Common faults and measures of plastic film blowing machine

The common problems of plastic film blowing machine are that the film is too sticky, poor toothing, poor transparency, wrinkled film, misty water texture, uneven film thickness, thick film, thin film thickness, poor heat sealing of film, poor longitudinal tensile strength of film, poor transverse tensile strength of film, unstable film bubble, rough film surface, uneven film, and peculiar smell of film.
1. The film is too sticky and has poor toothing performance
Cause of the problem: ① The model of the resin raw material is not correct, and it is not a blow film grade low density polyethylene resin particle, which does not contain a tooth opener or has a low content of tooth opener; ② The temperature of molten resin is too high and the activity is too high; ③ If the blowing ratio is too large, the teething property of the film will become poor; ④ The cooling speed is too slow, and the film is lack of cooling, which causes mutual binding under the pressure of the traction roller; ⑤ Traction speed is too fast.
Treatment method: ① change resin raw materials or add a certain amount of tooth opener to the bucket; ② Properly reduce the extrusion temperature and resin temperature; ③ Properly reduce the blowing expansion ratio; ④ Increase air volume, improve cooling effect and speed up film cooling; ⑤ Reduce the traction speed properly.
2. Poor film transparency
The reason for the problem: ① the extrusion temperature is low, the resin plasticization is poor, and the transparency of the blown film is poor; ② The blowing expansion ratio is too small; ③ The cooling effect is poor, which affects the transparency of the film; ④ Excessive moisture content in resin raw materials; ⑤ Traction speed is too fast, film cooling is insufficient.
Treatment method: ① properly improve the extrusion temperature to make the resin plasticize evenly; ② Properly improve the blowing expansion ratio; ③ Increase air volume and improve cooling effect; Stop drying the raw materials; ⑤ Reduce the traction speed properly.
3. The film is wrinkled
Cause of fault: ① uneven film thickness; ② Insufficient cooling effect; ③ If the blowing ratio is too large, the formation of membrane bubbles is unstable, and it swings back and forth from left to right, which is easy to show wrinkles; ④ The included angle of herringbone splint is too large, and the membrane bubble is compressed in a short interval, so the membrane is also prone to wrinkle; ⑤ The pressure on both sides of the traction roller is not different, high on one side and low on the other; ⑥ The axis between the guide rollers is not parallel, which affects the stability and ductility of the film, thus presenting wrinkles.
Treatment method: ① adjust the thickness of the film to ensure the average thickness difference; ② Improve the cooling effect to ensure that the film can be fully cooled; ③ Properly reduce the blowing expansion ratio; ④ Properly reduce the included angle of herringbone splint; ⑤ Adjust the pressure of the traction roller to ensure the average force of the film; ⑥ Check the axis of each guide shaft and make it parallel to each other
4. The film has foggy water texture
Causes: ① low extrusion temperature, poor resin plasticization; ② Moisture content of resin is too high.
Treatment method: ① Adjust the temperature setting of the extruder and properly improve the extrusion temperature. ② Dry the resin raw material, and the water content of the common resin shall not exceed 0.3%.
5. Uneven film thickness
The reason for the problem: ① The average of die gap directly affects the average of film thickness. If the die gap is uneven, some parts have larger gap, and some parts have smaller gap, thus forming more or less extrusion amount. Therefore, the film thickness formed is not different, some parts are thin, and some parts are thick; ② The temperature distribution at the die mouth is uneven, high and low, resulting in uneven film thickness after blow molding; ③ The air supply volume around the cooling air ring is not different, resulting in uneven cooling effect, which makes the film thickness uneven; ④ The blowing expansion ratio and traction ratio are not suitable, which makes the film bubble thickness difficult to control; ⑤ The traction speed is not constant and changes from time to time, which of course will affect the thickness of the film.
Treatment method: ① Adjust the die gap of the machine head to ensure the average difference at all places; ② Adjust the temperature of the die mouth of the machine head to make the local temperature of the die mouth vary evenly; ③ Conditioning and cooling installation to ensure the average air volume at the air outlet; ④ Adjust the blowing expansion ratio and traction ratio; ⑤ Check the installation of mechanical transmission to keep the traction speed constant.
