According to the formation mechanism and rule of NEP and hairiness, the direction of fiber operation and stress must be carried out in the whole process.
1. Relevant technical requirements
From a macro point of view, any fiber should meet the requirements of system, orientation, softness, smoothness and cleanness in the spinning process, and try to adopt the established principles that have been scientifically verified to improve the working efficiency, such as the odd and even principles for fiber hooks, the best control of drafting multiple, Union number and short pile rate, etc.; while from a micro point of view, it can meet the requirements of fiber holding, transferring In order not to damage the internal and external structure and physical properties of the fiber, the stress point and air flow direction of the fiber should be maintained as much as possible, so as to provide semi-finished products with perfect quality for the yarn.
1.1 the equipment shall be able to hold the fiber well
To keep the draft running smoothly, the holding force must be greater than the drawing force. Fiber gripping in the process of wire (surface) gripping, such as double roller gripping or roller and cotton feeding plate (roller and COT), to conduct directional opening, carding and drafting; a bit of thread gripping, such as the needle tip between carding cylinder and cover plate controls the fiber under the action of air flow. Under the directional carding of the front fixed cover plate, about 60% of the fibers held by the tip of the cylinder needle can be transferred smoothly. The straightened fiber extends to the back processing process, which is reflected in the more stable grip of the drawing, roving and spinning on the fiber whiskers, and the strong ability to control the floating fiber, that is, the fluctuation of the traction force is small, and it is not easy to slide.
The combing process also considers the reliability of the clamp plate to hold the fiber, to ensure the carding of the fiber hook by the cylinder, to prevent the problems such as too light a small volume, too thin a combed cotton net, holes and edges, poor grip of the clamp plate, etc., and to make the long fiber unable to hold effectively and become noil. For example, the weight of small roll is increased from 46.5g/m to 50.8g/m, the combing short fiber rate is increased from 5.21% to 5.49%, the NEP rate is increased from 20 to 22 and the noil rate is increased from 16.0% to 16.4%.
1.2 good transfer fiber performance
Transfer and holding are a pair of contradictions. To find a balance point, holding too much is not easy to transfer. The carding flow is conveyed by directional air flow, the fiber orientation is good and the fiber transfer is more smooth, especially for the cotton cleaning. Through reasonable air supplement and accelerating the cotton block transfer, the yarn and NEP in the cotton cleaning process can be reduced. For example, a filling air port is opened on the side of the grabbing bucket of fa002 cotton grabber to increase the air volume and the cotton suction efficiency, so that the grabbing block can be quickly separated from the blade, so as to prevent the stranded and repeated strike from causing the rope and short pile. In the same way, changing the air supply at the outlet of A035 and fa106 cotton openers to the tangential air supply at the cutter head can also make the cotton bundle quickly separate from the blade. On the other hand, high transfer rate is conducive to fiber directionality. Different speed of the carding machine determines different transfer rates. Generally, the speed is high, and the transfer rate is high, with a minimum of no less than 15%. The carding times of the carding machine and the cover plate should be at least 2-3 times.
The high-efficiency and high-yield doffer clothing must have enough grasping and holding power, that is, the transfer ability, to meet the smooth guidance of fiber orientation under the high-speed airflow of Xilin; at the same time, the depth of doffer's teeth increases, the capacity of fiber increases, the length of doffer's contact fiber is large, and the gripping and holding power of the clothing is large, which is conducive to fiber extension and transfer. The transfer rate of doff is too high, the return load of the cylinder is less, and the carding is not sufficient, which is not conducive to the uniform mixing effect and affects the evenness and weight of the strip; the transfer rate of doff is too low, which is easy to wind the cylinder and the prick roller, repeatedly rub and turn, and increase the neps. When doffer speed and needle tooth density decrease, the transfer rate decreases simultaneously. Different types of carding machine should have appropriate transfer rate for processing different fibers.
1.3 pay attention to the micro design and process effect of equipment
The following problems should be paid attention to in the micro design of carding equipment.
(1) in recent years, equipment design and process analysis have gradually focused on the surface micro level to meet the different processing requirements of a variety of fibers and solve quality problems more accurately. The most obvious is that the needle cloth design emphasizes the single fiber directional control, carding and transfer. In order to improve the transfer rate of doff, the design of Xilin needle cloth develops from single tooth to double tooth, single step to double step, and the combination of different tooth shapes changes to ensure the ability of holding, puncture and release. For example, a 2.0mm flat top high tooth and a 1.7mm sharp top short tooth are designed for the double teeth of the golden wheel, and the tooth density reaches 1400 teeth / (25.4mm 2). The transfer rate of doffer is increased to 30%. With the smooth edges and corners of the needle, the short pile rate is reduced by about 20%. In order to solve the problem of cellulose fibers being held down at the tip of teeth, hump clothing was developed to enhance the fiber extraction ability of cover plate, so as to improve the separation and straightness of fibers, improve the clarity of cotton mesh, and improve the quality.
(2) the design of white shark's high and low double step tooth shape combines penetration, flexible combing, release and transfer, reduces short hair by 0.5% - 1.0%, increases transfer rate by more than 35%, and increases production capacity by about 25%. With the combination of hump teeth and large flat top teeth, the DS tooth Xilin needle cloth is specially designed for the back of teeth, namely, straight tooth tip, large (long) tooth top, large arc, large front angle and large tooth pitch, which makes the fiber less damaged, more gentle carding, increase the effective carding length, improve the removal effect of straightness and NEP impurities, achieve the purpose of supporting the fiber, preventing deposition, and controlling the fiber to be combed at a specific position. The fiber holding depth was kept 0.05 m m below the needle tip, and the roughness of the needle surface was controlled at RA 0.06 μ M. The removal rate of NEP is over 90% (usually about 85%), and the increase of lint is controlled within 1%. DS18 series of Xilin needle cloth has been verified in an enterprise. 50% Pima long staple cotton + 50% Xinjiang fine staple cotton are blended with cotton, JC 9.8 tex yarn + 200% neps are less than 15 / km, JC 4.92 tex yarn + 200% neps are less than 40 / km.
(3) according to the wear rule of the fixed cover plate, Jinfeng clothing developed a fixed cover plate with the difference between the middle and the toe, which gradually combed the fibers, increased the number of working teeth involved, staggered the needle teeth by 5 ° or 10 °, the fibers moved forward in a curve, and arranged in a twill or transverse pattern to avoid the "passage" caused by the formation of fiber bundles and reduce the fiber comb leakage Damage, enhance the carding force. At the same time, about one third of the card clothing in the carding area of the cover plate is changed into a smooth platform to form a fiber lifting release area, so that the end of the carding fiber is raised, providing good conditions for the next tip carding, especially for spinning pure cotton fine tex yarn.
(4) for some problems such as poor surface friction performance of cellulose and chemical fiber, doffer's falling cotton net and hard to hold, the design of doffer's needle cloth focuses on two aspects: one is to add transverse lines on the side of doffer's needle teeth, which can improve the holding force by adjusting the number of lines, so as to prevent poor rotation and breakage of the cotton net; the other is to change the shape of the tooth tip without transverse lines, such as eagle mouth, arc and group The combination design of the basic tooth shape and the characteristic tooth tip is adopted. The working angle of the basic tooth shape is generally 60 °, while the working angle of the new doffer's needle cloth tooth tip is 25 ° - 45 °. Hall company developed the tooth tip of arc deformation angle earlier, which significantly improved the ability of the tooth tip to transfer the agglomerated fiber.
