Molds & Tooling
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PEI Internal Stress Cracking
Problem Phenomenon
PEI products generate internal stress during cooling, leading to deformation or cracking; cracks mostly originate from sharp corners and assembly stress points.
Cause Analysis
PEI's glass transition temperature is as high as 217℃, and fast cooling freezes molecular chains with large stress; excessive cooling speed or unreasonable mold design accumulates internal stress; unreleased stress triggers cracking during use.
Solution
①Use a high-temperature mold with mold temperature of 140~180℃ to reduce internal stress; ②sufficient cooling time but avoid overcooling; ③eliminate sharp corners in the structure with rounded transitions; ④anneal when necessary.
Key Takeaway
PEI internal stress management revolves around high mold temperature; the 217℃ Tg determines the process temperature level; structural rounded corners are the design bottom line.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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