Classification of cotton knots in yarn and analysis of the causes of formation

 Cotton knot is an important index for yarn quality assessment. The technical requirements of cotton yarn grade not only stipulate the total number of cotton knots and impurities in 1 g yarn, but also the number of cotton knots. The amount of cotton knot content not only affects the appearance quality of spinning yarn and fabric, but also affects the structure and uniformity of the yarn and the amount of yarn breakage rate.


  Causes of cotton knots

  Cotton knot is a single fiber or multiple fiber disorderly arrangement, entanglement and become a small round knot or granular fiber knot. The cause is the cotton fiber, immature cotton or stiff cotton due to ginning or spinning process is not handled properly set and become, the formation of the root cause of the knot is the fiber between the rubbing and rubbing turn. Cotton knot from the formation of its cause, divided into raw materials caused by the cotton knot and finishing process caused by the cotton knot of the 2 major categories.

  The knot caused by raw materials

  Cotton knots formed by raw materials include impurities, defects caused by cotton knots, such as cotton seed bark attached to the fiber formation of cotton knots, cotton wax adhesion formation of cotton knots and cotton knots formed in the process of collection. The number of cotton knots is to assess the quality of raw cotton indicators, low grade of raw cotton, impurities, high content of defects, fine fibers, poor maturity, the production process of the formation of cotton knots also more. Therefore, different raw materials spun by the number of cotton knots, impurities are not comparable, can not be used as an indicator of the performance of the spinning machine.

  The cotton knot caused by the finishing process

  The cotton knot caused by the finishing process contains the original cotton roughing gin and spinning production process caused by the cotton knot. The knot formed by the gin, mainly the saw tooth gin produced by the cotton knot; spinning process caused by the cotton knot, including fiber opening, carding the formation of cotton knot, fiber channel friction resistance and sticky, tangled, blocking, hanging the formation of cotton knot, as well as bent hook fiber in the drafting process produced by the cotton knot.

  The knots formed during fiber opening and combing

  At present, there are two ways to open and card the fiber, namely free loosening and holding loosening. In the process of opening and carding, the fiber is constantly subjected to axial and radial stresses and strains, and some of the fibers have strain problems, resulting in a decrease in their own strength and bending stiffness, resulting in bending deformation and twisting each other to form cotton knots. The free loosening effect is soft, resulting in small deformation and few knots; the grip loosening effect is intense, resulting in large deformation and many knots.

  The beater of the cotton cleaning machine and the card roller of the grip fiber opening and combing, is the main part of the fiber deformation and the formation of cotton knots, which are mostly loose large cotton knots. The combing machine alternately holds and combs the two ends of the cotton bundle, which produces a small amount of cotton knots and discharges many cotton knots by falling cotton. When combing or coalescing fibers between the tin and the movable cover, fixed cover and doffer, the fibers are easily detached due to the large centrifugal force on the surface of the tin needle cloth and the large separation distance, and are in the gap between the tin needle cloth and the adjacent needle cloth, losing the manipulation and becoming floating fibers. Because there is a large speed difference between the relative needle cloth, the floating fibers are easily rubbed into knots; the number of floating fibers affects the number of knots formed by rubbing and rubbing.

  The cotton knot formed by sticking, winding, blocking and hanging

  Sticky, tangled, plugging, hanging and other abnormal phenomena easily cause violent friction, which leads to fiber rubbing and rubbing the formation of cotton knots, mainly in the following aspects.

  (1) when the tin, cover and doff needle cloth rack is blunt or with reverse barbed, the fiber can not be smoothly transferred, some fibers floating between the rack, by the two rack surface of other fibers rub turn, it will form a cotton knot.

  (2) When the distance between the roller - Xilin is too large, the surface of the rack is rough, resulting in Xilin - poor stripping between the roller, the roller will return to the fiber back to the cotton board, with the cotton must occur rubbing and make the knot significantly increased.


  (3) the tin Lin needle cloth rack teeth rolling injury, rough, the teeth have oil rust spots, and tin Lin - Dawe spacing is large, the transfer rate is low, will make the tin Lin around the flowers, resulting in increased cotton knots.

  Friction resistance of the fiber channel formation of cotton knots

  As the fiber in the cotton, cotton channel tumbling friction will make the fiber rubbing the formation of cotton knots, therefore, should make the fiber channel clean, and improve the negative pressure in the cotton pipeline to ensure that the cotton flow is smoothly conveyed, not blocked.

  Bending hook fiber in the drafting process of the formation of cotton knots

  In the drafting process, the beard in the separate degree, parallel straightness of the fibers easily entangled, pulling into the cotton knot. Among them, the bent hook fiber is the main reason for the increase of knots during drafting. The straightened part will be bent by the airflow formed by the dovetail rotation, which makes the bent fiber become more and more knots will be formed in the drafting process.

  Other reasons for the formation of knots

  Open the cotton process when finishing the formation of the cotton mass, silk and not be discharged with fiber impurities, short fibers and harmful defects, in the carding process is also easy to transform into cotton knots; flying flowers fall on the knot formed on the strip; equipment there are mechanical defects, such as rubber ring wear or poor assembly, spindle eccentricity, wire ring wear and so on may also form knots.

  The number of knots is one of the important indicators of the grade of decision spinning yarn, to reduce the knot, first of all, to understand the knot, can not blindly say to reduce the knot, chaos on the technical means, to combine the actual situation of the spinning enterprise itself, choose effective, direct, also cheap means, that is useful.



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