Rotor spinning defects and their characteristics
Yarn defects are yarn defects produced during the spinning process and are an important part of assessing the quality of cotton yarn. Common yarn defects in rotor spinning are shown in the table below.
In addition to raw materials, feed product quality, and process configuration, the causes of rotor yarn defects are mainly related to the operating status of the equipment; operation, maintenance, management, and workshop temperature and humidity, etc., which are described below.
Equipment mechanical status and yarn defects
Poor mechanical condition of the equipment is the main cause of yarn defects and poor forming.
(1) Thick and thin yarn defects in the finished yarn are mainly caused by the poor condition of the feeding part. The mechanical reasons include damage to the feed horn, accumulation of flowers on the feed roller, damaged bearings, rolling and beating, improper clutch spacing, and gears. wear and tear etc.
(2) Slub yarn defects in the finished yarn are related to the poor condition of the opening roller, such as the opening roller has burrs, inverted teeth, broken teeth, excessive rotation speed, sluggish roller operation, improper clearance with the cover, etc. . When the gap between the rotor and the sealing cover is too large and the burrs in the condensation groove of the rotor are hung, slub yarn will also be produced.
(3) Weak twist in the yarn is mainly related to twisting components such as the spinning rotor. For example, if the spinning unit is not locked and air leakage occurs or the sealing ring fails, the pressing amount of the spinning rotor pressure wheel is too small or the rotation is inflexible, causing the spinning rotor to rotate. Slippage, low negative pressure in the spinning rotor, damage to the dragon belt, etc. will all cause weak yarn twist.
(4) When the twisting head, yarn guide tube, yarn guide and other mechanical parts are damaged and fluffed, they will inevitably rub against the yarn sliver and fuzz the yarn to form hairy yarn.
(5) When the impurity removal part is in poor condition, sesame yarn with dense neps and impurities will be produced. For example, the saw teeth of the carding roller are worn and affect the removal of impurities; the impurity discharge holes are clogged and the impurity discharge cavity is accumulated; impurities cannot be discharged when the process exhaust is blocked, etc. Especially for self-ventilating rotor spinning machines, when the process ventilation is not smooth, several spindles in the front part of the machine will be severely broken, making it difficult to drive. When hard impurities are embedded in the rotor condensation groove, it will also cause uneven regularity and uneven strength of the yarn.
(6) Poor bobbin formation is mainly caused by the poor condition of the yarn take-up winding part, such as grooves on the yarn take-up roller, improper pressure, excessive or too small tension draft, damage to the yarn guide, etc.
Running operations and yarn defects
Many yarn defects in rotor yarn are caused by improper operation of the turner.
(1) Flying flowers, yarn waste, and poor wrapping of cotton sliver joints during splicing will form slubs, details, or slub yarns in the yarn.
(2) The rotor is not thoroughly cleaned during splicing (self-ventilation type), and the yarn is not spliced for a long time after the end is broken; oil-hand splicing is used, and oil stains are brought into the splicing; bobbins falling to the ground, unclean containers, etc. will contaminate the yarn, causing Black and gray yarn and oily yarn.
(3) Mixing new and old cotton slivers or using the wrong cotton slivers during the check-in period will cause color difference or the yarn characteristics of the package to be inconsistent with the specifications.
Maintenance and yarn defects
The quality of maintenance work also directly affects the number of yarn defects in finished yarn.
(1) If the feed plate is pressurized too much or too lightly, the slivers will be delaminated and produce unexpected drafting, resulting in increased yarn weight unevenness.
(2) Improper installation of the feeding horn and premature feeding of cotton to the feeding roller during collective yarn spinning will cause thick spots or details in the yarn.
(3) Improper installation of the isolation plate, improper rotor cleaning cycle or incomplete cleaning will cause uneven yarn dryness and the formation of black and gray yarn. When the twist resistor is used incorrectly, the finished yarn will have color difference or hairiness due to uneven twist.
Working environment and yarn defects
The workshop working environment includes two aspects, namely the dust content of the workshop air and the workshop temperature and humidity. Both of them have a certain relationship with yarn defects.
(1) The dust content in the workshop directly affects the yarn defects of the rotor yarn. If there is a lot of dust in the workshop, the dust (including short velvet below 5mm) will be sucked into the spinning device along with a large amount of air. When accumulated to a certain extent on the yarn path, thick details will be produced, forming slub yarn defects and soot yarn. Therefore, reducing the dust content in the rotor spinning workshop is an important measure to improve yarn quality and reduce yarn defects. To reduce the dust concentration in the workshop air, we should start from two aspects. One is to place the rotor spinning machine in a separate workshop and separate it from the previous workshop where the dust is discharged larger. The other is to reduce the generation of its own dust source. That is, increase the dust suction air volume and process exhaust volume to prevent the exhaust duct from being blocked and dust from overflowing.
(2) The influence of temperature and humidity in the workshop on yarn defects. When the temperature is within a certain range, yarn defects are relatively stable. However, when the temperature and humidity exceed a certain limit, yarn defects show an upward trend. Therefore, the temperature in the rotor spinning workshop should be controlled at 28°C, it is more appropriate to control the relative humidity at 60% to 70%. However, due to the different effects of winter and summer climates, the temperature and humidity control requirements are also different. The temperature in winter should be greater than 20°C, and the relative humidity should be between 60% and 65%. , the summer temperature should be less than 30°C, and the relative humidity should be between 65% and 70%.
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