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The following points should be noted in rotor spinning

TIME:2023/2/25 14:27:00

       In the textile industry, rotor spinning is often used. Today, I will tell you a few things to pay attention to when I love rotor spinning.

       In the process of rotor spinning, the following tasks are mainly completed: the sliver is loosened and drawn to the single fiber state; Remove impurities from feed raw materials; Uniformly mix the fibers; Forming whiskers; Coagulation fiber; Improve uniformity by merging; Twisting; Winding forming.

       In theory, during the process of rotor spinning, a single fiber is condensed into a fiber ring in the condensing slot of the rotor, and then the fiber ring is pulled up in the opposite direction. But in fact, due to other reasons, fiber hooks, fiber rings, fiber chips and other deformations will occur in the process, which greatly affects the quality of rotor spinning.

       The quality of the yarn is affected by the quality of the sliver fed, mainly by the length of the sliver fiber, length uniformity, fiber fineness and impurity content. On the other hand, in the process of conveying and condensation, the better the separation state of the fiber, the better the yarn quality. The sliver quality is controlled by the pre-spinning process. Carding is the key process of rotor spinning. It mainly performs impurity removal, carding and uniform mixing of feed materials. Therefore, adjusting the carding process parameters has a great impact on sliver quality, and thus affects yarn quality.

       The following five main factors affecting the quality of rotor spinning are analyzed:

       1. Carding

       Xilin, cover plate and doffer play an important role in sorting. When the cylinder reaches the doffer with a layer of fiber, the end of the fiber touches the surface of the doffer and is grabbed by the doffer cloth, while the other end is still held by the cylinder cloth. When the cylinder passes through the transfer zone, due to its high surface speed, the fiber is pulled by the doffer cloth and generates tension. This condensation makes the amount of fiber per unit area of doff 2~3 times that of cylinder.

       If the speed of doffer increases, more needle teeth can participate in carding. As the speed of doffer increases, the coalescence effect will increase. Even if the linear velocity ratio of cylinder and doffer surface decreases, the fiber transfer effect will increase. However, if the speed of doffer increases too much, the coalescence effect will decrease. 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 load of the cylinder, which will increase the nep and reduce the evenness of the sliver. Therefore, the yarn quality will deteriorate, that is, the U% value will increase, and the strength and appearance grade of the yarn will decrease significantly.

       By adjusting the speed of the cover plate or the content of the cover plate flower, a better quality sliver can be produced from the cotton roll with general mixed quality. When all other parameters remain unchanged, only increase the speed of the cover plate, and the cover plate will increase. At the same time, due to the enhanced carding effect, the impurities in the sliver will decrease, and the short fiber will also decrease. The strength of the yarn can be improved, but the strength CV% value will decrease, while the measured yarn defects and U% value will not change, so the quality of the yarn and the appearance of the fabric will be improved.

       2. Fiber length

       The function of fiber length is different from that of ring spinning.

       The fiber length is related to the diameter of the rotor as follows: the diameter of the rotor=the length of the fiber pulled by hand * 1.2 twist is transferred down to a special point in the rotor condensing tank, called the stripping point. There is a cluster area in the rotor condensing tank, where the fiber is twisted. The length and stability of the bunching area are two parameters that determine the stability of the spinning process, thus affecting the yarn breakage rate.

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

       3. Fiber fineness

       Fiber fineness is one of the main factors that determine yarn breakage and spinning count. The optimal fiber number (nf) in the yarn section can be calculated by the following formula: nf=15030/(yarn count * mic) This formula shows that when the fiber becomes thicker, the yarn strength will decrease. Coarse fiber spinning will also lead to the deterioration of yarn line CV%, and high twist coefficient should be used to ensure the yarn strength.

       4. Fiber strength

       The strength of rotor spinning is linear with the fiber strength. Most of the fibers in rotor spinning are in a hook state, and the degree of fiber shortening increases with the increase of fiber length. The following relationship can be used to estimate the strength of the yarn CSP: CSP=K (ls/f) 0.35, where: K - constant; L - 50% of the fiber length range (mm); S - 1/8 of fiber strength (g/tex); F - fiber fineness (mic).

       5. Impurities

       Pre-spinning impurities are classified as follows: large impurities, fiber fragments and dust impurities. Large impurities can usually be effectively removed by the trash removal system of the rotor spinning machine. However, the kinetic energy exerted by the acceleration force will not deposit the dust between the needle teeth of the carding roller. The projection track of the dust to be removed will become flat due to the air buoyancy. Some slightly larger dust will enter the rotor and mix in the fiber ring, resulting in the increase of the yarn short segment unevenness, resulting in the reduction of the yarn strength and breaking elongation.

       Fiber chips include broken seeds, sterile seeds, fibrous seed chips, soft seed skins, etc., which are not easy to remove during the whole processing process. They affect the transfer of twist in the rotor and have a great impact on the yarn appearance. Even if they can be removed by the carding roller, they may still deposit in the condensation tank and cause flying flowers.

       The deposition degree of dust and impurities increases with the increase of impurity content in the sliver. The higher the rotor speed is, the smaller the diameter is, the higher the deposition degree is. Because of 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 in the spinning process will cause the number of broken ends of the yarn to increase. The causes and proportions of broken ends are as follows:

       Cotton bunches: 31.5%;

       Dust and flying flowers are deposited at the outlet and taken away by the rotor: 28.5%;

       Impurities that are not removed in the process of cleaning and carding in the sliver: 24%;

       Dust on the rotor: 16%.

       Therefore, selecting a good feeding material can reduce the impurity level and reduce dust accumulation in the rotor.

       6. Summary

       According to the above analysis, select appropriate spinning raw materials, appropriate spinning process parameters, strengthen raw materials and process management, especially adjust the process settings of the carding machine reasonably, thus ensuring the quality of the finished products.