Thick places are very harmful in the winding and subsequent weaving processes. They not only seriously reduce the winding and weaving production efficiency, but also cause poor appearance of the fabric and even cause the fabric surface to degrade.
In spun yarn production, what factors will cause thick spots to occur?
01 Neps, impurities and short lint in raw materials and semi-finished products High content
Short velvet not only affects the evenness, strength and hairiness data of the yarn, but also directly causes a significant increase in neps and thick places in the yarn. Reasons for the high lint content:
(1) The raw materials in the cotton blend contain more lint below 12mm;
( 2) Excessive opening, blowing and carding in the blowroom process will produce a large amount of short lint but little discharge.
02 Excessive carding and carding causes an increase in short pile and thick spots
Especially in spinning When using polyester/cotton, polyester/viscose, pure cotton and blended yarns, chemical fibers will produce parallel filaments, fiber bundles, etc. when they are cut into short fibers. If they are not fully opened during carding, it will cause problems during the spinning process. The bunches move and finally thick places appear in the fine yarn. Insufficient carding is due to:
(1) The quality of the card clothing selected is poor; the card clothing is not sharp enough, in poor condition, the needle copying is not timely, and the needle grinding accuracy is insufficient;
(2) The separation in the main carding area is inaccurate or the separation is too large;
(3) The cotton roll or cotton roll is not vertically correct Evenly, the cotton layer is poorly held by the cotton feeding roller and the cotton feeding plate. After being decomposed by the licker-in roller, most of the fiber bundles are transferred to the cylinder cover. The cylinder cover has a heavy carding load, resulting in poor carding;
(4) The small drain bottom spacing is too small; the low speed of the movable cover is also the main reason for the high content of short lint and neps in the card sliver.
03 The main production process of large thick spots
There are Part of it is caused in the pre-spinning process, mainly due to improper setting of the drawing gauge and insufficient holding power; improper setting of the roving drafting gauge and insufficient holding power; poor drawing and roving joints; and coarse yarns such as flying flowers or accumulated flowers caught in the roving. Yarn defects. The parts that cause thick spots in the spinning frame are:
(1) When the roving is fed into the spinning drafting mechanism, the accumulated slugs are brought in by the roving (accounting for about 10%-15%);
(2) In the drafting part, due to poor drafting process, inaccurate cradle pressure, poor stability; cracked rubber rollers, triple winding of rubber rollers, and poor collector function , the rubber ring is running out of time, the cleaning work is not in accordance with the cycle or the quality is poor (about 30%-50%);
(3) The pass rate of spun yarn stopper joints is low , the suction air of the end-breaking cotton suction device is insufficient, causing the yarn to fly and adhere to the yarn after yarn is broken (accounting for about 15%-25%);
(4) The traveler shaves the yarn or brings the winding flowers into the yarn (about 1%-3%); in addition, the unreasonable air supply system in the workshop leads to turbulent air flow in the workshop and a lot of flying flowers, resulting in short stubs.
04 Unreasonable spinning process configuration
(1) Roving twist The coefficient, basis weight, and draft ratio after spinning are unreasonable;
(2) Unreasonable apron tension and apron jaw spacing will cause thick spots;
(3) When spinning medium and low-number and low-count yarns, a high draft multiple of the spun yarn will easily cause more thick spots; this is mainly because the roving has a large basis weight and the fibers enter the front drafting zone. The movement stability is poor, the synchronization difference between the upper and lower aprons is large, and the apron operation and yarn unevenness are high, resulting in thick spots.
05 The influence of winding on thick places
With the increase of winding speed and yarn As the thread tension increases, the CV value of the evenness will deteriorate, and the coarse details and neps will increase.
(1) As the winding speed increases, the yarn’s accumulated friction from the yarn guide, tension controller and groove drum continues to increase;
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(2) The increase in winding tension will also cause sharp friction between the yarn and the winding part, causing an increase in surface hairiness. Part of the hairiness involved in the yarn body will also be exposed in the yarn body, or the accumulation of short velvet will cause Thick places or neps, and the cross-section of part of the yarn body are enlarged to form thick places. </p
