Weaving is the process of rewinding the twisted or simple yarn supplied by the spinning department to the weaving department into fibers that are suitable for the size of the shuttle and easy to weave.
If a general cotton textile factory produces low-grade fabrics, the weft yarn used is supplied from the fine yarn of the factory without going through the winding process, which is called direct weft yarn; The weft yarns used in woolen, silk, linen, and yarn dyeing factories all need to be rolled and re wound to form indirect weft yarns. In recent years, with the continuous development of production, the production of high-end fabrics has greatly increased, so many cotton textile factories often use indirect weft yarns.
By adopting the warp rolling process, the process performance of the yarn can be improved, and some defects, seed chips, and impurities on the yarn can be removed, thereby improving the quality of the weft yarn. At the same time, due to the high winding density after rewinding, which is about 120-150% of the direct weft yarn, this increases the yarn capacity of the fibers, reduces the number of weft changes on the loom, improves the efficiency of the loom, and reduces the number of weft changes and rewinding; And it can also reduce the occurrence of loom stoppage and weft defects in the fabric caused by weft changing. In addition, due to the tight winding and good forming, the occurrence of weft removal defects on the loom is also reduced.
The disadvantage of using indirect weft is that it increases the winding and weft rolling processes, thereby increasing the factory area and production costs. Whether to use the warp rolling process depends on the requirements of different varieties. At present, some weaving machines are equipped with a front end weft winding machine, which not only has all the advantages of connecting warp and weft, but also overcomes some of the disadvantages mentioned above, but the weaving machine cost is relatively high.
During the weaving process, when the tension of the weft yarn is too low and the twist of the weft yarn is too high When the elasticity is good and the anti twisting force is strong like polyester/cotton yarn, it may cause phenomena such as yarn shedding, yarn shrinkage, and loop formation. In order to avoid or reduce this drawback, in addition to reasonably reducing the yarn twist and increasing the tension during unwinding, methods such as wetting, heating, or a combination of both are often used to stabilize the yarn twist. This process is generally referred to as hot wet setting.
Under the action of heat and moisture, the rigidity of yarn decreases and its volume increases. For example, in an environment where the relative humidity increases from 45% to 100%, the volume of cotton yarn can increase by about 14%. The increase in volume is the increase in the diameter of the yarn, which increases the friction and interaction forces between yarns, thereby reducing the possibility of weft yarn shedding, weft shrinkage, and loop formation.
Appropriate moisture regain can reduce yarn shedding, but excessive moisture can deteriorate the physical and mechanical properties of the yarn, and form yellow stripes on the fabric, which can also cause difficulty in rewinding. So the wet treatment should be appropriate, otherwise it may lead to problems such as broken warp and thinning. The appropriate moisture regain for cotton weft yarn is 8-9%. The weft yarn from the textile factory usually has a moisture regain of only 5.6%, so it must be wetted before weaving in the factory, especially in winter.