Analysis of 5 Factors Affecting Air Spinning Quality

The following tasks are mainly completed in the open-end spinning process: opening and drafting the sliver to a single fiber state; removing impurities from the feed material; uniformly mixing the fibers; forming whiskers; agglomerating fibers; improving uniformity by merging degree; twisting; winding forming.

Theoretically, during open-end spinning, a single fiber is condensed into a fiber ring in the condensing groove of the rotor, and then the fiber ring is pulled up in the opposite direction, but in fact, fiber bending occurs during this process due to other reasons. Hooks, fiber loops, fiber sheets and other deformations greatly affect the quality of open-end spinning. The quality of the yarn is affected by the quality of the sliver fed, mainly by the length, length uniformity, fiber fineness and impurities in the sliver fiber. On the other hand, during conveying and coagulation, the better the separation state of the fibers, the better the yarn quality. The quality of the sliver is controlled by the pre-spinning process. Carding is the key process of air-jet spinning. It mainly removes impurities, carding and evenly mixing the fed raw materials. Therefore, adjusting the parameters of the carding process has a great impact on the quality of the sliver, and then affect the yarn quality. The five main factors that affect the quality of open-end spinning are analyzed below:

1. Carding cotton

Cylinders, covers and doffers play an important role in carding. When the cylinder arrives at the doffer with a layer of fibers, the end of the fiber touches the surface of the doffer and is grasped by the doffer clothing while the other end is still held by the cylinder clothing. High, the fibers are pulled and tensioned by the doffer clothing. This cohesion makes the amount of fibers per unit area of the doffer 2 to 3 times that of the cylinder per unit area. If the doffer speed increases, more needle teeth can participate in carding, and the agglomeration effect increases due to the increase of the doffer speed. Even if the ratio of the linear speed of the cylinder and the doffer surface decreases, the transfer effect of the fiber will increase, but if the doffer speed If it increases too much, the agglomeration 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 sliver, so the yarn quality will deteriorate, that is, the U% value will increase. , the strength and appearance rating of the yarn will decrease significantly.

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

2. Fiber length

Fiber length plays a different role than it does in ring spinning. The fiber length is related to the diameter of the rotor as follows:

Rotor diameter = fiber hand-pull length * 1.2

The twist is transferred down to a special point in the rotor condensate trough, called the stripping point, where there is a bundling zone where the fibers are twisted. The length and stability of the bundle area are two parameters that determine the stability of the spinning process, and thus affect 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 below the critical value and impurities hinder the transfer of twist, end breakage will occur. The longer the fiber length, the higher the length uniformity. , the more stable the spinning process is.

3. Fiber fineness

Fiber fineness is one of the main factors determining yarn breakage and spinning count. The optimal number of fibers (nf) in the yarn section can be calculated by the following formula:

nf=15030/(Yarn British count*mic)

This relationship shows that when the fiber becomes thicker, the yarn strength decreases. Thick fiber spinning will also lead to the deterioration of the CV% of the yarn evenness, and a higher twist coefficient should be used during spinning to ensure the strength of the yarn.

4. Fiber strength

The strength of open-end spinning has a linear relationship with the fiber strength. Most of the fibers in open-end spinning are in a hooked state, and the degree of fiber shortening increases with the increase of fiber length. The following relationship can estimate the strong CSP of the yarn:

CSP=K(ls/f)0.35

Among them: K——constant; l——take 50% of fiber length range (mm); s——take 1/8 of fiber strength (g/tex); f——fiber fineness (mic).

5. Impurities

The pre-spinning impurities are classified as follows: large impurities, fiber fragments, and dust. The large impurities can usually be effectively removed by the open-end spinning machine dust removal system. However, the dust and impurities will not be deposited between the needle teeth of the opening roller due to the kinetic energy exerted by the acceleration force. The air buoyancy becomes flat, and some slightly larger dust will enter the rotor cup and be mixed in the fiber ring, which will lead to an increase in the unevenness of short segments of the yarn, resulting in a decrease in yarn strength and elongation at break.

Fiber fragments include broken seeds, sterile seeds, fibrous seed chips, soft seed skins, etc., which are not easy to remove during the entire processing process. They affect the transfer of twist in the rotor and have a great impact on the appearance of the yarn. Even if they can be removed by the opening rollers, they can still deposit in the condensate trough and cause fly.

The degree of dust deposition increases with the increase of the impurity content in the fed sliver. The higher the rotor speed, the smaller the diameter and the higher the deposition degree. Because of the uneven twist caused by the deposition of dust and impurities, the fabric has "runs" and "cloud spots". Dust deposits also impair yarn evenness and increase yarn hairiness. Moreover, the deposition of dust and dirt during the spinning process can lead to an increase in the number of yarn breaks. The causes and proportions of broken ends are as follows:

Yield cotton bundles: 31.5%;

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

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

Dust accumulation on the rotor: 16%.

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

Summary

Based on the above analysis, appropriate selection of spinning raw materials and reasonable configuration of spinning process parameters, strengthening raw material management and process management, especially rational adjustment of card process settings, and taking measures to control, can ensure the quality of yarn.