Weak twist of spun yarn means that the twist is lower than the normal value. After the spun yarn is broken, the strength of the yarn is insufficient and the splicing is difficult. The short pieces of yarn are in a state of small twist, commonly known as weak twist.
Several situations in which weak twist occurs
1) One-placeness: The thick details produced by uneven drafting. During the twisting process, the twist is concentrated at the details. The twist at the thick places is small and the strength is low, or the details are too long, resulting in fragmented twist coefficient and low strength. .
The long details caused by roving result in insufficient twisting and low strength during the yarn forming process.
2) Whole single spindle: Single spindle is faulty, and the whole yarn is thicker than normal yarn. This type of yarn may be accompanied by friction on the steel ring.
3) Entire machine: caused by process errors.
Judging from the actual production process, the ones that have a greater impact are weak twist in one place and weak twist in the entire ingot.
If a weak twist in one place cannot be connected to the end, it will be a big concern for the lathe. The entire ingot is weakly twisted and will not rub the steel ring due to the forming, so it is not easy to be found and removed. This is the key task to control weak twist.
Weak twist in the entire machine is not easy to occur and is easy to detect, and generally does not cause negative effects.
The dangers of weakly twisted yarn
1) Strong decline;
2) Produces yellow-white gear, and the contrast becomes more obvious after color absorption;
3) Repeated yarn breakage increases;
4) It is easy to produce ring yarn grinding;
5) The number of ends broken on knitting and weaving machines increases;
6) Weak twist easily produces hairiness;
7) Weak twisting is prone to cotton balls (neps);
8) Use yarn with weak twist as warp yarn. Since it absorbs more color, it will produce long warp in the warp direction.
The main factors of uneven twist
1) When the roving frame does not use a false twister, the twist in the spinning section is far lower than the process design twist, so the elongation of the normally spun roving is also larger.
This is mainly because the top of the spindle flyer is the twisting point. The greater the friction at the top of the spindle flyer, the stronger the twisting phenomenon of the yarn sliver.
2) The evenness of the spun yarn is poor, especially the occurrence of thick spots and fine details, which have a greater impact on the twist unevenness of the yarn.
3) Uneven spindle speed is an important reason for uneven twist in yarn.
Uneven spindle speed is mainly caused by the difference in slippery rate between rollers, spindle conditions and spindle belt reels. The main factors affecting the slippery rate are the tension of the spindle belt, the quality of the inner and outer layers of the spindle belt, the taper of the spindle tip and the spindle Differences in disc diameter and spindle lubrication conditions.
4) The influence of spindle belt length and spindle belt tension on spindle speed: If the spindle belt tension is large, the slippage rate between the spindle belt and the roller plate will be small, and the slippage rate between the spindle plate and the spindle belt will also be small, and the spindle speed will be high. , so the twist of the yarn is large.
The influence of the length of the spindle belt on the tension of the spindle belt: if the spindle belt is long, the tension of the spindle belt will be small, and if the spindle belt is short, the tension of the spindle belt will be high.
If the spindle belt lengths of the spinning frame and the twisting machine on the same machine are inconsistent, it will cause a large difference in the tension of the spindle belts on the same machine, resulting in uneven spindle speeds on the same machine, which will affect the uneven twist of the yarn.
The spindle tape has poor lap, twisted and damaged burrs, excessive fly flakes adhere to the spindle tape, oil stains on the spindle, etc., causing the spindle and the spindle tape reel to rotate inflexibly, beating, etc., all of which will affect the twist unevenness of the yarn. produce a certain degree of impact.
5) Poor contact between the spindle and the bobbin, the inner hole at the top of the bobbin is worn or not rounded, the weight is too light, the spindle rod is bent and the spindle runs unstable, etc., which will cause the bobbin to jump or invisible jump during operation, causing Recovery of yarn twist unevenness.
6) Due to a weak sense of work responsibility and lax management of the workshop laboratory, the wrong number of twist conversion teeth was used, resulting in a large number of strong and weak twisted yarns, that is, wrongly twisted yarns.
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