Extrusion & Post
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Metallocene linear low density polyethylene blown film uneven thickness（Variant: Seasonal Change Scenario）
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, when the environment changes during seasonal alternation, 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） When the environment changes during seasonal alternation, 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 adjust parameters according to the environment, paying special attention to parameter stability when the environment changes during seasonal alternation
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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