Molds & Tooling
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Inconsistency between cavities of ABS multi-cavity mold
Problem Phenomenon
In a multi-cavity mold, some cavities have short shots and some have flash, and the product weight and dimensions of each cavity differ greatly.
Cause Analysis
The runner system is unbalanced, and the filling pressure/time of each cavity is different; differences in cooling water circuit efficiency also cause inconsistent shrinkage between cavities; ABS is sensitive to pressure and temperature, and the differences are amplified.
Solution
①Geometrically balance the runners with equal length and diameter or change to a naturally balanced layout; ②use the short shot method to test the filling balance of each cavity; ③check the water flow of each cavity; ④independent throttling of the hot runner when necessary; ⑤establish cavity number traceability.
Key Takeaway
For ABS multi-cavity, first test the 'filling balance' before talking about the process window: when the runners are unbalanced, adjusting the process is just robbing Peter to pay Paul; cavity-to-cavity consistency is guaranteed by the hardware balance of runners and cooling.
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