Rapier loom is a kind of shuttleless loom, which is a relatively common loom for weaving small and medium-sized batches of fabrics with frequent changes in varieties. During the production process, rapier looms use high-speed weft insertion, and the consumption of rapier heads and rapier belts accounts for more than half of the total material consumption of rapier looms. Therefore, how to effectively avoid the wear of the rapier head and rapier belt is crucial to saving production costs.
1. Dangers of wear and tear
The rapier head and rapier belt are key components for the rapier loom to complete the weft insertion task. During the weft insertion process of the rapier loom, the weft yarn is always actively controlled by the rapier head, resulting in fewer weft insertion errors and high reliability. Once the sword head is worn, it will cause weft insertion failure. In severe cases, it may even cause a large number of warp yarn breakages, affecting the quality of the cloth surface.
Assuming that the loom is running at 400 rpm and 20 hours a day, the sword head reciprocates 960,000 times a day. The sword head will inevitably wear out during long-term operation. The parts of the sword that are most susceptible to wear are the head, wings and bottom. Every time weft is inserted, the sword head will be rubbed by the warp, sword guide hook, sword running plate and guide rail when the sword is advanced and withdrawn. When the two wings of the sword head are severely worn and form a knife edge, it is easy to cause warp yarn breakage, and even cause the sword head to jump out of the shed without being controlled by the sword guide hook, causing a large number of broken ends.
2. Causes of wear and tear
Production practice has found that most rapier head damage is due to fracture damage caused by the impact of the weft feeding rapier head and the weft receiving rapier head. This situation is due to the gap formed by the long-term wear of the transmission device and the rapier belt, which leads to the swimming misalignment of the rapier head. For example, the weft-feeding rapier head of the GA749 rapier loom is relatively wide, and its frame is made of plastic, so most of the damage is to the weft-feeding rapier head. Most sword head breakage occurs at the yarn-blocking and yarn-holding parts of the sword head.
The wear of the rapier head of the rapier loom is also closely related to the type of weaving. Different varieties have different wear conditions of the rapier head, and the differences are large. Fabrics with coarse yarn count and high warp density will have serious rapier head wear and short service life. The service life of the rapier heads of chemical fiber products is shorter. This is because the rapier head rubs and heats back and forth on the chemical fiber warp yarns, generating static electricity, which causes a layer of hardened material to condense on the bottom of the rapier head, which can easily hang up the warp yarns.
The sizing composition used in warp sizing also has a great influence on the wear degree of the rapier head. Different sizing compositions also have different effects on the wear of the rapier head.
The process structure of the rapier loom also has a certain relationship with the wear of the rapier head. In particular, the higher the height of the back beam and the greater the tension of the bottom warp, the more serious the wear of the rapier head will be. Because the tension of the lower warp yarn is large, when the shed gradually closes, the lower warp yarn lifts up, which increases the lifting force of the supporting sword head correspondingly. The squeezing friction force on the sword guide hook is greater, so the wear on the sword head is greater.
The transmission between the rapier belt and the rapier wheel of the rapier loom is a special belt transmission: there is a rectangular hole on the rapier belt. During the transmission process, there is meshing between the tooth root part and the rapier belt hole wall contact teeth. Transmission, and friction transmission in which the rapier belt and the inner surface of the rapier wheel are in contact; the meshing angle of the rapier belt to the rapier wheel is usually 120°~180°. When the pitches are equal, the rapier wheel and rapier There is no relative sliding between the belts, and the pitch circle linear speeds of the two are equal; when the rapier wheel makes a swing rotation, a reciprocating linear motion of the rapier belt is formed. Because the flexible composite belt has a certain rigidity, the rapier belt needs to withstand a certain bending stress when bending. Therefore, an arc-shaped pressure plate is designed to make the rapier belt move close to the surface of the rapier wheel. However, the use of the arc-shaped pressure plate makes the rapier belt The friction between the second half and the back part is greatly increased and becomes thinner.
3. How to prevent wear and tear?
The tightness of the time coordination between the rapier weft insertion movement and the warp shedding movement directly affects the wear of the rapier head. If the warp opening time is too early, the weft feeding rapier head will have less contact with the warp yarn, while the rapier head will have more contact with the warp yarn when retracting the rapier, so the rapier head will rub and squeeze more with the warp yarn; similarly, if the warp yarn opening time lags, the retracting rapier head will contact the warp yarn. It will be less, but the weft entry rapier head has more contact with the warp yarn, so at this time there will be more friction and extrusion between the rapier head and the warp yarn.
When selecting the sizing composition used for warp sizing, chemical sizing should be used to reduce the wear of the sizing on the rapier head, which can greatly extend the service life of the rapier head. At the same time, further research on the coating technology of the sword head and enhancing the wear resistance of the coating on the surface of the sword head are of great significance for extending the life of the sword head.
In the technical structure of the loom, if the height of the back beam is small, the wear on the sword head will be small. However, it is worth noting that proper elevation of the back beam is beneficial to improving the quality of the cloth surface. The clarity of the cloth surface texture and the peak and valley depth of the texture are much better than when the back beam is 1000 mm. Therefore, a reasonable back beam height should be determined. When weaving fabrics with higher warp density, the height of the back beam is generally about 1040 mm, so that the weaving can proceed smoothly.
The coating quality of the sword head is of great significance to the use of the sword head. When the sword head enters and exits the shed formed by warp yarns at high speed, the warp yarns generate alternating compressive stress on the surface of the sword head, causing fatigue wear and peeling of the coating. The peeled debris becomes very hard abrasive grains, which cause abrasive wear on the sword head under the action of the warp yarns. Over time, a height difference is formed between the base body and the coating and a cutting edge appears, causing the warp yarns to be cut and the machine to stop.
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