Casting processes

Bastian Asmus
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A very brief introduction to casting processes

The production and casting of metals is a very old trade and is known at least for the last 7000 years or so. Early evidence for mining can be found at Ai Bunar, Bulgaria and Rudna Glava, Serbia from 5000 BC onwards. Casting is a very efficient and cheap way to manufacture a desired good. This is especially true for metals. Casting processes are can be discerned by the way a mould is produced. There are two possibilities: permanent moulds and lost moulds.
Lost moulds can be used only once. In order to retrieve the raw cast you have to destroy them. Permanent moulds can be used for multiple casts; they are usually made of two, three or more parts, to allow for the retrieval of the cast. Lost moulds require a pattern permanent moulds do not.

Lost moulds

Generally lost moulds are said to be moulds of the lost wax or cire perdu process. This is incorrect as sand moulds are also lost moulds.- With the lost wax-process the patterns are lost also, which requires an individual pattern per cast. Sand moulds on the contrary possess permanent patterns which are being reused every time a sand-mould is made.

Dies, permanent moulds

You do not need a model, but you have to engrave a three-dimensional negative into the moulding material. You also want to be careful as to ensure that the cast can be retrieved from the mould halves. This seriously restricts the design of your object and at least for prehistoric times this moulding technique yielded far less complicated cast products than the lost wax process. They are also more labour intensive to manufacture. The advantage is the re-usability of these, and many objects can be cast without much effort once a mould is made. The materials for permanent moulds have to be refractory and hard-wearing, e.g. stone and metal.

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