For pure cotton combed fine-gauge yarn, the harmful defects affecting the cloth surface in terms of hazard degree and frequency of occurrence are mainly thick places, small details, uneven evenness, flying flowers, neps and abnormal defects. What impact do these defects have on post-processing?
1. Thick places and details
Thick places appear as a prominent thick spot on the cloth surface. knots, affecting the appearance of the fabric and even causing degradation of the fabric surface. 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 normal yarns, they will form weak loops in the strength of the yarn, 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.
2. Uneven dryness
Affects the appearance of the fabric and causes degradation of the fabric surface, which is particularly serious Sometimes, the surface of the fabric appears as striped shadows or wood grains. In lighter cases, the surface of the fabric appears turbid, not smooth, and appears to have cloud spots. Uneven streaks can also cause uneven dyeing.
3. Neps
The cloth surface appears as cotton dots or white stars, and the stars are dotted on the cloth surface, affecting the fabric Exterior. 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 defects of this kind, 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 degradation of the cloth surface
4. Flying flowers
The performance of the cloth surface is between thick spots and large neps. Short slugs and loose fibers affect the smoothness of the cloth surface. It can be improved by manual repair.
5. Many abnormal defects
It manifests as long segments with low frequency of occurrence, such as double-thread yarns in single yarns, three-ply yarns and four-ply yarns in ply yarns, etc., as well as long slugs and 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 types of cloth 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 undergone special finishing 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 yarn nep requirements 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
Based on the impact of the main yarn defects on fabrics Impact analysis and different fabric types have different requirements for yarn quality. An effective quality data sharing and exchange mechanism can be established between yarn mills and fabric mills, so that fabric mills can use it in different applications based on the specific quality of each batch of yarn. On the cloth. 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.
1. Thick places and details
Cause: Common slubs on the fabric surface vary in length: 1 cm to 2 cm in majority, with the thick spots in the middle tapering off at both ends. Most of them are due to poor drafting of the spun yarn, free flying flowers around the drafting area, uneven roving segments, and roving It is caused by the attachment of defects, improper setting of winding yarn clearing parameters, etc.; a small number of cases are caused by poor spun yarn splices 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 the roving, that is, without increasing end breaks. Try to use a small roving twist; b) Ensure that the spinning and roving drafting elements are in good condition, maintain an appropriate rubber roller grinding cycle and apron replacement cycle, 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 large fluctuations; d) Optimize the spinning process, mainly the consistency of the gauge, upper pin position and cradle 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 clearer. Special attention needs to be paid to the splicing quality to avoid the secondary formation of slugs due to poor splicing. and details.
2. Uneven dryness
Cause: The cloth surface shows regular or irregular streaky shadows; mainly due to abnormal operation of the drafting elements (cots, aprons, rollers), rough and convex surfaces, cot-tangled spinning and backward spindles, etc.Caused by abnormal yarn components.
Measures: Optimize the process in the drafting area and maintain good condition of the rubber roller and apron; control the number deviation and evenness of the single and rovings, and isolate any abnormalities in time ; Repair broken and abnormal spindles of spun yarn in a timely manner, and require operators to report any abnormalities such as rubber rollers, aprons, rollers, etc. in a timely manner and notify relevant personnel to deal with them. Set the 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.
3. Flying flowers
Causes: In 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., flying particles increase and accumulate on the machine table, on the ground and in the air, and are attached to the yarn during spinning. Flying spots are formed in the body. 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. Air conditioning 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.
4. Causes of neps
: The round, flat, large or small fine particles or fibrous seed scraps formed by the accumulation of normal fibers, immature fibers, and cotton seed hulls due to improper handling during ginning or spinning are all considered neps. Mainly due to 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. Use card clothing in good condition and a lower speed for carding. Use dense card clothing for combing. Tooth cylinders and top combs, pressure rod spacers for spun yarns, and enhanced cleaning in each process are currently effective methods for reducing neps. From the perspective of quality control, during production, 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.
5. Abnormal defects
Cause: Long segments of double-thread yarn, three-ply yarn and four-ply yarn Yarns are common, mostly caused by yarn breakage during the winding, doubling and twisting processes and then drifting into adjacent spindles, or due to mistaken insertion of double yarns on the winding and only one yarn passing through the yarn clearer; long and thick The details of knots and lengths are mainly caused by obvious unevenness in the pre-spun singles and rovings, or a small amount of misbranching in the winding process that has not been discovered or effectively processed.
Measures: For the doubling and doubling-twisting processes, rationally arrange patrol routes to deal with broken ends in a timely manner to reduce the chance of random floating. The dropped full bobbin of yarn should be collected in time; for The phenomenon of double bobbins in winding must be dealt with through operator training and inspection. The frequency of abnormal defects is very low. They are generally caused by operational errors and failure to deal with them in time. Once they occur on the fabric surface, the damage will be greater. Therefore, we must strengthen the operation and inspection of the post-yarn process, and consider providing a mild post-processing reward. Pre-penalty measures should be taken to find and deal with it in the yarn mill workshop to avoid serious losses caused by final weaving on 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. Use scientific methods to find effective measures to control and improve various defects, and eliminate defects in the yarn production process. during production process. </p
