All cast metal shrinks during
solidification. If molten metal from the risers cannot reach isolated areas of the
casting, shrinkage voids will occur. The voids tend to be located in the center third of
the casting section -- the region which solidifies last. |
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In metal casting, it is prudent to evaluate
thin wall sections that have machining requirements to insure that, if shrinkage voids
occur, they will not be close to the inner face of the machining stock.
- As a guideline, the machining stock should be less than
1/3 of the casting thickness.
- If the machining requirement is large on thin walls and
solidification modeling shows potential center shrinkage problems, extra thickness may be
added to the opposite side to “pull” the center line shrinkage away from the
machine stock
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