Extrusion & Post
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Metallocene linear low density polyethylene film cooling line height instability（Variant: Color/Material Change Scenario）
Problem Phenomenon
The cooling line （frost line） height of the blown film fluctuates greatly, and film thickness and quality are unstable.
The cooling line height reflects the stability of cooling conditions and directly affects film performance.In particular, when changing materials or colors, this problem is more prominent and requires key attention.
Cause Analysis
（1） Air ring air volume or air speed unstable\
（2） Extrusion temperature fluctuates\
（3） Ambient airflow interference\
（4） Screw speed fluctuates\
（5） Cooling air temperature fluctuates\
（6） When changing materials or colors, process parameter fluctuations or equipment status changes aggravate this problem
Solution
（1） Check the air ring fan and valves, ensure stable air volume\
（2） Stabilize the extrusion temperature, fluctuation controlled within ±3°C （190-260°C range）\
（3） Install wind shields or isolation curtains to reduce ambient airflow interference\
（4） Stabilize the screw speed\
（5） Use constant-temperature cooling air to reduce temperature fluctuations\
（6） And do well in cleaning the transition material, paying special attention to parameter stability when changing materials or colors
Key Takeaway
Cooling line instability is caused by fluctuations in cooling or extrusion conditions, requiring stabilization of air ring parameters and environmental conditions.Targeted preventive measures need to be taken in different production scenarios.
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