The effect of the spinning process on the quality of the finished product

1. The definition and test method of nep

A large number of experimental studies have shown that 60-70% of the nep is caused by poor performance of raw cotton, but it is also caused by poor spinning process. According to the gb/t398-93 standard, the neps are made of fibers, immature cotton or frozen cotton, which are formed due to poor quality of the rolling mill or poor handling during the spinning process. The test method is: under the illumination of not less than 400lx, the light is injected from the left rear side, the installation angle of the inspection surface is 45[deg.]±5[deg.] from the horizontal plane, the line of sight of the tester is perpendicular to the sliver, the inspection distance The principle of effortlessness is based on the inspectors’ visual abilities.

2. The relationship between the properties of raw cotton and yarn-forming nep

With regard to the relationship between the physical properties of raw cotton and the nep of yarn, in recent years, a large number of studies at home and abroad have shown that a good maturity of cotton fiber, its small moisture absorption capacity, single fiber strength, natural curl, fiber Because of its good elasticity and rigidity, it has strong resistance to tension, compression, and bending. It is not susceptible to damage during processing. Fibers have less chance of being rubbed, kneaded, and entangled to form neps due to surface friction. At the same time, fibers In the process of opening, striking, carding and drafting, mechanical forces are applied to cause damage and breakage, and the increase of short fiber rate is small. Therefore, the chance of nep formation is small, and the maturation coefficient and yarn-forming cotton particles The relationship between the numbers is shown in Figure 1.

3. The relationship between carding process and yarn formation and nep

A large number of studies have shown that the number of nep in cotton nets basically determines the number of nep of the yarn. Therefore, how to reduce the number of cotton net neps and improve the carding effect of the carding machine is very important for controlling the yarn formation neps. Through our practice of factory internships, we mainly do the following tasks.

3.1 Rational distribution of combing cotton, improve the quality of lap structure

Large impurities that are generally large and easy to separate are eliminated by the open cleaning process; fine fibers with small adhesion are removed by the carding process. For the carding process itself, infertile seeds, stiff cotton, and dead fibers in the lap are excluded in the licker-in section, while fibers with fiber seed and fine fibers, neps, and linters are present in the cylinder plate. Partially excluded, at the same time, focus on improving the structure of the lap, pay attention to reduce the number of hook-shaped cotton skein and loose cotton skein in cotton laps that easily form cotton net nep. Under normal circumstances, the efficiency of the removal of the licker-in section is controlled between 50-60%, while the removal efficiency of the cylinder cover section is controlled at 3-10%, and the impurity content of the sliver is controlled below 0.15%. Therefore, the licker-in section is the key to the impurity removal in the carding process. By adjusting the process of the dislocation area of ​​the lickerin roller, the combing and impurity removing components, the length of the dislodgement area, and the main gauge can be changed in the area where the miscellaneous area is dislodged, thereby strengthening the impurities of the nep. exclude.

3.2 Improve the combing performance of the carding machine

The strong carding of the carding machine can increase the degree of monofilament of the fiber. This not only facilitates the separation of fibers and impurities, reduces the mutual entanglement of the fibers, but also can loosen part of the nep brought about in the lap. Therefore, we have selected new types of clothing with good carding effect for cylinders, covers, doffers, and lickerin clothings. We have also provided these parts with cylinder covers, cylinder liners, cylinder rollers, and licker-in rollers. Use a smaller gauge. This not only enhances the ability of the licker-in section to hold the comb, but also improves the performance of free combing and repeated carding of the cylinder and the cover.

Through experiments, we can see that the number of sliver neats at low speed is more than the number of high-speed nip neps; the gauze spacing increases, the number of sliver neps increases significantly; increase the speed of the cylinder, combing degree increases The fiber combing is adequate, and the nep is easily eliminated. At the same time, the average combing force on the unit needle surface and the fiber is reduced, the fiber is not easily stretched due to the force, and the formation of neps and fiber breakage due to fiber rebound can be reduced. Neps. The tight gauge makes the needle teeth more contact with the fibers, the fibers are easily held by the needle teeth, the needle teeth pierce into the fibers, the carding effect is enhanced, and the nep is easily removed.

3.3 Improve fiber transfer and reduce the formation of new neps

The fundamental cause of the formation of new neps on the carding machine is the twisting and rubbing of the fibers. The unusual phenomena such as flowering, flowering, and hanging flowers often cause severe friction, resulting in fiber twisting and rubbing. Neps. The main reasons for returning, winding, and hanging flowers are that the speed ratio or gage is not properly configured, or the sharpness of the opening combing element is not enough. Therefore, for the above reasons, we have taken the following corresponding measures to eliminate fiber twisting and violent friction. One is to correctly configure the speed ratio of the cylinder nip roller to ensure the normal transfer of fiber and reduce the return of flowers. The second is to attach importance to the state of the combing components. Only the “four fronts and one standard” can comb, the licker, the cylinder, the cover, and the doffer pin. The teeth are sharp, the puncture is good, and the gap between each part is accurate; the third is to ensure that the passage through which the fibers pass is smooth and smooth, so as to reduce the phenomenon of hanging flowers during the movement of the fibers.

3.4 Strengthen the management of temperature and humidity and control the return of fiber

Cotton fiber has high plasticity under high temperature and high humidity, poor bending resistance, easy adhesion between fibers, easy to form neps, especially raw cotton with poor maturity, under high temperature and high humidity, it is easier to absorb water and form neps. Fibers under high temperature and high humidity have poor elasticity, and they tend to turn into neps in the cover work area because they are not combed. Therefore, keeping the carding process at a relatively low relative humidity, generally 55-60%, allows the fibers to be continuously dehumidified to control the moisture regain of the semi-finished products, so that the cohesion between the fibers is reduced, and better elasticity is maintained. Rigidity is conducive to opening, cleaning, carding and transfer, reducing the friction between fibers and needle teeth and filling the phenomenon of needle gap.

4 Conclusion

From the above analysis, we can draw:

(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 the nep, and strengthening the effect of removing the nep impurities from the roll section. The principle of “tightly spaced, strong combing” should be implemented to properly increase the speed of the cylinder. And pay attention to doing a good "four front and one standard" to improve the fiber transfer, help to reduce the formation of new neps.

(3) The carding process should strengthen the control of temperature and humidity to reduce the formation of neps.

Knitted Fabric

Knitted Fabric,Ribbed Knitted Fabric,Rib Knitted Fabric,Polyester Knit Fabric

Shaoxing Longwell Tetxtiles Co.,Ltd. , https://www.longwellfabric.com