Introduction: The unique organizational structure of knitwear determines that the yarn used for weaving is not only Dry uniformity and coarse details are required, and rung defects cannot be caused. Taking C14.6tex knitting yarn as an example, the following brief description is given.
Causing rungs of knitwear yarn
Cause analysis
The main reason why knitted fabric rungs are on the yarn is that on the one hand, the uneven dyeing of knitted fabrics occurs due to the large differences in properties and uneven mixing of the raw cotton used. Dyeing rungs are formed on the surface of knitted fabrics. On the other hand, weaving stripes are formed due to yarn count variation, yarn twist variation, yarn hairiness variation, residual short pile rate of yarn, uneven humidification of package yarn, etc.
Countermeasures
01 Strengthen Raw cotton inspection and reasonable cotton allocation
(1) Cotton allocation is the basis. The variation of raw cotton (cotton allocation) is the main cause of rung defects, accounting for 70%. Factors such as yarn count variation, yarn twist variation, and yarn hairiness variation account for 30%. According to the requirements of knitted fabrics, the length, fineness, maturity, short staple rate, and harmful defects of raw cotton should be controlled. When producing knitted yarn, it is advisable to select a hand-drawn length of 28.5-30mm, a micronaire value of 3.6-4.5, a short staple rate of less than 16mm <12%, and harmful defects <2500/100 grams of raw cotton.
(2) When blending cotton, the micronaire value is the main body. The average micronaire value change of each cotton blend is less than ±0.1. When a single batch is taken from batch to batch, the difference in micronaire value It should be controlled within ±0.2. Since some cotton bale samples are inspected when raw cotton enters the factory, in order to prevent the mixing of cotton bales with large differences, the horse value of used cotton bales is re-inspected bale by bale every day to eliminate cotton bales with large differences.
(3) The number of pieces of cotton with multiple marks of the same variety is controlled at 8-10 batches, and incremental increases and decreases and cross compensation are implemented for successive batches. The proportion of each batch received shall not exceed 5%, and the amount of refinished cotton used shall be strictly controlled to prevent quality fluctuations and production instability caused by frequent replacement of raw cotton.
(4) Control of the moisture regain rate of raw cotton: hot drying and dehumidification treatment are carried out in winter and humidification treatment is carried out in summer to ensure that the moisture regain rate of raw cotton bales is controlled at 7.0-8.5%.
02 Strengthen uniform mixing
(1) When arranging raw cotton bales, the principle of “lateral staggering and vertical dispersion” must be followed. After the cotton bales are arranged, the bales should be filled with low bales and the seams should be filled with high bales so that the cotton piles are at the same height, which is conducive to evenly grasping the cotton. When the bales are returned to the bales, they must be packed and discharged twice, and loose bales are prohibited.
(2) When picking, opening and mixing cotton, the process principle of “fine picking, loosening more and beating less, early falling and less returning” should be implemented, and full mixing should be carried out to reduce short lint. regeneration.
(3) When using the card sliver, it is required that the card sliver produced by different carding machines be marked with the station number on the card sliver barrel; In combination, the same carding machine can produce no more than 2 slivers.
03 Strengthen process quality control
Control of card sliver quality requires uniform sliver dryness, less hairiness, and small weight difference in order to reduce rungs of knitted fabrics. The cleaning part adopts the process principle of “grasping frequently, loosening more, beating less, and mixing thoroughly”.
In order to ensure less fiber damage and reduce the blowing point and blowing intensity, the double axial flow opener of the blowing and carding unit is stopped, and the speed of the three beaters of the fine opener (the first beater) is reduced. The speed is reduced to 300r/min, the speed of the second beater is reduced to 500r/min, and the speed of the third beater is reduced to 800r/min); the carding adopts the principle of increasing carding, effectively eliminating short lint, and reducing fiber damage, and the cover plate speed is reduced to 300r/min. Appropriately increase to 230mm/min, adopt a tight distance between the cylinder and the cover plate, appropriately adjust the distance between the front and rear cotton net cleaners, control the temperature at 23℃-26℃, and control the relative humidity at 65%-70%. The external unevenness of the raw sliver weight is <1.5%, and the coefficient of variation of the sliver is <3.5%.
04 Quality control of cooked strips
(1) The quantitative control of cooked strips has a significant impact on controlling the weight unevenness and weight deviation of spun yarns. It is necessary to control the total unevenness on the basis of controlling the internal and external unevenness of cooked strips. Generally, the weight unevenness of cooked strips is <0.7%, and the dryness Coefficient of variation CV%<3.0%.
