With the continuous development of the modern textile industry, the market has increasingly demanded high-quality cotton yarn, which has put forward higher requirements for the quality of domestic cotton yarn. More neps in the yarn not only seriously affect the quality and appearance of the yarn and cloth, but also affect the continuity of the dyeing, finishing, spinning and weaving processes. Therefore, how to strictly control yarn neps during the production process to ensure the quality of the final product has become one of the current problems that need to be solved.
The relationship between raw cotton properties and yarn neps
Regarding the relationship between various physical properties of raw cotton and yarn neps, in recent years, a large number of studies at home and abroad have shown that cotton fibers with good maturity have small moisture absorption capacity, high single fiber strength, more natural curls, and fiber It has good elasticity and rigidity. Therefore, it has strong tensile, compressive and bending resistance, and is not easily damaged during processing. The fiber has less chance of being rubbed, kneaded and entangled by surface friction to form neps. At the same time, the fiber It is less damaged and broken due to mechanical force during the opening, blowing, carding and drafting processes, and the short fiber rate is less increased. Therefore, there are less opportunities for neps to form.
The relationship between carding technology and yarn neps
1 Reasonably distribute the blowing and carding waste to improve the structural quality of the cotton laps
Large impurities that are generally large and easy to separate and remove are removed by the blowroom process; small impurities with fibers that have strong adhesion are removed by the carding process. As for the carding process itself, the sterile seeds, stiff cotton, and dead fibers in the cotton rolls are removed at the licker-in part, while the fiber seeds, fiber fines, neps, short lint, etc. are removed on the cylinder cover. Partially eliminate, at the same time, focus on improving the structure of the cotton lap, and pay attention to reducing the number of hook-shaped cotton bundles and loose cotton bundles in the cotton lap that are easy to form cotton net neps.
Under normal circumstances, the impurity removal efficiency of the licker-in part is controlled between 50% and 60%, while the impurity removal efficiency of the cylinder cover part is controlled between 3% and 10%, and the impurity content rate of the card sliver is controlled at 0.15%. the following. Therefore, the licker-in part is the focus of impurity removal in the carding process. By adjusting the licker-in dust removal process, the carding and dust removal elements, the length and the main spacing of the dust removal area can be changed to strengthen the detection of nep impurities. exclude.
2 Improve the carding efficiency of the carding machine
The strong carding of the carding machine can increase the degree of fiber single fiberization, which is not only beneficial to the separation of fibers and impurities, reducing the entanglement of fibers, but also loosening some neps in the cotton rolls. Therefore, new card clothings with good carding effect are selected for cylinder, flat plate, doffer, and licker-in card clothings, and are used for cylinder flat plate, cylinder doffer, cylinder lick-in, and licker-in feeding plate. Smaller spacing. It not only enhances the ability of the licker-in part to hold combing, but also improves the efficiency of free combing and repeated combing of the cylinder and cover plate parts.
It can be seen from the test that the number of neps in the low-speed close-gauge card sliver is greater than the number of neps in the high-speed close-gauge card sliver; as the flat spacing increases, the number of card sliver neps increases significantly; as the cylinder speed increases, the carding degree increases, The fiber is fully carded and neps are easily eliminated. At the same time, the average carding force on the unit needle surface and fiber is reduced, and the fiber is less likely to be stressed and stretched too much, which can reduce neps formed due to fiber rebound and fiber breakage. Neps. The tight spacing makes the needle teeth have more contact with the fibers, and the fibers are easily held by the needle teeth. The needle teeth penetrate deeply into the fibers, which enhances the carding effect and makes neps easy to remove.
3 Improve fiber transfer and reduce the formation of new neps
The fundamental reason for the formation of new neps on the carding machine is the twisting and rubbing of fibers. Abnormal phenomena such as return, twisting and hanging can often cause severe friction, resulting in fiber twisting and rubbing. Neps. The main causes of return, twisting and hang-up are improper speed ratio or spacing configuration, or insufficient sharpness and smoothness of the opening and carding elements. Therefore, in response to the above-mentioned causes, the following corresponding measures have been mainly taken to eliminate fiber twisting and severe friction. The first is to correctly configure the speed ratio of the cylinder licker-in to ensure that the fiber can be transferred normally and reduce the return of flowers; the second is to pay attention to the status of the carding components. Only by “four fronts and one accurate” can carding be done well, including the licker-in roller, cylinder, cover plate, and doffer needle. The teeth are kept sharp and have good puncture performance to ensure accurate spacing of each part. The third is to ensure that the channel through which the fiber passes is smooth and smooth to reduce the fiber hanging phenomenon during movement.
4 Strengthen temperature and humidity management to control the moisture regain of fibers on the machine
Cotton fiber has great plasticity and poor bending resistance under high temperature and high humidity. It is easy to adhere to each other and form neps. Especially raw cotton with poor maturity is more likely to absorb water and form neps under high temperature and high humidity. Fibers under high temperature and high humidity have poor elasticity and tend to twist into neps in the cover work area because they are not combed out. Therefore, the carding process is maintained at a low relative humidity, generally 55% to 60%, so that the fibers are in a state of continuous moisture release to control the moisture regain of semi-finished products, reduce the cohesion between fibers, and maintain better elasticity. and rigidity�It is conducive to opening, impurity removal, carding and transfer, and reduces the friction between fibers and needle teeth and the filling of needle gaps.
Through the above analysis, it can be concluded that:
1) Fibers with poor maturity have a higher probability of forming neps during processing than normal cotton fibers.
2) The process configuration of the carding process is the key to affecting the number of neps. To strengthen the effect of removing neps and impurities in the nip roller part, the process principle of “tight gauge, strong carding” must be implemented, the cylinder speed should be increased appropriately, and Pay attention to the “four fronts and one accuracy” to improve fiber transfer and help reduce the formation of new neps.
3) The temperature and humidity control should be strengthened during the carding process to reduce the formation of neps.
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