Application of the hottest autoleveller technology

2022-07-26
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Application of self leveling technology in cotton spinning system

1 quality requirements for cotton yarn in the market

cotton yarn is a finished product of the spinning factory, but it is an intermediate product between raw fiber and fabric. It is the raw material for three kinds of fabrics in the clothing and decoration industry. In addition to the special requirements for industrial fabrics, the requirements for clothing and decoration are increasing with the improvement of people's living standards. In the face of such market demand, the production of the spinning factory, We must adapt to it. Now we only analyze its requirements for cotton yarn quality in terms of clothing

1.1 wearability and yarn

clothing is not only an adaptation to environmental temperature and humidity and physiology, but also a way for people to express their feelings, expand social contact, or shape their self-image, so as to reveal their spiritual realm, or decorate and beautify, so as to express etiquette, etc. in a word, service life and price have long been put in the first place. The clothing gradually tends to be personalized, and the requirements for design, color and variety are increasingly renovated. In addition to the general routine and multi-functional (warmth and odor prevention) requirements, the requirements for textile products also require bright colors, beautiful and generous, and can realize the appearance, body bones and style of people. With the change of wearability, the quality of raw yarn must be changed accordingly

1.2 requirements of fabrics on cotton yarn

in order to adapt to the diversity of wearability, the cotton spinning system has moved from pure spinning to blended spinning, between natural fibers, between chemical fibers, between natural fibers and chemical fibers, between general fibers and differentiated fibers, and between various raw fibers, or plain combing, or combing, or changing twist direction, or changing process parameters, forming cotton yarns of various specifications and different qualities, The main requirements for cotton yarn in comprehensive weaving and knitting are as follows:

1.2.1 cotton yarn with uniform dry

cotton yarn with uniform dry, smooth appearance, good dyeability (even and bright colors), and uniform dry, its unit strength CV value must be low, that is, its average actual strength has been improved, especially for those decorative lightweight fabrics, which have very high requirements for the evenness of cotton yarn, At the same time, it is required that the CV value of the sliver is small

1.2.2 strength

in the process of weaving, after a part of strength is lost due to stretching and friction, a certain strength should be retained to maintain a certain wear resistance and tear resistance after weaving into finished products (such as clothing). Therefore, the single yarn is required to have the strength matching the spinning number, and the strength CV value of the single yarn is required to be small

1.2.3 neps and impurities

the neps and impurities in cotton yarn will increase the breakage in weaving and reduce the weaving efficiency. If they remain on the cloth surface, they will also form dyeing spots, affect the appearance, and even become defective cloth

1.2.4 long, thick, pitch and detail

the long, thick and long details in cotton yarn can not be trimmed in textile products, which will affect the scoring until the first-class product rate in storage is reduced in batches. The streaks and streaks affect the luster and beauty of the cloth surface

the core of the above requirements for cotton yarn is the evenness of sliver. If we hold this key, the single strength CV ratio, impurity, length, thickness and length details will be reduced accordingly

1.3 users' requirements for cotton yarn quality

yarn users are often the final product factories (such as clothing, decorative fabrics, etc.) that make grey fabrics or fabrics. In particular, the final product factories have a strong desire to create their own trademark brands after China's entry into WTO. Cotton yarn quality can be of high, medium and low grades. What they require is not necessarily high-grade, but must be cotton yarn that can be stable in the same grade for a long time, which is extremely necessary for their brand effect

1.4 requirements of modern equipment

modern weaving technology, whether woven or knitted, tends to be "three high" (high quality, high speed and high efficiency). Compared with traditional equipment, the speed is doubled. It requires that the cotton yarn not only has enough strength to withstand its high-speed extension and friction without breaking its head, but also requires uniform yarn cross-section, less yarn defects such as impurity, length, coarseness and long details, and can smoothly pass through the reed eye (needle eye) without breaking its head, Because in the weaving process, some process dozens or hundreds of yarns at the same time (knitting). Sometimes thousands or tens of thousands of yarns are processed at the same time (woven). One of the yarns is broken, causing the whole machine to stop, which has a great impact on its production efficiency

from the above sections 1.2~1.4, it can be seen that the requirements of the market for cotton yarn quality, whether to meet the wearing performance, adapt to the processing of three high weaving equipment, or meet the requirements of users, involve a core problem of cotton yarn quality - the cotton yarn with uniform evenness, and can be stable at the same level for a long time. It is for this need that the self leveling technology is used in the cotton spinning system

2 the function and benefit of the self leveling device

2.1 the function of the self leveling device (hereinafter referred to as the self leveling device)

2.1.1 stable number

the process parameters and tolerance range can be set, compared with the products in process in real time, and controlled, so that the number weight deviation of cotton yarn spun on the subsequent spinning machine (hereinafter referred to as the deviation) can be stabilized within the tolerance range required by the user for a long time, making the user and the factory satisfied

2.1.2 make up for the merging function

the spinning system often combines multiple slivers on the drawing frame to improve the uniformity of products in process and control the number and weight deviation. But there are two defects: first, limited by the number of merging roots and drafting times, it can only improve the unevenness of short and medium segments, and can do nothing for long segments and ultra long segments; Second, the periodical draft wave (draft wave, mechanical wave, combing and jointing wave caused by the difference of fiber physical properties) with large fiber amount difference in the sliver section has not been improved. Since the autoleveller has the function of peak elimination and filling for the products in process, it can make up for the defect of random merging on the drawing frame

