Material Drying
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Plastic cracking around metal inserts is a common problem
Problem Phenomenon
Plastic cracking around metal inserts is a common problem
Cause Analysis
Large shrinkage difference between insert and cellulose acetate butyrate (metal almost does not shrink, PA shrinks 0.4-0.6%)
Insufficient wall thickness around the insert, stress concentration
Insufficient insert preheating, melt contacts the insert and rapidly condenses
Improper insert surface treatment, poor bonding force
After PA types absorb moisture, expansion stress around the insert is greater
Solution
Increase wall thickness and fillet R≥1mm around the insert
Preheat insert to 150-200°C to reduce temperature difference
Coat insert surface with adhesive or knurling treatment
Cellulose acetate butyrate shrinkage 0.4-0.6% requires design allowance
PA type insert products need conditioning before use
Key Takeaway
Insert molding requires preheating and increasing surrounding wall thickness
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