Extrusion & Post
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Uneven Thickness of High-Density Polyethylene Blown Film
Problem Phenomenon
The film thickness fluctuates greatly in the circumferential or longitudinal direction, with the 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）The die gap is uneven
（2）The temperature in the circumferential direction of the die is uneven
（3）The air ring cooling is uneven
（4）The extrusion output fluctuates
（5）The haul-off speed is unstable
Solution
（1）Adjust the die gap, with the circumferential error not exceeding ±0.01mm
（2）Check the die heating rings to ensure the circumferential temperature difference does not exceed ±3°C (180-260°C range)
（3）Check the air ring to ensure uniform air outlet, and clean the air ring regularly
（4）Stabilize the extruder screw rotation speed and temperature
（5）Stabilize the 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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