Prevention and treatment of defects in elastic denim weaved by air jet loom
Priority should be given to the flying conditions of the weft yarn. For example, if the opening is increased, the height of the heald frame should be as high as possible to ensure that the upper warp yarn is tangent to the upper edge of the special-shaped reed. The edge yarn should be threaded inside 1 or 2 heald frames, and the shed should match the ground weave shed (that is, the upper and lower warp yarns are on the same plane when the shed is fully open), because when the weft yarn enters and flies out, it is Use edge yarn shed. This measure can prevent weft shrinkage, bad edges and double weft defects.
1. Adjustment of loom technology
Priority should be given to the weft yarn flying conditions, such as increasing the opening amount, and the height of the heald frame should be as much as possible to ensure that the upper warp yarn is tangent to the upper edge of the special-shaped reed. The edge yarn should be threaded inside 1 or 2 heald frames, and the shed should match the ground weave shed (that is, the upper and lower warp yarns are on the same plane when the shed is fully open), because when the weft yarn enters and flies out, it is Use edge yarn shed. This measure can prevent weft shrinkage, bad edges and double weft defects.
2. Control of raw yarn quality
Weft yarn quality, especially its evenness and draft ratio, need to be strictly controlled to avoid weft shrinkage defects. When the weaving width is 1650mm and the drafting ratio is less than 3.5 times, the drafting force is easily satisfied. When it is greater than 3.5 times, weft shrinkage defects are easy to occur.
3. Adjustment of the weft yarn condition
On the premise of ensuring that the hardness of the yarn stored in the weft feeder is appropriate, the unwinding tension of the weft yarn should be as small as possible, and observe whether the length of the waste edges on the fabric is the same. Use weft yarn braking to reduce the peak value of weft insertion tension. The distance between the two main nozzles should be such that the weft yarn arrives early. This prevents double weft and weft shrinkage defects.
4. Selection of stretching nozzle
Use a straight-pull nozzle, add a stop in front of the special-shaped reed, or add a thin iron pick on the stop and put it inside the reed teeth. Increase the stretching effect. Vertical jet or suction stretching nozzles can also be used. In comparison, the suction type has better effect, strong variety adaptability, and fewer bad edges and defects. To minimize the static air flow and reduce the damage to the weft yarn, a yarn clamp can be used to prevent the main nozzle weft yarn from retracting and causing bad edges.
5. Setting of auxiliary nozzles
The auxiliary nozzles should be arranged at the same spacing to prevent the generation of turbulence. The injection range and pressure of the nozzle should be appropriate. When observing the flight curve, it should be as straight as possible, and the arrival time should be stable. This measure can prevent and cure double weft, bad edges and weft shrinkage defects.
6. Adjustment of the distance of the weft finder
The distance of the weft finder should be appropriate. The weft finder should be at a certain distance from the edge yarn (usually 10mm) to prevent damage and mistaking the warp yarn for the weft yarn. . In the absence of hundreds of feet, the sensitivity or level value of the second weft finder can be lowered, and the distance between the two weft finders can be appropriately lengthened to 160mm to reduce false detections. This measure is beneficial to preventing and treating driving marks.
7. Prevention and treatment of driving marks
The prevention and control of driving marks is a complex process. The height and depth of the back beam, opening time, opening size and heald frame height can be adjusted; weaving can also be used Port control, warp beam reversal or forward rotation, empty beat-up and other functions. Due to the uncertainty of the downtime and heald frame position during shutdown, the adjustment process becomes difficult and the effect is not good. In practice, the method of using a frequency converter with stepless beat-up force and a single weft start can effectively solve the problem of driving marks. In addition, improve the operating level of the operator, keep the equipment clean and in good working condition, so that the equipment efficiency is above 96%, which can well meet the quality requirements.
When weaving stretch denim with an air-jet loom, it is affected by various factors. Weft defects are prone to occur and cause downtime, thereby reducing the efficiency of the loom and affecting the quality of the fabric. In view of the four main weft defects that occur during the weaving process, reasonable prevention and control measures are proposed through practice from the aspects of raw material quality, loom status and process design, which are important for optimizing the weaving process, improving loom efficiency and product quality. practical significance.
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