Due to the difference in fabric structure and processing equipment, the problems exposed by cotton yarn in the weaving and dyeing process have different descriptions and focuses, but can be summarized as yarn stability, heterogeneous fibers, color difference, strips. Eight aspects of unevenness, coarse detail, neps, hairiness and strength. Now we only do an analysis of the quality control points of knitted and woven cotton yarn for home textiles, for your reference only.
1 stability
Fluctuations in quality ultimately affect the consistency of fabric quality and cause problems for customer delivery. The quality index is the main reference standard for yarn stability. The mill organizes the production according to the quality standards provided by the user, and keeps the intra-indicator index stable within the control range acceptable to the user. If the indicator is found to have signs of trend change, it is necessary to take timely technical and technical measures or rationally adjust the cotton blending ingredients. Some customers cannot provide quality requirements, and it is necessary to carry out proofing and weaving. After confirmation, the corresponding internal control standards are formulated and mass production is carried out. Do not blindly ship, so as to avoid quality deviations and economic losses.
When the batch number is different, it needs to be re-sampled to bring trouble to the dyeing factory. Cotton spinning enterprises should, as far as possible, obtain raw materials with the same source, consistent processing standards and close performance in order to reduce the batch number, meet the needs of large single customers, and strive for long-term pleasant cooperation with good service.
2 heterogeneous fibers
Heterofibers have the characteristics of low content, high damage and uncertainty, which are difficult to remove during processing. Various yarn defects and color defects can be formed on the cloth surface, which reduces the production efficiency and product price, and causes great losses to the textile enterprises.
From the current situation of China's cotton processing enterprises, foreign fiber control is still not ideal. At present, the best way to remove foreign fibers in cotton mills is to manually pick and clean the foreign fiber cleaning machine, and the electronic yarn clearer with the foreign fiber detection function, which is supplemented by careful and meticulous manual process. For varieties with higher requirements for foreign fibers, the per capita picking volume has been reduced to more than 30 kilograms, and the employment has accounted for 10 to 20% of the total employment.
Despite this, it is still difficult to meet the requirements of high-grade fabrics. The cloth factory still has to organize personnel to repair the foreign fiber on the fabric, and there is also a service team that the yarn factory sends a special person to the user to repair the cloth, which often causes hair pulling, pollution and yarn breakage.
3 color difference
The main cause of chromatic aberration is the difference in fiber color and color absorbing rate caused by excessive difference in maturity of raw cotton, and the difference in dyeing that occurs when the cotton is uneven. Therefore, cotton mills must not only test and control the average maturity of cotton fibers, but also test and control the immature fiber content. The immature fiber content with a maturity coefficient of less than 0.5 should be controlled within 14%. Generally, the bleached blank can be used with raw cotton with a lower maturity, while the dyed blank requires raw cotton with better maturity.
Due to the shortage of cotton resources, China's cotton is sourced from many countries in the world, and the performance of cotton in different regions of China is also very different. However, the development of short-flow cleaning and combing in China is not conducive to the better blending of cotton. The mixing effect of the winding and clearing process is even more difficult to achieve uniformity. In the selection of raw materials, cotton with concentrated production and similar performance should be used. Cotton with a large difference in performance can be premixed and added to achieve uniform mixing. Conditional companies can also try single-spinning.
The yarn mill should indicate the batch number and the tips that cannot be mixed when delivering the same batch of long-term multi-batch. Some mills do not have strict batch number limits when producing the same variety, and the production date is used as the batch number of the yarn. The maximum time range for mixing cotton yarns should be indicated to avoid quality accidents caused by customer inattention.
4 dry uneven
The unevenness of the strip is the primary indicator for determining the grade of the cotton yarn. The woven fabric of the cotton yarn with uniform evenness has a smooth and smooth appearance, fine hand feeling, good dyeability (even color and even color), and can obtain a better appearance of the cloth surface. Especially for those decorative thin fabrics, the requirements for the uniformity of the cotton yarn are extremely high. Generally, the CV value of the strip is up to 25% of the Uster bulletin in 2001, which can meet the requirements of high-grade fabric quality.
Low-grade raw materials for high-quality yarns are only reflected in the improvement of certain indicators, but can not really improve the yarn grade, because the main characteristics of yarn coloring, strength, elongation and so on depend to a large extent on fiber properties. Therefore, according to the characteristics of the yarn used in the fabric, it is an important research topic of the yarn mill to make reasonable selection of raw materials and make economical yarns.
Over-emphasis on the stem, the use of critical processes is likely to cause an increase in the difference between the ingots, and the requirements for equipment are also high. For example, if the strip is dry, but the mechanical force caused by abnormal factors such as roller torsional vibration and apron under the apron due to excessive drafting force, the stem value is seriously affected, although the average value is improved, the strip is discrete. The increase in degree causes a difference in the cloth surface.
Due to the regular strips caused by the failure of the front yarn roller and the front roller, the damage to the fabric is high, and the spinning machine should produce high-grade cotton yarn without mechanical corolla.
5 thick, detail
Knitwear has higher requirements for details and woven fabrics have higher requirements for thick sections, just because the fabric structure and yarn density are different, and the chances of appearance of coarse and detailed are different. Roughness and detail are the main factors affecting the efficiency of weaving production, and the requirements in the production process are equally important.
