The roving frame plays a key role in the textile industry, connecting the past and the future. How to make good use of roving equipment? Roving tension and process control are essential.
Roving tension control
1. In order for the roving to be smoothly wound onto the roving tube, the winding speed of the tube must be slightly greater than the speed of the front roller output yarn, so tension and tension draft are generated on the yarn between the front roller and the thick tube. , it is the key to roving production. It not only affects whether the roving life is good, but also directly affects the quality of the finished yarn.
2 According to the requirements of spinning quality, the maximum elongation is generally not more than 3%. The elongation difference between yarns of the same machine size, between front and rear rows, and between machines of the same type should be controlled at 1.5%. The following is appropriate.
3. The yarn section from the front roller to the top of the spindle flyer has a small twist due to the twisting phenomenon, and the distance is long. At the same time, when the spindle flyer rotates at high speed, there is a shaking phenomenon, and accidental elongation is most likely to occur. According to experience, it should be adjusted to: when the small yarn is wound from the starting point to the lower part of the bobbin for the second layer, the yarn can shake slightly, but it is better not to cause waves. If the upper yarn is tight, it means that the winding speed is too fast and the elongation is too large. The starting position of the cone pulley belt should be moved upward to the big end of the cone pulley. The non-cone pulley should be controlled and adjusted from the inverter. The ultimate goal is to achieve consistent Slightly jittery. If the yarn gradually becomes tight during the spinning process, it means that the conical pulley belt moves too little each time, and the number of tension teeth should be reduced. Otherwise, the number of tension teeth should be increased.
4 Factors that affect changes in roving tension include: roving basis weight, front roller speed, twist, raw cotton quality, temperature, humidity, mechanical state and other conditions. Therefore, a roving quality ledger should be established during production, which is completely necessary to ensure production. The size, difference and unevenness of the roving tension will affect the evenness and weight unevenness of the roving. It is an important indicator that affects the quality of the roving, so it must be strictly controlled. Because the number of fibers in the cross-section of the roving is much smaller and the twist is lower than that of the spun yarn, it is prone to unexpected elongation after being subjected to greater tension, worsening the evenness of the roving and increasing breakage.
5 When the tension difference is large, the roving weight unevenness increases significantly, and should generally be controlled within 1.0%. When the roving tension is small, the roving becomes loose and difficult to store, transport and unwind, which not only affects the quality of the roving itself, but also increases the uneven weight and weight deviation of the spun yarn. For example, when spinning pure cotton roving on a roving frame with poor false twist effect, the quality index of the front row is worse than that of the rear row. Under the same spinning conditions, different tensions in the front and rear rows will cause quality differences. Of course, under conditions where the false twist effect is good, the spinning tension of the rear row may be greater than that of the front row. Therefore, in terms of roving quality management, in addition to paying attention to the influence of the drafting part on quality, we should also grasp the changes in roving tension.
Process control of roving frame
The process parameters of the roving frame mainly include: basis weight, spindle speed, draft multiple, roller holding distance and apron jaw spacing, roller pressure, twist coefficient, winding density, collector and bell mouth diameter, pressure palm winding Number of detours.
1 The ration of roving is determined based on the drafting capacity of the spinning machine, the number of spinning yarns, and the quality of the product, mainly based on the number of spinning yarns. The heavier the roving being spun, the thicker the yarn, but if it is too heavy, the fine yarn will increase with the draft multiple, which will have an impact on the evenness of the finished yarn. Now there are products that increase the basis weight to 10 g/(10 m), change the spun yarn to a “V” type draft, and the finished yarn is also good, and it is worthy of promotion.
In short, the total draft ratio of the roving frame is determined not only based on the number of spinning yarns and the ration of cooked sliver, but also the drafting type of the roving frame. Since the spinning frame is currently developing towards high-multiple drafts, the roving can be configured with a lower draft. Stretch ratio is good for quality. When using double short apron drafting roving, the drafting multiple can be slightly higher than the three up and four down curve drafting, generally 5 to 12 times.
2. The drafting distribution of the roving frame is determined according to the drafting type and the total drafting multiple. When the drafting capacity of the main drafting zone is large, the drafting multiple of the main drafting zone should be large. The double short rubber ring drafting It is a kind of drafting zone with a large capacity. Practice has proved that when the feeding sliver quantity and the roving quantity remain unchanged, the larger the post-drafting multiple, the worse the roving evenness. Therefore, in the main drafting zone, the process When the conditions are good, the rear drafting ratio should be controlled on the small side.
