Molds & Tooling
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PA6 Product Post-crystallization Dimensional Drift
Problem Phenomenon
Product dimensions continued to change after being placed, and precision assembly exceeded tolerance.
Cause Analysis
PA6 molded at low mold temperature has low crystallinity and continues to crystallize and shrink after demolding; ambient temperature and humidity also participate; post-crystallization is the aging characteristic of crystalline materials; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience.
Solution
①Appropriately increase mold temperature to improve the melt's replication and fit to the cavity surface;②extend in-mold cooling;③perform annealing treatment when necessary to eliminate residual stress;④uniformly specify the measurement aging time (such as 24 hours after molding);⑤stabilize the environment.
Key Takeaway
PA6 post-crystallization = 'the crystallinity given by mold temperature is insufficient': raising mold temperature to lock crystallization is fundamental; dimensions must be managed 'after aging', and parts molded at low mold temperature must especially guard against post-crystallization.
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