The heated pattern plate is placed on top of a box containing special resin sand. The box and pattern are inverted so that the resin sand covers the hot plate. When the box and pattern are returned to their original positions a thin 'shell' of sand stays on the pattern. Normally this takes place automatically on a shell moulding machine. The shell is removed and the two matching shells are glued or clamped together to form a mould.
Molten metal is poured into the completed mould.
The finished casting, including the shape of the channels that carried the molten metal, is removed from the mould. The extra pieces of metal are removed and the casting machined and ground to the finished size. The finished casting in place, in this case a crankshaft in a 2 cylinder engine. This type of casting differs from other methods in that the mould is made of a durable material, usually heat resistant metal, and can be used many times. The cost of producing a complex die is very high, but similar to the shell moulding method, large numbers of accurate castings can be made so that individual casting costs are low.