NEP Is The Biggest Problem Of Spinning. How Does It Come Into Being? How To Deal With It?

Neps in cotton are fibers that are tightly intertwined with cotton fibers. The big one is called "Silk cluster", and the small one is called "white star".

Reasons for forming Neps

Neps are round nodules or granular fibers entangled by a single fiber or a plurality of fibers. The reason is that cotton fibers, immature cotton or stiff cotton are gathered due to poor handling in the process of cotton ginning or spinning. The basic reason for forming neps is rubbing and rubbing between fibers. Neps can be divided into two categories according to their causes.

The first type is raw material. The neps formed by raw materials include neps caused by impurities and defects, such as neps attached to cotton seed skins, cotton neps formed by cotton wax adhesion, and neps formed during the process of cotton collection. The number of neps is an index for evaluating the grade of raw cotton. Raw cotton with low grade, high impurity, high defect content, fine fiber and poor maturity are also used to produce neps. Therefore, the neps and impurities of different raw materials are not comparable, and can not be used as an index to measure the performance of spinning machines.

The second category is caused by the processing process, which is caused by raw cotton rough processing, cotton ginning and spinning. The neps formed by embossing are mainly neps produced by sawtooth cotton gin. Neps resulting from spinning process include neps formed during loosening of fibers, frictional resistance of fiber channels and neps formed by sticking, wrapping, blocking and hanging, and neps produced by draft fibers during drafting.

　　 Sticky, entangling, blocking, hanging and other abnormal phenomena, often cause severe friction, resulting in fiber twisting and rubbing to form neps. For example, when the cylinder, the cover plate and the doffer needle / teeth are blunt or reverse, the fibers can not be transferred smoothly. Some fibers float between the needle / tooth surface and are rubbed by the other two fibers on the needle / tooth surface, which will form more neps. When the gap between the thorn roller and the cylinder is too large and the teeth are not clean, it will cause bad stripping between the roller and the back of the roller. It will bring the fiber back to the cotton board. The cotton will be rubbed and the neps will be increased obviously. The cylinder parts of the cylinder will be damaged and rough, the needle / teeth are covered with oil stains, and the gap between the cylinder and the doffer is too large, and the transfer rate will be low.

When the draft is drawn, the fibers that are separated from the strip and the parallel straightness are easily entangled and drawn into neps. Crooked fibers are the main reasons for the increase of neps during drafting. The fibers exposed to the surface of the doffer card and the fibers that are held tightly are exposed by the tin bar. When they come out of the condensation zone with doffer, they are stripped from the cotton stripes and form a web of cotton. One end of the comb is held at the front, and one end is held on the end of the comb. The fiber hooks are held by doffer, while the extension part is outside the doffer clothing. The extension part will be blown by the air flow formed by doffer, so that some of the crooked crooked fibers will become crooked fibers. The more the hook fibers are, the more neps will be formed in the drawing process.

In addition, cotton pits, wires and unexcluded fiber impurities, short fibers and harmful defects formed during processing of cotton cleaning process are also easily transformed into neps in the carding process. Neps, mechanical defects, such as apron wear or improper assembly, spindle eccentric and ring wear may also cause neps.

　　 Two. Eliminating neps.

Through the noil removal and carding of the neps, the main parts of cotton neps are removed, including cotton cleaning, carding, belly dropping and covering, and Combing Noil. Combing can effectively eliminate fiber entanglement and reduce neps; through the careful combing of cylinder and cover, some loose cotton neps are combed into single fibers, and the neps are decomposed into single fibers or small neps; at the same time, short staple is also increased.

Three, measures to reduce neps

By breaking loose, combing and pulling into a set of single fiber rods, the neps will be gradually removed and the neps will be inevitable. However, the neps and neps should be reduced as much as possible. There are many reasons for forming neps. It should be considered systematically so as to make the spinning components and equipment in good condition. The reasonable allocation of technological parameters is a guarantee. Good mechanical state and reasonable process design can significantly reduce yarn neps.

　　 The carding machine without additional carding parts can appropriately increase the front and rear fixed cover and suction device, so as to improve carding quality, remove fine dust and reduce neps. Reasonable control of noil, cover flowers and combed noil and more neps can reduce neps. Cover plate reversing or increasing the speed of the cover plate can effectively reduce neps.

According to the characteristics of raw cotton, select process parameters, such as fine fiber and poor maturity, should be low speed and loose loose, do not use three wing blade and porcupine beater, use low speed three wing comb needle to beat hands; stab roller and doffer low speed, control the speed ratio of thorn roller to cylinder, speed ratio is small, NEP is more, speed ratio is big, NEP is less; pure cotton should be controlled at about 1:2.

　　 Four, neps detection methods and changes.

In China's cotton textile enterprises, most manufacturers use traditional hand feel method to detect the content of Neps in semi finished products and finished products of textile processes. A few manufacturers use AFlS single fiber testing system to detect. The neps in visual inspection are defined as one or more fibers, which are composed of one or more fibers. The synthetic knob or granular fiber knot, also known as white star, is placed on a black glass plate after being artificially tested in the fiber laboratory. The black spots on the black glass plate can be seen as neps when the light is projected above. This NEP is a fiber bundle that is twisted by many root fibers to be recognized. 1 big neps can also be broken down into multiple neps. The result depends on the eyesight of the tester. The diameter of a single fiber is nearly 20 / m, and the diameter of a small NEP formed by a single fiber is nearly 60 / M. Due to the limitation of human eye resolution, many objective small neps can not be observed. The weight difference between neps is very different. The test reports that the neps only have 1.4% of the cotton NEP weight. Only the neps are measured, and the neps are not observed, which can not reflect the real situation of neps.

The AFIS single fiber test system defines the NEP as the core part. The non single fiber whose projection diameter exceeds the specified value (100 m) is NEP. It can be detected by two small fibers, which are not easy to be identified by the naked eye. Such neps are much smaller than the visible neps, so that the neps can be detected and reflect the real situation of neps.

Because there are different definitions and testing methods for Neps, 1 neps can be measured by AFlS as many neps. Therefore, the number of neps measured by visual inspection is small, and the neps measured by AFlS are large. Because the neps data measured by different methods are not comparable, neps must be marked with test methods.

　　 Five, concluding remarks

Neps are mainly produced by cotton fibers in the process of carding and carding. Holding loosening is the main part of neps. The key to increase or decrease neps is carding quality. The neps change is only an ideal trend without fixed rules. In actual production, the performance of the neps varies with the properties of the raw materials and textile machines.