   The unevenness of the yarn into the yarn is one of the main indicators for measuring the quality of the yarn, and is closely related to the efficiency of the post-process and the appearance quality of the fabric. In recent years, with the advancement of textile technology and the increased capital investment of spinning mills, the equipment level has been improved. Key spinning equipment such as new rubber rollers and non-mechanical corollas are widely used, such as roller, rubber roller eccentricity and gear defects. The unevenness of the strip caused by mechanical defects has been rare, and the sudden unevenness of the strip is particularly prominent. It not only increases the defective product, reduces the pass rate of the joint, but also affects the efficiency of the post-process, which is the main defect of the yarn. Especially in the spinning process, it is characterized by a long duration, a short period of time, a strong sporadicity, and a high rate of cloth surface appearance. Therefore, it is necessary to find out the cause of the sudden unevenness of the cloth surface and take effective preventive measures. necessary.
   1, yarn evenness sudden wavelength ranges and characteristics of the unevenness
    According to the theory of strip unevenness spectrum, the wavelength range of the unevenness of the spun yarn process is: π D ～ π D ′ E ; wherein D and D ′ are the front and rear roller diameters respectively, and E is the total draw ratio of the spun yarn. Take D, D cotton spinning frame 'are both 25 mm, E take 35 times (generally 20 to 45), the yarn a wavelength range of from about 7.8 cm ~ 274.7 cm Unevenness article.
    In the initial occurrence of sudden strips of dry cloth, for reasons that cannot be determined, it is often tested on the strip dryer after the fabric is unwound; then the process and the general cause are inferred based on the results of the test spectrum, and then the inspection is carried out in a targeted manner. repair. After several years of accumulation, it is concluded that the sudden unevenness of the cloth surface is mostly generated in the spinning process ( 83% for the general spinning process , 11% for the pre-spinning process , and 6% for the other processes ) , which is characterized by suddenness. Strong, the cloth surface appears obvious; because of the strong chance, the duration is different, sometimes even if the reason is not found, it will disappear after a period of time.
    In the long-term follow-up of sudden stripe unevenness ( disassembly test and corresponding inspection test ) , the typical two cases of spun yarn sudden unevenness spectrum and uneven curve are shown in Figure 1 and Figure 2 . . Figure 1 shows the mechanical wave, which is characterized by a “chimneyâ€-like peak in the 195px to 9.0 cm region, most of which have obvious harmonics near 2.5 cm ( λ /3) and 4 cm ( λ /2 ) ; 2 is the draft wave, and the peak in the spectrum is significantly higher than the normal peak curve.
    Sudden CV value CV value of a yarn evenness deteriorated significantly as compared to the normal yarn, yarn defects often made also immediately increased significantly (see Table 1).
    2 , the cause
    Cause of mechanical waves
    Mechanical defects of front roller and front rubber roller, including eccentricity of roller or rubber roller, lack of oil in bearing, wear, rubber roller blade injury, etc. With the strengthening of management of textile enterprises, the quality of equipment maintenance, and the improvement of the quality of spinning equipment such as rollers and rubber rollers, such problems have been rare.
    The front roller or the rubber roller is embedded with a flower coat, a cotton knot and the like. Due to the sugar in the raw cotton, the unfinished impurities, etc., it is completely exposed after the drawing process, and the temperature and humidity ( especially summer ) and other factors are easy to stick into the roller groove ( occasional rubber roller) Adhesive ) , so that the roller or rubber roller forms a similar eccentricity or ellipse to produce unevenness of the strip, and its harmonics are obvious in the spectrogram. Individual adhesive inclusions will fall off on their own after a period of operation, which is why sometimes the sudden dry strips disappear after a period of time. In addition, the dust and oil tidbits blown down by the air-conditioning wind in the old air-conditioning ducts are also a cause of the sticking of the rollers. The unevenness spectrum produced by such defects and the eccentricity of the front roller ( rubber roll ) are not generated. The uniform spectrum comparison is shown in Figure 3 .
    The front rubber roller is wrapped at one end and then spun at the other end. Due to the influence of the entanglement of the front rubber roller, the front rubber roller which is spinning at the other end is axially pressed unevenly, thereby causing mechanical unevenness of the strip.
    Cause the draft wave
    Theoretically, the front and rear areas of the yarn drawing have the possibility of producing the uneven wave of the drafting wave; in practice, the drafting wave generated by the rear drafting area is not uniform. Appeared; therefore, here is mainly to discuss the reasons for the unevenness of the strip in the front drafting zone.
    Draw tooth defects. Unevenness caused by defects such as poor maintenance or light and heavy tooth wear and poor meshing during operation.
    Up and down sales are invalid. Including the upper pin moving spring piece loss, deformation, the lower pin is not installed in place, the upper pin lacks the spacer block, the spacer block paper, the upper and lower rubber rings are sandwiched between ( roving ) work paper, dead flower, etc. The ring is defective, the upper and lower aprons are not in grip, and the roving is twisted in the rear area.
   3. Preventive measures
    Strengthen equipment maintenance and basic management
    In the above analysis, due to the mechanical proportion of rubber roller, roller eccentricity, lack of oil, tooth wear and other mechanical reasons, this is based on the premise of higher equipment maintenance quality; therefore, improve the maintenance quality of equipment ( roller, gear ) and The quality of rubber roller production and the quality inspection and check of all aspects of equipment maintenance are of vital importance. It should be in line with the actual situation of the enterprise, using high-quality roller, rubber roller and bearing, etc., to master the wear rules of key components and equipment, and solve the problem before sudden bursts of unevenness, such as rubbing the roller with alcohol during the maintenance cleaning cycle Once again, it can effectively reduce the unevenness caused by the sticking of the roller, and it should be shortened in the summer; the maintenance and quality inspection of various equipment should be incorporated into the normal working system to ensure a better equipment foundation. In order to make the sudden unevenness caused by mechanical defects such as rollers and rubber rollers keep less.
    Set special personnel inspection and maintenance
    Special personnel are required to carry out special inspection and maintenance on the roller or rubber roller stuck in the debris, the failure of the upper and lower pins, the damage of the roller or the rubber roller at any time (the handle roller, the rubber roller, the front and rear areas of the eye are abnormal, and the problem is repaired by the card yarn ) At the same time, taking into account the feedback and tracking work of sudden and uneven distribution, find out the cause and try to control the problem in the initial stage, so that the unevenness of the strip can be effectively controlled.
    Establish a sense of group defense
    Strengthen the quality awareness training for value lathes, doffing workers, operation maintenance workers, etc., establish a sense of inspection of all employees , and may cause accidents such as upper and lower aprons ( dead flowers ) , spacer block defects, and failure of loading and unloading. The problem can only be solved at any time and found to be able to minimize the sudden and uneven distribution caused by it.
    Short cycle pull inspection
In the case of conditions, the net-type full detection method with a short period ( not more than 3 days) can be used to find the backward spindles and repair them in time, thereby reducing and eliminating the occurrence of sudden unevenness. After several years of hard work, we have explored effective measures to control sudden and uneven behavior, and incorporated them into daily work, forming a system to be fixed, so that the sudden and uneven distribution rate is from the original 2.5% decreased to 0.13% to 0.4% in recent years and can be stably maintained.
    Conclusion
    With the improvement of the quality of equipment and the quality of its maintenance, the causes of sudden and uneven drying of the spinning process have undergone major changes. The random problems in normal production operations have become the main reason; therefore, the law is found and effective prevention is taken. Measures are the key to reducing sudden unevenness. Incorporate effective measures to control sudden and uneven behavior into daily work, and form a system to prevent problems before they occur.
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