Extrusion & Post
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Metallocene linear low density polyethylene film cooling line height instability（Variant: Startup Commissioning 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, during new machine commissioning or the initial startup period, 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） During new machine commissioning or the initial startup period, 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 parameter recording and archiving, paying special attention to parameter stability during new machine commissioning or the initial startup period
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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