The quality of blended yarn depends on the uniformity of the blending of the multi-component fibers in the yarn, and sliver blending is a process necessary for mixing fibers. The movement of fibers directly affects the distribution and mixing of fibers in the sliver. In this paper, the sliver blending process was simulated, and a method for the evaluation of sliver blending irregularity was proposed. The effects of passages of drawing and blending ratio on the sliver mixing uniformity were studied and verified both by experiment and simulation. The results show that the blending irregularity decreases gradually and tends to be stable with the increase of the passages of blending drawing. The more similar the blending ratio of the two components with approximately equal linear densities, the easier it is for the component fibers to mix evenly in the sliver. The simulation results are in good agreement with the measured values and previous research results. In addition, the blending irregularity of fiber components in the blended sliver can be predicted by the simulation method.
Frictional force distribution in the drafting zone is a key factor to control the fiber movement during drafting, and hence to determine the quality of the drafted strands. The frictional force is usually expressed by pressure acting on the strand or fibers in the drafting zone. In order to investigate the pressure distribution in the drafting zone, a device was designed with a film pressure sensor, by which the pressure distribution in different drafting forms and drafting parameters was measured. The effects of drafting parameters, such as the linear density of the strand, roller settings, etc., on the pressure distribution were discussed.
Double apron drafting is the general drafting form in the front zone of the ring spinning frame. In the double apron drafting system, the top apron and the bottom apron form an elastic tensor gauge, which can better control the movement of floating fibers and improve yarn quality. In order to investigate quantitatively the influence of the top apron and bottom apron on fiber movement and yarn quality in the double apron drafting system, the differences of fiber acceleration point distribution, yarn irregularity and yarn strength spun by double apron drafting, single apron drafting and simple roller drafting under different process conditions were compared. Compared with simple roller drafting, double apron drafting and single apron drafting can effectively control the fiber movement in the drafting zone. With the increase of fiber length, the difference between the distribution of fiber acceleration points obtained by double apron drafting and that obtained by single apron drafting gradually decreases. When the fiber length is greater than 32 mm, the difference is small. Besides, by analyzing the improvement rate of the top apron and bottom apron on yarn irregularity and yarn strength under different drafting settings, it was found that the overall improvement rate of the bottom apron on the yarn quality was higher than that of the top apron, especially for manmade fiber yarns. Even in some cases, the strength of viscose yarn spun by the single apron drafting process is higher than that of the double apron drafting process.
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