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How does casting shape metal parts?

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Diagram of a zinc-lead blast furnace system showing ore and coke entering through charge hoppers, with labeled furnace, air preheater, blower, taphole for slag and lead bullion, and a connected lead-splash condenser using rotors to separate and cool lead and zinc, with pathways for molten metals and off-gas. — metallurgy A zinc-lead blast furnace and lead-splash condenser. This technology is utilized mainly for producing zinc while managing both lead and zinc from raw materials, a technique that was highly influential in 20th-century smelting.

Casting is a fundamental manufacturing process in which molten metal is poured or forced into a mold to solidify into a desired shape. This method is highly valued for producing complex geometries, ranging from intricate jewelry to massive industrial machinery.12

The process generally involves these steps:
* Pattern Creation: A pattern of the intended part is created, typically slightly oversized to compensate for shrinkage as the metal cools.34
* Mold Preparation: A cavity is formed using materials like sand, ceramics, or metal. In sand-casting, sand is packed around the pattern, which is then removed to leave a void.43
* Filling: Molten metal is introduced into the cavity. While gravity is most commonly used to fill the mold, some processes employ centrifugal force or pressure injection.53
* Solidification: The metal cools and hardens within the mold, taking on its internal shape.12

Techniques like die casting use metal molds and high pressure to produce parts with thinner walls and finer grain structures, though the high cost of dies makes them suitable primarily for mass production.67