3. Post-drafting ratio: The post-drafting ratio has a great influence on the evenness of the roving. In general, the double rubber ring drafting device has strong friction in the rubber ring part and an elastic jaw, which can stabilize the drafting force and move the fiber speed change point forward, which is both concentrated and stable. Therefore, the general post-draft ratio is configured between 1.08 times and 1.4 times. In production practice, we use 1.1 times the post-draft on the A454, FA468E, FA458A, and FA421 roving frames to achieve optimal roving evenness. Of course, the dry quality is also related to the pressure of the apron roller. When determining the rear draft ratio, you should first understand the slippage rate of the lower apron to the center roller, and try to reduce the slippage rate of the upper and lower apron rings.
In addition, when the basis weight of the roving is too heavy, in order to prevent the delamination of the whiskers, a larger post-draft ratio can be used. When spinning knitting yarn, in order to prevent the details of long segments of fine yarn, a smaller total draft ratio should be used. In this case, the draft ratio of the rear area should also be controlled on the small side. For the three-up and four-down drafting type, due to the rear�There is an anti-enveloping arc on the third roller. When the cooked strip weight is light, the draft ratio of the rear area should also be controlled on the small side, generally 1.17 times to 1.36 times.
4. When using a large package and high roving frame, the spindle speed can reach 1000 r/min ~ 1500 r/min. The roving weight should not be too light, otherwise it will increase unexpected drafting and lead to more breakage of thick and fine yarns, making life difficult.
5 Twist coefficient: When the fiber is long, uniform and fine, the twist number should be small, and vice versa. Only when the roving has twist can it withstand the tension in winding and unwinding, and is conducive to the drafting of the rear area of the spun yarn. Control of fiber. But if the twist coefficient is too large, not only will the strength of the roving be uneven, but the spun yarn will also cause rubber roller slippage, hard ends, and increased breakage; on the contrary, if it is too small, accidental drafting will occur, and breakage will increase, making the product uneven.
6. Roller spacing and pressure: The roller spacing should be determined according to the fiber length. If it is too small, it will damage the fiber and even produce hard ends. If it is too large, the fiber movement will be irregular and the CV value of the evenness will be deteriorated. The purpose of roller pressurization is to ensure that the roller The jaws have sufficient holding power to prevent the yarn from slipping and excessive delamination under the roller jaws. During the drafting process, whether the roller jaws can effectively control the fiber directly affects the evenness and weight unevenness and the occurrence of roving defects. On a roving frame pressurized by a spring cradle, the upper pin and The jaws are controlled by the pin apron under the ladder, and the original spacing of the jaws is determined according to the quantitative change of the roving. When the quantitative quantity is more than 5 g/(10 m), the original spacing of 4.5 mm, 5 mm, 5.5 mm, and 6 mm should be used. When selecting, it should be equipped with a smaller jaw under sufficient spring pressure conditions. It is beneficial to have a uniform product, but the spring pressure should be corrected regularly. If the pressure is inconsistent, it will cause a large difference between ingots. If the jaw is too small, it is easy to spit out hard heads.
7. The front and middle area collectors of the roving frame are also equivalent to an additional friction zone. Their diameters are as follows: the front area should be compatible with the roving weight, and the middle area should be compatible with the cooked strip weight.
8. The spindle is vertical and has no oscillation, and is controlled within 0.03 mm. The bending is too large, resulting in increased breakage and irregular thickness.
9. The spindle flyer should be dynamically and statically balanced, not skewed, the passage should be smooth, and the pressure palm should be appropriately tight. If the yarn is too tight, it will be hairy, and if it is too loose, it will easily fall off. If the arm opening is large, the arms will collide with each other; if the arm opening is small, the yarn will be worn. If the curvature of the pressing palm is not up to standard, the roving winding elasticity and rationing will be uneven, and even defective products will be produced, resulting in increased ends breakage. In order to maintain the normal operation of the machine and reduce wear and tear, it must be calibrated and wiped regularly.
In short, the correct use of the roving frame is a key link in textile engineering. Only by deeply understanding the connotations can we make better use of the roving frame and spin high-grade products.
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