Molds & Tooling
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PC assembly stress control
Problem Phenomenon
Screw boss roots crack, snap-fits break after assembly, problems appear only days after assembly
Cause Analysis
Excessive screw torque and interference fit keep PC parts in a stressed deformation state for a long time, cracks initiate and propagate during creep and stress relaxation; rigid mismatch between metal parts and PC aggravates local stress
Solution
①Screw torque set at 70% of material yield strength with elastic washers added; ②Avoid interference fit, leave creep allowance on mating surfaces; ③Add ribs and rounds to strengthen stressed areas
Key Takeaway
Assembly stress is a typical cause of delayed cracking; assembly loads must be included in the stress budget of PC parts at the design stage；After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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