The original casting method, known for thousands of years, by which a mould is made of sand. A quick way to produce in small numbers, large parts and/or with a complicated shape, making it unsuitable in other methods.
Note: this is a genereal description. Please contact us if you wish to know more.
What you need is a pattern, made from plastic. The pattern is made to make the moulds. We use a chemical binder in our sand, witch makes it set in a matter of minutes. There may also be cores made, forming the voids inside a part. The mould and the core(s) are assembled and filled with aluminium. After the solidification the mould is broken up, you cut away the ingate system, grind it and blast it. Sound easy enough? There a few things to consider, and we have been doing that every day since 1955…
There is one thing in particular that concerns all foundry men (and women): Shrinkage. The difference in volume between liquid and solidified metal creates shrinkage, voids when the metal solidifies. Shrinkage can not be totally avoided, but one can move the shrinkage to the part of the casting material that will not be used. You use a feeder, which feeds melted metal so that it doesn’t miss material. The feeder is often isolated to stay warm so that it stiffnes last.