What is the reason why the roving does not open out of the hard head?

　The root cause is that the drafting force is greater than the holding force. Any factor that affects the drafting force and holding force may cause the draft not to open.

　　1. Roving twist factor

　　When the twist factor of roving is large, the tightness of the roving increases, the holding force is good, the friction resistance between the fibers increases, the drafting force increases, and the distance between the yarn after the spacing, the drafting multiplier in the back area remains unchanged, resulting in the strip not being effectively untwisted, with a larger twist back into the main drafting area, and the draft does not open. However, the twist factor of roving should not be too small, too small, when feeding into the spinning machine is easy to produce accidental drafting, produce details, affecting product quality.

　　2、Yarn guiding range

　　When the moving direction of the yarn guide is the same as the twist direction of the yarn guide, the drafting force is large, and the holding force is smaller than the drafting force, and when the twist direction of the yarn guide is opposite to the moving direction of the yarn guide, the drafting force is smaller, which is beneficial to reduce the draft.

　　3. Roving weight

　　In the same state of rubber rollers and in the back area of the draft multiplier, the twist factor of the roving is certain, the holding force of the roving needs to be greater than the holding force of the roving needs to be lighter, so the roving weight has higher requirements for the holding force of the roving. The roving quantification should be adapted to the distance between the jaws, so that the yarn does not fluctuate sharply at the jaws during the drafting process, which may affect the normal drafting of the yarn.

　　4. Yarn roller spacing

　　The small distance between rollers is beneficial to the manipulation of the floating fiber in the strip, so that the strip in the drafting process to increase the drafting force, easy to draw the phenomenon of not open. After increasing the distance, the manipulation ability of the floating fibers in the strip is weakened, so that the fibers can be well manipulated and drawn normally, and the phenomenon of non-drawing can be avoided.

　　5、Drawing after the yarn area

　　After the increase of the draft multiplier, the main drafting area into the cross-section of the fiber in the strip is reduced, the draft force is reduced, which is conducive to the draft jaws to manipulate the fiber in the strip and reduce the draft phenomenon, but in general, it is not conducive to the improvement of yarn quality. Now most of the manufacturers adopt a larger center distance of the spinning roller and a smaller draft multiplier and a larger twist factor of the roving.

　　6、Fine yarn jaw spacing

　　Smaller jaw spacing block is conducive to strengthening the rubber ring jaws on the draft yarn manipulation ability, in the fiber shift on the edge of the strip of fiber manipulation ability, so as to improve the yarn dry. After the spacing block is adjusted to a larger size, the manipulation force of the rubber ring jaws on the strip is weakened, which can reduce the phenomenon of non-drawing, but has a definite effect on the yarn quality.

　　7. Yarn roller pressure

　　If the pressure of roller is small, the manipulation force of drafting jaws on fiber is weak, so that the fiber in the strip is not well manipulated and the phenomenon of not open. After the pressure of the roller increases, the friction of the drafting jaw increases, so that the fiber in the strip can get good manipulation and normal drafting. The pressure should be reasonably distributed in the front, middle and back of the shaking frame to avoid the failure of drawing in the back area and the phenomenon of not drawing.

　　8、Fine yarn leather roller

　　For the new rubber roller with coating layer, the surface coating is thicker, and the grip force on the surface of the rubber roller is weakened greatly, so the slippage rate is higher in the drafting process, so that the yarn is not effectively manipulated and the hard head is simple. The old roller surface coating layer is thinner, the friction factor of the roller surface is bigger, the holding force of the roller on the yarn strip is bigger than the drawing force of the yarn strip, so the strip can be drawn normally. The surface of untreated rubber roller is not chemically treated, the surface of rubber roller can contact with the strip directly, the friction coefficient is large, and the holding force is larger to overcome the larger stretching force, which is an effective measure to solve the phenomenon of non-drawing. In winter, due to the lower temperature, no treatment leather roller hardening, slippery rate increases, simple hard head.

　　9、Raw material condition

　　Daily production, raw materials are in a state of flux at any time, sliver fiber quality length lengthening (such as increased combing strip content) or length neatness, the friction coefficient between the fibers in the strip become larger, in the drafting process its drafting force response increased, in the case of the same yarn technology, drafting jaws can not be applied to the fiber in the strip to effectively manipulate, resulting in the strip can not get the normal drafting and stretching does not appear It is necessary to adjust other processes.

　　10、Temperature and humidity

　　When the humidity in the workshop increases, the friction coefficient between the fibers in the strip becomes bigger, and the friction resistance response increases, which increases the drafting force of the strip, and in the case of the same yarn craft, the drafting jaws cannot exert effective manipulation on the fibers in the strip, and the draft does not open. The workshop should manipulate the temperature and humidity reasonably according to the seasonal changes, raw materials and other factors to ensure normal production, to avoid the phenomenon of stretching does not open.