With the rapid development of spinning technology, carding technology is also constantly improving. At present, the yield of the carding machine is getting higher and higher, the carding area is increasing, and there are more and more additional carding elements, and the traditional carding concept of "tight spacing and strong carding" can no longer meet the requirements of the current carding technology. Therefore, the industry has developed a new type of carding technology characterized by "flexible carding".
1. Sort out the characteristics of technological development
At present, the development of spinning technology requires carding technology to adapt to the following requirements:
(1) High-speed: the output speed can reach 100-360m/min.
(2) High quality: the quality index of yarn (CV value of strip dry, kilometer nep, etc.) reaches the optimal state, and the kilometer nep is close to zero.
(3) High yield: the yield can reach 50-130 kg.
(4) Intelligent: to meet the requirements of intelligent spinning process, easy to operate.
(5) New raw materials: a variety of new fibers emerge in an endless stream, and fibers with different characteristics are needed to be spun.
(6) New equipment: various new models of carding machines are emerging, the width is also increasing, and the carding technology should also have a certain universality to various types of carding machines.
(7) New process: the adaptability to the carding process should be good to ensure that the fiber damage is minimized.
(8) New technology: It is adaptable to different spinning forms such as vortex spinning, rotor spinning, and siro spinning.
2. Analysis of the key points of the new carding technology
2.1 Carding Essentials Analysis
In the process of carding cotton bundles into single fibers, there is "one center, one set of contradictions, and six laws".
(1) One center: The core of the new carding technology is "thorough removal of impurities (defects), fine carding, minimization of linter growth, maximization of nep removal, and full improvement of fiber straightness".
(2) A set of contradictions: the contradiction between the increase of carding work area, good fiber carding effect, high impurity removal efficiency, high nep removal rate and fiber damage, linter growth, cotton dropping, floating fiber flipping and rubbing, and insufficient straightening.
2.2 Six rules of carding process
(1) Reasonable selection of card clothing models, combined with the characteristics of card clothing to optimize the carding process parameters, to ensure that the card clothing "five edges and one accurate", can achieve the effect of "good carding effect, high impurity (defect) removal rate, less cotton dropping, less fiber damage", can achieve "improve carding, efficient impurity removal and knotting, control the growth rate of linters", on the contrary, it will affect the quality index of yarn.
(2) With the increase of the carding area and additional carding elements of the carding machine, the chance of the fiber being carded increases, the nep and impurities (defects) are eliminated, and the straightness of the fiber is improved, but the short linter and cotton drop increase.
(3) The more fully the opening of the rear barbed roller part, the more fully the impurities (defects) are removed, and the greater the decrease in neps, but the increase of short linter and cotton drop (long fiber).
(4) The fine carding interval of the cylinder cover plate is tight, and the floating fiber between the two needle surfaces is less, the carding strength increases, and the fiber straightness becomes better, but the fiber damage is serious, the cotton drop increases, and the wear of the card clothing accelerates.
(5) The transfer rate of Sillindorf is too high, the carding is not sufficient, the fiber straightness is poor, but the transfer rate is too low, the number of repeated carding is too large, the short collar increases, and the fiber back hook increases, which affects the small yarn defects in yarn.
(6) The carding card clothing generates air flow during movement, but the carding effect is affected by the air flow movement. If the airflow is too large, it is easy to cause the airflow to carry the fiber overflow and the wallboard to accumulate flowers.
2.3 Five keys to solving the difficulties of carding
(1) Deal with a pair of contradictions, so that "impurities (defects), neps, linters, straightness" are taken into account.
(2) According to the type of fiber combing, the miscellaneous division of labor is reasonable. The increase in cotton shedding is conducive to the removal of impurities (defects) and linters, but the loss of spinnable fibers will increase.
(3) In the carding work area, reduce the kneading and flipping of the fiber as much as possible to ensure the carding effect, reduce the fiber damage, control the growth rate of the linter, and provide good conditions for the drafting of the post-process. The combination of impurity discharge, carding and transfer, cotton fiber removal is given priority and combing is taken into account, while non-cotton fiber transfer is given priority and carding is taken into account.
