As one of the mainstream shuttleless looms in modern textile enterprises, the rapier loom is widely used due to its strong adaptability to varieties and stable and reliable weft insertion.
However, in the actual production process, the problem of weft breakage has always been a key factor affecting the efficiency of the loom and the quality of the product. Weft breakage in rapier looms refers to the phenomenon where the weft yarn breaks or the weft insertion fails during the weft insertion stage of weaving, causing the loom to stop automatically. According to the location and manifestation of the weft breakage, it can be divided into three major categories: weft breakage at the weft storage device, weft breakage at the weft guide plate, and weft breakage inside the weaving area.
1. Weft breakage at the weft storage device:
Weft breakage at the weft storage device mainly includes weft breakage at the tensioner behind the weft storage device and weft breakage on the weft winding drum of the weft storage device.
It is usually related to poor weft yarn unwinding and poor weft yarn quality. 1.1 Weft breakage at the tensioner behind the weft storage device: This type of weft breakage is mainly caused by poor weft yarn unwinding and poor weft yarn quality, and can be divided into the following situations.
Tube bobbin issues. Poorly formed tube bobbins cause the yarn to not come off the bobbin smoothly during unwinding or get caught on the bobbin, leading to the weft yarn being pulled apart. Solution: Replace with well-formed tube bobbins. For some long filament weft yarns, due to their smooth surface, they tend to slide down and come off the bobbin during unwinding, causing entanglement and the weft yarn to be pulled apart; Solution: Cover the bobbin with a plastic bag or elastic sleeve to eliminate the unwinding air ring and yarn slippage. Additionally, the joint may have come apart -> Check the joint quality, the tube bobbin may be overly fixed or the weft yarn may not be correctly positioned in the weft tensioner of the weft storage device. The quality of the empty tube bobbin.
The storage roller, tensioner and the position of the spindle. If the three are not on the same straight line, it is likely to cause poor air ring formation during the winding of the weft yarn and result in the yarn hanging on the cylinder or the tensioner; the distance between the storage roller and the spindle should be moderate. If the porcelain eye of the tensioner is damaged or there are damages on the cylinder, it is also likely to cause weft breakage.
Weft yarn quality. Poor weft yarn joints and weak twisting often cause breakage during rewind. 2. Weft yarn breakage on the winding drum of the weft storage device. Poor weft yarn joints and weak twisting often lead to weft breakage. Solution: Replace the weft yarn with qualified ones. Adjust the feeding tensioner according to the type of yarn to prevent excessive tension or tension deficiency. Short fibers and long filaments > 20 tex: Metal; Long filaments < 20 tex: Ceramic; High-twist yarn: Encircling type or revolving type; Decorative yarn + Shetland wool yarn: Tension plate; Check the maximum speed of the weft storage device: Fragile yarns (wool, high-twist yarns, silk) are set at 800 rpm, while other yarns are set at 1200 rpm. Set the direction of the weft storage device = the yarn twist direction. Especially for wool yarns, if there are yarn loops between the storage drum and the yarn tensioner: Adjust the tensioner flex/bristle closer to the storage drum. Weft storage device winding drum has burrs or the guide for weft shedding is deformed and the weft winding disc is damaged, which can cause weft breakage during winding and rewind. Use fine sandpaper to repair the yarn drum, replace the deformed guide for weft shedding and damaged winding disc.
3. Weft breakage at the tension head of the weft storage device, weft breakage at the yarn tension plate. Check if the tension is too high:
The normal value for wool and fine yarns is 20 cN, for coarse yarns it is 40 cN. Check if the E-flex (tension disc) or tension plate type tensioner is damaged. Use the correct type of tensioner: It is best to use a brush + tension plate (select the S or Z direction of the brush according to the yarn twist direction, use a brush in the center direction for coarse yarns). If there is debris accumulation, clean the storage drum (color yarn or high-twist yarn). Disk-type tension head has accumulated cotton dust, which can easily cause the moving plate of the tension head to be unresponsive, resulting in weft breakage; It is necessary to promptly clean the tension head adjustment spring and select the appropriate tension head spring to ensure the appropriate weft tension. The tension plate of the sheet-type tension head has worn grooves or feather-like debris at the yarn clamping area, which can also cause weft breakage during weaving. It is necessary to promptly replace, clean the tension plate, and select the appropriate tension plate to ensure the appropriate weft tension.
