Theoretically, the quality of open-end spinning 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 mixing the feed raw materials, so adjusting the carding process parameters has a great impact on the quality of the sliver, which in turn affects the quality of the yarn.
The following is an analysis of the five main factors affecting the quality of air-jet spinning:
01 Carding
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 captured by the doffer card clothing while the other end is still held by the cylinder card clothing When the cylinder passes through the transfer zone, due to its high surface speed, the fibers are pulled by the doffer card clothing 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.
By adjusting the flat speed or flat flower content, better quality slivers can be produced by mixing cotton rolls of average quality. When all other parameters remain unchanged, if only the flat 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 The % value will be reduced while the measured number of yarn defects and the U% value remain unchanged, so the quality of the yarn and the appearance of the fabric are improved.
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 neps and reduce the evenness of the card sliver. , so the yarn quality deteriorates.
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02 Fiber length
The length of fiber plays a different role than 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.
During the spinning process, the length of the bundled area fluctuates around an average value. Once the length of the bundled area is lower than the critical value and impurities hinder the transfer of twist, end breakage will occur. It will happen that the longer the fiber length and the higher the length uniformity, the more stable the spinning process will be.
03 Fiber fineness
Fiber fineness determines the yarn One of the main factors of end-breakage and spinning count, the optimal number of fiber roots (nf) in the yarn cross section can be calculated by the following formula: nf=15030/(Yarn count *mic) This relationship shows that when the fiber As it becomes thicker, the yarn strength decreases. Coarse fiber spinning will also cause the yarn dryness CV% to deteriorate, and a higher twist coefficient must be used during spinning to ensure the strength of the yarn.
04 Fiber strength
The strength of air-end spinning has a linear relationship with the fiber strength. Most of the fibers in the yarn are in a hooked state, and the degree of fiber shortening increases with the increase in fiber length.
05 Impurities
The classification of impurities before spinning is as follows: large impurities, Fiber fragments and dust.
Large impurities can usually be effectively removed by the impurity removal system of the air-jet spinning machine. However, the kinetic energy exerted by the acceleration force prevents the dust from being deposited between the teeth of the opening roller. , the ejection track of the dust to be removed will become flat due to the buoyancy of the air, and 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 Yarn strength and elongation at break are reduced.
Fiber fragments include broken seeds, infertile seeds, fibrous seed scraps, soft seed skins, etc., which are difficult to remove during the entire processing process. They affect the transfer of twist in the rotor. , which 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 speed of the rotor cup and the smaller the diameter, the higher the degree of dust deposition. Due to the uneven twist caused by 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.
Based on the above analysis, appropriately select spinning raw materials and rationally configure spinning process parameters, strengthen raw material management and process management, especially rationally adjust the settings of the carding machine process, and adopt Measures are taken to control, so that the quality of the yarn can be guaranteed. </p
