Moulding – Coremoulding

The molding operation consists in producing a mold, generally made of refractory materials, which bears the negative imprint of the part, this imprint being obtained from a model reproducing the part to be manufactured.

The casting operation is one of the most important in the foundry's industrial process. Based on the model, it determines the shape of the part to be cast, its dimensions and their precision, its surface finish, its cooling, and plays a major role in many of the parameters influencing its quality. Along with coremaking, it is also the most costly of the various manufacturing operations. For example, in large-scale production runs, molding-coring operations frequently account for around 40% of the cost price excluding materials (molding 30%, core-making 10%).

Care must therefore be taken when choosing a molding process, so as not to penalize future production, either in terms of quality or cost price.

A wide range of molding processes are available: in frames, in clods, in pits for very large parts, on the trousseau for circular parts, for example, in lost models (polystyrene), in lost wax for precision parts or works of art, in metal shells by gravity, under pressure for non-ferrous metals, in centrifuged shells for pipes, etc., all of which are described in the following paragraphs.

This wide variety of processes makes it necessary to classify them for presentation purposes. We have chosen to classify them according to the moulding and hardening methods used to make the mould or cores (table 1 ) and the nature of the models, which must be compatible with the processes used:

• permanent models (wood, metal, resin, etc.) (§ 2 , 3