Carding technology is one of the most critical technologies in the cotton spinning production process. The quality of fiber carding directly affects the realization effect of processes such as impurity removal and drafting. Neps are fibrous knots that are tightly intertwined with cotton fibers, and some neps contain non-fibrous substances such as seed stalks, leaves, stems and other impurities. Too high neps content will directly affect the quality of yarn in the later stage, and the carding process can reduce neps. How to effectively reduce the neps on the card?
Stable and unobstructed airflow
According to the reasons for the formation of neps, they can be divided into three categories. The first type is caused by raw materials, the second type is caused by ginning of raw cotton, and the third type is caused by the production process. These three types of neps existed before the carding machine, so the task of reducing the neps in the carding process is more onerous. When the fiber and neps are running with the airflow attachment layer in the cover-cylinder combing area, they tend to be separated from the cylinder needles and thrown to the cover under the effect of centrifugal force. Due to the heavy weight of neps and the short length of single fiber, it is easier to get rid of the grip of the cylinder, while the single fiber is lighter and longer, which makes it easier to be held by the cylinder. At the same time, because the fibers thrown to the cover plate are longer, the gap in the combing zone of the cylinder cover is smaller, so it is easy to be grasped by the cylinder needle again, and the probability of the neps being grasped again is smaller. Through the effective cooperation of the cylinder and the cover plate, the purpose of reducing neps can be achieved in the end. In this process, the combing, transfer, and separation of fibers and neps are inseparable from the role of airflow, so a stable airflow is one of the prerequisites for effectively reducing neps.
The principle of airflow control of the card is: reasonable removal of waste and noble, uniform and stable airflow control, to prevent the thickness of the surface layer in the key parts (especially several triangular areas) and the direction of the supplementary airflow to produce fiber movement and the structure of the cotton net influences. The methods and means of controlling airflow mainly consist in controlling the amount of airflow generated. The overlying layer produced by the high-speed rotation of the cylinder is the main cause of the air flow, followed by the licker-in. Therefore, reasonable cylinder and licker-in speeds are essential to stabilize the airflow. The methods of rationally distributing the airflow at each point (especially the triangular area) are: using the process separation of the hood plate, the bottom of the leak, etc., to reasonably distribute the airflow; using low pressure hoods, cotton net cleaners, dust and debris removal and other negative pressure The suction port guides and relieves the air flow that releases the high pressure area. Reasonable airflow replenishment helps to stabilize the nodding and support the cotton net.
The process spacing of the card should be considered as a whole. If the outlet gap of the bottom of the large leak changes, it will directly affect the airflow and pressure at the licker-cylinder triangle. Moving a point may involve multiple changes. Therefore, these factors must be considered comprehensively, and the most important thing is to optimize according to the actual conditions of the equipment.
Maintain good mechanical condition
For businesses, reducing neps is a simple and complex task. If the mechanical condition is bad, such as machine vibration, poor balance, eccentricity of cylinders, doffers, and licker-in rollers, etc., there will be twisted fibers during the carding process, forming a lot of neps. Therefore, under the premise of ensuring airflow control, mechanical control must be done. When the mechanical condition allows, tightly spaced and strong carding is an important method for carding to reduce neps. The gap between the licker-roller and the cylinder is too large, and the jaggedness is not smooth, which may cause poor stripping between the cylinder and the licker-in, and the lint roller will return to the flower, which will significantly increase the neps. Cylindrites cause coiling and increase neps.
When the cylinder, cover, and doffer needle teeth are dull or have burrs, the fibers cannot be repeatedly transferred between the two needle surfaces, and they easily float between the two needle surfaces, and are twisted by other fibers to form more neps. Pay attention to equipment configuration, improve carding degree and reduce rubbing fiber. In addition, reasonable removal of impurity removal efficiency allows large impurities with poor adhesion rate to be discharged from the licker-in roller, and small impurities with strong adhesion rate to be discharged from the cover plate, which can also reduce the neps effect.
Needles should have good puncture ability to the fiber, and can penetrate deep inside the neps. Because only when the needle teeth penetrate deep inside the neps, it is possible to fully loosen the neps under the effect of the combing force. If the needle teeth are blunt, they cannot effectively puncture the neps, but if they touch the surface of the neps, the neps rubbing will become tighter and tighter. At the same time, the needle teeth cannot effectively hold the fibers, and the originally separated fibers will pass. Knead into new neps.
Reasonable division of labor in each district
Removal of impurities in each part of the carding machine should be reasonably divided. Generally, the impurities that are relatively large and easy to separate should implement the principle of early fall and less crushing, while the impurities with larger adhesion, especially those with long fibers, should not fall early when it is not separated from the fibers, and should be combed The card is cleaned after being fully carded. In addition, when the maturity of the raw cotton is poor and there are many fiber impurities, the nodding and impurity removal burden of the card should be appropriately increased.
The hoisting roller part of the card is the focus on the impurity dropping area. Broken seeds, slabs and impurities with short fibers should be discharged in this area, so as to avoid the impurities being crushed or embedded between the teeth of the cylinder needles and affecting the carding effect. Therefore, in addition to a small amount of adhesive impurities, the licker-in part should fall early and fall more. The reasonable configuration of the licker-in roller speed and the rear car technology has obvious effects on improving the impurity removal efficiency of the licker-in section and reducing the neps.
The specifications of the clothing of the cylinder and the cover and the distance between the two needle surfaces, the position of the front upper cover, the distance between the front upper cover and the cylinder, and the speed of the cover all affect the neps in the sliver. The amount of impurities. Therefore, for raw cotton with poor maturity and many defects, attention should be paid to the role of the cover to eliminate impurities.
Reasonably adjust the opening degree and temperature and humidity
Before the fiber enters the card, it should have a good openness. Through the analysis of neps research data, it was confirmed that the types of neps were different and the sizes were different. Generally, a neps made of only fibrous materials contains at least 5 or more fibers, and the average number is close to 16 or more. Therefore, before the fiber enters the carding machine, it has a good opening degree, so that the neps can be more exposed, and the needle teeth can more contact the neps, laying the foundation for carding the neps.
Temperature and humidity also have a greater impact on neps impurities. Control and reasonable adjustment of temperature and humidity must be strengthened. When the moisture regain of raw cotton and cotton laps is low, the impurities are easy to fall, and the neps and tulle can be reduced. The carding workshop should control the lower relative humidity, increase the rigidity and elasticity of the fiber, reduce the friction between the fiber and the needle teeth and the filling between the tooth gaps, and reduce the neps. However, the relative humidity is too low, on the one hand, it is easy to generate static electricity, and the cotton net is easy to be broken or broken, on the other hand, it will reduce the sliver regain, which is not good for the subsequent process drafting.
