Foundry casting (fonderie in French) covers the processes that make a part by pouring a liquid metal or alloy into a hollow mould of the required shape. The metal solidifies, then the rough part, called a casting, is removed from the mould. Functional surfaces are then finished by machining.
Four processes dominate. Sand casting uses an expendable mould, destroyed with each part, for large parts, one-offs or medium runs, in cast iron, steel, aluminium or bronze. Gravity die (permanent mould) casting uses a reusable metal mould, by gravity or low pressure, for medium runs, mainly in aluminium. Pressure die casting injects the alloy (aluminium, zinc, magnesium) into a steel mould: high volumes, thin walls, good surface finish, but expensive tooling. Investment casting (lost wax), or precision casting, gives complex, fine shapes in stainless steel or superalloys for aerospace and medical. A pattern (wood, resin or 3D printed) and cores for cavities prepare the mould. After pouring, the casting is shaken out, the runners and risers are cut off, then it is heat treated and machined. Shrinkage on cooling, draft angles and the risks of porosity or shrinkage cavities are dealt with at the design stage.
Foundries produce housings, pump and valve bodies, engine blocks, hollow parts and large complex parts that would be too costly to cut from solid. Cast iron (grey or spheroidal graphite), aluminium and bronze are the classic materials. For small runs, the pattern or mould weighs heavily on cost: machining or additive manufacturing may then be preferable. See also forging for highly stressed parts, and the guide from prototype to series.
In a quote request. Specify the material with its standard (for example EN-GJL-250 or EN-GJS-400-15), annual quantities, mass and dimensions, the process you want or leave to the foundry’s judgement, machining allowances and material soundness inspections. Also settle the ownership of the pattern and the mould, and the lead time for making them.