With the development of society and the advancement of textile science and technology, people’s use of fabrics The requirements for performance and grade are getting higher and higher. While textiles are required to be durable and comfortable, the requirements for smooth and defect-free appearance are also getting higher and higher. This makes it urgent to produce high-quality yarn to meet market and consumer needs. How to improve yarn quality to meet fabric needs?
The impact of main yarn defects on fabrics
For pure For combed cotton high-count yarn, the harmful defects affecting the fabric surface in terms of hazard degree and frequency of occurrence are mainly thick places, small details, uneven evenness, flying flowers, neps and abnormal defects. The following first introduces the impact of these defects on the post-processing process.
1. Thick places and details:
Thick places appear as a prominent thick place on the fabric surface, which affects the appearance of the fabric. It may even cause 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 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. In particularly severe cases, the fabric surface It manifests as striped shadows or wood grains. In lighter cases, the cloth surface looks turbid, not smooth, and seems to have cloud spots. Uneven stripes 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, such as Color spots affect the appearance of fabrics just as they affect the beauty of a girl’s face. 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.
4. Flying flowers:
The cloth surface performance is between slugs and large neps, shorter and The fibers are loose and affect the smoothness of the cloth surface. It can be improved by manual repair.
5. Abnormal defects:
Mostly manifested as long segments with low frequency of occurrence, such as double yarns in single yarns , three-ply yarn and four-ply yarn in the strands, etc., as well as long thick places, 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, such as: 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 yarn quality requirements are different. The requirements for neps 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 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 previous analysis of the impact of main yarn defects on fabrics and different fabric types Each yarn quality requirement has its own emphasis. An effective quality data sharing and exchange mechanism can be established between yarn mills and fabric mills, so that fabric mills can use it on different fabric types based on 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.
1. Thick places and details:
Cause: Common thick places on cloth vary in length: mostly 1-2cm. The thick ends in the middle are gradually tapered, which is mostly caused by poor drafting of the spinning yarn, the attachment of free flying flowers around the drafting area, uneven roving sliver fragments, attachment of roving defects, improper setting of winding clearing parameters, etc.; a small number of them are caused by spun yarn joints It is caused by defective 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: For thick spots and details caused by poor drafting of spun yarns, we can prevent and correct them from the following four aspects:Solution:
a. Reduce the roving twist, that is, try to use a small roving twist without increasing end breaks;
b. Ensure that the fine yarn and roving drafting elements are in good condition, maintain an appropriate top 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 gauge, top pin position and rocking Rack pressure consistency. 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 quality of the twist to avoid secondary formation of slugs due to poor twisting. and details.
2. Uneven stripes:
Cause: the cloth surface shows regular or irregular strip shadows; the main reason It is caused by abnormal operation of drafting elements (top rollers, aprons, rollers), rough and uneven surfaces, abnormal spinning parts such as top rollers, twisted yarn, and backward spindles.
Measures: Optimize the process in the drafting area and maintain good top roller and apron condition; control the count deviation and evenness of the single and roving yarns, and isolate any abnormalities in a timely manner ; Repair broken and abnormal spindles of spun yarn in a timely manner, and require workers to promptly report any abnormal situations such as top rollers, aprons, rollers, etc. during their rounds 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:
Cause: due to untimely cleaning, failure of the cotton collection device, and sudden end breakage during spinning production Increasing air conditioner temperature and humidity, or poor air flow, etc., cause fly particles to increase and accumulate on the machine table, on the ground, and in the air. During spinning, fly particles are attached to the yarn body to form fly 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. 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. Neps:
Cause: normal fiber, immature fiber, cotton seed hull due to ginning or spinning process If not handled properly, the round, flat, large or small fine particles or fibrous seed chips formed by the accumulation are regarded as 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 (three or four strands of yarn on the cloth, long details, long thick spots, etc.):
Causes : Long fragments of double-thread yarn, three-ply yarn and four-ply yarn are common. Most of them are caused by yarn breakage and drifting into adjacent spindles during the winding, doubling and twisting processes, or due to the mistaken insertion of double yarns on the winding. Only one yarn passes through the yarn clearer; long slubs and long details are mainly caused by pre-spinning singles, obvious unevenness of rovings, or a small number of misaligned branches in the winding process that are not 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. </p
