spinning;The number of yarn faults of the yarn spun by double S soft drafting was less than that of the yarn spun by ring spinning,and the+35%thick places of the yarn spun by double S soft drafting was signif icantly better than the yarn spun by ring spinning.The yarn hairiness of the yarn spun by double S soft drafting was quite with the yarn spun by ring spinning;The spindle difference of the yarn spun by double S soft drafting was significantly greater than that of the yarn spun by ring spinning.(2)Research on the influence of service time of lattice aprons that was an important part of double S soft drafting on yarn quality.The study of this paper found that the abrasion of lattice aprons,which resulted in the accumulation of short fibers,was one of the main reasons for the large spindle difference of double S soft drafting.It could reach the conclusion by the use of the"Independent-Samples T-test"method to compare the signif icant difference of yarn evenness and spindle difference of three kinds of yarns spun by the double S soft drafting device with the lattice aprons used for one month,three months and six months,respectively:The evenness of the yarn with the lattice aprons used for 3 months significantly worsened and the spindle difference signif icantly increased.In order to study the influence of abrasion of lattice aprons on yarn quality,the front and back side of lattice aprons,which had been used for the above three kinds of service time,were observed and contrasted by Scanning Electron Microscope(SEM).Comparative analys is found that:(1)The strips had a large friction force on the front of the weave yarn of lattice aprons,which caused the local damage of weave yarn,thus leaving the fiber head end and hanging the fiber of the strips.As the spinning process,the fibers were drawn out from the strips and accumulated on the surface of lattice aprons,forming the accumulation of fibers and affecting yarn quality.(2)The back abrasion of lattice aprons was faster and severer than the front.The back abrasion of lattice aprons was mainly aggravated by the knurled roller,which made the lattice aprons easy to slip and caused the increasing of spindle difference.(3)Explore the effect of lattice aprons'specification on yarn quality.By using the"Independent-Samples T-test"method,the yarn evenness and spindle difference of double S soft drafting device that used the lattice aprons with 120 mesh number("120 mesh"for short,similar ly hereinafter)and the lattice aprons with 140 mesh number("140 mesh"for short,similar ly hereinafter)were analyzed in this paper,it could get conclusion:The yarn evenness of double S soft drafting device that used the 120 mesh lattice apron was significantly better than that of the yarn which used the 140 mesh lattice apron,and its spindle difference which had no signif icant difference with the device used 140 mesh lattice apron was greater than the one that used the 140mesh lattice apron.The SEM was also used to compare the front and back sides of the above two kinds of lattice aprons with different mesh numbers,both of them had used for one month.Comparative analysis found that:the front and back abrasion of the 120 mesh lattice apron was worse than the 140 mesh lattice apron.Because the mesh number of the 120 mesh lattice apron was less than the 140 mesh lattice apron,the contact area of its back side with the knurled roller was large,therefore it was subject to greater pressure.It was easier to be worn and slipped than the140 mesh lattice apron,thus the bearing and control of the strips were weakened,which caused that fiber speed change was not sufficient and affected the yarn evenness and spindle difference.(4)Aiming at the problem of double S soft drafting system,some suggestions for improving Double S soft drafting were proposed.In the practical application of double S curves soft-drafting technology,the phenomenon of crackers mostly occured in the process of replacement the roving and piecing.If operator specialized in the wrapping technology,it could reduce the likelihood of this problem.By adjusting the distance between S-shaped plates and middle rollers in the post processing and cleaning up f ibers in time c ould solve the problem of short fibers'accumulation.It was easy to cause large spindle difference due to the inconformity of the equipment parameters of double S soft drafting caused by full-manual installation.In view of the above problems,a solution by using the mechanical tools and carrying out professional training on operator was proposed.What's more,aiming at the problem of the abrasion of lattice aprons in the double S soft drafting system and combining with the advantage of double S soft drafting system that the distribution of the friction field in the main drafting zone was extended to the front jaw,this paper further explored a wave-shaped drafting device with integrating function.The main features of the device were as follows:(1)The apron which had longer working life and better wear resistance was still used on the fiber to be carried and controlled.(2)The front end of the wave-like upper pin was closer to the front roller surface than S-shaped plates.The distribution of the friction field in the main drafting zone was maximally extended to the front jaw;to substantially improve the yarn evenness.(3)Two arc grooves were set in the front end of the wave-like upper pin,which can make the strips fixed position mechanically gathered in the drafting process,thus improving yarn hairiness;(4)The curve structure of the wave-like upper pin was changed to a special wave-like structure,which could change the spinning varieties without changing the cradle and increase the spinning fiber type of the cradle.In summary,this paper systematically compared the difference of yarn quality between the double S soft drafting and ring spinning and studied the reasons that affect the yarn quality of double S soft drafting.The study of this paper found that the abrasion and accumulation of short fibers caused by abrasion of lattice aprons was one of the main reasons for the large spindle difference of double S soft drafting,and the problem of the double S soft drafting system that was easy to cause large spindle difference due to the manual installation,as well as crackers and accumulation of short fibers between S-shaped plates and middle rollers.In view of the above problems,combined with the advantage of double S soft drafting system that the distribution of the friction field in the main drafting zone was fully extended to the front jaw,this paper further explored a wave-shaped drafting device with integrating function.Thus the new spinning technology could exert its greatest advantage,which provided practical support for the research of drafting theory,popularization and application of double S soft drafting,and realized the technological innovation of the traditional double aprons drafting.