ABSTRACT
Investment casting, lost foam casting and shell moulding are employed where greater accuracy is required than can usually be achieved by sand casting especially with small intricate castings. The completed wax pattern assembly is first given a primary coat or investment by dipping it in a ceramic slurry of very fine particle size to make a complete one-piece mould. When the primary coat is dry, the secondary investment or back-up coats are applied to build up the shell to the required thickness. The lost foam casting process is used in the automotive industry in the production of cylinder heads, engine blocks, crankshafts and exhaust manifolds, in the electrical industry for electric motor frames. A patented process has been developed known as counter gravity low pressure air melt (CLA) casting process, which is the same as the metal pouring stage. The shell-moulding process can be used to produce castings in bronze, aluminium, magnesium, copper and ferrous alloys.