4. Weft loops fall off from the weft storage device. Check the input tension. If weft yarns with a lot of flying yarns are woven, increase the spacing of the weft loops on the storage drum:
The button (indicated by the red arrow) will move the yellow circle next to a (green) scale, adjust the reed to a more horizontal position, and reduce the speed of the less frequently used channels in the irregular color patterns: this can reduce the number of stops. Ensure that there are enough yarn loops on the yarn storage drum to facilitate acceleration
5. The warp yarn on the yarn storage drum is pulled out too much or the yarn storage is excessive
Adjust the spacing between the yarn loops on the yarn storage drum (for filament yarn it is 0.5mm, for wool yarn it is 1mm) - the button (indicated by the red arrow) will move the yellow loop to an adjacent (green) scale if a photoelectric sensor is used - emptying/retaining warp excess: Fine warp yarn -> Check the sensitivity of the yarn (whether it reflects light) and whether there is any oil contamination? If necessary, replace the sensor's porcelain eye. If a mechanical sensor is used - Check if the sensor is clean: The middle sensor should be able to move freely up and down, check the maximum speed of the retaining loom (for sensitive yarns such as wool yarn, high-twist yarns and silk it is 800rpm, for other yarns it is 1200rpm) and acceleration, if possible, increase the speed, check if the retaining loom is working correctly: Communication is normal. 2 Warp yarn guide plate breakage
1. Left guide head yarn clamping is poor The left guide head yarn clamping device holds the yarn unstable, the analysis is that the lower yarn clamping plate is loose, the rubber pad block is de-gummed or falls off, or the upper yarn clamping device pressing plate is deformed, the cutting time of the yarn is an important cause of yarn breakage, it needs to be repeatedly tested and carefully adjusted. The yarn hanging position behind the left guide head, after long-term use, will be worn by the rear yarn guide rod or collide with the right guide head, causing damage, resulting in the yarn not being able to enter the yarn clamping plate or not being in the normal position, causing yarn breakage or failure of connection, forming yarn breakage. Solution: Repair, polish or replace the left guide head, at the same time check and adjust the yarn guide rod and the junction position of the guide head.
2 Incorrect selection of the guide finger position The height of the selection guide finger is too high, which is likely to cause yarn breakage. The height of the selection guide finger is too low, which is likely to cause double yarn. Solution: Adjust the height of the selection guide finger, so that when the selection guide finger is at its lowest position, the yarn hole is 2mm to 3mm away from the yarn guide rod and 5mm to 7mm below the yarn guide rod, ensuring that the yarn is stable when the guide head clamps the yarn; at the same time, ensure that the yarn does not rub against the frame.
3 Position of the warp yarn guide plate The position of the warp yarn guide plate is very important, too close to the teeth, it is likely to cause friction between the teeth and the warp yarn guide plate at the moment of weft breaking, causing the warp yarn to be broken, forming yarn breakage; too far from the teeth, the warp yarn cannot smoothly enter the hook of the guide plate, and during the weft cutting, it is likely to cause cutting failure and the warp yarn not entering the cutting position, forming yarn breakage. The height of the warp yarn guide plate needs to be strictly set, too high will cause the warp yarn not to be able to enter the hook of the guide plate, too low will cause the warp yarn to collide with the cutting blade of the cutting device when cutting, unable to perform cutting smoothly, forming yarn breakage. The correct position of the warp yarn guide plate should be 1mm away from the cutting blade, 1mm away from the teeth edge, the blade groove is slightly higher than the cloth plate 1mm, to ensure that the warp yarn can be correctly and smoothly entered into the warp yarn guide plate during weft breaking, weft drawing and cutting.
4 Warp yarn cutter
If the position of the weft cutting knife is not adjusted properly, it will cause the weft to fail to enter the cutting slot, preventing it from being cut smoothly, resulting in weft breakage. The adjustment method is as follows: First, turn the main shaft of the loom to 30°, loosen the locking screw of the weft cutting cam, adjust the lower knife to the lowest position, loosen the locking screw on the knife arm, adjust the distance between the lower blade and the green velvet fabric to 5 mm, and the distance between the upper knife blade and the green velvet fabric to 20 mm. Then, make fine adjustments according to the cutting time. Whether the weft can be cut smoothly and whether the cutting head can properly grip the weft depend not only on the reasonable cutting time but also on the good coordination of the cutting knives. If the knife coordination is not good, the weft cannot be cut smoothly, resulting in weft breakage or damaging the cutting head and machine parts. After adjusting the position of the cutting knives, the coordination of the two blades should also be adjusted.
Weft breakage in the weaving area In the weaving process, sometimes there will be a situation where the weft breaks inside the weaving area after the machine stops, but the system shows a situation of weft breakage and machine stop. This is often caused by the incorrect detection of the weft. To address this issue, we need to conduct a series of checks and adjustments. First, ensure that the cam position of the weft detection photoelectric tube is correct. By turning the main shaft of the loom, align the tip of the right cutting head with the last yarn on the fabric edge, and adjust the separation position of the cam sensing piece and the photoelectric tube.