Twist: the twist angle of the yarn is one turn. The number of twists per unit length of yarn is called twist. The twist of cotton yarn in China adopts special number system, which is expressed by the number of twists within 10 cm yarn length; The twist of combed wool yarn and chemical filament is expressed by the number of twists per meter; In addition, there are English twists in twists per inch.
Twist factor: twist can not be used to compare the degree of twist of different yarn thickness, because the same twist, the inclination of coarse yarn is greater than that of fine yarn. In practical production, twist factor is often used to express the degree of twist of yarn. Twist factor is the relative value of yarn twist degree combined with linear density, which can be used to compare the twist degree of different thickness yarns. Twist factor can be calculated according to yarn twist and yarn linear density.
Twist direction: twist direction refers to the inclined direction of single yarn in single yarn or single yarn in strand after twisting. It can be divided into Z-twist and S-twist. After twisting, the twisting direction of the yarn inclines from the lower right corner to the upper left corner, and the direction of inclination is consistent with the middle of "s", which is called s-twisting or smooth twisting; The twist direction of yarn inclines from the lower left corner to the upper right corner, and the inclination direction is consistent with the middle of "Z", which is called Z twist or backhand twist. In general, single yarn usually adopts Z-twist and strand yarn adopts S-twist.
The twist direction of strands is indicated by the twist direction of successive twists. For example, if the single yarn is Z-twist, the first twist is S-twist and the second twist is Z-twist, the twist direction is represented by zsz.
The twist direction of yarn has a great influence on the appearance and handle of fabric. By combining the twist direction of warp and weft yarn with fabric structure, fabrics with different appearance and handle can be woven.
