Extrusion & Post
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Uneven Thickness of Polypropylene 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 use performance in precision films.
Cause Analysis
(1) The lip gap of the T-die is uneven
(2) The temperature distribution of the die is uneven
(3) The airflow of the air knife is uneven
(4) The temperature of the chill roll is uneven
(5) The extrusion output fluctuates
Solution
(1) Adjust the lip gap of the T-die, and use a feeler gauge to check the uniformity
(2) Check the distribution of the die heaters to ensure the transverse temperature difference does not exceed ±3°C (range 200-280°C)
(3) Check the air knife to ensure uniform air output, and clean the air knife opening
(4) Check the temperature uniformity of the chill roll, with a temperature difference not exceeding ±2°C
(5) Stabilize the screw speed and temperature of the extruder
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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