The economic benefits of weaving production are mainly reflected in the output of the loom, and the weaving speed and weaving efficiency of the loom are the two main factors that determine whether the loom can achieve high output. High-speed looms are the basis for enterprises to improve economic benefits, but high-speed looms may not necessarily achieve high benefits because benefits are also affected by weaving efficiency. Warp and weft fault shutdown of the loom is a key factor affecting weaving efficiency. For air-jet looms with high speed and high automation, weft fault shutdown has a particularly prominent impact on weaving efficiency. Only by reducing the weft stop of the air-jet loom can the weaving efficiency of the air-jet loom be improved and the high efficiency of the weaving production of the air-jet loom be truly realized. This article discusses the main reasons affecting the weaving efficiency of air-jet looms and measures to improve weaving efficiency by analyzing the fault shutdown of air-jet looms in actual production.
Although the weaving efficiency of the air-jet loom during the production process is not directly proportional to the ratio of weft stoppage to loom stoppage, the impact of weft stoppage on weaving efficiency There is a positive correlation, and weft yarn failure is the main factor affecting the weaving efficiency of the air-jet loom. According to research, the weft stop of air-jet looms accounts for about 60% to 85% of all stops of looms. However, due to the different raw materials and fabric structures used in various fabrics, the main causes of weft stop failures are also different. Table 1 shows the number of weft yarn failures per 100,000 picks of different types of weft finders. As can be seen from Table 1, for 1# polyester-viscose twill fabric, whether it is nozzle 1 or nozzle 2, the number of weft yarn faults detected by weft finder 2 is much more than that of weft finder 1. The former is on average more than 1.8 times that of the latter. . The weft faults detected by the weft detector 2 are mainly weft insertion anomalies such as broken weft and long weft when the weft flies beyond the specified position. Therefore, as far as polyester and viscose twill fabrics are concerned, weft yarn breakage is the main cause of weft yarn failure.
Observe and analyze the causes of weft stop failure caused by weft yarn breakage in the actual production process. The main reasons are: The reason is that the strength of the weft yarn is insufficient, especially because the weakly twisted parts and details of the weft yarn cannot withstand the large spray tension and are blown off, resulting in weft yarn breakage. The average single yarn strength of polyester/viscose (65/35) 16.4tex weft yarn is 11.76cN/tex, which is smaller than the single yarn strength of weft yarn used for air-jet weft insertion, which should be controlled above the limit of 12cN/tex, thus causing an increase in weft yarn breakage. Secondly, the main and auxiliary spray pressure of some machines is too high, and the weft yarn is blown off under the impact of high-speed airflow during weft insertion, causing weft stop failure. Especially when the unwinding is close to the bobbin foot and when the bobbin is full, the unwinding is not smooth, causing the weft yarn to break and the weft yarn to unwind from the bobbin at a fast speed, causing decoupling, causing weft breakage or long weft and weft stop.
It can also be seen from Table 1 that for most fabrics, the number of weft yarn faults detected by weft detector 1 is more than that detected by weft detector 2, especially for high-quality fabrics. The high-density polyester-cotton down fabric is more prominent. The former is on average 24 times more expensive than the latter. The least is cotton plain fabric, but it also reaches 1.5 times. The weft faults detected by the weft finder 1 are mainly weft insertion anomalies such as short weft and shrinkage and the weft flight does not reach the specified position. Therefore, in the case of these fabrics, pick-up is the primary cause of weft failure.
After observation and analysis, weft snagging is the reason why the weft yarn fails to reach the specified position and causes weft stop failure. Weft snagging is mainly caused by unclear opening and hairiness and yarn defects of the weft yarn. Secondly, the warp density of the fabric is too high, and there is a lot of friction between the warp yarns, which makes it difficult for the shed to open and trap the weft yarns. 3# cotton poplin uses two kinds of weft yarns. The weft yarn failures of short fiber yarns are far more than those of filament yarns, which is 13.9 times of filament yarn failures. This is due to more hairiness on the surface of short fiber yarns. Therefore, for this type of fabric, weft yarn defects and hairiness are the main causes of weft stop failure.
In addition, the tripping weft is related to the opening mode of the shedding mechanism and the formed shed. The 1# fabric weave is twill. When weaving with the cam shedding mechanism, the shedding mode is Fully open shed, the formed shed is clear, and the stability and clarity of the shed are better than other fabrics with plain weave. Therefore, for twill fabrics woven with a cam shedding mechanism, the main cause of weft stop failure is not unclear shedding, but broken weft yarns.
Through the analysis of parking failures of various types, it can be seen that it is necessary to improve The weaving efficiency of the air-jet loom should reduce the occurrence of weft breaks and weft snags. Therefore, the key to improving the weaving efficiency of air-jet looms is to improve the yarn quality and shed clarity of the weft yarn.
