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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 or metal. 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.
Engineers in Houfeng decide where the sprues, gating systems, and risers are placed with respect to the pattern. Where a hole is desired in a casting, a core may be used which defines a volume or location in a casting where metal will not flow into. Sometimes chills may be placed on a pattern surface prior to molding, which are then formed into the sand mould. Chills are heat sinks which enable localized rapid cooling. The rapid cooling may be desired to refine the grain structure or determine the freezing sequence of the molten metal which is poured into the mould. Because they are at a much cooler temperature, and often a different metal than what is being poured, they do not attach to the casting when the casting cools. The chills can then be reclaimed and reused.
The design of the feeding and gating system is usually referred to as methoding or methods design. It can be carried out manually, or interactively using general-purpose CAD software, or semi-automatically using special-purpose software.
It is not required for every investment casting, but in some cases is necessary, and is used in conjunction with the main wax tooling. For some parts with complicated inner structure, Engineer will arrange the soluble wax core or Ceramic core to cast the parts with the best quality. And Every core makes the investment casting more effective.
After the pattern wax has solidified, we are left with a composite assemble of the two waxes fused together, and then we simply etch away the soluble wax to reveal the inner geometries.
Wax coring is utilized in applications where the resulting internal features are able to be shelled during the standard investing process. If the internal features cannot be shelled due to size and/or location, then a solid ceramic must be utilized.