Stable and smooth airflow
Based on the causes of their formation, neps can be divided into three categories. The first type is caused by raw materials, the second type is caused by the initial processing and ginning of raw cotton, and the third type is caused by the production process. These three types of neps already exist before the carding machine. Therefore, the task of reducing neps during the carding process is relatively arduous. When fibers and neps move with the air flow boundary layer in the cover plate-cylinder carding area, they tend to break away from the cylinder needle teeth under the action of centrifugal force and be thrown to the cover plate. Because the neps are heavy in weight and short in length compared to the single fibers, they are more likely to escape the grip of the cylinder. The single fibers are light in weight and long in length, making them easier to be held by the cylinder. At the same time, because the fibers thrown to the flat plate are longer and the spacing of the carding area of the cylinder flat plate is small, it is easy to be grabbed again by the cylinder needle teeth, and the probability of the neps being grabbed again is small. Through the effective cooperation between the cylinder and the cover plate, the purpose of reducing neps can finally be achieved. In this process, the carding, transfer, and separation of fibers and neps are all inseparable from the action of air flow. Therefore, stable air flow is one of the prerequisites for effectively reducing neps.
The principles of air flow control of carding machines are: reasonable discharge of waste and waste, uniform and stable air flow control, and prevention of boundary layer thickness, The direction of the supplementary airflow affects fiber movement and web structure. The methods and means of controlling air flow mainly lie in controlling the amount of air flow generated. The boundary layer produced by the high-speed rotation of the cylinder is the main cause of air flow, followed by the licker-in. Therefore, reasonable cylinder and licker-in speeds are crucial to stable air flow. Methods to reasonably distribute the airflow at each point (especially the triangle area) include: using the process separation at cover plates, drain bottoms, etc. to reasonably distribute the airflow; using negative pressure at low-pressure hoods, cotton mesh cleaners, dust and impurity removal, etc. The suction port guides and relieves the airflow in high-pressure areas. Reasonable air flow helps stabilize waste and support the cotton web.
The process spacing of various parts of the carding machine should be considered as a whole. If the spacing of the outlet of the large leakage bottom changes, it will directly affect the air flow in the licker-in-cylinder triangle area. and pressure, moving one point may involve multiple changes, so these factors must be considered comprehensively, and the most important thing is to optimize according to the actual condition of the equipment.
Maintain good mechanical condition
For enterprises, reducing neps is a simple task And complex work. If the mechanical condition is poor, such as machine vibration, poor balance, cylinder, doffer and lick-in roller eccentricity, etc., fibers will be twisted during the carding process and a large number of neps will be formed. Therefore, on the premise of ensuring air flow control, mechanical control must also be done. When the mechanical conditions permit, tight gauge and strong carding are an important means of carding to reduce neps. The distance between the licker-in roller and the cylinder is too large and the saw teeth are not smooth, which can easily lead to poor stripping between the cylinder and the licker-in roller, and the licker-in roller can return to flower, resulting in a significant increase in neps; the distance between the cylinder and the doffer is too large, which can easily cause the neps to increase. The cylinder produces winding flowers and increases neps.
When the teeth of the cylinder, cover plate and doffer needle are blunt or have burrs, the fiber cannot be transferred repeatedly between the two needle surfaces and is easy to float between the two needle surfaces and be affected by Other fibers are twisted and twisted to form more neps. Therefore, attention should be paid to equipment configuration, increasing the degree of carding, and reducing fiber twisting. In addition, reasonable allocation of impurity removal efficiency, so that large impurities with poor adhesion rate are discharged from the licker-in part, and small impurities with strong adhesion rate are discharged from the cover plate can also achieve the effect of reducing neps.
The needle teeth should have good penetration ability into the fiber and can penetrate deep into the neps. Because only when the needle teeth penetrate deep into the neps, it is possible to fully loosen the neps under the action of carding force. If the needle teeth are blunt and cannot effectively penetrate the neps, but only touch the surface of the neps, the rubbing of the neps will become tighter and tighter. At the same time, the needle teeth cannot effectively hold the fibers, and will also cause the previously separated fibers to pass through. Rubbing turns into new neps.
Reasonable division of labor in each district
There must be a reasonable division of labor in each part of the carding machine for impurity removal. For impurities that are generally large and easy to separate, the principle of falling off early and breaking less should be implemented. For impurities with greater adhesion, especially impurities with long fibers, they should not fall off early when they are not separated from the fibers. They should be combed before combing. After the cotton is fully combed, it is removed. In addition, when the maturity of raw cotton is poor and there are many fiber impurities, the waste and impurity removal burden of the carding machine should be appropriately increased.
The carding roller part of the carding machine is a key impurity area. Broken seeds, stiff flakes and impurities with short fibers should be discharged in this area to prevent impurities from being hit. Broken or stuck between the teeth of the cylinder needles, affecting the combing effect. Therefore, except for a small amount of adhesive impurities, the licker-in part should fall off early and fall off more. Reasonable configuration of the licker-in speed and the back-turning process has a significant effect on improving the impurity removal efficiency of the licker-in part and reducing neps.
The specifications of the cylinder and cover plate card clothing and the distance between the two needle surfaces, the position of the upper front cover plate, and the distance between the front upper cover plate and the cylinder And the flat speed, etc., all affect the number of nep impurities in the card sliver. Therefore, for raw cotton that is less mature and contains more harmful defects, attention should be paid to the role of the cover work area in eliminating impurities.
Reasonably control the opening degree and temperature and humidity
Before the fiber enters the carding machine, it should have Good openness. Through the analysis of nep research data, it is confirmed that nep types and sizes vary. Generally, it is composed only of fiber materials.The neps of �� contain at least 5 or more fibers, and the average number is close to 16 or more. Therefore, good opening before the fiber enters the carding machine can expose more neps and make the needle teeth more in contact with neps, laying the foundation for carding out neps.
Temperature and humidity also have a great impact on neps and impurities, and it is necessary to strengthen control and reasonably adjust temperature and humidity. When the moisture regain of raw cotton and cotton rolls is low, impurities tend to fall, and neps and bundles can also be reduced. The carding workshop should control a low relative humidity to increase the rigidity and elasticity of the fiber, reduce the friction between the fiber and the needle teeth and the filling of the tooth gaps, and reduce neps. However, if the relative humidity is too low, on the one hand, it is easy to generate static electricity, and the cotton mesh is easy to be damaged or broken. On the other hand, it will reduce the moisture regain of the card sliver, which is detrimental to the drafting process in the subsequent process. </p
