Extrusion & Post
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Uneven thickness of linear low-density polyethylene cast film
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 lip gap of the T-die is uneven
(2) Die temperature distribution is uneven
(3) Air knife airflow is uneven
(4) Cooling roll temperature is uneven
(5) Extrusion output fluctuates
Solution
(1) Adjust the T-die lip gap and check uniformity with a feeler gauge
(2) Check the die heater distribution to ensure the transverse temperature difference does not exceed ±3°C (190-250°C range)
(3) Check the air knife to ensure uniform air output, and clean the air knife opening
(4) Check cooling roll temperature uniformity, with temperature difference not exceeding ±2°C
(5) Stabilize extruder screw 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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