Green-Sand, Dry-Sand, and Skin-Dried Moulds:

In green-sand moulding, the mould material is made of sand with water, a binder of clay, and additives. Tooling costs are low, and the whole process is rather inexpensive. Almost any metal might be cast, and there are few restrictions on the, shape, size, weight, and complication of the products. Usually design limitations are associated to the rough surface finish, weak dimensional accuracy, and the need for subsequent machining. Still other problems might be attributed to the low strength of the mould material and the moisture that is exists in the binder.

Because some intricate big parts are hard to cast to needed size and dimensions by green sand techniques, dry sand is frequently used as the mould material for casting such parts. The dry sand mix involves base sand that is coarser than that utilized in green sand moulding to facilitate natural venting and mould drying. Pitch is added up as a carbon material along the cereal, molasses, glutrin , dextrine and resin. These additives thermoset at the drying temperature of 149 to 316ºC (300 to 600ºF) to generates high strength and rigid mould walls. Dry sand moulding contains green sand modified by baking the mould at 204 to 316ºC (400 to 600ºF). Generally Moulds are dried in large mould ovens; on the other hand, large heaters might be used.