1 Draft wave
The unevenness caused by the drafting of the cotton sliver is expressed in a waveform and is called draft wave. This is due to the speed change point caused by the fluctuation of the speed point position of floating fibers during the drafting process: the fiber head end in the drafting area changes from the rear roller speed to the front roller speed, that is, from slow fiber to fast fiber) The spectrum shape is like a hill (large channel).
2 Mechanical wave
Due to poor mechanical condition. For example: the drafting gear is damaged, the rollers and rubber rollers are bent, eccentrically beating, and the roller bearings and rubber rollers are seriously short of oil. Unevenness caused by wear, poor meshing, poor processing and manufacturing of the drafting gear, loose keys, screws, gear eccentricity, etc., is expressed in a waveform and is called a mechanical wave. The shape in the spectrogram is like a chimney (channels 1~2).
3 Reasons for uneven roving
The pressure is too light and the rubber roller is too heavy Can’t hold it down. The distance between rubber rollers and rollers is incorrect; the bending eccentricity of rubber rollers and rollers exceeds the normal range or the surface is damaged. The rubber rollers and roller bearings are short of oil and damaged; the draft transmission gear is in poor condition, the gear is eccentrically damaged, the meshing is poor, worn out, the pin keys are loose, the drafting parts are defective, the bell mouth is skewed and damaged, the upper pin is deformed, and the jaws are abnormal; The upper pin hits the rubber roller, the rubber ring is broken, the rotation is not flexible, the lower pin rod is bent, and the opening of the cotton collector is incorrect, too large, too small, or damaged. The design of each process parameter is unreasonable, the tension is too large or too small, the drafting configuration is inappropriate, the roller spacing is unreasonable, the elongation is too large, the spindle wing is loose, and the head shakes seriously, etc.
4 Roving tension and elongation
It depends on the roving basis weight, coil size, raw cotton quality and temperature. Changes due to factors such as humidity and mechanical condition. Therefore, adjusting the roving tension is also more complicated and requires accumulating experience in practice. Once the yarn is doffed, the tension of the small yarn usually elongates abnormally. Adjust the starting position of the iron cannon belt. The small yarn is normal, but the tension of the middle yarn and large yarn is too large or excessive. Adjust the small tension ratchet or coaxial gear. The tension of small yarn and large yarn is appropriate. If the tension of medium yarn is too tight or too loose, adjust the tension compensation gear. The tension of the roving is not appropriate, and the accidental elongation is not necessarily certain. It will be too tight or too loose during winding, which will affect the winding length or evenness, increase the roving breakage and yarn defects, affect the output and quality, and cause the fine yarn to break when unwinding. Heads and blemishes bring disaster. The elongation of roving is generally controlled between 1.5% and 2.5%, and the difference in elongation of large and small yarns is controlled within 1.5%. The weight unevenness (long segment 5 meters) is about 1.5%.
5 Roller gauge
Roller gauge is directly related to fiber length and basis weight. The gap cannot be less than the fiber length, otherwise the fiber may be held by two pairs of rollers at the same time and broken at a certain moment. If it is greater than the fiber length, it will be difficult to control fiber movement during the drafting process, and there will be more floating fibers, which will affect the evenness of the evenness. Therefore, if the gap is too large or too small, it will be detrimental to the quality of the semi-finished product. Generally, the roller gauge is determined according to the fiber quality length. The quality length is long, the gauge is large, the semi-finished roving is quantitatively heavy, and the roller gauge is slightly enlarged.
The roving tension is low, and the roving twist coefficient is related to product quality and output. If the twist coefficient is too small, accidental drafting may easily occur, causing end breakage and uneven products; if the twist coefficient is too large, the drafting force may be too large when the spun yarn is stretched, resulting in uneven yarn formation or the appearance of “little mice” under the hard ends. “.
6 Roving twist coefficient
Pure Cotton or chemical fiber is determined by many factors. Generally, chemical fibers have long fibers and high strength, and the twist coefficient can be smaller. The twist coefficient is selected to be large, generally based on fiber length, fineness, roving basis weight, and spinning back zone technology. There is a lot of twist. At the same front roller speed, only by speeding up the spindle speed or slowing down the front roller speed at the same spindle speed can we meet the process requirements. Therefore, the twist is large and the output is low.
