English Views: 7 Author: Site Editor Publish Time: 2022-01-05 Origin: Site
In the air spinning process, the following tasks are mainly completed: open and draft the sliver to a single fiber state; remove impurities from the feed material; uniformly mix the fibers; form strands; aggregate fibers; improve uniformity through merging Degrees; twisting; winding forming.
Theoretically speaking, during air spinning, a single fiber condenses 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, due to other reasons, the fiber bends in the process. Hooks, fiber loops, fiber sheets and other deformations, etc., greatly affect the quality of air spinning. The quality of the yarn is affected by the quality of the fed sliver, which is mainly affected by the length, length uniformity, fiber fineness and impurities in the sliver fiber. On the other hand, in the process of conveying and agglomeration, the better the fiber separation state, the better the yarn quality. The quality of the sliver is controlled by the pre-spinning process. Carding is a key process of air spinning. It mainly removes impurities, carding and uniform mixing of the feed materials. Therefore, adjusting the carding process parameters has a great impact on the quality of the sliver. Affect yarn quality. The following analyzes the five main factors that affect the quality of open-end spinning:
Cylinder, cover and doffer play an important role when combing. 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 clothing while the other end is still held by the cylinder. When the cylinder passes through the transfer zone, its surface speed is very high High, the fiber is pulled by the doffer clothing and generates tension. This kind of cohesion makes the amount of fiber per unit area of Doffer is 2 to 3 times the amount of fiber per unit area of cylinder. If the doffer speed increases, more needle teeth can participate in the carding. As the doffer speed increases, the cohesion will increase. Even if the ratio of the cylinder and doffer surface linear speed decreases, the fiber transfer effect will increase, but if the doffer speed If you increase too much, the cohesion will decrease, and the transfer effect is closely related to the formation of fiber hooks. When the 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, so the yarn quality deteriorates, that is, the U% value becomes larger. , The strength and appearance grade of the yarn will be significantly reduced.
By adjusting the speed of the flat plate or the content of the flat plate flower, a good quality sliver can be produced by mixing cotton laps of general quality. When all other parameters remain unchanged, only increase the speed of the flat plate, the flat flower will increase, and at the same time, due to the enhanced combing 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 decrease and the measured yarn defects and U% value will not change, so the quality of the yarn and the appearance of the fabric are improved.
The role of fiber length is different from its role in ring spinning. The fiber length has the following relationship with the diameter of the rotor:
Rotor diameter=fiber hand pulling length*1.2
The twist is transmitted down to a special point in the rotor congealing groove, called the peeling point. There is a bundling area in the rotor congealing groove, where the fibers are twisted. The length and stability of the bundling zone are two parameters that determine whether the spinning process is stable, and thus affect the rate of yarn breakage.
During the spinning process, the length of the bundling area fluctuates around an average value. Once the length of the bundling area is below the critical value and impurities hinder the transmission of twist, end breakage will occur. The longer the fiber length, the higher the uniformity of the length. , The spinning process is more stable.
Fiber fineness is one of the main factors that determine 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. Crude fiber spinning will also cause the deterioration of the yarn evenness CV%, and a higher twist coefficient must be used during spinning to ensure the strength of the yarn.
The strength of air spinning has a linear relationship with fiber strength. Most of the fibers in air 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 strength of the yarn CSP:
CSP=K(ls/f) 0.35
Among them: K-constant; l-take 50% of the fiber length range (mm); s-take 1/8 of the fiber strength (g/tex); f-fiber fineness (mic).
The classification of front spinning impurities is as follows: large impurities, fiber fragments, dust impurities. Large impurities can usually be effectively removed by the air spinning machine's trash removal system. However, the kinetic energy exerted by the acceleration force prevents the dust from being deposited between the needle teeth of the opening roller. The ejection track of the dust to be removed will be caused by The air buoyancy becomes flat, and some slightly larger dust will enter the rotor and be mixed in the fiber loop, resulting in an increase in the unevenness of the yarn fragments, resulting in a decrease in yarn strength and elongation at break.
Fiber fragments include broken seeds, sterile seeds, fibrous seed crumbs, soft seed skin, etc., which are not easy to remove during the entire processing process. They affect the transmission of twist in the rotor and greatly affect the appearance of the yarn. Even if they can be removed by the opening roller, they may still be deposited in the condensation groove 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, the higher the degree of deposition. Because of the uneven twist caused by dust deposition, the fabric produces "rails" and "clouds". 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 increase the number of yarn breaks during the spinning process. The causes and proportions of broken ends are as follows:
Produce cotton tuft: 31.5%;
Dust and flying flowers deposited on the discharge opening and taken away by the rotor: 28.5%;
Impurities in the cooked sliver that have not been removed during the cleaning and carding process: 24%;
Dust accumulation on the rotor: 16%.
Therefore, choosing a good feed material can reduce the impurity level and reduce the dust in the rotor.
6. Summary
Based on the above analysis, appropriate selection of spinning raw materials and reasonable configuration of spinning process parameters, strengthening of raw material management and process management, especially reasonable adjustment of carding machine process settings, and taking measures to control, so that the quality of the yarn can be guaranteed.
