Long slubs and long details are yarn defects that are easy to occur in spinning mills and are extremely harmful. They will cause thick warp and wrong weft (woven) or rung defects (knitted) to form on the cloth. Such yarn defects are difficult to repair and may even cause shearing to drop, resulting in large losses and sometimes financial claims from customers. So what are the main causes of such yarn defects? Let’s discuss it from the three basic management aspects of process, equipment and operation.
In the process of spinning from blowroom → carding → combing → thickening → spun yarn, there are excellent semi-finished products which are the basis for spinning good yarn, so we must find out The reason is to pay attention to the possible problems at the source. For example: improper stacking and arrangement of cotton bales, poor loosening and grasping; uneven cotton rolls, heavy and light rolls, and failure to close the cotton table; uneven light and heavy rolls of winding rollers, rubber rollers, and raw slivers, and failure to take out the combed cotton web Holes or overlapping glue rolls; long thick sections and long details are formed after rough drafting. Occasional long thick places and long details are mainly caused by the thickening process of pre-spinning, mainly due to equipment and operation reasons. Improper technology can also cause such defects. In response to the above problems, it is necessary to improve the quality awareness of the on-duty lathes, and promptly remove all defective slivers caused by falling (cotton mesh, cotton sliver), entanglement, sticking, and hanging to prevent yarn defects from flowing into the next process.
Processing reasons
► And, The distance between the roughing process rollers is too small, or the draft distribution is improper, resulting in thick spots.
► Because the roller spacing is too large or the down-suction air volume is too large, the effectively available fibers in the sliver are taken away during operation, resulting in details. Solution: Open the fan side door of the draw frame, adjust the position of the fan baffle, and observe the air volume. It is appropriate for the air volume to make the short fibers fall without taking away the long fibers. You can also open the rear small air door 1/3 to supplement the air.
► Drawing and roving are not properly pressurized, and thick pressurization should be dealt with in detail based on the ration of the yarn sliver. A big principle to grasp is: the holding force and drafting force are balanced. If the holding force is greater than the drafting force, details will be formed; conversely, if the holding force is less than the drafting force, thick joints will be formed. At present, when the basis weight of draw spinning blended varieties is 18 g/(10 m) ~ 20 g/(10 m), the general pressure is controlled at 120 N ~ 160 N. However, if the yarn number is spun with a fixed weight, the pressure must be increased accordingly. .
Poor pressure is also reflected in the position of the rubber roller. Based on the roller level, the pressure of the rubber rollers is not on the same level, so that the cotton sliver is affected when passing through the pressure nip. The power is different. The diameter of the rubber rollers on the same truck must be consistent within the allowable range, because the larger the diameter of the rubber roller, the greater the positive pressure area it receives, and the holding force on the whiskers is also larger, and the corresponding drafting force is larger; On the contrary, the drafting force will be small. When the required drafting force is different, coarse details will be formed to varying degrees. This requires that the loading status of the rubber rollers should be checked when the equipment is leveled, inspected and wiped. In terms of technology, the loading status of the spinning equipment parts should also be checked regularly.
Equipment reasons
► Coarse details generated by mechanical waves in the roughening process are formed after drafting Long thick sections, long details.
Based on the length of the mechanical wave, the problem can be found using the formula L (wavelength) = 3.14 × d (roller diameter) × E (draft multiple of the problem component to the front roller) location.
► The photoelectric automatic stop device of the drawing process is not used properly, and the production is still carried out after overlapping or missing strips, resulting in a large number of rough details.
► The opening of the cotton collector after drawing is too small, causing the slivers to overlap, and the cotton slivers cannot be stretched during drafting, resulting in thick spots. Therefore, in the process of changing the yarn number, especially when changing varieties, it is necessary to observe the arrangement of the slivers.
► The position of the rear rubber roller of the roving, the rear rubber roller and the bell mouth are too close, the sliver is easy to be blocked, and the overlapping sliver is fed to form thick spots. After the bell mouth is broken, the position is wrong, and the sliver is easy to deviate or even not pass through the rear rubber roller. In this way, the draft multiple in the rear area becomes invalid, resulting in long slub yarn defects (this phenomenon also occurs in the spinning process).
► Faulty roving winding and forming. The ribs are knocked out during operation and the upper and lower aprons rotate intermittently, which will also produce thick details.
The above-mentioned process and equipment reasons are prone to produce rough details, which requires more viewing, touching, and inspection of the equipment and the use of spinning equipment and parts. ; Equipment should be leveled, inspected, and wiped carefully, problems should be discovered and solved in a timely manner, and all possible causes should be nipped in the bud.
Operation reason
► And, The lathes in the rough and fine processes will not wrap the strips properly. If there are too many or too few ends, rough details will be produced accordingly. The operation level of the turner can be improved by increasing the intensity of operation inspection, and the operation level of the turner on duty can be checked regularly; the operation method can also be improved, such as: changing the joint at the back of the machine to the joint at the front of the machine; changing the drawing and roving to Centralized bobbin changing; the 120 bobbins after the roving are divided into 6 sections, each section has 20 bobbins, divided equally according to the 6 sections, the length of each section is 6/6, 5/6, 4/6, 3/6, 2/6, 1 /6, set the combined and thick fixed lengths according to the required length. Under the condition of sufficient turnover drum, this can effectively reduce coarse and fine yarn defects caused by poor wrapping when changing yarn and sliver.
► When turning on and off the machine at the end, not all the defective slivers were removed; the slivers were split and stacked behind the roving frame, and the yarn slivers floated into the adjacent yarn after the end was broken in front of the machine. , not removed in time; the defective yarn is not removed when the roving cradle is relieved, etc., which will also cause thick and thin yarn defects.
► Spun yarnProcedure: When the roving runs empty, the tail yarn is caught in the adjacent yarn strips to form a double feed; when changing the roving, the end is not wrapped and the feed is chased, resulting in long slugs. The single siro spinning varieties will not end before the feeding time, but one missing sliver will produce long details.
In view of the above operational factors, it is necessary to improve the quality awareness of the operators, hold more quality analysis meetings, and carry out more defect catching and prevention activities. Only by continuously improving the details can we reduce the occurrence of yarn defects. </p