7 Effect of temperature and humidity on product quality
Strength, weight and elongation of cotton fiber Physical properties such as elasticity and elasticity are closely related to the relative humidity in the workshop. When the temperature is lower than 18 ℃, the relative humidity is too low, the surface of the cotton fiber becomes waxy, the plasticity is reduced, the fiber is fragile, the strength is reduced, static electricity is generated, and it is easy to wind around the roller. The rubber roller will cause the evenness to deteriorate; when the temperature is between 24 ℃ and 26 ℃, the relative humidity is suitable, the cotton wax is soft and hard, and the raw cotton is easy to decompose or the single fiber is conducive to opening, dust removal and drafting; the temperature is too high and the relative humidity is too high When it is large, the cotton wax softens and the friction between fibers increases, affecting normal drafting and causing uneven evenness. Therefore, the relative temperature in the roughening workshop is too high, and it is easy to wind the rollers, rubber rollers, and the hollow arms of the spindle flyers. The resistance is large, there are many ends breakage, and the yarn is too tight, which affects normal drafting and hard ends occur; the relative humidity is too low, static electricity The effect is enhanced, resulting in more fly flakes, loose roving, poor roving molding, many broken ends, and poor fiber cohesion, which affects uneven evenness and strength, increases the labor intensity of the machine operator, and affects output.
The temperature and humidity of the roughening workshop are generally controlled at:
Winter: temperature 22 ℃ ~ 24 ℃; relative humidity: 60 ℃ ~ 65 ℃
Summer: temperature 30 ℃~32 ℃; relative humidity: 55 ℃~65 ℃
8 How to solve various problems of poor roving forming?
1) The up and down angles are different: correct the level of the scalloped rod and the balance frame, when the flyer pressing palm hole is in the center of the bobbin. Adjust the length of the top wire of the upper cradle to be consistent, and adjust the tension teeth to the same angle each time to make the iron cannon belt move equidistantly.
2) Roving head and feet: When correcting the direction change of the lower beam, the reciprocating wheel (and…Teeth and square box gears) reciprocate flexibly without skipping, and the forming mechanism is inflexible (three actions for forming reversal: 1. The iron cannon belt shifts, changing the lifting speed of the lower rail (slowing down) and changing the winding speed; 2. Promote the reciprocating rotation to change the movement direction of the lower rib; 3. Shorten the lifting stroke of the lower rib and make both ends of the roving tube conical). The three functions of deceleration, reversal and shortening must be completed when the roving is wound to the bobbin. At one end, it happens at the same time and is completed instantly, so the function of the forming mechanism is to use the lifting and lowering of the lower rib as a trigger to complete the three actions of deceleration, reversal, and shortening the stroke. The related screws of the molding device are loose, the gear meshing is poor, the related parts are damaged, the tension spring tension is improperly adjusted, the device is poorly debugged, and the lifting of the lower rib is severely frustrated (the rib is uneven, the gear and rack are poorly engaged, and the pin keys and screws are loose). The spindle wing is loose and the weight of the fed sliver is too light.
3) Shoulder loss: Due to the tension, improper adjustment of the cannon belt, the cannon jumping (poor dynamic balance of the cannon, improper installation), poor temperature and humidity, relative humidity, etc.
4) Hard yarn and rotten yarn: the rear rubber roller is lifted up, and the drafting effect in the rear area is poor. The rubber roller moves, the pressure is abnormal, the tension is too tight, the sliver is unevenly fed, the press palm is hung, the hollow arm of the spindle flyer is hung, the number of yarn winding passes on the press palm does not meet the requirements, the gear screws related to the forming are loose, causing the long rack to move Inflexible or too small, the long rack moves equidistantly each time, the relative humidity is too large or too small, and the process configuration is improper.
5) Waist hoop: The forming device does not work well, and the square box reciprocating gear 100T has poor meshing. The gap between the dovetail pin and the dove head of the center cradle is too large. The cannon belt is too loose, the cannon bearing is damaged, the gear is loose, etc., causing the lower cannon to not rotate, the lifting gear, and the lifting intermediate wheel to mesh poorly, and the screw pin is loose. The tension spring of the forming device is not adjusted too loosely, etc. </p
