DME University

Cavity Forming Method

The toolmaker has several choices in forming or shaping mold cavities. Usually a combination of methods is used to produce a finished shape. The typical methods are:

  • Conventional Machining
  • Hobbing
  • Computer Numerical Control (CNC )
  • Casting
  • Electrical Discharge Machining (EDM)

Conventional Machining:
This involves the production of cavities and cores by a machinist using the engine lathe, milling machine, drill press, and grinders.

Computer Numerical Control (CNC):
A computer programmed and controlled machine tool is used to drive tool motion to produce the desired cavity or core shape.

Electrical Discharge Machining (EDM):
Controlled electrical sparks, from an electrode machined to the desired shape, are used to erode a matching shape into the mold cavity or core steel. The electrode is typically graphite, while the mold steel part is typically submerged in a dielectric fluid.

Hobbing produces a cavity by forcing a hard and polished hob, made in the shape of the molded part, into the mold cavity material. This process eliminates a lot of machining and produces identical, multiple cavities, with a highly polished surface.

A variety of casting methods have been developed to produce cavities or cores.

Ceramic Casting:
This method is used to produce cavities or cores where accurate surface reproduction is needed such as a wood or leather grain effect.

Pressure Casting:
Cavities and cores can also be made by casting materials such as beryllium copper. The molten alloy can be poured over a hard, polished master, and pressure applied until the metal cools to the desired shape.



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