Continuous Dimensional Change of the Product After Demolding (Post-Shrinkage)

After demolding, the product dimensions continue to shrink over days or weeks. Such defects mostly occur in thick-walled transition areas of the product and at the far end of the gate, gradually appearing during the cooling and setting stage. This problem causes product dimensions to exceed the tolerance range, affecting assembly accuracy and product function.

(1) In terms of shrinkage control: molecular chain segments continue to shrink during post-curing, uneven volume shrinkage leads to internal stress and dimensional deviation. (2) In terms of stress distribution: slow release of internal stress causes dimensional changes, internal stress concentration causes the product to crack or deform during subsequent use. (3) In terms of materials: the resin system has a large curing volume shrinkage rate and lacks effective constraint. (4) In terms of the process: the curing rate is too fast, and the shrinkage stress has no time to relax and release. (5) In terms of design: large wall thickness differences cause inconsistent shrinkage in various regions.

(1) Post-treatment: perform sufficient post-curing treatment to complete shrinkage in advance, formulate a reasonable post-treatment temperature curve to eliminate internal stress and stabilize product dimensions. (2) Formula optimization: add low-shrinkage components to the formula, determine the optimal addition amount through small-batch tests and verify its impact on the comprehensive performance of the product. (3) Implementation measures: fix the product on a setting fixture for cooling after demolding., formulate a specific operation plan based on actual production conditions and verify the implementation effect. (4) Preventive measures: establish a shrinkage database, preset shrinkage compensation amounts according to product structure and material type, and regularly calibrate mold dimensions.

The core of shrinkage defects lies in the contradiction between material curing volume change and insufficient process compensation, which needs to be comprehensively controlled through formula optimization and process adjustment.