Extrusion & Post
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Material overflow at PU vacuum section
Problem Phenomenon
Material overflows at the vacuum section in PU extrusion, vent hole clogged
Cause Analysis
PU melt viscosity low, overflowing at vacuum section; vacuum section temperature too high, viscosity even lower, aggravating overflow; vent hole design improper
Solution
1) Lower vacuum section temperature by 5-10°C to increase viscosity; 2) Add baffle above the vent hole to prevent overflow; 3) Increase screw speed to accelerate conveying and reduce residence
Key Takeaway
Overflow is caused by low melt viscosity; temperature reduction and baffle are key
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