Investment Casting

Investment castings can be cast in air or in vacuum.  Vacuum casting gives cleaner metal and often superior properties.  Prior to casting, the investment moulds are heated to remove any residual wax, to induce chemical and physical changes in the refractory material to ensure that the mould achieves maximum strength and stability and to minimise any reaction between the mould surface and the molten metal.  Most castings are gravity poured, relying on the static pressure of the molten metal head to fill the cavity.

Vacuum-assisted casting involves placing the mould in a vacuum chamber with only the mould opening exposed to the atmosphere.  The vacuum applied to the mould helps to evacuate the air from the cavity through the pourous mould wall, creating a difference in pressure, which helps to fill thin sections and fine details on the casting.