Fabric quality includes the intrinsic quality and appearance quality of the fabric. With the increasing awareness of internationalization and branding of clothing companies, the market demand for defect-free yarn and defect-free cloth has prompted textile companies to have increasingly strict requirements on the length and size of yarn defects in the appearance of cotton fabrics. For this reason, in the production process of cotton yarn, yarn defect testing, data analysis and control of 100,000 meters have received more and more widespread attention and attention, especially with the development of electronic yarn clearing technology of automatic winding machines, the improvement of splicing quality It provides an effective guarantee for reducing cotton yarn defects.
01 Strengthen equipment maintenance and parameter settings
From the perspective of the root cause, A2 yarn defects are raw material yarn defects, which appear as short, small, and numerous distribution states on the cloth surface. This kind of yarn defect is usually caused by the high shortness rate, low maturity and high defect content of the raw materials. To reduce small yarn defects in cotton yarn, it is necessary to set strict cotton blending standards for raw materials and continuously correct the yarn clearer parameters N and S values in the winding process.
During the spinning process, immature cotton fibers tend to form a large number of hooks and produce many small yarn defects. Therefore, it is necessary to control the quality of raw cotton. When formulating raw cotton quality control standards, we must not only consider the quality requirements of different cotton yarn numbers in terms of quantity control of small yarn defects, but also consider the quality requirements of cotton yarn for weaving and dyeing products. To blend cotton well, you must not only control the cotton grade, length, and linear density, but also appropriately control the immature fiber content and short fiber content.
Due to the existence of short fibers in cotton, the high-speed operation of spinning equipment will cause a large amount of short fibers to become flying flowers and dust. These flying flowers and dust adhere to the spinning equipment or yarn channels, causing many yarn defects in the cotton yarn produced. Therefore, in order to reduce yarn defects such as flying flowers and slubs, it is necessary to strengthen the standardization of the operating cleaning system, the institutionalization of equipment maintenance and wiping, and the institutionalization of special parts inspection and inspection. These must be implemented item by item, and record inspections must be strengthened to ensure that the machinery in each process does not accumulate dust, No flowers hanging, no wrapping, no sticking, and no damage to the yarn structure.
The winding process is the last quality control process in spinning and the first quality control process in weaving. Electronic yarn clearer is an important means to control yarn defects. In addition to completing the task of removing yarn defects, the yarn defect detector also plays a very important role in controlling the operating efficiency of the automatic winding machine. The setting of the yarn clearing process of the electronic yarn clearer should be based on the requirements of the fabric to determine whether it should be relaxed or tightened. For high-end fabrics, the main function of the electronic yarn clearer is to remove some neps N and short slugs S. Relatively speaking, its flaw cleaning load is relatively heavy. In production practice, yarn clearer parameters N and S should be constantly corrected, and the suitability of the process can be verified by rewinding the package. Through these measures, A2 yarn defects can be significantly reduced.
02 Properly set up the electric cleaning process to reduce the number of yarn defects
With the continuous development of electronic technology, the functions of electronic yarn clearers are becoming more and more powerful. However, blindly pursuing the minimization of yarn defects while ignoring production efficiency will cause excessive shearing. Intensive shearing will lead to a higher miscutting rate. Although small yarn defects are reduced, harmful large yarn defects are difficult to remove and knots will increase. The winding efficiency will also decrease significantly and the cost will increase. Therefore, reasonable electro-cleaning process parameters must take into account both quality and efficiency.
When setting the electric cleaning process parameters, the company can set the initial electric cleaning process based on the yarn defect inspection results of 100,000 meters of spun yarn, and then optimize the electric cleaning process parameters based on the yarn defects of 100,000 meters of package yarn. Of course, you can also set the electro-cleaning process parameters first, and then detect hundreds of yarn defects. Divide 200 spun yarn bobbins into two equal parts, and successively relax and tighten the electric clearing process parameters on the same machine and spindle position for yarn rewinding. At the same time, the empty cutting rate is calculated and tested. If the initially determined process parameters are too much for air cutting, and many small yarn defects will be cut out, but after relaxing, more large yarn defects will be cut out, it means that the original process parameters are too tight; if the initially determined process parameters are for less air cutting, and there will be more large yarn defects cut out, it means that the original process parameters are too tight. There are many defects and few small yarn defects. After tightening, the number of small yarn defects increases significantly. If it meets the customer’s requirements (the quality requirements are not high), the original process can be maintained. Otherwise, twice electric cleaning will be considered.
In short, the setting of electric cleaning process parameters should be consistent with the inherent quality of yarn and user requirements. The focus is to analyze the types and causes of yarn defects, and take effective measures from the aspects of process, equipment, operation, temperature and humidity, etc., to reduce the number of yarn defects. To improve yarn quality, it is not advisable to use the statistical data of the electronic yarn clearer and combine it with physical objects to guide the quality control of the previous processes. It is not advisable to rely too much on electric clearing to improve quality.
03 Strengthen the maintenance of spinning machine status to reduce spindle belt slippage and twist yarn defects
In order to reduce mechanical twist yarn defects, the spindles, spindle belts, tension discs and roller discs were tested for yarn twist under bad conditions, and five key control items were selected for cause analysis based on the degree of impact.
a) The spindle belt is hung on the spindle belt tension reel or protective hook. The main reasons are: first, the doffer hangs the spindle belt off when cleaning the spindle belt tension disk; second, the tension disk shakes due to lack of oil or the bearing is worn and stops, causing the spindle belt to slide out of the spindle belt disk.
b) The spindle belt is seriously deflected, that is, the spindle belt runs out of the spindle tray. The main reason is that the doffer pulls the spindle tape out when cleaning the spindle plate with a brush. The diameter of the deviation position of the spindle belt is smaller than the diameter of the spindle disc, resulting in strong twisted yarn. On the contrary, it is a weakly twisted yarn.
c) Pressure failure. JWF15The spindle tension and pressure arm of the 16-type spinning machine is designed with a lever-staged and open hanging weight structure. Compared with the screw-locked weight structure of the old machine, the pressure adjustment operation is simple and the maintenance is convenient, but a weight is added. The probability of falling off and hanging in the wrong gear.
d) The roller lock fails. The rollers of the JWF1516 spinning machine and the locking sleeves that fix the rollers are both plastic parts, which are easily deformed, aged and hard and brittle, which affects the locking elasticity, resulting in an increased chance of the nut loosening. If the nut completely loosens, the roller locking will fail.
e) The spindle sinks. Damage to the spindle support bearing or wear of the spindle tip causes the spindle to sink, causing the spindle to run unstable and swing, affecting the spindle speed, thereby causing a reduction in twist.
Based on the analysis of the reasons, the following measures are taken: Strengthen on-the-job training for new workers, strengthen awareness of responsibility, and correctly implement operating methods; strengthen maintenance to ensure mechanical condition; strengthen detection and tracking; appropriately expand the scope and quantity of twist testing; inspect low-strength yarns detected in the test , The alarmed bobbins removed by the automatic winding machine were subjected to twist testing, and twisted yarn defects were found to be tracked to eliminate bad mechanical conditions; the work quality inspection of night shift maintenance workers and doffing workers was strengthened; bad mechanical conditions were recorded and corrected. The above measures have achieved obvious results. According to statistics, the number of mechanical defective items has been reduced by an average of 61.11% per month, the correction rate has increased from the original 77.81% to 100%, and twist yarn defects have been significantly reduced.
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