| Due to the problem of drafting type of traditional ring spinning frame,the back draft ratio is usually small,and the control of fiber is also weak,which seriously limits the improvement of the total draft ratio,while with the development of spinning equipment,more and more new drafting devices are used in the drafting mechanism of spinning,which not only strengthens the control of fiber movement,but also effectively improves the drafting efficiency.Therefore,this paper invents a new type of pressure bar and studies its application effect in back drafting zone,the purpose is to solve the contradiction that high-efficiency production and high-quality yarn cannot be achieved simultaneously in the spinning process,so as to lays a certain foundation for the development of "heavy weight,large drafting" efficient process.Firstly,the structure of the traditional pressure bar is innovated,and an embedded pressure bar with sinusoidal carding function is designed.The control mechanism of fiber motion in the process of sliver drafting is theoretically analyzed,and its control effect on sliver is further compared by finite element simulation analysis.The results show that the sinusoidal microstructure of the pressure bar can increase the contact area of the sliver,and can separate the sliver into multiple micro units to sort out the arrangement state of the fibers,so as to realize the omni-directional and accurate control of the fiber movement.The simulation results show that,compared with non-pressure bar and traditional pressure bar,sinusoidal pressure bar can significantly improve the control stress of sliver with the increase of drafting force,and the control stress of sliver is the largest under the same drafting force;Secondly,the spinning technology of adding double pressure bar in back drafting zone is discussed.When the drafting multiple changes,sinusoidal pressure bar is used for spinning comparison experiment with non-pressure bar and traditional pressure bar.The results show that whether it is the change of back draft ratio changes or the change of total draft ratio changes,when the back draft ratio is small(1.2-1.8),the traditional pressure bar is slightly better to improve the yarn evenness and slubs,while when the back draft ratio is large(2.1-3.0),the embedded pressure bar is better to improve the yarn evenness and slubs.The improvement of hairiness is not obvious,but the improvement of strength is more obvious,and the improvement effect of traditional pressure bar is better.However,in general,the embedded pressure bar can greatly improve the yarn evenness and reduce the number of slubs while ensuring that hairiness and strength are not deteriorated,or even improved;Finally,the control effect of the thermal-softening characteristics in back drafting zone and the additional friction field of the pressure bar on the fiber is studied.Firstly,the thermal properties of the cotton fiber are characterized,and then the performance of the traditional pressure bar and the embedded pressure bar are improved,A thermal-field pressure bar which can heat the sliver on line is designed,and the spinning comparison experiment was carried out using it with non-pressure bar,traditional pressure bar and embedded pressure bar.The results show that when the total draft ratio increases and the back draft ratio changes,the thermal-field pressure bar improves the yarn evenness and yarn defects most obviously,and the higher the heating temperature is,the better the improvement effect is.Compared with the traditional thermal-field pressure bar,the sinusoidal microstructure structure on the surface of the embedded thermal-field pressure bar is more conducive to the control and deformation of the fiber,so it can greatly reduce the CVM value of the evenness and reduce the formation of yarn defects,but the back draft ratio should be small,otherwise it will have a certain impact on the hairiness and strength. |
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