Material Drying
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Internal voids of PU
Problem Phenomenon
1-3mm voids appear inside PU products, concentrated in the thick-wall center
Cause Analysis
Insufficient holding, thick-wall center not compacted; gas entrapped and cannot be discharged; raw material moisture vaporized
Solution
1) Increase holding pressure to 60-80MPa for full compaction; 2) Increase mold venting; 3) Fully dry raw material
Key Takeaway
Internal voids are caused by insufficient holding and gas entrapment; high-pressure holding and venting are key
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