Extrusion & Post
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Uneven thickness of linear low-density polyethylene blown film
Problem Phenomenon
Film thickness fluctuates greatly in the circumferential or longitudinal direction, with thickness deviation exceeding ±10%.
Uneven thickness affects the mechanical properties and service performance of the film, and may cause deviation or film breakage on automatic packaging machines.
Cause Analysis
(1) Die gap is uneven
(2) Die temperature is uneven in the circumferential direction
(3) Air ring cooling is uneven
(4) Extrusion output fluctuates
(5) Haul-off speed is unstable
Solution
(1) Adjust the die gap, with circumferential error not exceeding ±0.01mm
(2) Check die heating bands to ensure circumferential temperature difference does not exceed ±3°C (190-250°C range)
(3) Check the air ring to ensure uniform air output, and clean the air ring regularly
(4) Stabilize extruder screw speed and temperature
(5) Stabilize haul-off speed and use a high-precision haul-off control system
Key Takeaway
Uneven film thickness is caused by uneven die gap, temperature or cooling and needs to be solved from mold precision and process stability.
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