Neps and impurities are a difficult problem to solve in cotton spinning, and the main control point is in the carding process. So, what points should be taken to strengthen the effective removal of neps and impurities in the carding process? By mastering and doing the following points in production, it is relatively easy to control the impurities of yarn-forming cotton.
1. Enhanced carding
Enhanced carding can promote fiber straightening, break down into single fibers, and promote the separation of fibers from impurities, while also loosening neps. Therefore, the “correctness” of the main opening spacing and the sharpness of the opening elements are extremely important.
2. Impurities should be divided reasonably
It is most beneficial to know which impurities fall in which process and position, that is, to eliminate impurities, it is necessary to divide the labor reasonably, and the various parts of the carding machine itself must also reasonably divide the labor to remove impurities. For impurities that are generally large and easy to separate and exclude, the principle of early fall and less broken should be implemented, and early fall in the cleaning process. Impurities with fibers with high adhesion, especially those with long fibers, are more advantageous to be eliminated on the carding machine. Therefore, when the maturity of the raw cotton is poor and there are many harmful defects in the fiber, the carding machine should be appropriately increased to remove impurities and waste. The licker-in section of the card should eliminate broken seeds, stiff flaps and linters, as well as fine impurities with shorter fibers. The cover plate is suitable for eliminating fine impurities, neps, short lint, etc.
For general domestic cotton, the total noil rate of carding is greater than that of opening and cleaning. The impurity removal efficiency of cotton cleaning (impurities for raw cotton) should be controlled at 50%~65%, the impurity removal efficiency of carding licker-in rollers (impurities for cotton laps) should be controlled at 50%~60%, and the cover plate removes impurities The efficiency is controlled at 3%~10%, and the impurity content of the raw strip should generally be controlled below 0.15%.
The focus of controlling impurities on the carding machine is the licker-in part, which is achieved by adjusting the process parameters of the small leakage bottom and the dust removal knife, such as the small leakage bottom entrance gap and the fourth point gap, the height of the dust removal knife, etc. When the maturity of the raw cotton is poor and the lap contains a lot of impurities, resulting in an increase in the impurities in the sliver, the gap at the entrance of the small drain bottom should be adjusted, and the length of the falling area should be increased to adjust. The suction pipe on the cover of the licker-in cover should not be blocked, otherwise it will cause abnormal noils and whitening in the rear belly. The length of the chord of the small leaking bottom is too long, and the specification of the licker-in teeth is not suitable, etc., which will increase the impurity content of the raw strip. The specifications of the card clothing between the cylinder and the cover, the distance between the front upper cover and the cylinder, the height of the top of the front cover, and the speed of the cover also affect the amount of impurities and neps in the sliver.
3. Reduce rubbing
The neps generated on the carding machine are mainly formed due to re-patterning, winding and fiber rubbing. For example, when the distance between the cylinder and the doffer and the cylinder and the cover plate is too large and the needle teeth are blunt, the fibers will be excessively rubbed. Severe rolling in the opening and cleaning process, high moisture regain of cotton laps, too much mixing ratio of recycled cotton and recycled cotton, or uneven feeding, etc., will increase the neps of the sliver.
Reasonable cotton distribution and strengthening of temperature and humidity management have a considerable effect on reducing neps and impurities. When blending cotton, several indicators that have a great influence on yarn knots, such as maturity, harmful defects, impurities, etc., should be strengthened to control the difference of their indicators. When the moisture regain of raw cotton and cotton laps is low, impurities are easy to fall, and the end silk of cotton can also be reduced. Therefore, the moisture regain of cotton laps should not exceed 8%~8.5%, and the raw cotton should not exceed 10%~11%. Control the low relative humidity in the carding workshop, for example, the relative humidity is controlled at 55%~60%, so that it can release moisture, increase the rigidity and elasticity of the fiber, and reduce the friction and stuffing between the fiber and the card clothing. However, if the relative temperature is too low, static electricity is easily generated, and the cotton web is easily broken, adhered or broken. Especially when spinning chemical fibers, this phenomenon is more obvious. If the relative humidity is too low, the moisture regain of the sliver will be reduced at the same time, which is unfavorable for the subsequent drafting process.
The use of high-quality card clothing, strengthening of the carding function, and increasing the suction point and air volume on each card can greatly reduce sliver knots.
Post time: Aug-10-2023
