In Casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process
Patterns used in sand casting may be made of wood, metal, plastics or other materials. Patterns are made to exacting standards of construction, so that they can last for a reasonable length of time, according to the quality grade of the pattern being built, and so that they will repeatably provide a dimensionally acceptable casting.
A pattern is simply an exact model of what is to be cast. They are traditionally made of wood, but can also be made of resins, fibreglass, plastics and even polystyrene. A sand mould is formed around the pattern, so that when the pattern is removed it leaves a cavity into which molten iron is poured forming the casting.
The pattern is designed to ensure not only a perfect replication of the original design, but also with the minimum waste or cost in its manufacture. So with any job, either one off or more especially multiple castings, involving the foundry early in the design process will lead to better quality and also savings in production costs.
Another critical element of pattern design is the method system. This ensures the metal flows into the mould correctly, neither too quickly or slowly, too hot or too cold.
Patterns are traditionally made from wood, although other materials are used today. Pattern makers need exceptional craft skills to replicate precisely the object to be cast, whether in wood, fibreglass or resin. They also need a thorough knowledge of foundry process.