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During the opening, blending, impurity removal, and foreign fiber removal processes of raw cotton, neps and short fibers are generated. Therefore, the interaction between neps, short fibers, and impurities must be properly addressed when selecting the processing technology. Our company's cotton cleaning process adopts the principle of "multi-bundle grabbing, fine cotton grabbing, multi-bin blending, increasing free-beating, reducing gripping, and combining carding and beating, with carding as the primary method." Specifically, a slightly higher beater speed allows for free opening; increasing the distance between dust bars reduces the gripping force, minimizing fiber damage and effectively controlling nep formation.
The carding process is the most critical step in reducing neps. Proper equipment maintenance and process selection can achieve a nep removal rate of approximately 83% in raw sliver. Increasing the carding intensity can improve the nep removal rate but increases fiber damage. To balance this, carding must adhere to the design philosophy of "moderate carding transfer, balancing neps, impurities, and short fibers." The operating speed of the cylinder, licker-in roller, and flats, as the main carding mechanisms, also affects nep formation.
Cylinder Speed
Increasing the cylinder speed enhances carding and impurity removal, thins the fiber layer between the cylinder and the flatbed needles, reduces the load on the carding needles, improves carding quality, and is beneficial for reducing neps.
Licking-in Speed
Appropriately increasing the licker-in speed enhances carding and impurity removal, reduces neps, but increases short fibers. Therefore, for fibers with poor raw cotton quality and low maturity, a slightly lower licker-in speed should be selected. In other words, the licker-in speed should be chosen based on the quality of the raw cotton. Furthermore, increasing the linear speed ratio between the cylinder and the licker-in can improve the doffer transfer rate, reduce fiber damage, prevent cotton re-burdening, and reduce neps.
Rotating Flatbed Linear Speed
A higher rotating flatbed linear speed reduces the load on the rotating flatbed needle cloth, increases the number of flatbed threads exiting the working area per unit time, significantly improves carding efficiency, improves web quality, increases yarn strength, and facilitates thorough impurity removal. 
The Influence of Process Spacing on Neps
a) The cylinder-doffer spacing should be relatively small to reduce the load on the carding surface, enhance carding, and improve the transfer rate of the doffer card cloth. Conversely, a larger spacing will affect the transfer rate of the doffer card cloth and increase neps. Furthermore, the sharpness of the doffer card cloth teeth must be ensured; otherwise, fibers will repeatedly transfer and rub between the two carding surfaces, forming neps. The doffer card cloth must have smooth teeth, no burrs, and no reversed needles to facilitate the removal of tangled fibers and reduce neps.
b) The cylinder-front and rear fixed cover plate spacing and the licker-in-hand and pre-carding plate spacing should both be relatively small (for better carding effect); however, too small a spacing will cause significant damage to the fibers, leading to an increase in short fibers and impurities in the sliver.
c) The feeder plate-licker-in-hand spacing should be relatively large. Our company currently uses a combined cleaning and carding system with a thicker, fluffier, and higher basis weight cotton. Choosing a larger spacing will increase the striking length of the feeder plate-licker-in-hand, reducing neps caused by excessive carding force. d) The gap between the dust collector knife and the licker-in roller should be kept relatively small. The dust collector knife removes small impurities, and a smaller gap increases the cotton waste rate, but it is effective in reducing neps and impurities.
The Influence of Cylinder Wire Cloth on Neps
The new type of cylinder card cloth increases the tooth density, and the metal card cloth teeth used are characterized by being small, pointed, short, shallow, and thin. Optimal use of this new type of cylinder metal card cloth improves fiber combing and transfer rates, significantly reducing neps and short fibers. Our company currently uses the A2-30-950-NF type double-tooth cylinder metal card cloth teeth (hereinafter referred to as double-tooth cylinder card cloth), characterized by two teeth per tooth section (one flat-topped high tooth and one pointed-top low tooth). During combing, the fibers are held at the tooth tips, preventing them from slipping to the tooth roots, which facilitates combing. In addition to the main combing teeth, the side teeth also have a certain combing effect on the fibers, thus improving the combing effect. Practice has shown that compared with ordinary metal card cloth teeth, the use of double-tooth metal card cloth teeth significantly reduces neps and impurities in the fibers after combing. Before using the double-tooth cylinder card cloth, it is recommended to use a copper brush to polish it and remove tiny burrs and harmful deposits from its surface.
The Impact of Carding Equipment Maintenance on Neps
a) Increasing the airflow of each negative pressure nozzle ensures that impurities and short fibers from all areas are promptly removed, reducing cotton return, fly waste, and blockages. This significantly reduces neps. Generally, the airflow of a single carding machine should reach 100 m³/h.
b) To ensure effective carding, the carding cloths in all areas must be in good condition. Maintenance workers should replace severely damaged carding cloths regularly according to equipment maintenance standards.
c) Operators must strictly follow the cleaning chart to clean lint, impurities, and cotton fibers from all areas on time to ensure smooth carding.
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