Extrusion & Post
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Metallocene linear low density polyethylene blown film uneven thickness（Variant: Strengthened Measures）
Problem Phenomenon
The film thickness fluctuates greatly in the circumferential or longitudinal direction, with thickness deviation exceeding ±10%.
Uneven thickness affects film mechanical properties and service performance, and may cause tracking deviation or film breakage on automatic packaging machines.In particular, extra attention is needed on top of the original basis, this problem is more prominent and requires key attention.
Cause Analysis
（1） Die gap is uneven\
（2） Die circumferential temperature is uneven\
（3） Air ring cooling is uneven\
（4） Extrusion output fluctuates\
（5） Haul-off speed is unstable\
（6） On top of the original basis, extra attention is needed: process parameter fluctuations or equipment status changes aggravate this problem
Solution
（1） Adjust the die gap, circumferential error not exceeding ±0.01mm\
（2） Check the die heater bands, ensure circumferential temperature difference does not exceed ±3°C （190-260°C range）\
（3） Check the air ring, ensure uniform air outlet, clean the air ring regularly\
（4） Stabilize the extruder screw speed and temperature\
（5） Stabilize the haul-off speed, use a high-precision haul-off control system\
（6） And strengthen process monitoring; on top of the original basis, extra attention is needed, paying special attention to parameter stability
Key Takeaway
Film thickness unevenness is caused by die gap, temperature or cooling unevenness, and needs to be solved from mold precision and process stability.Targeted preventive measures need to be taken in different production scenarios.
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