In recent years, the textile industry has developed into a new normal, the market competition has become extremely fierce, and the quality requirements for textile industry products have become increasingly higher. Downstream customers often complain to textile factories about quality problems and defective products after manufacturing, dyeing and finishing. The thorny problem that plagues spinning mills is the analysis and processing of rungs in fabrics, which is complicated. At present, there is no testing agency in China that can make a conclusive judgment on the quality of rung cloth. It is relatively simple to analyze the fabric surface of rungs that appear on woven fabrics, but it is more difficult to analyze and judge the reasons for the formation of rungs and stripe defects on circular woven fabrics. Exploring and mastering the causes of the formation of related fabric rungs and their analysis methods will help the production management of all links in the industrial chain, and provide reliable objective factual basis for reducing the occurrence of rung defects and avoiding unexpected economic losses.
1. Characteristics and hazards of fabric rungs
Stripes with inconsistent colors appear on the natural gray fabric or after dyeing and finishing. The rungs of circular woven fabrics are mostly characterized by regular bars. Exceptionally, the strips on the cloth surface are composed of one or more yarns. There will be certain differences between the yarn at the rung and the yarn at the normal fabric surface in terms of color difference, thickness, composition, twist, hairiness, loops, density, and stretch yarn tension. The factors that form the rungs of circular knitting fabrics include yarn reasons, circular knitting manufacturing reasons, and dyeing and finishing reasons.
The occurrence of circular knitting fabric rungs is caused by the wrong manufacturer and the wrong variety, raw material fluctuations from batch to batch, uneven cotton mixing, use out of sequence according to production time, mixed batch use of yarn or spandex yarn, and uneven yarn feeding tension of the circular knitting machine. and many other situations. Circular woven fabrics with horizontal grades appear, generally in large quantities, ranging from a few strips to dozens of strips. If it does not appear in time during the use of downstream processes, the consequences will be more serious. The harm caused by defective fabrics on the rungs is greater. In addition to the base material, auxiliary materials, processing fees of the weaving factory and the dyeing and finishing fees of the dyeing factory, the cost of defective products is much higher than the value of the original yarn, or even higher than the original yarn. Value doubled.
Circular woven fabrics are of high quality and difficult to trim. Because there are multiple loops between the fabric veil paths, the distance between the rungs is only about 3cm to 5cm, making it impossible to cut, and fading and color changes will also incur a lot of costs. Master the causes and analysis methods of the formation of fabric rungs, and find the objective and real factors that form defective rungs, so as to prevent and reduce the occurrence of rung defects and reduce unexpected economic losses.
2. Reasons for the formation of fabric rungs
1 Factors causing rungs in circular woven fabrics in spinning mills
(1) Factors such as the origin, batch, color, whiteness, performance, cotton maturity, and micronaire value of spinning raw materials will be affected by differences in raw material quality, which will cause fabric rungs.
The fabric surface of the rungs formed by using mixed batches The fabric surface of the rungs formed by using staggered yarns
(2) Improper handling of the transitional batch of raw materials, especially when the quality of the raw materials of the subsequent batch is significantly different from the previous batch. The longer the transition time, the smaller the increment of raw materials input into the subsequent batch, and the less likely it is to cause fabric rungs. On the contrary, the more.
(3) Uneven mixing of raw materials from different origins, different batches, and different specifications, as well as uneven mixing of raw materials with different components in blended varieties, will cause fabric rungs.
(4) There are generally two ways of mixing raw materials: bag blending and strip blending. Strip blending has a more accurate blending ratio than bag blending fiber mixing. However, it is important to control the weight unevenness of carded sliver and add the blending process when necessary, which is an important factor in controlling the accuracy of the blending ratio.
(5) When wrapping on the cotton table, pay attention to arranging the bags evenly, cutting them high and filling them flat. Especially the cotton rolls at the beginning and end are easy to mix unevenly and need to be unrolled for use. The rewinding, stripping and pattern rewinding should be uniform and uniform in the longitudinal direction. The cotton picking beater should catch the cotton more frequently and less frequently to keep the cotton picking machine operation rate above 92%.
