Production & Quality
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POM snap-fit fatigue application
Problem Phenomenon
POM snap-fits break after repeated assembly and disassembly, and automotive door lock mechanisms fail after a million cycles
Cause Analysis
POM-H has a fatigue limit of about 35-40MPa (10^7 cycles) and is the first choice for snap-fits and moving mechanisms; but stress concentration and assembly interference greatly reduce fatigue life
Solution
①Round the snap-fit root to eliminate stress concentration; ②check the working stress against the fatigue limit of 35MPa; ③select homopolymer grades for high-cycle parts such as door locks; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
POM's fatigue performance is the capital for its dominance in moving parts; design verification must include the stress concentration factor in the fatigue account; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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