What is strongly twisted yarn?
In order for the yarn to have certain physical and mechanical properties such as strength, elasticity, elongation, etc., the cotton yarn must be changed through twisting. Yarn twisting is achieved by fiber structure. In fact, the relative angular displacement between cotton yarn cross-sections is used to tilt the originally straight and parallel fibers and the yarn axis to change the yarn structure. The width of the thick strips gradually shrinks during the twisting process. The yarn is rolled into the center to form a twisted triangle, which changes the width and cross-section of the cotton sliver from a flat ribbon to a cylindrical yarn.
The comprehensive performance of strongly twisted yarn fully meets the requirements of modern people, and it contains a large amount of cotton and uses plant fibers, so it does not cause any harm to the human body. It has strong plasticity and can be used to make a variety of clothes. It is very comfortable to wear, soft to the touch, and has a strong drape. It has no smell after burning and is a healthy and green textile.
Highly twisted yarn is mainly used in woven weft yarns, which can produce a unique style of wrinkling on the cloth surface. As a special yarn, strong twisted yarn has always occupied the yarn market. a place. 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.
01 Pre-spinning
The pre-spinning production process and quality control of strongly twisted yarn are basically the same as those of conventional yarn, except for the spun yarn The twist coefficient 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, and the higher the weight CV value and strength CV value; at the same time, in order to obtain a relatively high The production efficiency of spinning yarn is generally not lower than that of woven yarn of the same number. Many of the above factors increase the breakage of fine yarns and increase the difficulty of production. Therefore, the cotton grade of strongly twisted yarns should be higher than that of woven yarns 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.
02 Spinning yarn
Spinning yarn twist. In order to achieve the special effect of wrinkling on the cloth surface, the twist of strongly twisted yarn is more than 1.5 times that of 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.
Spin yarn quality (weight) and quantity control. The drafting efficiency of the spinning frame is affected by many factors such as raw materials, mechanical conditions, processes, temperature and 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 the process gears are adjusted.
Bobbin winding density. The bobbin winding and forming needs to be tightly wound, with clear layers and no entanglement. The bobbin must not be decoupled during unwinding in the subsequent process, and the package size must be appropriate. 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.
Control of yarn breakage. The average strength of strongly twisted yarn is low, the strength CV value is larger than that of woven yarn of the same number, the yarn breakage rate is high, and splicing is difficult. More broken ends affect the yarn output and quality, and increase the labor intensity of the workers. It must be paid great attention to 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 when the yarn is large or small; select a machine with the steel ring in the mature stage, and shorten the length of the wire ring appropriately. Replacement cycle; strengthen maintenance inspections, promptly correct crooked spindles, concave rubber rollers, apron deviation, loose yarn guide hooks, dirty yarn guide hooks, etc., which is effective in reducing 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.
03 Winding
The winding machine should be adjusted and inspected spindle by spindle to ensure that all parts and components are spliced. The movements are well coordinated and the equipment is operating in good condition. Insufficient untwisting and untwisting of the yarn ends at the winding splicing point of strongly twisted yarns and the phenomenon of climbing at the yarn joints are easy to occur.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 yarn has low strength, many yarn defects, frequent electronic yarn clearing actions, and the winding speed is lower than that of conventional yarn. 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 basic technical management such as the operation of process equipment and strengthen spinning equipment. Maintenance, 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 phenomenon of yarn end climbing at the splicing point. </p
