For pure cotton combed fine yarn, the harmful defects affecting the cloth surface in terms of the degree of damage and frequency of occurrence are mainly thick places, details, unevenness, flying flowers, Neps and unusual defects. What impact do these defects have on the post-processing process?
Thickness and details
Thick place, the cloth surface appears as a prominent thick place, which affects the appearance of the fabric and even causes the cloth surface to degrade. Fabric factories can improve the appearance through manual picking and repairing, but the picking and repairing operation is difficult, time-consuming and labor-intensive; because the details are thinner than the normal yarn, it will form a weak loop in the yarn strength, causing breakage in the preparation and weaving process, affecting preparation and weaving. The efficiency is high, even if no breakage occurs, the fabric surface will show up as finer than normal yarn defects, which cannot be repaired. If the number is large, the fabric surface will be degraded.
Uneven strips
Affects the appearance of the fabric, causing the fabric surface to degrade. In particularly serious cases, the fabric surface appears as striped shadows or wood grains. In lighter cases, the cloth surface appears turbid, not smooth, and appears to have cloud spots. , uneven dryness will also cause uneven dyeing.
Neps
The cloth surface appears as cotton dots or white stars. The stars are dotted on the cloth surface, affecting the appearance of the fabric. Fabric factories can reduce cotton spots through manual picking and repairing, but when the number is too large, picking and repairing cannot achieve good results and is time-consuming and labor-intensive. When there are many or large such defects, the yarn breakage rate will increase during preparation and weaving, which will affect the efficiency of preparation and weaving, affect the appearance and smoothness of the fabric, and cause the cloth surface to degrade.
Flying flowers
The performance of the cloth surface is between thick neps and large neps, which are shorter than the thick neps and have loose fibers, which affects the smoothness of the cloth surface. It can be improved by manual repair.
Abnormal defects
Mostly manifested as long segments with low frequency of occurrence, such as double yarns in single yarns, three yarns in strands andFour-ply yarn, etc., as well as long slubs, long details. Such defects seriously affect the appearance of the fabric and cause the fabric surface to degrade. Garment factories generally need to avoid cutting, which will reduce the utilization rate of the fabric. In more serious cases, it may even delay the delivery of the order and compensate the customer for their losses.
It can be seen that yarn defects have a great impact on the subsequent processes, especially the surface effect of the fabric. Judging from the product types of cloth factories, different fabric types have different quality requirements for yarns: Solid color cloth types (plain fabrics with warp and weft yarns of the same color or different colors): According to the contrast of the warp and weft colors, the cotton quality of the yarn Knot requirements are different. The greater the color contrast between warp and weft, the higher the requirements for neps. Especially the fabric types that have been specially finished have higher requirements for thick places and neps. Mitong strip fabric (fabric with different colors of adjacent yarns in the warp, weft or warp and weft directions): The greater the yarn color contrast, the higher the requirements for the uniformity of thick spots, neps and evenness. White cloth varieties (white or extra white cloth in both warp and weft): relatively low requirements for thick places, neps, etc. Striped fabric types: Wide striped fabrics have higher requirements on yarn neps than narrow striped fabrics (when the color contrast is the same). Inlay fabric (single or several yarns with high color contrast embedded in ordinary plain fabric): Usually inlay yarn has higher requirements on yarn thick places, neps and uneven evenness.
Analysis of causes of main yarn defects and improvement measures
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Based on the previous analysis of the impact of main yarn defects on fabrics and the different requirements for yarn quality of different fabric types, an effective quality data sharing and exchange mechanism can be established between yarn mills and fabric mills so that fabric mills can It is used on different fabric types according to the specific quality of each batch of yarn. At the same time, cloth mills can also put forward grade requirements for yarns based on the requirements of different fabric types, so that the mills can reasonably control quality costs based on the quality of raw materials and the status of spare parts. Of course, in order to effectively meet customer requirements and control quality costs, yarn mills must find the causes of these defects during the spinning production process and take effective measures to control and reduce defects, thereby improving yarn quality.
Thickness and details
Cause: Common slugs on the cloth surface vary in length: 1 cm ~ 2 It is mostly thick in the middle and tapers at both ends. Most of them are caused by poor drafting of the spinning yarn, attachment of free flying flowers around the drafting area, uneven roving segments, attachment of roving defects, improper setting of winding and yarn clearing parameters, etc.; in a small number of cases, It is caused by poor yarn splicing or poor twisting of the winding machine. The details are mainly caused by poor drafting of the spun yarn and poor twisting of the winding.
Measures: Thick places and details caused by poor drafting of spun yarns can be prevented and solved from the following four aspects: a) Reduce the twist of roving, that is, without increasing the breakage. Try to use a small roving twist under the premise of reducing the number of ends; b) Ensure that the fine yarn and roving drafting elements are in good condition, maintain appropriate rubber roller grinding cycles and apron replacement cycles, and check whether there are grooves, scratches and other problems at any time and solve them at any time; c) Maintain constant temperature and humidity to avoid short-term There will be large fluctuations; d) Optimize the spinning process, mainly the consistency of the gauge, top pin position and weighting arm pressure. The slugs and details produced during spinning can only be removed by the winding clearer. This will cause an increase in the number of cuts by the yarn clearer. Special attention needs to be paid to the splicing quality to avoid the secondary formation of slugs due to poor splicing. and details.
