Molds & Tooling
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GPPS Product Brittle Cracking
Problem Phenomenon
Transparent PS products crack upon demolding or slight force, and cracks mostly start at corners, rib positions or weld lines.
Cause Analysis
Material overheating or over-shearing reduces molecular weight and makes it brittle; improper molding conditions produce high internal stress, and one-sided rapid cooling causes stress differences, all of which make GPPS brittle and crack.
Solution
①Check barrel temperature to prevent overheating degradation; ②optimize molding conditions to reduce internal stress; ③balance cooling to avoid one-sided rapid cooling; ④when cracking occurs at weld lines, move the gate to change the filling pattern.
Key Takeaway
GPPS brittle cracking should be investigated along two lines: material degradation and internal stress; transparent parts can use polarizers to observe stress distribution to assist positioning.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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