The warp tension during weaving not only directly affects production operations but also significantly impacts product quality. Issues such as rib snagging, minor snagging, and single-sided snagging caused by manual pressing of the warp surface are all due to improper warp tension. Specifically, the impact of warp tension on product quality can be summarized in the following aspects:
1. Impact on decapitation rate
From the warp beam to the finished fabric, the warp threads undergo thousands of stretching and friction cycles through guide rollers, heddles, and reeds. Increased tension on the warp threads during weaving increases fatigue and can lead to breakage at weak points. Therefore, excessive weaving tension is a major cause of warp breakage. An experiment was conducted on a specific fabric, adjusting factors such as warp tension, heddle flatness, and warp position, reducing the warp breakage rate from 0.839 warp ends/machine hour to 0.175 warp ends/machine hour. Does this mean that lower weaving tension results in a lower breakage rate? Analysis shows that weft insertion on most fabrics is not at a 90° angle. Therefore, the weft insertion force can be decomposed into a force F along the fabric direction and a force f perpendicular to the fabric direction. When the weft insertion force remains constant, a decrease in warp tension will inevitably reduce the weft insertion force F along the fabric surface, thus increasing both the fabric formation zone and the weft insertion zone. This increases the friction between the warp yarns and the heddles, and also causes the warp yarns to become "stuck" in front of the reed, leading to more yarn breaks. Therefore, too little warp yarn tension on the loom is also detrimental to weaving.
2. Effect on fabric shrinkage
If the warp tension is high, during warp and weft interlacing, the warp yarns compress the weft yarns, causing the weft yarns to buckle more, thus increasing the internal stress of the weft yarns. When the fabric is wound into the take-up roller, especially after it comes off the machine, the warp tension disappears, and the weft yarns, due to the "resistance" of their internal stress, will exert a greater counter-pressure on the warp yarns, resulting in an increase in warp shrinkage and a decrease in weft shrinkage.
3. Effects on fabric feel and appearance
The tension of the warp threads on the loom has a significant impact on the feel and appearance of the fabric. If the warp tension is properly controlled, the fabric surface will be smooth and the weave will be clear, with a good feel. However, if the warp tension is too high, the fabric surface will not be full enough due to excessive stretching. Moreover, if the warp tension is too high, the fabric is likely to have "sparse edges".
