Injection Molding
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Large shrinkage rate fluctuation of PET injection parts
Problem Phenomenon
Unstable dimensions of PET injection products, shrinkage rate fluctuates between 0.2%-0.8%, affecting assembly accuracy.
Cause Analysis
Insufficient holding pressure and holding time, mold temperature fluctuation causes crystallinity differences, uneven cooling rate, material IV value differences.
Solution
Increase holding pressure to 60-80% of injection pressure, extend holding until gate solidification; stabilize mold temperature ±2°C; control IV value 0.75-0.85dL/g.
Key Takeaway
PET shrinkage rate is dominated by crystallinity and holding pressure; process stability is the guarantee of dimensional accuracy.
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