Extrusion & Post
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Unstable Cooling Line Height of High-Density Polyethylene Film
Problem Phenomenon
The cooling line (frost line) height of the blown film fluctuates greatly, and the film thickness and quality are unstable.
The cooling line height reflects the stability of the cooling conditions and directly affects the film performance.
Cause Analysis
（1）The air ring air volume or air speed is unstable
（2）The extrusion temperature fluctuates
（3）Environmental airflow interference
（4）The screw rotation speed fluctuates
（5）The cooling air temperature fluctuates
Solution
（1）Check the air ring fan and valves to ensure stable air volume
（2）Stabilize the extrusion temperature, with the fluctuation controlled within ±3°C (180-260°C range)
（3）Install wind shields or isolation curtains to reduce environmental airflow interference
（4）Stabilize the screw rotation speed
（5）Use constant-temperature cooling air to reduce temperature fluctuation
Key Takeaway
Unstable cooling line is caused by fluctuations in cooling or extrusion conditions, and the air ring parameters and environmental conditions need to be stabilized.
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