Injection Molding
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Severe PVA internal stress concentration
Problem Phenomenon
PVA product internal stress >15MPa causing cracking during storage
Cause Analysis
Injection speed too fast, large orientation stress; uneven cooling freezes thermal stress; improper gate position, concentrated flow orientation
Solution
1) Reduce injection speed to reduce orientation; 2) Uniform mold temperature to reduce thermal stress; 3) Annealing 80°C/4h to release stress; 4) Optimize gate position
Key Takeaway
Internal stress is caused by fast injection and uneven cooling; speed reduction, uniform cooling and annealing are the key
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