Extrusion & Post
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Uneven Thickness of High-Density Polyethylene Cast Film
Problem Phenomenon
The transverse thickness deviation of the cast film is large, exceeding the tolerance range.
Uneven thickness affects the film winding quality and subsequent processing, and affects service performance in precision films.
Cause Analysis
（1）The lip gap of the T-die is uneven
（2）The die temperature distribution is uneven
（3）The air knife airflow is uneven
（4）The cooling roller temperature is uneven
（5）The extrusion output fluctuates
Solution
（1）Adjust the T-die lip gap and check the uniformity with a feeler gauge
（2）Check the die heater distribution to ensure the transverse temperature difference does not exceed ±3°C (180-260°C range)
（3）Check the air knife to ensure uniform air outlet, and clean the air knife opening
（4）Check the cooling roller temperature uniformity, with the temperature difference not exceeding ±2°C
（5）Stabilize the extruder screw rotation speed and temperature
Key Takeaway
Uneven cast film thickness is caused by uneven die gap or temperature, and needs to be solved from mold precision and temperature uniformity.
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