Molding Process
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PA66 shrinkage rate 1.5-2%
Problem Phenomenon
Product dimensional deviation is large, sink marks are obvious in thick-wall areas, and shrinkage is inconsistent at different wall thicknesses
Cause Analysis
PA66's semi-crystalline nature makes the shrinkage rate reach 1.5-2% with obvious directionality; the thicker the wall the more complete the crystallization and the greater the shrinkage, differential shrinkage between thick and thin causes warpage and dimensional out-of-tolerance
Solution
①Reserve allowance in the mold according to 1.5-2% shrinkage rate and correct by trial molding; ②Make wall thickness as uniform as possible and strengthen holding pressure in thick-wall areas; ③Lowering mold temperature and raising pressure can reduce shrinkage but internal stress warpage must be prevented
Key Takeaway
PA66 shrinkage rate ranks first among nylons; mold allowance reservation, wall thickness uniformization, and holding pressure compensation are the three axes of dimensional control; after confirming effectiveness, fix the parameters and practices into the work instructions to prevent recurrence
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