Rule
No. 5:
". . . and Big Bubbles
are Worse!"
The outgassing of cores can lead to huge defects, filling
whole areas of the tops of castings. However, even a small
blow from a core can leave a bubble trail that can create
a leak defect. To avoid blows from cores, the core must be
vented to the atmosphere. (Click here
to view diagram of a core blow.)
An ultimate test is for the foundry to video record the filling
of the mould with the top of the mould open, so the metal
can be clearly seen covering the cores in turn. Any blowing
off cores is then immediately clear.
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