With the continuous improvement of customers' requirements for yarn quality, spinning enterprises pay more attention to the strict control of yarn quality. At present, the harmful defects affecting the fabric surface quality mainly include coarse knots, details, unevenness, flying, neps and abnormal defects. By standardizing production operation, paying attention to equipment maintenance, process adjustment and quality control, spinning enterprises can control yarn defects within the normal range.

Reasonably Dispose Technological Parameters to Reduce Spinning Yarn Defects

Reducing the yarn defects of semi-finished products in spinning section can effectively reduce the yarn breakage rate per thousand spindles, while reducing the yarn breakage rate can increase the output, reduce the cost per ton of yarn, stabilize the yarn quality, and create favorable conditions for improving the product competitiveness of enterprises. We summarized several specific practices.

In the combing process, a good carding effect can be achieved by optimizing the configuration and management of combing and carding components. Regularly check the tension and wear of the draft toothed belt and the grooved stick toothed belt, and reasonably adjust the coil tension, which can reduce the probability of overhead end breakage while reducing the congestion of the coiler.

Reduce the jaw gauge, roller center distance and draft multiple of back zone of roving appropriately. However, the tightening of the above processes will inevitably increase the sliver drawing force and the floating fiber control force. The normal drafting can only be achieved if the holding force and the drawing force, the guiding force and the control force are developed simultaneously, and the bad drafting caused by the poor roving process, the defects of the drafting element and the pressurizing mechanism can be prevented. Therefore, the nip gauge, roller center distance, draft multiple of back zone and total draft multiple of roving shall seek an optimal combination.

At the same time, it is necessary to strengthen the operation and management, reduce the influence of factors such as dirty machine flying flowers attached to the sliver and the bad effect of winding mechanism on the sliver. If these defects are serious, they may cause occasional yarn defects on the spinning yarn.

In the drawing process, after the sliver is combed in the combing process, the fiber separation, parallelism and straightness are good, but the cohesion between fibers is poor, which is easy to loose and hairiness. At the same time, the fibers will not have carding opportunities in the next process. Therefore, the roughing process should reduce the deterioration of the internal structure of the sliver caused by the drafting effect before twisting the sliver, reduce the factors that cause bad edge fibers, reduce the attachment of short fibers and flying flowers to the sliver, and reduce the friction, kneading, entanglement and twisting of the sliver during unwinding and winding, so as to reduce the neps formed by friction, kneading, entanglement and twisting.

First, reducing the drafting ratio and force can reduce the growth rate of lint and neps, thereby improving the evenness. Secondly, according to sliver ration, selecting a smaller sliver bell mouth diameter can improve sliver tightness, reduce the probability of local sliver breakage when sliver is fed behind the roving frame, and thus improve sliver evenness and hairiness. Third, reasonable fixed length shall be designed according to the quantity of sliver and the capacity of sliver barrel to avoid excessive extrusion between the top sliver and the bottom plate of coil sliver caused by too full sliver capacity, which will increase friction, kneading and twisting to form neps. Fourth, it is necessary to control the weight deviation of the sliver, reduce the CV value of the sliver, and prevent the long yarn details caused by bad factors in the drawing process. Therefore, the drawing process should reduce the evenness CV value of the ripe sliver on the premise of eliminating long details. These are mainly achieved through reasonable design of process route, configuration of drafting elements and pressure mechanism, strengthening operation management and machine cleaning.

In roving process, both roving evenness CV value and sliver fiber structure will affect yarn evenness CV value and common yarn defects. The CV value of roving quality will affect the CV value of spinning quality, and roving yarn defects will affect the sporadic yarn defects of spinning.