(4) Reasonably select the geometric size of the card clothing, and improve the five degrees of card clothing (wear resistance, flatness, sharpness, finish, quenching uniformity), so that the fiber does not penetrate into the bottom of the tooth and remains at the tip position of the needle tooth, so as to create conditions for improving the third degree of the fiber.
(5) Reasonably control the airflow, ensure the good running state of the fiber in the carding area, evenly distribute it on the tooth surface, and eliminate impurities (defects) and neps in time.
3. Difficulties of new carding technology and card clothing configuration
3.1 Barbed roller pre-combing area
3.1.1 Factors influencing the effect of rear carding
The main function of the barbed roller part is to pre-open, remove impurities, and maximize the single fibrosis rate.
(1) The pre-opening is insufficient, and the impurities are wrapped in the fiber bundle, and the exposure effect is poor.
(2) The speed is low, the centrifugal force of the roller is small, and the impurities cannot be thrown out;
(3) The space for impurities is limited, and the fine impurities cannot be effectively removed, and the cotton falling is uneven.
(4) If the geometric dimensions of the card clothing are not properly configured, it is easy to cause in-depth or insufficient impurities.
(5) There is more fiber damage and increased short-linting.
3.1.2 Design of rear process
(1) The speed of the barbed roller is low to control the growth rate of the short liner, which is generally controlled below 870r/min when producing cotton fibers and 700r/min when producing non-cotton fibers, and the centrifugal force of the barbed roller is reasonably used to eliminate small impurities.
(2) Barbed roller-cotton roller spacing: appropriately tighten the grasp to improve the ability of the needle teeth to grasp the fiber. However, the large separation is conducive to reducing fiber damage, and the general control is about 0.30mm when the reverse cotton is fed, and about 0.50mm when the cotton is given in the forward direction.
(3) The spacing between the barbed roller and the pre-carded plate: the traditional process is generally greater than 1.0mm to reduce fiber damage. The new carding process is tightly controlled, generally controlled at about 0.50mm, so as to improve the pre-carding effect.
(4) Thorn roller discharging impurities and controlling cotton dropping process. The length of the first and second impurities is reasonably allocated, so as to effectively collect impurities and improve the efficiency of impurity removal.
Increase the cotton shedding process: dust removal knife-barbed roller 12-17 filament, dust removal knife angle 85°, 6mm lower than the frame, in order to increase the first and second miscellaneous areas, and reasonably control the third miscellaneous area.
Reducing the cotton shedding process: dust removal knife-barbed roller 20-40 inch wire, dust removal knife angle 90°, 6-20mm higher than the frame, in order to reduce the first and second miscellaneous areas, and reasonably control the third miscellaneous area.
3.1.3 Examples of improving carding quality and reducing linting
(1) The barbed roller adopts low speed, increases the tin spur ratio, improves the transfer force, is conducive to protecting the fiber, and improves the product quality, see Table 1.
Table 1 Effect of barbed roller speed on product quality
(2) The use of large tooth pitch to reduce fiber damage, improve the strength of the yarn, and at the same time can use the centrifugal force of the barbed roller to remove impurities, see Table 2.
Table 2 Effect of barbed roller speed on product quality
3.2 Cylinder cover carding area
The carding area of the cylinder cover plate (main carding area) is characterized by fine carding, which is the key part to improve the third degree of fiber, and is also the key part of impurities, short linter and nep control.
3.2.1 Influencing factors of the main comb area
(1) The orientation of the feeding fibers (rear process).
(2) If the fiber sinks into the tooth root, it will affect the carding effect, resulting in inlay, sticking, winding, hanging and winding phenomena.
(3) If the card clothing is not properly configured, the tooth density and tooth shape of the card clothing are poorly matched, which will seriously affect the carding effect.
(4) The interval of carding is too large, too small or improperly set, resulting in too fast transfer or repeated carding, which will cause insufficient carding or too high growth rate of short colluters.
3.2.2 Process design of the main carding area
(1) Reasonable design of cylinder-cover plate spacing, tight grasp is conducive to combing between fibers, generally controlled at 7-10 inch wire.