(2) Optimize the front and rear zone distance and drafting configuration. The first part adopts 5 or 6 combined fibers and a large back area drafting; the end part adopts 8 combined fibers and a small back area drafting, so that the fiber can be drafted smoothly, fully straightened and parallel, and the bell mouth is too small to control. To enhance fiber cohesion.
(3) Equipment maintenance personnel work with the regular script machine to keep each channel smooth and free of burrs, and check the photoelectric automatic stop every shift to prevent small strands from flowing into the next process and causing wrong yarn count; operation Personnel should clean the drafting area at all times, and check whether the transfer top rollers and pressure rods are in the correct position during the handover shift.
(4) Do not neglect to control the weight of half-cooked slivers in each shift, strengthen the control of the weight of uncooked slivers, and control the slivers of top and uncooked slivers every day to prevent Quality fluctuations due to mechanical condition or poor drafting elements.
05 Roving quality control
(1) The friction factor of cotton fiber increases with the increase of air humidity in the workshop. The increase of the friction factor between the yarn and the machine parts increases the friction resistance between the yarn and the spindle cap and the pressure palm, and intensifies the damage. Therefore, according to the workshop According to the temperature and humidity, adjust the number of buckles of the pressure palm appropriately.
(2) Use a smaller draft in the rear area and a smaller gap in the front area. It is conducive to the control of floating fibers; in order to ensure that the fine yarn is not drafted out of hard ends and ensures quality, the roving adopts a larger twist coefficient. Use a heavier basis weight to prevent accidental drafting during roving unwinding, which may affect uneven weight and uneven evenness..
(3) Equipment maintenance personnel regularly correct the pressure of the cradle, regularly clean the spindle flyers with a spindle flyer cleaning machine to keep the spindle flyer channels smooth and free of burrs, and the operators draft The cleaning cycle of the parts is shortened, and the accumulated dust on the velvet cover and velvet board can be removed at any time. The roving weight unevenness is <0.9%, and the evenness coefficient of variation CV% is <4.5%.
06 Spinning yarn quality control
(1) Due to the large twist coefficient and heavy weight of the roving, to prevent hard ends from coming out, appropriately enlarge the rear roller spacing and rear drafting multiple, reduce the front nip spacing, appropriately increase the cradle pressure, and select low Hardness rubber roller, a process that increases the forward momentum of the front rubber roller to move the fiber speed change point forward. In order to stabilize the yarn hairiness in the long term, the steel ring uses a bearing steel ring with a longer period, and the number of the traveler is controlled without touching the yarn bobbin head.
(2) Strengthen the maintenance and repair of equipment, and try to eliminate problems such as top roller eccentricity, roller bending, poor gear meshing, roller movement, large or unstable pressure deviation, apron Regular uneven drying caused by poor mechanical conditions such as slugging, hanging apron, cracked top rollers, and uneven yarn passages.
(3) Reduce uneven twist. Conduct regular and irregular inspections of the mechanical status of the twisting part, strengthen patrol inspections, and eliminate the spindle belt from sliding to the edge of the spindle plate and the spindle belt from being deviated. Weak twist phenomenon caused by looseness or inconsistent tension, lack of oil or damage to the spindle bladder, burrs on the spindle belt, poor joints, pulley supports, etc.
(4) Equipment maintenance personnel will correct the crooked spindles and crooked balloons every day, eliminate backward spindles, and regularly calibrate the cradle pressure, especially the front rubber roller pressure, and at the same time The difference between the front and rear rollers is controlled at 0.6mm-1.0mm.
(5) Strengthen the control of temperature and humidity to reduce regional differences. The temperature is 27.5℃-29.5℃, and the relative humidity is 55%-60%. The coefficient of variation of the weight of spun yarn per 100 meters is CV. %<1.7%, twist variation coefficient CV%<3.5%, 3mm hairiness value<3.5, hairiness variation coefficient<3.8%, evenness variation coefficient CVb<2.2%.
07 Strengthen training to improve operation level
(1) Strengthen the training of turners to improve their operating level, standardize operating procedures, and perform cleaning and on-site work in a timely manner;
(2) Strictly operate the “six rates” Assessment focuses on the implementation rate and out-of-grade rate. Establish a reward mechanism for cleanliness and on-site assessment. Pay attention to preventing yarn defects in semi-finished products.
(3)Continuously summarize and promote new operating methods. For example, it is forbidden to raise the strips, match the light and heavy wool strips, the slivers after the roving machine are not wrapped, and the broken slivers are eliminated and the roving ends are not wrapped, etc.
(4) Strengthen operational production management, implement fixed supply, and adhere to the principle of first-come-first-served.
Conclusion
By strengthening the In terms of quality control of cotton and cotton blending work and each process, in the past three years, no knitting factories have complained about rung problems, and the company has no economic losses due to rung claims.
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