What five factors affect the quality of air-jet spinning?

In the air spinning process, the following tasks are mainly completed: opening and drafting the cotton sliver into a single fiber state; removing impurities from the feed raw materials; uniformly mixing the fibers; Forming whiskers; condensing fibers; improving uniformity by combining; twisting; winding.

From Theoretically, during air-jet spinning, a single fiber condenses into a fiber ring in the condensation groove of the rotor, and then the fiber ring is pulled up in the opposite direction. However, in fact, fiber hooks will be produced during this process due to other reasons. , fiber loops, fiber sheets and other deformations, which greatly affect the quality of air-jet spinning. The quality of the finished yarn is affected by the quality of the fed sliver, which is mainly affected by the length, length uniformity, fiber fineness and impurity content of the sliver fiber. On the other hand, the better the separation state of the fibers during the conveying and cohesion processes, the better the yarn quality. The quality of sliver is controlled by the pre-spinning process. Carding is a key process of open-end spinning. It mainly removes impurities, carding and evenly mixes the feed raw materials. Therefore, adjusting the carding process parameters has a great impact on the quality of sliver, and then Affect yarn quality.

Cylinder, cover plate and doffer play an important role during carding. When the cylinder arrives at the doffer with a layer of fiber, the end of the fiber touches the surface of the doffer and is grabbed by the doffer card clothing while the other end is still held by the cylinder card clothing. When the cylinder passes through the transfer area, due to its very high surface speed High, the fibers are pulled by the doffer wire and generate tension. This cohesion makes the fiber amount per unit area of ​​the doffer 2 to 3 times that of the cylinder unit area. If the doffer speed increases, more needle teeth can participate in carding. The aggregation effect increases due to the increase in the doffer speed. Even if the linear speed ratio of the cylinder and the doffer surface decreases, the fiber transfer effect will also increase. However, if the doffer speed If it is increased too much, the cohesion effect will be reduced, and the transfer effect is closely related to the formation of fiber hooks. When other parameters remain unchanged, increasing the output by increasing the doffer speed will increase the needle surface load of the cylinder, which will increase the neps and reduce the evenness of the card sliver. Therefore, the yarn quality will deteriorate, that is, the U% value will become larger. , the strength and appearance grade of the yarn will decrease significantly.

By adjusting the flat speed or flat flower content, better quality slivers can be produced by mixing cotton rolls with average quality. When all other parameters remain unchanged, only the cover is increased If the plate speed is increased, the flat pattern will increase. At the same time, due to the enhanced carding effect, the impurities in the card sliver will be reduced, and the short pile will also be reduced. The strength of the yarn can be improved, but the strength CV% value will decrease and the measured yarn The number of defects and the U% value remain unchanged, so the quality of the yarn and the appearance of the fabric are improved.

The length of the fiber plays a different role from its role in ring spinning. The fiber length has the following relationship with the diameter of the rotor cup: diameter of the rotor = hand-pulled length of the fiber * 1.2. The twist is transmitted downward to a special point in the rotor condensation tank, called the peeling point. There is a point in the rotor condensation tank. Bundling area, where the fibers are twisted. The length and stability of the bunching area are two parameters that determine whether the spinning process is stable, thus affecting the spinning end breakage rate.

The length of the bundled area fluctuates around an average value during the spinning process. Once the length of the bundled area is lower than the critical value and impurities hinder When the twist is transferred, breakage will occur. The longer the fiber length and the higher the length uniformity, the more stable the spinning process will be.

Fiber fineness is one of the main factors that determines yarn breakage and spinning count. The optimal number of fibers (nf) in the yarn cross section can be calculated by Calculated by the following formula: nf=15030/(Yarn count *mic) This relationship shows that when the fiber becomes thicker, the yarn strength will decrease. Thick fiber spinning will also cause the yarn backbone CV% to deteriorate. Moreover, a higher twist coefficient should be used when spinning to ensure the strength of the yarn.

The strength of open-end spinning is composed of fiber strength Linear relationship, most of the fibers in open-end spinning are in a hook state, and the degree of fiber shortening increases with the increase in fiber length. The following relational expression can estimate the strength CSP of yarn: CSP=K (ls/f) 0.35 where: K——constant; l——takes 50% of the fiber length range (mm); s——takes the fiber strength 1/8 (g/tex); f——fiber fineness (mic).

The classification of pre-spinning impurities is as follows: large impurities, fiber fragments, and dust. Large impurities are usually It can be effectively removed by the air-jet spinning machine’s impurity removal system. However, the dust will not be deposited between the needle teeth of the opening roller due to the kinetic energy exerted by the acceleration force. The ejection path of the dust to be removed will be changed due to air buoyancy. into a flat shape, some slightly larger dust will enter the rotor and mix in the fiber ring, resulting in an uneven increase in the short segments of the yarn, resulting in a reduction in yarn strength and breaking elongation.

Fiber fragments include broken seeds, infertile seeds, fibrous seed scraps, soft seed epidermis, etc., which are difficult to remove during the entire processing process. They affect the transfer cup The transfer of twist has a great impact on the appearance of the yarn. Even if they can be removed by the carding roller, they may still accumulate in the condensation tank and cause fly flakes.

The degree of dust deposition increases as the impurity content of the fed sliver increases. The higher the rotor speed, the smaller the diameter. The higher the degree of deposition. Due to uneven twist due to dust deposition, the fabric will produce “rungs” and “cloud spots”. The deposition of dust will also damage the evenness of the yarn and increase the hairiness of the yarn. Moreover, the deposition of dust will cause an increase in the number of yarn breaks during the spinning process. The causes and proportions of broken heads are as follows:

Produces tufts: 31.5%;

Dust and flying dust are deposited in the waste outlet and taken away by the rotor cup: 28.5%;

cooked strips in clear flowers and Impurities not removed in the carding process: 24%;

Dust accumulation on the tumbler: 16%.

Therefore, choosing good feed materials can reduce impurity levels and reduce dust accumulation in the rotor cup.

Based on the above analysis, appropriately select spinning raw materials and rationally configure spinning process parameters, and strengthen raw material management and process management, especially It is necessary to rationally adjust the settings of the carding machine process and take control measures, so that the quality of the yarn can be guaranteed.