Twisting yarn refers to the relative rotation of the two cross sections of the yarn, when the fibers in the yarn that are parallel to the yarn axis incline into helix. For short fibers, twisting is mainly to improve the strength of the yarn. The twisting of filament can not only improve the yarn strength, but also produce three-dimensional effect. The amount of yarn twist and the combination of twist direction and twist in fabric have great influence on the appearance and performance of products. Therefore, the price of twisting yarn is higher than that of the original drawing yarn. Twist direction refers to the inclined direction of single yarn in single yarn or single yarn in strand after twisting. There are two kinds of S-twist and Z-twist, S-twist = free hand twist and Z-twist = backhand twist. Any single strand has a twist
