Excessive curing shrinkage rate

Product dimensions are significantly smaller than mold dimensions after demolding. Such defects mostly occur in thick-wall 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) Shrinkage control aspect: large volume shrinkage rate of the resin system; uneven volume shrinkage causes internal stress and dimensional deviation. (2) Shrinkage control aspect: low reinforcement material content cannot effectively suppress shrinkage; uneven volume shrinkage causes internal stress and dimensional deviation. (3) Material aspect: resin system curing volume shrinkage rate too large, lacking effective constraint. (4) Process aspect: curing rate too fast, shrinkage stress has no time to relax and release. (5) Design aspect: large wall thickness differences causing inconsistent shrinkage in various regions.

(1) Material selection: select low-shrinkage resins (such as epoxy > unsaturated polyester); establish material selection evaluation standards and determine the optimal solution through comparative tests. (2) Formulation optimization: increase fiber volume content to a reasonable range; determine the optimal addition amount through small-batch tests, and verify the impact on the comprehensive performance of the product. (3) Formulation optimization: add low-shrinkage additives., determine the optimal addition amount through small-batch tests, and verify the impact on the comprehensive performance of the product. (4) Preventive measures: establish a shrinkage rate database, preset shrinkage compensation amounts based on 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 requires comprehensive control through formulation optimization and process adjustment.