1 Negative pressure fan exhaust volume and negative pressure pipe negative pressure
The size of the negative pressure in the negative pressure tube is the most direct and critical factor affecting the quality of compact spinning yarn. The accumulation in the air box of the negative pressure fan is also a key factor affecting the negative pressure of the negative pressure pipe. In daily production, the accumulation in the air box must be cleaned in time to keep the negative pressure stable. According to actual testing and production, the negative pressure of compact spinning needs to be maintained at 24-30 mbar. If the negative pressure is too low, the breakage rate will increase, the hairiness will increase, the length of the hairiness will be long, and the hairiness unevenness will be large. According to actual measurements, under the same temperature and humidity conditions, when the negative pressure is 24-27 mbar, the negative pressure difference between the front and rear of the car is about 1.5-3.5 mbar, and the hairiness difference is about 30%. Production practice has proved that the 1008-spindle spinning frame can choose a 4.2 kW negative pressure fan, and the 512-spindle spinning frame can choose a 2.4 kW negative pressure fan. Appropriately increasing the speed of the negative pressure fan can reduce the negative pressure difference between the front and the rear of the car and minimize the impact of the negative pressure difference on yarn quality. Every time you wipe the car, you can turn on the negative pressure fan to suck out and clean the dust accumulated in the negative pressure air cylinder.
2 The movement state of whiskers on the negative pressure tube
The movement state of the whiskers on the negative pressure tube is an extremely important factor that affects the yarn dryness. When the negative pressure is normal, the whiskers move from the roller to the negative pressure tube as well as on the negative pressure tube. During the movement, the whiskers move in a relatively straight and continuously converging state. However, affected by certain factors, the movement state of the whiskers will change.
In actual production, due to factors such as excessive cradle pressure, static electricity accumulation, poor surface of the top roller, and low negative pressure of the negative pressure tube, the whiskers fall or skew left and right in the “uncontrolled area” between the roller and the negative pressure tube. phenomenon, the yarn dryness will be significantly affected. Therefore, the pressure of the compact spinning weighting arm should be kept small to prevent the accumulation of static electricity, maintain the surface smoothness of the rollers and top rollers, prevent tangling and sticking, and keep the negative pressure of the negative pressure tube normal. At the same time, try to use anti-static mesh rings and choose mesh rings with a reasonable mesh number.
3 Influence of workshop temperature and humidity
During the compact spinning production process, due to the effect of suction and exhaust air, the workshop temperature will be obviously uneven at the front and rear of the car. This unevenness will show seasonal differences. The temperature difference in winter is about 2-4℃, while in summer it is about 3-6℃. Temperature and humidity are an important factor affecting hairiness. According to actual measurements, the number of hairiness and neps at the rear of the car is about 40% higher than that at the front of the car, see Table 1. Therefore, maintaining the normal temperature and humidity in the workshop and reducing the temperature and humidity difference is an important measure to improve product quality.
4 Weighting arm pressure
The weighting arm pressure directly affects the yarn quality. Excessive weighting arm pressure will easily shorten the service life of the front rubber roller, cause the front rubber roller to be concave, and may also cause mechanical waves of the rubber roller. The normal use cycle of the front rubber roller is about 2 months. When the pressure is too high, it will become weak in holding the roving after one and a half months of use, resulting in a rapid increase in breakage. Therefore, the pressure for compact spinning should not be too large, and is generally controlled at 160-180N/double spindles.
5 Effect of spinning process on yarn quality
The floating zone is a key factor affecting yarn quality. The size of the floating area should be consistent, and the pressure rod should be in a moderate position. The pressure rod should not grind the front roller or grow an apron. If the pressure rod is positioned too far back, the floating area will be too large, and the fiber cannot be effectively controlled, and even the apron may be worn. If the pressure rod is positioned too far forward, the roving will “run up” and the pressure rod will not be able to perform its function. If the pressure rod grinds the front roller, it will also cause mechanical waves on the roller. In production, the forward stroke of the rubber roller is approximately 2-3mm, and the maximum should not exceed 3mm. If the forward stroke is too large, it is easy to form an anti-enveloping arc, resulting in a decrease in yarn quality and an increase in end breaks. Excessive floating area in compact spinning can easily cause the large top roller of the front rubber roller to press the grid ring. When the whiskers move to both sides of the yarn guide stroke, the whiskers swing left and right at the suction groove, affecting the yarn quality.
Reasonable draft distribution is also an important factor in improving yarn quality. When choosing the draft ratio, you cannot blindly pursue good yarn lines and neps. As the draft ratio continues to increase, the unevenness of the long segments of the yarn will also increase. When selecting the compact spinning process, beyond the critical draft multiple, the back zone draft multiple can be appropriately increased and the spindle speed can be appropriately increased, thereby increasing yarn output and improving efficiency.
6 Conclusion
Optimizing yarn quality is a complex project, and the factors that affect yarn quality are also complex and diverse. Therefore, all aspects must be considered when optimizing yarn quality to obtain the best yarn quality.
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