Influencing Factors of Warp Upper Machine Tension

The tension on the machine refers to the static tension of the heald, which is the basis of the tension of the warp in each period, and should be specified as a process parameter when the machine is on. The tension on the machine will have a significant impact on the warp breakage rate, the clarity of the shed, whether the beating is smooth or not, 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 the production efficiency, and enable the fabric to obtain good internal and external quality, appropriate tension on the machine should be used. Appropriate tension on the machine can minimize the breakage rate and make the fabric have better appearance 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 goes smoothly or not. It is also necessary to consider the quality of the weaving shaft and whether the warp tension is uniform. Proper warp tension is necessary for shedding, weft tightening and fabric formation. The warp yarn tension in the weaving process consists of two parts: the upper machine tension and the weaving tension. On a running loom, the tension on the warp yarns increases gradually from the weaving shaft to the weaving fell. The warp tension from the heald frame to the weaving fell is more than double the warp tension from the weaving shaft to the back beam. The tension of the warp during the opening process is the sum of the tension of the upper machine and the tension of the warp due to the opening movement. The warp tension during fabric formation includes the sum of three parts: the upper machine tension, the opening tension during beating, and the tension generated by the beating resistance during beating. The opening tension and the tension caused by the beating-up resistance during the beating-up change periodically during the whole weaving process. The upper-machine tension 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 on the warp yarn (1) The shuttle loom usually adopts“Large shed, small tension”The shed height of the shuttleless loom is smaller than that of the shuttle loom, so it is more necessary to use“Small shed, high tension”Process (2) Gripper 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 small on both sides. The side warp must be clearly opened (3) The jet loom is a passive weft insertion, and the use of high tension on the machine can improve the clarity of the shed, make the weft insertion go smoothly, and reduce the occurrence of weaving defects. In addition, the tension on the warp yarn should also change with the form of the beating-up structure. For example, the connecting rod beating-up loom with non-separated box base is equipped with a large beating stroke of the connecting rod and a long front shed.“Large shed, less tension”process, which is similar to the conjugate cam beating-up loom with separate box base, which adopts“Small shed, high tension”The process is different and attention should be paid to it. 2. The influence of yarn quality and weaving process on the tension on the warp yarn (1) When the warp density of the fabric is high or the warp yarn hairiness is large, the tension on the machine should be appropriately increased to facilitate the opening and cleaning of the shed (2) The weft density is relatively large or For fabrics with many warp staggers, the tension on the machine should be appropriately increased to facilitate tightening the weft. (3) The yarn linear density is small, and the tension on the machine is smaller; the yarn linear density is large, and the tension on the machine is large. (4) When the tension difference between the upper and lower warp yarns is large, the tension on the upper machine should be larger to prevent the upper warp yarn from loosening and the opening is unclear. (6) The warp tension in the preparation process is relatively uniform, and the tension on the machine can be smaller to protect the warp evenness. When the warp tension is uneven, the tension on the machine should be appropriately increased in order to open the shed and make the fabric even. 3. The influence of different types of fabrics on the tension on the warp yarn Generally, the tension on the single yarn on the loom is not greater than 30% of the breaking strength of the spun yarn. In order to meet the requirements of straight warp, warp and weft and prominent particles, poplin should not have too much tension on the machine; but if the tension on the machine is too small, it will affect the evenness of the cloth surface, and the streak will be more serious, and it is easy to produce due to the large warp density. Star jump, shrinkage and other defects. Therefore, in production, the tension of the poplin on the machine is generally slightly larger than that of the plain cloth, but when the tension of the warp yarn in the preparation process is relatively uniform, the tension on the machine should be smaller under the condition that the opening is clear. Generally, the cloth width on the machine (the width of the cloth) is 4-6mm smaller than the standard cloth width. In order to make the fabric even and easy to tighten the weft, the tension of the warp yarn on the machine should be large. Generally, the width of the fabric on the machine is 8mm smaller than that of the finished fabric. Twill and khaki fabrics strive for clear twill lines, that is, the twill lines are required to be deep (the ratio of warp and weft buckling wave heights is large), uniform (the twill should be equidistant), and straight (the warp and float lengths are equal). When the tension on the machine is small, the warp yarn is easy to bend, and the lines appear deep, but when the tension on the machine is small, the uneven tension of the warp yarn cannot be improved, which will make the cloth surface uneven and the lines not straight. Therefore, the tension of the twill and khaki fabrics on the machine should not be too small, and it is usually woven with a larger tension on the machine, and the width of the fabric on the machine is usually 6mm smaller than the specification. If the warp tension is uniform and the winding is uniform, a smaller upper machine tension can be used. For various chemical fibers and blended fabrics, the tension of the machine used should be treated differently according to their fiber characteristics. Viscose fiber fabric: The recovery coefficient of viscose fiber after stretching is low, and the process configuration of small tension should be adopted in weaving. Polyester-cotton blended fabrics: The weft shrinkage of polyester-cotton blended fabrics is larger than that of pure cotton fabrics. Therefore, the tension on the warp yarn should be slightly smaller than that of pure cotton fabrics, but it should not be too small, because the polyester-cotton grip spinning yarn sticks when opening. If the phenomenon is serious, if the tension on the machine is too small, there will be three jumps and breakage defects. Cotton stick fabric: The general parameters can be the same as those of pure cotton fabric. If the tension on the machine is too high, it will increase the friction damage of the warp yarn and affect the uniformity of dyeing. For high-purple density dimensional/cotton khaki, the tension on the machine can be the same as or slightly larger than that of pure cotton fabrics to reduce the sticking phenomenon of the shed.