Drafting Mechanism Of The Roller Drafting System Under The High Frequency Micro-undulating Vibration

The strand drafting is the basic technology of staple yarn manufacturing on the drawing frame, roving machine and spinning frame. In the roller drafting system, the drafting wave caused by floating fibers has being the bottleneck of modern textile technology, which affects the strand uniformation and the fabric's quality. It's the important task to minimize drafting waves in mordern textile manufacturing.Based on the hypothesis to minimize the drafting wave with the high frequency micro-undulation vibration, this project focuses on the system including roller drafting device, staple fiber stand and high frequency undulation vibration, and developes following research and experiment:1) Based on the theory of friction and the fiber's friction characteristic, the model of fiber's friction coefficient with the influence of a high frequency micro undulation motion is established, and the controlling factor of friction coefficient is deduced. It is shown that the high frequency undulation motion could weaken the bonding in the fiber bundles, reduce the the contacting areas between fibers and change the fiber's contact state in which dynamical friction is priority to static frictional, and reduce the friction coefficient between the fibers.2) According to the conventional drafting mathematical models of roller drafting system, the theory of fiber's evenness and the theory of drafting force, the project has improved the mechanical model of fibers during drafting pulled out from the fiber strands by friction with the roller surface, and the drafting force model to attenuate the strands.3) Based on the hypothetical ideal drafting conditon, the different fiber distributions in draft area are sorted; the lengths and quantities of three kinds of fibers are given, and the program of randomized sampling is present to simulate the random process of fiber distribution in fiber bundles. The theoretical model of drafting force subjected to the high frequency micro-undulation vibration is deduced on the assumption that the relative velocity between the fibers was the main factors affecting the friction coefficient.4) With the help of the roller drafting system which can be imposed high frequecy micro-undulation and test drafting force online, several strand samples and some drafting controll factors are considered in the drafting experiment. The fiber's behavior during drafting with high frequecy micro-undulation motion is observed with the drafting force curve, micrograph and the measuring instrument of strand uniformity.It is shown by theorical analysis and experiment that with the influence of high frequecy micro-undulation vibration, the fiber's friction coefficient can be weakened; the drafting wave can be minimized while the strand's uniformation is improved effectively, but the change of fiber's straight state is uncertain.This project has extended the fiber's motion theory in roller drafting, and got some principium conclusion. However, during the theory analyzing, some factors such as fiber's curl state haven't considered, and the precision of roller drafting experiment system is need to be improved.