(2) Reasonable design of cover speed, taking into account carding and cotton dropping. The cover plate is fast, the cleanliness is high, and the loss of long fibers is more. Development trend: generally mastered at 220-350/min.
(3) Reasonable design of cylinder speed. The high speed of the cylinder can improve the carding effect, and the centrifugal force is large, which is conducive to the elimination of fine impurities. Development trend: cotton is more than 430r/min, and differentiated fiber is more than 330r/min.
3.3 Additional carding equipment
3.3.1 Influencing factors
(1) Improper configuration of tooth density, tooth shape and arrangement form results in poor carding effect.
(2) The fibers sink into the tooth root, causing impurities.
3.3.2 Process design of additional carding equipment
(1) Cylinder-rear fixed cover. The distance between the rear fixed cover plate and the cylinder should be appropriately enlarged to give the fiber full release space and reduce the fiber damage caused by extruding the fiber. Generally, 0.38-0.70mm is used.
(2) Cylinder - front fixed cover. Shrink as much as possible to enhance the finishing effect of the fibers. Generally, 0.18-0.25mm is used.
(3) Cylinder - front and rear cotton cleaner. The rear cotton net cleaner needs to increase the removal effect of large miscellaneous and short liners, and the separation distance is slightly larger. The spacing of the front cotton net cleaner should be as small as possible to increase the exclusion of linter and silk chips. The process configuration of the front and rear cotton cleaners is the key to the reasonable distribution of cotton drop and the elimination of impurities.
3.4 Doffer transfer process and card clothing selection
Improve the transfer rate of one-time carding in the carding area, improve the fiber straightening effect, and maintain the parallel straightness of the fiber.
3.4.1 Factors influencing the transfer effect of the doffer
(1) The distribution state of the fiber on the needle surface.
(2) The straightening state of the fiber after transfer and the state of the cotton net.
(3) Card clothing tooth shape, ability to control and transfer fibers (excessive or insufficient carding, contradiction between linters and neps).
(4) The impact of high-speed airflow on the cotton net in the Xilindorf triangle, the problems of large leakage bottom flower absorption, and downfare return to flowering.
3.4.2 Doffer process design
(1) When designing the Cylinder-Doffer spacing, the expansion coefficient should be considered (see Table 3). In principle, the smaller the spacing, the better, and it is generally controlled at 0.15mm.
Table 3 Effect of expansion coefficient on spacing
(2) Doffer - lower cover plate spacing. Divert the airflow as much as possible to reduce the impact of the airflow on the triangle area and the doffer cotton net.
(3) Doffer speed. Maximize the one-time transfer rate and reduce repetitive carding. From the point of view of carding, light weight is conducive to the full straightening of fiber, and light weight can be used in the production of cotton fiber to improve the arrangement structure of fibers in the cotton net; from the point of view of transfer, heavy weight is conducive to fiber transfer, and heavy weight can be used in the production of non-cotton fiber, so as to facilitate fiber transfer and increase yield.
Fourth, the control of airflow and the key points of process design
Controlling the airflow movement is equivalent to controlling the movement of the fiber, and at the same time, the airflow can be used to remove impurities, discharge linter and fine dust, reduce the scattering of fibers, and achieve the effect of improving product quality.
The distance between cover plate and cylinder is small, and the distance between the four cover plates and cylinder is designed according to the design of the carding machine to ensure the stable operation of the airflow.
As much as possible, the fibers do not sink into the bottom of the tooth, and the carding transfer capacity of the cylinder and cover plate or the cylinder and other carding elements is improved.
The inlet and outlet of the front and rear and upper and lower cover plates control the inlet and output of the airflow (see Table 4), which can change the movement form of the airflow, so as to effectively control the airflow and improve the fiber carding effect.
Table 4 Principle of process design of baffle plate
V. Conclusion
Carding technology is advancing, through the configuration of card clothing and the cooperation of process parameters, it can effectively solve the problems that cannot be solved by the traditional carding process, and realize the effect that the traditional carding process cannot achieve, so as to achieve high-quality, high-yield and efficient carding results.
Source: Liu Guigui Xinjiang Tumshuke Donghengxing Textile Technology Co., Ltd
Editor: China Yarn Network New Media Team
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