Reduce weight unevenness, make the fibers in the sliver straight and parallel, reduce hooks, make the linear density comply with regulations, and mix different types or different quality raw materials evenly to achieve the prescribed mixing ratio. At the same time, the suction device of the draw frame can reduce impurities and short lint in the sliver. Therefore, in the process of daily use and maintenance of the draw frame, the function of the draw frame must be fully utilized.
Process parameter setting principles
a) The number of merging roots should be less but not too many. The total draft ratio should be small but not large. The draft ratio of the rear area of the pre-merging should be large but not small. It is recommended that when 5 strands are combined in the pre-merging, the draft ratio of the rear area should be controlled. At 1.7~1.8 times.
b) The holding distance of the pre-joined rear area should be large rather than small. It is recommended that the roller holding distance be appropriately increased by 12 mm to 20 mm based on the fiber length to ensure the straightening and parallel effect of the fibers.
c) The drafting multiple of the rear area of the unjoined area should be small but not large, and the drafting multiple of the front area should be large but not small. The greater the drafting multiple of the front area, the better the straightening effect of the rear hook. In order to maximize the drafting multiple of the front area. If the possibility is large, the draft ratio in the rear area should be reduced. Generally, the drafting ratio of the rear area is 1.15 to 1.20 times in order to concentrate the drafting of the front area. When using an autoleveling draw frame with six strands combined, it is recommended that the draft in the rear area be controlled at 1.16 times.
Frequently asked questions and solutions
a) The setting of autolevelling parameters is unreasonable
If the thick section alarm threshold is too loose, the A% (draw frame weight deviation alarm) range will be large and the number of thick sections will be large.
b) Autoleveling parameter settings are inconsistent
Just like a car, the average points of the two eyes are quite different. Measures: Perform statistical analysis on the indicators monitored and recorded by the draw frame every day. Once abnormal fluctuations in the monitoring indicators are found, the reasons must be found and analyzed in a timely manner.
c) Leveling alarm
Inconsistency in process parameters of the same type, or even inconsistency in process parameters between two eyes of the same machine, is one of the common reasons that affects the leveling effect, and is also one of the reasons for leveling alarms in draw frames.
There are many reasons for leveling alarms. It is recommended to pay attention to the following points during the production process:
① The reference voltage values of the autoleveling displacement sensor and concave and convex rollers must be accurate;
② The leveling length, leveling intensity, low-speed leveling settings of the autoleveller draw frame must be reasonable, and calibration must be performed every 2 weeks to ensure that the above parameters can meet the requirements of changes in production conditions such as raw materials, temperature and humidity;
③ The CV value, A% and thick place alarm value should be set reasonably. It is recommended to set and adjust based on the laboratory test results and the draw frame monitoring results. For combed cotton products, it is recommended that the A% alarm value be set within 2.0%. The setting and length of thick places are based on the fixed length of the can, and the monitoring value is set according to the actual thick places.
④ Carry out weight calibration test every 2 hours to ensure that A% fluctuation is within the specified control range.
⑤ Ensure timely cleaning and stable temperature and humidity. Large changes in humidity are also one of the causes of leveling alarms.
d) Operation management issues
Some companies have problems with the operation and management of the draw frame. Even the most basic cleaning of the draw frame is difficult to ensure, which may even lead to the occurrence of defective strips. At the same time, the operation management does not pay attention to the standardization of operating techniques, and there are a series of operational problems such as high strips, top strips, joint rubbing, and strip moving.
Measures: It is recommended that in the operation and management of the draw frame, it is necessary to standardize the operation and management, realize the overall section change, and ensure that the draw frame is in good clean condition. At the same time, it is necessary to standardize the operating techniques to reduce or even eliminate the draw frame defects caused by improper operation.
For non-autoleveling draw frames, the focus should be on the offline quality monitoring results of sliver quality, and the status maintenance and operation quality supervision and inspection of the draw frame should be carried out based on the quality indicators of offline monitoring.
e) Common quality issues
A common quality problem is that the mechanical wave and fiber straightening are not parallel, resulting in hooked fibers. Therefore, it is necessary to promptly check the gear meshing status of the draw frame, the lubrication and surface condition of the rubber rollers, the flower and sticky conditions of the rubber rollers, the dust accumulation of the pressure rods, etc., and at the same time check the roller spacing and draft distribution. and other process parameters to be optimized.