Molding Process
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PTFE Poor Dimensional Stability
Problem Phenomenon
PTFE precision parts' dimensions change significantly with ambient temperature, they go out of tolerance after machining and placement, and tolerance marking according to metal part requirements causes disputes.
Cause Analysis
PTFE has a large thermal expansion coefficient that changes irregularly with temperature; large cold-hot shrinkage changes; ambient temperature changes after sintering, cooling, or machining cause dimensional changes; thermal expansion is 10 times greater than iron.
Solution
①Mark tolerances according to PTFE's actual expansion characteristics; ②Measure critical dimensions at use temperature; ③Reserve expansion clearance in design; ④Communicate material differences of tolerance standards with customers.
Key Takeaway
PTFE dimensional management must follow material characteristics rather than metal habits; the 10-fold thermal expansion difference is a communication point; measurement at use temperature is a pragmatic method.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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