2.1 Measures to improve the quality of weft yarn
Although the main reasons for weft stop failure of different fabrics Not the same, but the occurrence of weft breakage and weft snagging are related to the yarn quality of the weft yarn, that is, to the strength, strong unevenness, hairiness, yarn defects, etc. of the weft yarn. Therefore, the strength and unevenness of the weft yarn should be strictly controlled, and we should learn from foreign countries.��Excellent slurry serves as the main adhesive. And when sizing, a wet twisting rod should be used to make the hairiness as close as possible to avoid the regeneration of new hairiness during weaving.
2.2.2 Optimized weaving process parameters
(1) Moderately increase the machine tension
The amount of friction and movement of the warp yarn in the heald eye during beat-up is inversely proportional to the tension on the upper machine. The tension on the machine is small, and the warp yarns are easily worn and fluffed in the heddle eye, causing unclear openings and resulting in weft snagging. And the warp yarns are excessively worn, causing end breaks to increase. Therefore, appropriately increasing the tension on the machine can reduce warp fluff, improve shedding clarity, reduce stops caused by weft snagging, improve uneven warp tension, reduce “three-jump” weaving defects, and improve weaving efficiency and quality.
(2) Appropriately reduce the height of the back beam
Using a high back beam can form an unequal tension shed with upper and lower tension, reducing the number of holes. The weft resistance is conducive to tightening the weft yarn, and can also cause the warp yarn to move sideways to eliminate square holes and reed marks. However, the higher the back beam is, the easier it is for the upper warp tension to be too small, resulting in unclear openings and weft snagging. Therefore, when the same fabric is woven on an air-jet loom, the height of the back beam should be appropriately lower than when produced on other looms.
(3) Increase the opening height and shorten the shed length
The larger the shed opening, the greater the warp elongation and tension. , the shed is clear, so it is conducive to the flying of the weft yarn and less weft snagging. And because the air-jet loom uses a small shed, its opening height is much smaller than that of the shuttle loom. Therefore, appropriately increasing the opening height will not cause warp yarn breakage.
The warp yarns are sent out from the weaving beam to form a fabric at the weaving mouth. Friction occurs between the warp yarns and between the warp yarns and the machine parts, causing the warp yarns to fluff and cause weft snagging. The friction of the warp yarns is mainly concentrated in the friction between the alternating warp yarns up and down in the opening part. Therefore, shortening the shed length can reduce the friction length of the warp yarn and reduce the fluffing of the warp yarn. At the same time, after the length of the shed is shortened, the length of the front part of the shed is also reduced while the front and rear symmetry of the shed remains unchanged. The shed formed by the same opening height will have a larger front shed angle, as shown in Figure 1.
As can be seen from Figure 1, the heald frame moves forward from position A to position B, and the shuttle The front length of the mouth decreases from LA to LB, and the front shed angle increases, that is, αB>αA. Therefore, shortening the length of the shed will not only help reduce the friction between the warp yarns and prevent the warp yarn from raising and causing the shed to be unclear, but also increase the space for weft insertion in the shed. Both can reduce the occurrence of weft snagging and improve the quality of the shed. Weaving efficiency of air-jet looms.
2.2.3 Reasonable selection of shedding mechanisms
The shed formed by different shedding mechanisms, Their shed stability and clarity are different. When a shedding mechanism with a fully open shed is used, not all warp yarns return to the warp position line in each shedding cycle. Instead, only the warp yarns that need to be displaced up and down are moved according to the lifting sequence, and the warp yarns that do not need to be displaced are moved. , then stay above or below the shed. Therefore, the warp movement of the fully open shed is less, the shed is relatively stable, and the warp yarns have less friction with each other, which is not easy to fluff. The shed is clear, which is conducive to the weft yarn passing through the shed and reducing weft snagging.
When weaving twill fabrics, the cam opening mechanism should be used as much as possible, because the opening mode of the cam opening mechanism is a fully open shed, and the shed formed is a clear shed. , the stability and clarity of the shed are better than those of the dobby opening mechanism and the jacquard opening mechanism.
3 Summary
The main factor affecting weaving efficiency is weft yarn failure , and weft breakage and weft snagging are the main causes of weft yarn failure. Only by reasonably improving and controlling the quality of the weft yarn, including the strength, hairiness, winding formation, etc. of the weft yarn, and rationally configuring the process parameters of the winding machine and the weaving process parameters, can we reduce the occurrence of weft breaks and weft snagging, and improve the quality of air-jet weaving. The weaving efficiency of the machine. However, for single weaving mills, due to the purchase of yarn for weaving production, it is difficult to control the quality of the weft yarn. Therefore, the focus of reducing weft stoppages should be on the reasonable selection of weaving production process parameters, improve shed clarity, and reduce The generation of weft. </p
