Production & Quality
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PC Internal Stress Polariscope Detection
Problem Phenomenon
The products crack after storage or use for a period of time, and obvious colored fringes are visible under the polariscope
Cause Analysis
During PC molding, molecular chain orientation is frozen to form residual stress; when the internal stress exceeds the crack resistance, cracking occurs; the polariscope can visualize the stress distribution, and birefringence exceeding 30nm/cm indicates high risk
Solution
①Use a polariscope to sample the stress distribution, focusing on the gate and wall thickness transition areas; ②control the residual stress within 20% of the yield strength; ③anneal the out-of-spec parts and re-inspect
Key Takeaway
Polariscope detection is a quantitative tool for PC stress management; only by turning invisible internal stress into a measurable indicator can preventive control be achieved; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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