Weft winding is to supply the skein or simple yarn from the spinning department to the weaving department, and the weft winding machine rewinds it into fibers suitable for the size of the shuttle and easy to weave.
Generally, if cotton mills produce low-grade fabrics, the weft yarns used are supplied by the factory’s spun yarn without going through the weft winding process, which is called direct weft yarns; while the weft yarns used in wool, silk, linen and yarn-dyed factories all need to go through Weft winding, rewinding and forming, is called indirect weft yarn. In recent years, with the continuous development of production, the production of high-grade fabrics has greatly increased, so many cotton mills often use indirect weft yarns.
Adopting the weft winding process can improve the technological performance of the yarn, and can remove some defects, seeds and impurities on the yarn, 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 fiber and reduces the number of weft changes of the loom, which not only improves the efficiency of the loom, but also It reduces the return of weft change; and it can also reduce the stoppage of the loom and the weft defect of the fabric caused by weft change. In addition, due to tight winding and good formation, there are also fewer weft pick-off defects on the loom.
The disadvantage of using indirect weft is that it increases the winding and weft winding process, thereby increasing the workshop area and production costs. Whether to use the weft rolling process depends on the requirements of different varieties. At present, some looms have been equipped with a head weft winder, which not only has all the advantages of interlocking weft, but also overcomes some of the above-mentioned shortcomings, but the cost of the loom is relatively high.
In the weaving process, when the weft yarn tension is too small and the weft yarn twist is large, or when the weft yarn has good elasticity and strong reverse twist force like polyester/cotton yarn, weft detachment, weft shrinkage and looping may occur. In order to avoid or reduce this disadvantage, in addition to reasonably reducing the weft twist and increasing the tension during unwinding, wetting, heating or both methods are often used to stabilize the yarn twist. This process is generally called heat-moisture setting.
Under the action of heat and humidity, the yarn’s rigidity decreases and its volume increases. For example, when the relative humidity of cotton yarn increases from 45% to 100%, the volume can increase by about 14%. The increase in volume means that the diameter of the yarn increases, so the friction and interaction force between the yarn and the yarn also increases, which reduces the possibility of weft yarn delamination, weft shrinkage and looping.
Appropriate moisture regain can reduce weft slipping, but too much moisture will deteriorate the physical and mechanical properties of the yarn, and will form yellow stripes on the gray fabric, which will also cause difficulty in unwinding. Therefore, the wet treatment must be appropriate, otherwise it will cause disadvantages such as broken wefts and thinning. The proper moisture regain of cotton weft is 8-9%. The moisture regain of the weft yarn from the spinning mill is usually only 5.6%, so it must be moistened before weaving in the weaving mill, especially in winter.
Polyester fiber usually accounts for 65% in polyester/cotton weft yarn, so polyester fiber plays a leading role in determining yarn properties. For the polyester fiber with good elasticity and thermoplasticity, the relaxation process of its molecules can be accelerated by heating, so that it can achieve the purpose of stabilizing the twist of the yarn when it is recooled. The setting temperature should not exceed 100C, so as not to damage the strength of the yarn, and must not exceed the setting temperature of the printing and dyeing factory, otherwise it will affect the style of the final product. For polyester/cotton weft yarns, soaking and wet setting are also used instead of heat setting.
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Post time: May-26-2023