6. The thickness of the film is too thick
The reason for the problem: ① The die gap and extrusion amount are too large, so the film thickness is too thick; ② The air volume of the cooling air ring is too large, and the film cooling is too fast; ③ Traction speed is too slow.
Treatment method: ① Adjust die gap; ② Properly reduce the air volume of the air ring to further expand the film, so as to make its thickness thinner; ③ Properly improve traction speed
7. Thin film thickness
The cause of the problem: ① The gap between the die and the resistance is too small, so the film thickness is too thin; ② The air volume of the cooling air ring is too small, and the film cooling is too slow; ③ If the traction speed is too fast, the film will stretch excessively, which will make the thickness thinner.
Treatment method: ① Adjust die gap; ② Properly increase the air volume of the air ring to speed up the film cooling; ③ Reduce the traction speed properly.
8. The thermal sealing of the film is poor
The cause of the problem: ① The dew point is too low, and the polymer molecules are oriented, so that the performance of the film is close to that of the directional film, resulting in the reduction of the heat sealing performance; ② If the blowing ratio and traction ratio are not appropriate (too large), the film will stretch and orientation, which will affect the heat sealing performance of the film.
Treatment method: ① adjust the air volume in the air ring to make the dew point higher, and stop blowing and pulling under the melting point of plastic as much as possible to reduce the molecular stretching orientation caused by blowing and pulling; ② The blow-out ratio and traction ratio should be appropriately small. If the blow-out ratio is too large, the traction speed is too fast, and the transverse and longitudinal stretching of the film is too high, then the performance of the film will tend to biaxial stretching, and the thermal sealing of the film will become worse.
9. Longitudinal tensile strength difference of film
Cause of the problem: ① The temperature of the molten resin is too high, which will reduce the longitudinal tensile strength of the film; ② The traction speed is slow, and the longitudinal orientation of the film is not enough, which makes the longitudinal tensile strength worse; ③ If the blowing expansion ratio is too large, it will not match the traction ratio, which will improve the transverse orientation and tensile strength of the film, while the longitudinal tensile strength will become worse; ④ The cooling speed of membrane is too fast.
Treatment method: ① properly reduce the temperature of molten resin; ② Properly improve the traction speed; ③ Adjust the inflation ratio to make it conform to the traction ratio; ④ Reduce the cooling rate properly.
10. Transverse tensile strength difference of film
The cause of the problem: ① The traction speed is too fast, and the difference between the expansion ratio and the expansion ratio is too large, resulting in longitudinal fibrosis, and the transverse strength becomes worse; ② Cooling speed of cooling air ring is too slow.
Treatment method: ① properly reduce the traction speed to match with the expansion ratio; ② Increase the air volume of the air ring, make the blown film cool quickly, and prevent it from being stretched and oriented at high temperature and high elastic state.
11. The membrane bubble is unstable
The reason for the problem: ① the extrusion temperature is too high, the activity of the melt resin is too large, the viscosity is too small, and it is easy to shake; ② The extrusion temperature is too low, and the output is small; ③ The air volume of the cooling air ring is unstable, and the film bubble cooling is uneven; ④ It was disturbed and affected by strong external airflow.
Treatment method: ① adjust the extrusion temperature; ② Adjust the extrusion temperature; ③ Check the cooling air ring to ensure that the surrounding air supply volume is evenly different; ④ Prevent and reduce the interference of external air flow.
12. The film surface is rough and uneven
Cause of the problem: ① The extrusion temperature is too low, and the resin plasticization is poor; ② Extrusion speed is too fast.
Treatment method: ① adjust the temperature setting of extrusion and properly improve the extrusion temperature to ensure good resin plasticization; ② Reduce the extrusion speed properly.
13. The film has peculiar smell
Cause of the problem: ① resin raw material has peculiar smell; ② The extrusion temperature of molten resin is too high, forming resin synthesis, thus producing peculiar smell; ③ The bubble is lack of cooling, and the hot air in the bubble is not cleaned.
Treatment method: ① change resin raw materials; ② Adjust the extrusion temperature; ③ Improve the cooling efficiency of the cooling air ring and make the film bubble cool sufficiently.