Uneven strips
Cause: The cloth surface shows regular or irregular striped shadows; mainly due to abnormal operation of the drafting elements (cots, aprons, rollers), rough and uneven surface, cot-wound spinning and backward spindles, etc. Caused by abnormal spinning components.
Measures: optimize the process of the drafting area, maintain good rubber roller and apron condition; control the order and The number deviation and evenness of the roving should be detected and any abnormalities should be immediately isolated; broken spindles and abnormal spindles of the spun yarn should be repaired in a timely manner. Workers should be required to report any abnormalities such as rubber rollers, aprons, rollers, etc. in a timely manner and notify relevant personnel to deal with them. . Set count variation and bead chain yarn defect shearing and alarm parameters on the yarn clearer on the winding machine to remove defects and remove problematic bobbins.
Flying flowers
Cause: In the spinning production, due to untimely cleaning, failure of the cotton collection device, sharp increase in end breaks, abnormal temperature and humidity of air conditioning or poor air flow, etc., the flying particles on the machine table, the ground and the air increased and accumulated, causing spinning The yarn is attached to the yarn body to form flying defects. In addition, improper cleaning operations in each process will also cause cleaning flowers to be attached to the yarn body.
Measures: The cleaning cycle must be specified according to the cleaning status of the workshop and strict inspections must be arranged. All types of cotton collection devices should be maintained and inspected regularly as normal spinning equipment to avoid unexpected failures. Check the speed of the spinning machine and control the use cycle of steel rings and travelers to avoid a sharp increase in breakage. nullThe dispatching personnel strengthen patrols and control to maintain stable temperature and humidity and ensure smooth air flow in the workshop. The yarn clearer can be used to remove flying defects that have formed before the winding process, but the yarn clearing process parameters need to be adjusted and the relationship between the number of cuts and quality needs to be balanced. Standardize the specific operations of yarn channel cleaning for machine operators to prevent cleaning flowers from being attached to the yarn body during the cleaning process.
Neps
Cause: normal fibers, immature fibers, cotton seed hulls are aggregated into round, flat, large or small fine particles or fiber-laden seed crumbs due to improper handling during ginning or spinning. Considered as neps. The main reasons are unreasonable cotton distribution of raw cotton, bad card clothing or the card clothing has reached the back-grinding cycle, poor condition of the combing machine, poor finish of the spinning channel in each process, mismatch in technology and speed of each spinning process, and poor operator operation. Improper, abnormal temperature and humidity, etc.
Measures: Use cotton with low impurity content, good rolling process and low immature fiber content, and use it for carding Card clothing in good condition and at a lower speed, using fine-tooth cylinders and top combs for combing, using pressure rod spacers for spun yarns, and strengthening cleaning in each process are currently effective methods for reducing neps. From the perspective of quality control, we pay attention to the nep test results from raw cotton to finished yarn, rationally configure each process process, and regularly wipe the main spinning channels to keep the quality of raw cotton to semi-finished products and finished products under control.
Abnormal defects
(Three strands of yarn, four strands of yarn, long details, long thick spots, etc. appear on the cloth surface)
Cause: long fragments of double-thread yarn, three-ply yarn and four-ply yarn are common. Most of them are caused by yarn breakage during the winding, doubling and twisting processes and then drift into adjacent spindles, or due to winding Double yarns are mistakenly inserted and only one yarn passes through the yarn clearer; long slubs and long details are mainly caused by the obvious unevenness of the rovings before spinning, or a small number of miscounts in the winding process that are not discovered or missed. Caused by effective handling.
Measures: For the doubling and doubling twisting processes, reasonably arrange the tour route to deal with broken ends in a timely manner to reduce random floating opportunity, the fallen full bobbin of yarn should be taken away in time; for the phenomenon of double bobbins in winding, the operation training and inspection of the operator must be started. The frequency of abnormal defects is very low, usually due to operational errors or unscheduledIt is caused by timely treatment. Once it forms on the cloth surface, it will cause great harm. Therefore, we must strengthen the operation and inspection of the post-spun yarn process, and consider adding mild measures of reward after punishment and before punishment. If it is found and dealt with in the yarn mill workshop, Avoid causing serious losses after weaving onto the cloth surface. Long slubs and long details need to be prevented by strengthening the quality control of pre-spinning, and setting the yarn clearing parameters reasonably and using the yarn clearer to remove them. Improve the skills of yarn inspectors so that they can detect abnormal defects during finished product inspection.
In short, it is very important to control the yarn quality during the yarn production process, and use scientific methods to find Effective measures to control and improve various defects to eliminate defects in the production process.
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