1 enhanced carding
Enhanced carding can make the fiber straighten, separate the fiber from impurities, and loosen the neps. Therefore, the accuracy of the main carding gauge and the sharpness of the carding elements are important.
The division of labor should be reasonable
It is beneficial to know what impurities fall in what process and position, that is, to eliminate impurities, a reasonable division of labor should be made, and so should each part of the carding machine itself. For the impurities which are large and easy to be separated and eliminated, the principle of early falling and less crushing should be carried out, and the early falling should be carried out in the opening and cleaning process. The impurities with larger adhesion force, especially those with long fibers, can be eliminated on the carding machine. Therefore, when the maturity of raw cotton is poor and there are many harmful defects with fiber, the carding machine should be appropriately increased to remove impurities and neps. Broken seeds, stiff petals, short fibers and fine impurities with short fibers should be eliminated in the taker in part of carding machine. The cover plate is suitable for eliminating fine impurities, neps, short fibers, etc.
For general domestic cotton, the total noil rate of carding is greater than that of opening and cleaning. The impurity removal efficiency of cleaning (for raw cotton) should be controlled at 50% - 65%, the impurity removal efficiency of carding licker (for cotton coil) should be controlled at 50% - 60%, the impurity removal efficiency of cover plate should be controlled at 3% - 10%, and the impurity content of sliver should be generally controlled below 0.15%.
The impurities are controlled in the taker in part of the carding machine. In production, the process parameters of the small bottom leakage and dust removal knife are adjusted, such as the inlet spacing and the fourth point spacing of the small bottom leakage, and the height of the dust removal knife. When the maturity of raw cotton is poor and there are more impurities in the coil, which leads to the increase of impurities in the sliver, it should be adjusted by small gap at the entrance of bottom leakage and increasing the length of impurity dropping area. The straw on the cover of the taker in roll should not be blocked, otherwise it will cause abnormal droppings and more white spots. Too long chord length of small bushing and improper specification of taker in roller will increase the impurity content in the sliver. The card clothing specifications of cylinder and cover plate, the distance between the front upper cover plate and cylinder, the position of the upper opening of the front upper cover plate and the speed of the cover plate also affect the impurity content and NEP quantity of the sliver.
3 reduce rubbing
The neps produced on carding machines are mainly formed by returning flowers, winding flowers and rubbing fibers. If the interval between cylinder and doffer and cylinder to cover plate is too large and the needle teeth are blunt, the fiber will be excessively rubbed, and the neps will be increased if the taker in roller returns and the cylinder is wound. The neps of sliver will increase if the winding is serious, the moisture regain of cotton coil is too high, the ratio of recycled cotton to recycled cotton is too large or the feeding is uneven.
Reasonable cotton blending and strengthening temperature and humidity management can reduce neps and impurities. It is necessary to strengthen the control of the differences of several indexes, such as maturity, harmful defects and impurities, which have great influence on yarn neps during cotton blending. When the moisture regain of raw cotton and cotton roll is low, the impurities are easy to fall down, and the end yarn of cotton can also be reduced. Therefore, the moisture regain of cotton lap should not exceed 8% - 8.5%, and raw cotton should not exceed 10% - 11%. The relative humidity of carding workshop should be controlled at a low level, such as 55% - 60%, so as to release moisture, increase the rigidity and elasticity of fiber, and reduce the friction and filling between fiber and card cloth. However, if the relative temperature is too low, it is easy to generate static electricity, and the cotton net is easy to be broken, adhered or broken. Especially in the spinning of chemical fiber, this phenomenon is more obvious. If the relative humidity is too low, it will reduce the moisture regain of the sliver, which is unfavorable to the later drafting process.
Using alloy copper card clothing, strengthening carding function, increasing dust collection point and air suction volume of each carding machine can reduce sliver impurities to a great extent.