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Classification and Cause Analysis of Yarn Nodule Formation

Sep. 17, 2020

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The cotton nodule is an important index to evaluate the quality of yarn, and the cotton nodule number is not only stipulated in the technical requirements of the grade of cotton yarn, but also stipulated in the total number of nodule and impurity in the 1 g yarn.The amount of knot content not only affects the appearance quality of yarn and fabric, but also affects the yarn structure, evenness and breakage rate.

The cause of cotton knot:

Cotton nodule is a circular or granular nodule formed by disordered arrangement and entanglement of single or multiple fibers.Its cause is that cotton fiber, immature cotton or dead cotton is formed due to improper aggregation in the process of cotton ginning or spinning, and the root cause of cotton knot is the rolling and rubbing of the fibers.From the perspective of the causes of its formation, it can be divided into two categories: the cotton node caused by raw materials and the cotton node caused by processing.

1.Cotton knot caused by raw material:

The knots formed by raw materials include those caused by impurities and defects, such as the knots formed by the fiber attached to the cotton seed skin, the knots formed by the cotton wax adhesion and the knots formed during the cotton collecting process.The number of cotton knots is the index to evaluate the grade of raw cotton. The low grade raw cotton has high content of impurities, defects, fine fiber, poor maturity, and more knots formed in the production process.Therefore, the number of knots and impurities spinning from different raw materials is not comparable and cannot be used as an indicator to measure the performance of the spinning machine.

2.Cotton nodule during processing:

The nodule during processing includes the nodule during rough cotton processing and the nodule during spinning.The cotton nodule formed by the ginning is mainly the cotton nodule produced by the serrated cotton gin;The knots caused by the spinning process include the knots formed when the fibers are loosened and carded, the knots formed by the friction resistance of the fiber channel and the knots formed by sticking, winding,

blocking and hanging, as well as the knots produced by the hooked fibers during the drafting process.

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3.A knot formed when fibers are loosened and carded:

At present, there are two ways to open and comb the fibers, namely free release and holding release.During the process of fiber opening and carding, the fiber is constantly affected by axial and radial stress and produces strain. Some fibers have fatigue problems, resulting in the decrease of their strength and flexural rigidity, resulting in bending deformation and mutual kinking to form cotton knot.The effect of free release is soft, resulting in little deformation and little cotton knot;The release of grip is intense, resulting in large deformation and many cotton knots.

The role of the beater of the cleaner and the licker of the card in loosening and carding the holding fiber is the main part of producing fiber deformation and forming cotton knot, which is mostly loose and large cotton knot.The combing machine holds the ends of the bundle alternately, which not only produces a small number of knots, but also eliminates a lot of knots by dropping.When combing or condensing the fibers between cylinder and movable cover, fixed cover, and Doffier, due to the large centrifugal force of the fibers on the surface of cylinder needle cloth, the fibers are easy to be separated when the spacing is large, and they are in the gap between cylinder needle cloth and adjacent needle cloth, losing control and becoming floating fibers.Because of the great difference of velocity between the relative needle cloth, the floating fibers are easy to be rubbed into knots.The amount of floating fiber affects how much cotton is formed by rubbing and rubbing.

4.A cotton knot formed by sticking, winding, blocking, or hanging

Adhesion, entanglement, blocking, hanging and other abnormal phenomena are easy to cause severe friction, which leads to the spinning and rubbing of the fiber to form a cotton knot, mainly manifested in the following aspects:

(1) When cylinder, cover plate and Doff needle cloth rack is blunt or with reverse thorns, the fibers cannot be transferred smoothly, some fibers floating in between the rack, by the two other fibers on the rack rub turn, will form a cotton knot.

(2) When the distance between cylinder and cylinder is too large, the rack surface is rough, resulting in poor stripping between cylinder and cylinder, the return of roller will bring the fiber back to the feeding board, and the cotton must be rubbed to make the cotton node increase significantly.

(3) Cylinder needles and cloth rack teeth were scratched and rough, the rack had oil rust spots, and the cylinder - Doff separation was too large, low transfer rate, which would cause cylinder to produce winding, resulting in increased cotton knot.

A knot formed by the frictional resistance of a fibre channel

Because the rolling friction of the fiber in the clearing and conveying channels will make the fiber turn into a cotton knot, the fiber channel should be made smooth and clean, and the negative pressure in the conveying pipes should be increased to ensure the smooth and non-clogged cotton flow transportation.

5.A nodule formed during the drafting of a hooked fiber

In the process of drawing, the fibers with poor separability and parallel straightness in the whisker are easy to be entangled and drawn into knots.Among them, the hook fiber is the main reason for the increase of cotton knot during drafting.During the drafting, the fiber crooked part is held by the Doffer needle cloth rack, while the straightened part is exposed to the doffer needle cloth rack. The straightened part will be bent by the airflow formed by the doffer rotation, which makes the crooked fiber become more and more cotton knots formed by the strips during the drafting process.

6.Nodule of other causes

In the process of clearing cotton, the cotton mass, wire and the impurities with fiber, staple fiber and harmful defects formed in the process of clearing cotton are easily converted into cotton knots.A knot of cotton formed by flying flowers falling on a whisker;The equipment has mechanical defects, such as rubber ring wear or poor assembly, eccentric spindle, steel ring wear and so on May also form cotton knot.

The number of knots is one of the most important indexes to determine the grade of yarn. To reduce the knots, the first thing is to understand the knots, not to blindly reduce the knots, but to use technical means. The most effective, most direct and cheapest means should be selected in combination with the actual situation of the spinning enterprise.

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