Long thick and long details are generally produced in the front spinning. When the roving is the same, when the yarns of different counts are spun, the lengths of the long and thick details are greatly different. If the winding process is long and thick, the details are cut. If the length of the ç–µ is set to the same, the length and length of the low-yarn yarn will not reach the set clear length, but it cannot be detected by the electronic yarn clearer, which reduces the yarn defect removal rate. .
Two batches of cotton yarns at the same level as the Uster bulletin have the same level of user response. One of the reasons is the difference in the number of small defects. Some high-end customers have added the coarseness index of the conventional index (IPI value). Strict, as well as small yarn defects other than the 9th grade harmful yarn defects, which are the internal control standards set by the customer according to the quality of the cloth. Another reason is the difference in raw material properties and production processes.
The mill should determine the requirements of the fabric type on the yarn according to the appearance and concealability of the coarse and fine details of the fabric. At the same time, combined with the yarn grading of the 100,000-meter yarn grading diagram, the number of yarn defects of the fabric is controlled at ten. The 10,000-meter yarn enamel is reflected on the grading chart.
6 neps
Cotton neps are often caused by poor processing and immature fibers, especially pests and cotton and stiff cotton fibers. Because of its small size, it is easy to be entangled and adhered by yarns and cloths, which is difficult to remove during the entire textile printing process. During the printing and dyeing process, since the cotton fibers are twisted together, only the surface hair is burned in the singeing process, and the cotton fiber mass cannot be burned. When the cotton fiber mass is attached to the cloth surface, the adhesion is stronger after printing and dyeing, and it blocks the color soaking cloth surface when printing and dyeing. After the printing and dyeing cloth is dried, the cellulose crystallization zone in the fiber changes under the action of chemical dyes after printing and dyeing, and the adhesion is reduced and falls off. There are numerous irregular unstained whites on the cloth surface. Defectively, the printing and dyeing cloths are reduced in batches. The damage is serious and the loss is huge.
As long as the quality of the raw materials is stable, the nep index is generally stable. At present, the lightweight and slow process adopted in China is mainly reflected in the carding process, which is the most effective measure to reduce the neps; the recently introduced “heavy quantitative and efficient process†makes full use of the cohesion between the fibers to make the entanglement The filaments can be better stretched for better control of the neps.
7 7, hairiness
The hazard of yarn hairiness is mainly manifested in three aspects: First, the uneven distribution of hairiness on the yarn can cause the zonal stripes of the woven fabric, and the yarns with more hairiness are less than the hairiness, and are formed after dyeing. The yarns are of different shades, the weaving of the fabric to form a strip of flowers causes the fabric to fall, and the hairiness in the weaving will form a new neps; the second is the production of high-density fabrics, especially when weaving on an air jet loom, the hairiness will make the phase The adjacent warp yarns are intertwined and entangled, which will make the weft insertion difficult. Thirdly, the hairiness on the yarn falls off due to friction in the downstream processes, forming flying flowers, polluting the environment, endangering human health, and the yarn itself has many hairiness, which must affect The pilling of the fabric. In particular, polyester-cotton blended yarns and cotton/wool blends are more stringent in pilling requirements.
Cotton yarn hairiness is 75% or more shorter than 1 mm, and is less than 3 mm, which is less than 1% of the total hairiness. The long hairiness is mainly caused by the friction of the yarn by the winder (especially the automatic winder). Self-winding installation of hairiness reduction device can have obvious effects and enhance the competitive advantage of yarn.
The method for measuring the hairiness of the yarn has the H value measured by Uster's hairiness meter. For the same variety, the hairiness H is comparable and the H value is relatively stable; another method for measuring hairiness is the hairy number counting method. In terms of production and subsequent use of yarn, the number of hairy feathers is more practical.
8 strong
Modern weaving technology, whether it is woven or knitted, tends to be three high (high quality, high speed, high efficiency). Compared with traditional equipment, the speed is doubled, and the cotton yarn is required to have enough strength to reduce breakage and ensure production efficiency.
The air jet loom is faster, the process speed is generally above 500r/min, and the weft insertion rate is generally above 1300m/min. In order to obtain clear opening under high speed conditions, large tension and small opening process are adopted, and the warp yarns are subjected to a large tension. In the process of opening and beating, when the tension peak of the warp yarn overlaps with the strong weak loop of the warp yarn, the probability of breakage occurs. It is high. Jet weft insertion is a passive free-end weft insertion, and its weft insertion tension peak is much larger than other weaving machines. When it encounters a strong weak ring, the probability of weft breaking is also large.
What really affects efficiency and quality is the strong weak ring. In particular, high-density and high-density fabrics have fine yarns and low strength. The key points are to control the strength unevenness rate and the minimum strength. The minimum strength should reach 80% of the average strength.
The spinning process has a great influence on the yarn strength unevenness and the lowest strength index. It is necessary to strengthen the process research and focus on the backward spindle.
Concluding remarks: The yarn mills and the weaving and dyeing factories often communicate with each other to jointly develop the quality standards for fabric yarns, and constantly modify and improve them to make them more suitable for fabric characteristics. Properly purchase raw materials with good processing quality and consistency, maintain relatively stable cotton blending and production; strengthen process research, promote technological progress, give full play to the effectiveness of existing equipment; produce the most economical yarns that are satisfactory to customers, to obtain the most Good economic benefits are the inevitable choice for cotton spinning enterprises to develop benign
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