As customers’ requirements for yarn quality continue to increase, spinning companies pay more attention to strictly controlling the quality of finished yarn. At present, the harmful defects that affect the quality of cloth mainly include thick places, small details, uneven evenness, flying flowers, neps and abnormal defects. By standardizing production operations and focusing on equipment maintenance, process adjustment and quality control, spinning companies can control yarn defects within normal limits. This issue of Frontline Exchange introduces some technical measures adopted by enterprises to reduce yarn defects, hoping to be helpful to readers.
Reasonable configuration of process parameters to reduce spinning yarn defects
Reducing yarn defects in semi-finished products in the spinning department can effectively reduce the end-break rate of spun yarns per thousand spindles, while reducing the end-break rate of spun yarns can increase output, reduce costs per ton of yarn, stabilize yarn quality, and create favorable conditions for improving the competitiveness of enterprise products. We have summarized several specific practices.
In the combing process, the optimized configuration and management of combing and combing elements can achieve better combing effects. Through active and effective selection of corresponding technical measures, the mosaic phenomenon of top combs and cylinders can be minimized. Prevent fibers from entering the cotton mesh in a bundled structure and reduce the chance of breakage in the next process. Regularly check the tension status and wear of the drafting toothed belt and coiling toothed belt, and reasonably adjust the coiling tension, which can reduce the congestion of the coiler and at the same time reduce the probability of overhead breakage of the drawing frame.
Appropriately reducing the nip distance of the roving, the center distance of the rollers, and the draft ratio of the back area will help reduce the CV value of the spun yarn. However, the tightening of the above-mentioned process will inevitably increase the yarn drafting force and floating fiber control force. The holding force and drafting force, the guiding force and the control force must be developed simultaneously to achieve normal drafting and prevent the roving due to poor craftsmanship. Poor drafting caused by defects in the drafting elements and pressurizing mechanism. Therefore, the optimal combination is sought for the nip gauge of the roving, the roller center distance, the back draft ratio and the total draft ratio.
At the same time, it is necessary to strengthen operation and management to reduce the influence of factors such as the attachment of unclean flying particles on the machine to the yarn sliver and the adverse effects of the winding mechanism on the yarn sliver. If these defects are serious, they may cause spun yarns to produce occasional yarn defects.
Improve and control the quality of semi-finished products in rough processes
In the drawing process, after the cotton sliver has been combed through the combing process, the fiber separation, parallelism, and straightness are good, but the cohesion between the fibers is poor, and it is easy to become loose and hairy. At the same time, the fibers will no longer have any problems in the subsequent processes. Sort out opportunities. Therefore, the roughening process should reduce the deterioration of the internal structure of the cotton sliver due to the drafting effect before twisting the sliver, reduce the factors causing defective edge fibers, reduce short lint and fly particles from attaching to the sliver, and reduce the unwinding and curling of the sliver. It can reduce the friction, rubbing, entanglement and twisting during winding, thereby reducing the neps formed by friction, rubbing, entanglement and twisting.
First, reducing the draft ratio and draft force can reduce the growth rate of short linters and neps, thereby improving evenness. Secondly, according to the sliver quantity, choosing a smaller outlet bell diameter can improve the tightness of the sliver, reduce the chance of local sliver breakage when feeding after the roving frame, thereby improving sliver dryness and hairiness. Third, according to the sliver quantity and sliver barrel capacity, design a reasonable fixed length to avoid excessive sliver capacity causing excessive squeezing between the top sliver and the coiled sliver bottom plate, thereby increasing friction, rubbing, twisting and curling to form neps. Fourth, it is necessary to control the weight deviation of the cooked sliver, reduce the CV value of the cooked sliver, and prevent long spun yarn details caused by poor factors in the drawing process.
Therefore, the drawing process should reduce the CV value of cooked strips on the premise of eliminating long details. These are mainly achieved through reasonable design of process routes, configuration of drafting elements and pressurizing mechanisms, and strengthening of operation management and machine cleaning.
In the roving process, the evenness CV value of the roving and the structure of the yarn fibers will affect the evenness CV value and frequent yarn defects of the yarn. The CV value of roving quality will affect the CV value of spun yarn quality, and the yarn defects of roving will affect the occasional yarn defects of spun yarn.
Adjust moisture regain to reduce yarn defects in thick blended yarn
In response to users’ reports of high yarn defects and many broken ends in R/C65/3542tex yarn, our company identified the causes of the above problems by reversing the bobbin and analyzing hundreds of yarn defects. By taking a series of measures, the yarn quality meets user requirements.
By analyzing a certain batch of yarn, it was found that 56% of yarn defects were found in the pre-spinning process. After investigation, it was found that the moisture regain of this batch of semi-finished yarn products was small. The standard moisture regain after mixing the slivers was 11.4%, but the actual moisture regain was only 7.5% to 7.8%. We take measures such as viscose fiber pretreatment, disc humidification, and moisturizing during the carding process to achieve a moisture regain rate of 9.5%. The production area of the drawing process is also humidified accordingly, and carbon black rubber rollers are used to prevent the rubber rollers from sucking and wrapping. The actual moisture regain rate after the sliver is mixed reaches more than 8.5%. Through humidification, spinning production is significantly improved and yarn defects are significantly reduced.
When spinning coarse yarns, the front roller speed of the spinning yarn is relatively high, so it is advisable to adopt a large spacing, heavy pressurization process, and a reasonable pressurization gear to ensure that the drafting force and holding force are compatible, and to reduce the impact on the rubber roller. , damage caused by the rubber ring.
Because it is a thick yarn, if the joint parameters are not adjusted properly during the splicing process, this yarn will be damaged.�A defect will be formed and appear on the cloth surface. Therefore, during the splicing process, parameters such as blown yarn tail, yarn tail superposition, air jet splicing, and winding speed must be optimized. By adjusting the splicer and splicing cavity, the drum speed is reduced to 1200 m/min. The main yarn clearing process parameters are short and thick + 130% × 1 cm, long and thick + 30% × 15 cm, long and thin – 40% × 20 cm, the number of yarn defects reached about 4 for 100,000 meters of rewinding.
Through the implementation of the above measures, the production of this type of yarn has been stable, and yarn defects in hundreds of tubes have been significantly improved, which has been recognized by users.
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