Strongly twisted yarn is mainly used in woven weft yarns to create a unique wrinkled style on the fabric. Due to the above unique functions, highly twisted yarn as a special yarn has always occupied a place in the yarn market. Strongly twisted yarn can be produced without improving equipment or adding accessories, and the product has high technical content and added value. However, the production of strongly twisted yarn is difficult and the product quality is difficult to control. Production companies must have certain technical capabilities and management experience.
Strongly twisted yarn The pre-spinning production process and quality control are basically the same as those of conventional yarns, except that the twist coefficient of the fine yarn exceeds the critical twist coefficient of the yarn, and the yarn strength is lower than that of conventional woven yarn. The larger the twist coefficient, the lower the yarn strength. The higher the weight CV value and strength CV value; at the same time, in order to obtain relatively high production efficiency, the spinning spindle speed is generally not lower than the same number of woven yarns. Many of the above factors increase yarn breakage and increase production difficulty. Therefore, the cotton grade of strongly twisted yarn should be higher than that of woven yarn of the same size. Strongly twisted yarns generally have short delivery times and small batches, and sometimes it is difficult to mix cotton separately. At this time, combing waste should be increased, and draw frames and roving frames with good mechanical conditions should be selected to organize production. The quality of rovings is the quality of strongly twisted yarns. guarantee.
01 Spinning yarn twist
In order to achieve the special effect of wrinkling on the cloth surface, the twist of the strongly twisted yarn is more than 1.5 times that of the woven yarn of the same number. The specific twist value is generally specified by the manufacturer according to the fabric requirements. Due to factors such as the slippage rate of the spindle belt, in order to ensure that the twist requirements of the customer are met, the calculated twist of the spun yarn should generally be controlled on the large side. The twist coefficient of strongly twisted yarn is large, that is, the twist angle is large, and the fiber stress in the inner and outer layers of the yarn is seriously unevenly distributed. During the untwisting and twisting test, some fibers move and cannot be restored to their original state. Sometimes there are falsely high twist values, which need to be eliminated at any time during the test.
In daily production, in terms of process management, it is necessary to ensure that the spinning process parameters are accurately loaded on the machine. In terms of equipment management, it is necessary to eliminate crooked spindles, resolutely overcome “unfortunate” spindles, and maintain spindle belt tension. It is uniform and the spindle belt joint is good, so that the average twist value is basically stable and the twist CV value remains at a good level. The twist CV value of spun yarn directly affects the single strength CV value and weight CV value.
02 Spinning yarn quality (weight) and quantity control
The drafting efficiency of the spinning machine is affected by raw materials, mechanical conditions, processes, and temperature. It is affected by many factors such as humidity. Among them, due to twist shrinkage, the drafting efficiency of yarns with different twist coefficients varies greatly. Strongly twisted yarn has a larger twist shrinkage, and the drafting efficiency is generally 85% to 92%. Only by mastering the spinning drafting efficiency of the production variety can we effectively control the weight deviation and produce yarn that meets the specified weight requirements. During process design, drafting efficiency is considered based on experience and the drafting conversion gear is initially determined. During machine production, timely samples are taken for weight testing and process gears are adjusted.
03 Cop winding density
The bobbin winding forming needs to be tightly wound, with clear layers and no entanglement. It does not come out of the loop during unwinding in the post-process, and the package size is suitable. If the package size is too large, the yarn will easily wear the steel ring, causing yarn damage; if the package size is too small, the number of doffing times will increase, the number of winding and pipe changes will increase, the labor intensity will increase, and the production efficiency will decrease. Strongly twisted yarn has high twist and tightness, good elasticity and small cross-sectional diameter, and the bobbin shape is obviously too small. When the bobbin is doffed, the automatic doffing car cannot pull out the bobbin normally, resulting in increased doffing workload and affecting production efficiency. . The winding density of the bobbin must be appropriately increased.
04 Control of yarn breakage
The average strength of strongly twisted yarn is lower, and the strength CV value is higher than that of woven yarn of the same number. The yarn used must be large, the yarn breakage rate is high, and the splicing is difficult. More broken ends affect the yarn output and quality, and increase the labor intensity of the operator, so we must attach great importance to it from many aspects of operation and management.
Practice has proved that by using the frequency conversion speed regulation technology of the spinning frame, the spindle speed can be lowered for large and small yarns; select a machine with the steel ring in the mature stage, and shorten the length of the traveler appropriately. Replacement cycle; strengthen maintenance inspections, and timely correct measures such as crooked spindles, concave rubber rollers, apron deviation, loose yarn guide hooks, and unclean yarn guide hooks, which are effective in reducing spun yarn breakage. The output of the strong-twisting yarn table is not high, and the operator is not under great pressure to change the roving. He should concentrate on cleaning the machine, strengthen patrols, and connect broken ends in time.
The winding machine should be adjusted spindle by spindle and inspected and accepted spindle by spindle to ensure coordinated movements of all spliced parts and components. In place, the equipment is operating in good condition. The splicing joints of strongly twisted yarn windings are prone to insufficient untwisting and untwisting of the yarn ends, and the phenomenon of climbing at the yarn joints. The amount of air pressure for untwisting and twisting must be ensured. The untwisting and twisting scales must be adjusted from the maximum point, and the overlap length must be adjusted to the optimum. Strongly twisted yarn has high elasticity, the yarn package is tightly wound, and the winding pressure should be below 50 MPa. Highly twisted yarns have low strength and many yarn defects, frequent electronic yarn clearing actions, and the winding speed is lower than conventional yarns. Carded strong twisted yarn has many neps and impurities, which is lower than the production efficiency of combed strong twisted yarn of the same number.
In short, strongly twisted yarn products have high technical content and are difficult to produce and process. It is necessary to do a good job in technical basic management such as the operation of process equipment, strengthen the maintenance of spinning equipment, and reduce the difference between spindles. Ensure the untwisting and twisting air pressure of the winding, and adjust the overlap length and other process parameters to improve the joint quality and reduce the yarn end climbing phenomenon at the twist joint. </p