Material Drying
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PA66 water absorption dimensional change
Problem Phenomenon
Products swell in dimension and lose rigidity after moisture absorption, precision assembly fails.
Cause Analysis
PA66 equilibrium water absorption at 50%RH is about 2.5%, dimensional change 0.5%~1%; precision fails in hot-humid environments; this is the material nature of PA66.
Solution
①Indicate measurement state on the drawing (dry state/conditioned state); ②measure dimensions after product conditioning stabilizes; ③correct and compensate the mold for wet-state water absorption expansion; ④evaluate low-water-absorption grades such as PA12 for high-humidity precision applications; ⑤do a good job of sealing and moisture-proofing, control environmental and storage humidity.
Key Takeaway
PA66 precision parts 'must define dry/wet state': water absorption expansion is its nature; design by wet state, measure after conditioning, otherwise dimensions will never match; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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