2.1.3 prevention of sudden yarn defects

for all sudden yarn defects (NEPs, impurities, coarse knots, etc.) beyond the control range, the self leveling device has the function of automatic shutdown and prohibition, and sends an alarm to prompt the car stopper to eliminate them in time, which is faster and more accurate than manual defect prevention and catching

the above three points are exactly what users require for cotton yarn quality

2.2 compared with the current off-line detection, the autoleveller has four advantages

2.2.1 fast feedback

the detection, feedback and control of the autoleveller are carried out between electronic circuits. The speed is up to millisecond (MS). The off-line detection is a human plus instrument. After the test results are calculated and compared, they are adjusted through the exchange of draft change gears. The detection, feedback and control are carried out between people and machines. The exchange of gears also requires shutdown, a long distance and a long time delay, which is incomparable with the electronic circuit control

2.2.2 high precision

the self leveling device uses an electronic computer to control the servo actuator, changes the drafting multiple in real time to achieve the purpose of leveling, works stably and reliably, and the accuracy error is within 1%. During off-line detection, the operation method, proficiency and heart of the tester have a great impact on the detection accuracy and feedback results. Compared with the stable computer control loop, the unstable human factor has incomparable accuracy and reliability

2.2.3 the representative large

autoleveller is used for detection. For the detected work in process, it can follow up in real time without any leakage, and the detection rate reaches 100%. Off line inspection can only be used for sampling test of work in process, which is limited to manpower and material resources. Its quantity is larger than, and its representativeness is very small

2.2.4 cotton saving

the self leveling device only performs contact or non-contact testing on the test samples, and is nondestructive to the products in process. For off-line detection, destructive tests must be carried out on the samples to obtain the required process data. This also determines that the sampling must not be excessive and must be limited to a certain range. Even so, there will be a certain loss of raw materials over the years

2.3 benefit of self leveling device

the self leveling device is a subsystem of the spinning system, and its benefit is also reflected from the normal production and operation of the spinning equipment. If the production benefit is all calculated on the self leveling device, it seems biased, but its superior role cannot be ignored

2.3.1 it is suitable for users' needs and can expand sales channels. (see the above)

2.3.2 reduce the probability of the finished product to reduce the grade and wave

2.3.3 reduce raw material consumption. In addition to saving cotton by sample detection, the evenness of cotton yarn can be improved after adjustment by the evenness device, and neps, impurities, slugs and other defects can be strictly controlled, which can reduce the breakage of the weaving processing system. It has been calculated that if the cost loss of a broken end of the winder is 1, the cost loss of a broken end of the finishing machine is 700, that of the paddle yarn machine is 2100, and that of the cloth machine is 490. It can be seen that end breakage has a great impact on weaving cost

2.3.4 improve production efficiency

after the self leveling device replaces the pure mechanical iron gun (cone wheel) leveling device of cotton cleaning, the positive coiling rate of the coiler is generally increased to 99~100%, and the weight unevenness is also reduced to the range of process requirements. The increase in the positive roll rate has led to a corresponding increase in the yield, that is, saving cotton, electricity and material consumption. It has also improved the production efficiency and reduced the labor intensity of workers. Some enterprises [Note 1] have calculated that after one year of use of four sets of self Levellers, under the condition that the output in 1998 increased by 2.54% over the five months in the same period in 1997, the power consumption decreased by 30.02%, the consumption of machine parts decreased by 26.36%, and the cotton lint decreased by 6.94%, The average monthly consumption of electricity is 5582 yuan, the consumption of accessories is 681 yuan, and the consumption of combed yarn with cotton is 741 kg. Of course, it includes other effective work, but it should also be recognized that the self leveling device has played a certain role. The use of self leveling device on carding, blowing carding unit and drawing frame does not involve the yield, but involves the important indicators of deviation and evenness of cotton yarn, which affects the grade evaluation and sales price of finished products. Rieter of Switzerland tracked and compared the American factories using its rsb-d30 drawing frame (Rieter claims that the core part of rsb-d30 is its new, fully digital self leveling system [Note 2]). In the weaving process, the number of weft breaks per 100000 weft insertion decreased by 1.34, and the efficiency of the weaving process increased by 0.5%, reaching 98.8%, According to Rieter's calculation, each rsb-d30 can save up to US $40000 per year [Note 2]

3 the principle, type and characteristics of the self leveling device

3.1 principle

change the drafting multiple in the drafting area to realize the leveling of the work in process. Basic equation:

v2=v1e (1 ± △ t/t) or v1=v2 [e (1 ± △ t/t)]... (1)

(1) where: V1 and V2 are the linear speed of feeding and spinning roller respectively, v2/v1= actual drafting multiple =d

e is the rated (Design) drafting multiple

g is the actual unit weight of feeding product, and the thickness t is the actual unit weight and rated (Design) drafting multiple of feeding product

△ g(1) the difference of unit weight, expressed in thickness change △ t

when V1 is a constant, V2 the thickness of the feed changes linearly. When V2 is constant, V1 changes hyperbolically with the thickness of the feed

3.2 there are three types of self leveling: separate loop, closed loop and mixed loop

3.2.1 open loop: the control loop is non closed, the detection point is located behind the roller after the machine is fed, and the control point is located somewhere at the spinning point, which works according to the compensation principle

3.2.2 closed loop: the control loop is closed, the detection point is set in front of the spinning front roller of the machine, and the control point is set somewhere at the feeding point. It works according to the feedback principle

3.2.3 mixing ring: in the draft adjustment system, there are both open-loop and closed-loop systems, which have the advantages of both.

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