Molds & Tooling
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Post-shrinkage dimensional change of ABS parts
Problem Phenomenon
The product dimensions continue to change slightly after being placed for 24~72 hours, precision assembly is affected, and the measurement results are inconsistent before and after.
Cause Analysis
After demolding, the residual stress relaxes and the material continues to shrink, more obvious at thick-wall areas; inconsistent measurement timing (just demolded vs after placement) causes the illusion of 'dimensional drift', which is actually normal post-shrinkage.
Solution
①Uniformly specify the measurement aging (e.g., 24 hours after molding); ②fully cool and shape before demolding; ③anneal to accelerate stress release when necessary; ④correct the mold shrinkage rate according to actual measurement; ⑤SPC tracking of aging for key dimensions.
Key Takeaway
For ABS dimensions, first 'unify the measurement time point' before talking about compensation: standardize the measurement aging, and many 'drifts' disappear; residual stress relaxation is gradual, and aging management is the key.
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