Comparative analysis on friction fields derived from different bottom pins in the drafting system of ring spinning and their effects on yarn properties

In the drafting process, the strength and distribution of the friction field determines the fiber movement state, affecting the yarn formation process and yarn properties directly. The bottom pin, as an important part in the drafting zone, forms an elastic friction field with the top pin through the apron, which has an important influence on yarn properties. This work is aiming to compare the different friction fields generated by two bottom pins and its mechanical effect on fibers, revealing the influence of the friction field on the quality of yarns with different counts. Theoretical and experimental results show that a larger and stronger friction field was formed by the smaller surface curvature and flatter transition level of bottom pins, imposing a positive effect on the yarn evenness and strength. The difference in evenness between yarns spun with the two types of pins vary from 4.3% to 9.8%, while the yarn spun with a flatter bottom pin has higher strength (maximum difference to 17.1%). This study on the influence of the friction field on yarn properties can clarify the adaptability of different bottom pins for the production of different yarn counts, showing great significance on the actual control of yarn properties and property improvement.