What is self-twisted yarn?

Self-twisted yarn is another important new type of yarn. The key component of the self-twisting spinning machine is a pair of twisting rollers that rotate and traverse back and forth. One end of the two strands output by the front roller is held by the front roller, and the other end is held by the merging hook. In the middle of the two holding points, the strands are subjected to the false twist of the twisting roller, so that the beards on both sides of the twisting roller A twist in the opposite direction occurs on the strip.　　 Due to the continuous rotation and reciprocating traverse of the twisting roller, periodically alternate sections are formed on the two strands-Z-twisted zone, non-twisted zone and S-twisted zone.　　 When two yarns with the same twisting direction periodically and alternately meet at the merging hook, the self-twisting action takes place due to the respective untwisting moments, so that this area of u200bu200bthe two yarns is twisted together. When the areas with opposite twisting directions of two yarns meet at the merging hook, the untwisting moments in different directions cause the two yarns to twist in opposite directions, without self-twisting, forming a twist-free zone. When the twisted area of u200bu200bone sliver meets the untwisted area of u200bu200banother sliver, a weaker self-twisting effect occurs, forming a weakly twisted area, so the self-twisted yarn is a double-stranded yarn whose twist direction changes periodically. . The twist direction of the self-twisted yarn is opposite to the twist direction of the single yarn, and the fibers in the yarn are nearly parallel to the yarn axis.　　 Since the twist direction of the self-twisted yarn changes alternately, the reflection is inconsistent. Due to the presence of untwisted areas and large twist unevenness, the yarn strength is low. Before use, it is generally necessary to perform double-twisting on an ordinary yarn machine to produce twisted self-twisted yarn or self-twisted yarn with the same twist direction but large twist unevenness.　　 There are mainly self-twisting lines (ST line) and plus-twisting self-twisting lines (STT line). The latter is to use the self-twisting thread to add another twisting angle on the threading machine, so that the twisting direction of the whole line basically tends to be the same. There are also 2ST lines and (2ST) T lines, which are four-strand lines formed by merging two sets of self-twisting lines with a phase difference of 90°, or add weak twisting on the twisting machine. (ST) The 2nd line is the second self-twisting line, or the 3 strands of the second self-twisting line.　　 When a single filament is used to replace a single yarn in the self-twisted thread, STM thread and (STM) T thread can be formed. The characteristic of this kind of thread is that it can adapt to the fine pitch warp knitting machine. On the basis of the above, other varieties can be derived, such as color-spun blended thread and fancy thread.　　 The self-twisted yarn has a strong sense of wool, soft and full-feel, and good loop-forming performance. It can be used to produce weft-knitted chemical fiber wool-like knitted fabrics and colored fabrics, such as knitted outer clothing. Weaving yarns (especially warp yarns) need to be twisted and self-twisted, because the twisted and self-twisted yarn relies on the additional twist to make it strong and abrasion resistant, and can withstand the scraping of the reed and the shedding movement of the loom. The frequent stretching action of the yarn, and because the whole yarn is twisted in the same direction, it can improve the surface gloss of the fabric. When the additional twist is offsetting the twist in the opposite direction, there will be a short section of the double yarn parallel without twist on the self twist line (the double yarn still has a strong twist). This situation is called When 'dual' appears, the additional twist level at this time is called dual twist. There are too many dual sections on the twisting line, which will cause the illusion of 'bad evenness' on the surface of the fabric. Therefore, the actual additional twist level should slightly exceed the dual twist. However, if the additional twist is too much, the yarns will be tight, the fabric will be rough and hard, which will damage the hand and hair style, and the level of curved edge grinding will also decrease.　　 The automatic spinning machine is generally 4 to 5 heads/set, with a self-stop device for end breaks, and the splicing operation is relatively simple. Therefore, it is convenient to change varieties and is suitable for the production of small batches, multiple varieties, medium and dark colored yarns. However, self-twisted spinning cannot supply single yarn, and chemical fiber products are limited to wool-like products.　　 Since the twist of the self-twisted thread is not uniform throughout the body, it is easy to form a streak on the surface of the fabric. Article keywords: 　Self-twisted yarn