How To Deal With The Three Jumps Defect Of The Shuttle Loom?

1. Start from the spinning and semi-finished product processes.
1. For the cleaning of fibers and debris, by adjusting the distance between the a036 and a076 dust brushes, the debris removal rate increased from 2.57% to 4.43%; for the combing process of fibers and debris, by adjusting the debris removal distance in the rear box, the debris removal rate decreased from 5.2% to around 6.5%. After the adjustment, the number of broken fibers and fibers on the surface of the yarn decreased, and the chances of intermingling during weaving also reduced, which could lead to a 20% to 30% reduction in "three jumps" defects.
2. The twill loom has strict requirements for the quality of the raw yarn. The shorter the unevenness of the yarn segment, the better. Generally, it should be within 3% to 4%. The yarn consistency CV value should be 20% to 25%, and the single yarn strength CV value should be 18% to 20%.
3. Improve the quality of the joint. The end length is generally 1.5mm to 4mm, which is the best. Special precautions should be taken for joints with a high twist to prevent the formation of small tangles.
4. The winding process must ensure "three functions", namely, the tension ring should rotate flexibly, the brake should operate smoothly, and the automatic stop function for broken yarn should be reliable. At the same time, the edge yarn should be slightly heavier to ensure uniform tension across the entire width of the yarn.
5. Improve the quality of the yarn coating, enhance the clarity of the warp yarn openings, and select the coating material and set the coating rate based on the fabric type. Generally, an 8% to 9% coating rate for linen-cotton fabrics can ensure that a smooth and wear-resistant coating film is formed on the surface of the warp yarns. Correctly control the moisture regain rate. In the weaving workshop, if the relative humidity is above 80%, the moisture regain of the yarn coating can be controlled at around 7% to 8%; reasonably control the elongation rate of the yarn coating, keeping the woven fabric at below 1%; and the elongation rate range should be around 10% to 15%, which can meet the requirements of the warping loom fabrics.
2. The timing of opening the mouth and inserting the sword should be appropriately coordinated.
The yarn skipping defects usually occur more frequently on the side of the weft insertion bar. Therefore, different configurations can be adopted to adjust the weaving parameters on both sides. Specifically, the insertion time of the weft insertion bar should be appropriately delayed, while the insertion time of the weft receiving bar should be appropriately advanced, so that the weft insertion bar can enter a clearer weaving opening.
For general cotton and linen varieties, the opening time should be 290° to 300°, and the entry into the loom should be 70° to 75°. When entering the loom, the position of the weft guide head should be 4 to 6 guide plate segments away from the wefting point, and the position of the guide head for joining the weft should be 2 to 4 guide plate segments away from the wefting point. It is also necessary to ensure a slow entry and a fast exit, so that the loom has sufficient time to pass through a clear loom path, thereby reducing the chance of yarn jumping.
III. After adjusting the position lines
Adjusting the height of the position line usually only involves adjusting the height of the stop frame and the rear beam. When the stop frame and the rear beam are raised, the tension of the upper and lower layers of yarns will increase. When the weft opening is full, the lower layer of yarns is tight while the upper layer is loose, which ensures the even arrangement of the yarns and results in a more full fabric surface.
If the height is set too high, the upper warp yarns will be too loose, causing the yarns to stick together and making the opening unclear, which may lead to star jumps. Generally, for cotton and linen varieties, the height of the rear beam is 70mm to 80mm, and the height of the stopper frame is 30mm to 40mm. Both ends should be kept level.
IV. Correct Specifications for Hoisting Lifting Rings
Generally, the lower warp yarns should be slightly lower rather than higher. It is best to start weaving with the needle tip so that it does not collide with the upper and lower warp yarns. For the upper shaft and maintenance work, the hanging loom frame needs to be adjusted to ensure "three alignments" - the loom frame is aligned, the treadle rod is aligned, and the tread plate and rotor are aligned. "Four levels of flatness" mean that the loom frame (warp beam) is flat, the hanging loom bolts are flat, the hanging loom plate is flat, and the treadle rod is flat.
If it is still不合格, then check whether the support clamp has fallen off, whether the top screw of the footplate is loose, whether the bearing pad of the lifting support is worn, whether the lifting belt is deformed, etc. Generally, the front and rear positions of the lifting support are about 110mm to 120mm, and the movement should not exceed 0.8mm. The height of the lifting support is 400mm to 410mm.
The above measures were tested on a GA747 loom for weaving 8s×8s 42×38 jute-cotton plain weave fabric. The loom efficiency was increased from 50% to 65%, and the "three-jump" defects in 90 meters of fabric decreased from 500 to around 200. These data were obtained through dedicated machine tracking.