Metal casting is the process of turning molten metal into a solid shape. That can be as simple as casting an ingot, whose final form and properties are refined later by forging, or as demanding as producing a complex near-net-shape component that needs minimal machining.
The five stages of sand casting
- Pattern-making. A pattern is a replica of the exterior of the casting, typically made of metal, wood, plastic or plaster. This stage is critical for industrial parts, where precise calculations are needed for pieces to fit and work together.
- Core-making. If a casting is hollow, an additional piece of metal or sand - the core - shapes the internal form. Cores are strong but collapsible, so they can be removed from the finished casting.
- Moulding. The mould is formed around the pattern using moulding sand. In casting, the mould held in a frame is called a flask, and green sand is packed into the flask around the pattern. An alternative is a two-piece, non-destructible metal mould that can be reused to cast identical parts.
- Melting and pouring. The molten metal is poured into the mould and left to solidify. The shakeout process then vibrates the mould to remove the sand from the casting, and that sand is collected, cooled and reclaimed for future castings.
- Cleaning. The casting is removed from the mould and fettled - cleaned of any moulding material, with rough edges removed.