Casting

Understanding Casting

Casting is a manufacturing process where a liquid material is typically poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to solidify.
The solidified part is known as a casting, which is ejected or broken out of the mould to complete the process.
Materials that are commonly cast include metals, plastic, glass, and concrete, among others.
The use of a mould means the same pattern or design can be replicated many times with great accuracy.

Sand casting is the most common method. The mould is formed from a sand mixture around a pattern of the object to be cast.
The mould is then split apart and the pattern is removed. The cavity left behind is then filled with molten metal.
This method is relatively cheap and flexible, but the finish quality can be poor and the rate of production is slow.

Die casting involves forcing molten metal under high pressure into a die cavity.
The die is designed in two halves to allow removal of the casting.
This produces a smooth and precise casting, but the casting equipment is expensive and likely more suited for mass production.

Investment casting, also known as precision casting or lost-wax casting, involves creating a wax pattern which is then covered in a ceramic material.
The wax is melted out and the ceramic mould is filled with molten metal.
The process produces parts with exceptional accuracy, excellent surface finish, and requires less machining.

In the casting process, controlling the temperature of the molten material and the conditions of the mould is critical.
In metal casting, shrinkage of the metal as it cools must be anticipated in the mould design to ensure accuracy.
Post-casting finishes can be applied to enhance the appearance or functionality of the casting. This may include grinding, polishing, painting, and plating.
The type of material being cast and the properties of the finished product will often dictate the choice of casting method.
A proper understanding of casting processes allows precision creation of parts and components in design and technology applications.