Molding Process
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GPPS Stress Whitening
Problem Phenomenon
White powdery marks appear after snap-fit assembly or at ejection positions of the product.
Cause Analysis
PS produces craze microcrack structures under stress, which scatter light and appear white; concentrated ejection force or assembly overstress are common causes.
Solution
①Enlarge ejector pins, increase quantity and polish to disperse ejection force; ②optimize snap-fit structure and enlarge fillets; ③select stress-whitening-resistant grades; ④reduce assembly stress.
Key Takeaway
Stress whitening is the apparent manifestation of the PS craze mechanism; low-stress design of structure and process is the core of prevention.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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