A.
The permeable mold is positioned in a closed chamber with a vacuum
valve. An open, impermeable sprue pipe at the base of the mold
extends down out of the chamber.
B. The sprue pipe of the
mold is lowered into the molten metal in the crucible. An applied
vacuum draws the molten metal up into the mold cavity in a
controlled flow.
C. The molten
metal fills the mold cavity and the castings solidify, while the
central sprue stays molten.
D. When
the vacuum is released, the still
molten metal in the central sprue returns to the crucible for
reuse. The chamber is raised, and the separate, solid
castings remain in the mold.
