ABSTRACT
There are many ways of making a casting, but all moulds must (a) have the desired shape and size but with allowances made for metal contraction during
solidification and cooling (for steels this is typically 2 per cent, for cast iron 1 per cent and for aluminium 1.25 per cent)
(b) be made from a material that is capable of withstanding the inrush of molten metal before solidification occurs (molten metal is just as heavy when liquid as it is when solid!)
begins to solidify
(d) not cause a restriction to solidification and contraction of the metal after pouring (e) allow easy escape of gases from the mould during pouring (f) not cause undue difficulties in removing the casting after cooling.
