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Influencing factors of warp yarn tension
Machine tension refers to the static tension of healds at peacetime. It is the basis of warp tension in various periods and should be specified as a process parameter during machine operation. The tension on the machine will have a significant impact on the rate of warp yarn breakage, the clarity of the shed, whether the beating is smooth, and the appearance of the fabric. It is a process parameter throughout the weaving process. Therefore, in order to make the process go smoothly, improve production efficiency, and enable the fabric to obtain good internal and appearance quality, appropriate machine tension should be used. Proper tension on the machine can minimize the end breakage rate and make the fabric have better appearance effects and physical and mechanical properties. To determine the warp tension of the fabric, it should be based on the type of loom, the structure of the fabric and its quality requirements. It is necessary to consider whether the process is smooth or not. The quality of the weaving shaft and the uniformity of the warp tension should also be considered. Proper warp tension is a necessary condition for clearing the shed, tightening the weft and forming the fabric. The warp tension of the warp yarn in the weaving process consists of two parts: the machine tension and the weaving tension. On a running loom, the tension on the warp yarns gradually increases from the weaving shaft to the weaving mouth. The warp tension in the section from the heald frame to the weaving mouth is more than double the warp tension in the section from the weaving shaft to the back beam. The tension of the warp during the shedding process is the sum of the tension of the upper machine and the tension of the warp increased by the shedding movement. When the fabric is formed, the warp tension includes the sum of the machine tension, the shedding tension during the beating-up and the tension generated by the beating-up resistance during the beating-up. Shedding tension and the tension produced by the beating-up resistance during beating-up are cyclical changes throughout the weaving process. The tension on the machine is related to the type of loom, yarn quality and weaving process. 1. The influence of the type and mechanism of the loom on the tension of the warp yarn (1) Shuttle looms usually use the 'large shed, small tension' process, and the shuttleless loom requires a smaller shed height than the shuttle loom. Therefore, it is often necessary to adopt the 'small shed, high tension' process. (2) Projectile looms and rapier looms for weaving wide fabrics should use a larger upper machine tension. This is because the warp tension is large in the center and on both sides. If the tension of the upper machine is excessively reduced, the warp yarns on both sides of the loom must be unclear. (3) The jet loom is a passive weft insertion, and the high tension of the machine can improve the clarity of the shed and make the weft insertion smoothly. .Reduce the occurrence of weaving defects. In addition, the tension of the warp yarn on the machine should also vary with the form of the beating-up structure. For example, the connecting rod beating-up loom with a non-separated box seat has a large connecting rod beating-up stroke and a long front shed, so it is equipped with a 'large shed, lower tension' process, which is conjugated with the use of a separate box seat The cam beating-up loom adopts a 'small shed, high tension' process that is different, so attention should be paid. 2. The influence of yarn quality and weaving process on the tension of warp yarns (1) When the fabric warp density is large or the warp yarns are hairy, the tension of the machine should be increased appropriately to facilitate the opening of the shed. (2) The weft density is relatively large or For fabrics with many warp interlacing times, the machine tension should be appropriately increased to facilitate the tightening of the weft. (3) If the yarn density is small, the tension on the machine should be smaller; if the yarn density is large, the tension on the machine should be greater. (4) When the tension difference between the upper and lower warp yarns is large, the upper machine tension should be larger to prevent the upper warp from slack and unclear opening. (5) The warp quality is not good or the sizing quality is not good, the upper machine tension should be smaller. (6) The warp tension in the preparation process is relatively uniform, and the upper machine tension can be smaller to protect the warp yarn evenness. When the warp yarn tension is uneven, the machine tension should be increased appropriately to make the shed and the cloth surface even. 3. The influence of different types of fabrics on the tension of the warp yarn is generally not more than 30% of the breaking strength of the spun yarn on the single yarn on the loom. In order to meet the requirements of straight warp, warp and weft, and prominent particles in poplin, the tension of the upper machine should not be too large; but if the tension of the upper machine is too small, it will affect the evenness of the cloth surface, and the streak will be serious, and it is easy to produce Defects such as star jumps and warp shrinkage. Therefore, in production, the upper machine tension of poplin is generally slightly larger than that of plain cloth, but when the tension of the warp yarn in the preparation process is relatively uniform. The upper machine tension should be smaller under the condition of ensuring a clear opening. Generally, the cloth width (cloth width) on the machine is 4-6mm smaller than the standard cloth width. In order to make the fabric surface even and easy to tighten the weft, the tension of the warp yarn on the machine should be large. Generally, the fabric width on the machine should be 8mm smaller than the finished fabric width. Twill and khaki fabrics strive to be clear, that is, the twill must be deep (the warp and weft yarn has a large ratio of buckling wave height), uniform (equal distance between the twill), and straight (equal warp and float length). When the upper machine tension is small, the warp yarns are easy to bend and the lines appear deep, but when the upper machine tension is small, the uneven warp tension will not be improved, and the cloth surface will be uneven and the lines will not be straight. Therefore, the upper machine tension of twill and khaki fabrics should not be too small, and they are usually woven with a larger upper machine tension. Usually, the upper machine tension is 6mm smaller than the specification.
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