Extrusion & Post
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Metallocene linear low density polyethylene cast film uneven thickness
Problem Phenomenon
The transverse thickness deviation of the cast film is large, exceeding the tolerance range.
Uneven thickness affects film winding quality and subsequent processing, and affects service performance in precision films.
Cause Analysis
（1） The T-die lip gap is uneven\
（2） The die temperature distribution is uneven\
（3） The air knife airflow is uneven\
（4） The cooling roll temperature is uneven\
（5） Extrusion output fluctuates
Solution
（1） Adjust the T-die lip gap, use a feeler gauge to check uniformity\
（2） Check the die heater distribution, ensure transverse temperature difference does not exceed ±3°C （190-260°C range）\
（3） Check the air knife, ensure uniform air outlet, clean the air knife opening\
（4） Check the cooling roll temperature uniformity, temperature difference not exceeding ±2°C\
（5） Stabilize the extruder screw speed and temperature
Key Takeaway
Cast film thickness unevenness is caused by die gap or temperature unevenness, and needs to be solved from mold precision and temperature uniformity.
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