(6) When implementing the raw material bag mixing method, in the absence of a multi-silo cotton mixing machine, secondary rolling is implemented when necessary. The primary rolling on the cotton table, middle and lower layers must be classified and discharged evenly to make different fibers The mixing will be more complete and consistent; or a cotton mixing process can be added to pack the pre-mixed raw materials into bags, and then put them on the bale grabber to enter the blowroom process.
(7) When implementing the strip-mixed fiber mixing method, the feeding positions of the slivers of different fibers should be fixed and consistent, and the position and structure of the various fibers in the yarn sliver should be kept the same.
(8) When producing multi-component blended varieties with more than 3 types of fibers, a combination of bag-blending and strip-blending can be used. After selecting part of the fiber to be bag-blended into strips, it is then mixed with another part of the fiber strips to ensure that the multi-component fibers are mixed evenly.
(9) To produce the same variety, arrange the production of equipment of the same model to maintain process consistency and avoid differences in cotton yarn quality due to differences in machine models and inconsistent processes. Different models of equipment produce the same productDifferences in accuracy may be caused by inconsistent coil size or tension.
(4) After dismantling the fabric, use a spinning test instrument to test the twist, yarn count, evenness, and hairiness of the yarn at the rung, and compare whether the yarn at the rung is different from the normal yarn.
(5) For rung fabric samples containing spandex elastic yarn, according to the FZ/T 01057.4-2007 standard, use the “chemical dissolution method” to dissolve the spandex yarn in the fabric, and then wash and dry it, so that only the yarn fibers remain. Look at the fabric surface to see whether the characteristics of the rungs are consistent with the characteristics of the original cloth surface. If there are no stripes in the pure yarn fabric sample, the rungs caused by yarn factors can be ruled out.
(6) Similarly, use the “chemical dissolution method” to dissolve the yarn fibers in the fabric, then wash and dry it. From the surface of the cloth with only spandex silk left, see whether the characteristics of the rungs are consistent with the characteristics of the original cloth surface. If it is purely There are parallel bars on the surface of the spandex yarn, which can be confirmed to be caused by the tension problem of the spandex yarn in the knitting factory.
(7) Observe with a fiber fineness meter, slice the longitudinal and transverse sections of the yarn, and analyze whether there are any changes or abnormalities in the fiber structure, fiber state and blending ratio within the yarn. When slicing, use colored wool as a medium to isolate the fibers. The thickness of the cut section will be more appropriate and the image will be clearer.
(8) Preparation of a solution containing cellulose blended fabrics containing spandex fibers and insoluble spandex fibers: first inject 75 mL of water into the beaker, then slowly inject 25 mL of 98% concentrated sulfuric acid along the glass rod, and then stir continuously to prepare into a 40% sulfuric acid solution.
(9) Method for dissolving cellulose blended fabrics containing spandex while retaining the spandex: Put the elastic fabric sample into a beaker containing 40% dilute sulfuric acid, heat it to 95°C in a water bath, and use Stir gently with the glass rod continuously. It will take about 30 minutes. Pour out the solution, wear rubber gloves, clean the spandex silk cloth sample, and dry it to check the shape of the cloth surface.
5 Summary
Since there are many factors that cause the formation of fabric rungs, their shape distribution also has various states, and they are highly concealed and have a long latency time. Most of them will not be obvious until after weaving or dyeing and finishing. There are various methods to analyze rung defects, and the analysis process is cumbersome and complex. In addition, cross-industry professional and technical analysis of the industrial chain has become more difficult. A specific analysis should be made based on the specific situation of circular woven fabric rungs. The elimination method can be used to eliminate items one by one, and finally carry out targeted evidence collection. Although fabric rung analysis is complicated, there are not many common types of rung defective fabrics. Strengthen the analysis and research on fabric rungs, understand in detail the causes and solutions of circular woven fabric rungs, and be proficient in their analysis methods and operating steps. The generation of rung defective fabrics will be effectively controlled and the resulting rungs will be defective. Waste will be greatly reduced. From the industrial chain, raw materials, spinning, weaving, dyeing and finishing and other production links, combined with the many factors that cause cloth surface rungs, strengthen various management tasks in response to problems existing in the management of raw materials, equipment, processes, operations, etc. The occurrence of defective fabrics on horizontal rails will be fundamentally controlled.
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