Quick Facts

The investment casting process is generally considered for the production of small parts in which intricacy of shape or detail as well as high accuracy, dimensional reproducibility are prime considerations.  While investment casting are generally more expensive than forged parts or those parts produced by other casting methods, they make up for the higher cost by the reduction of machining which is achieved through the near net shape tight tolerances that can be held.

The Process

Wax is injected into an aluminum die to produce a pattern that is an exact replica of the part to be produced.  The patterns are then clustered around a coated sprue and repeatedly dipped into an agitated vat of ceramic and allowed to dry.  After a shell thickness of approximately 3/8" has been built, the molds are dewaxed by either flash firing at high heat (1400 degrees F.) or autoclaving (pressure and steam).  The hollow shells are then preheated to 800-2000 degrees F, depending on the alloy to be poured.  The molten metal is cast immediately into the hot shell.  After cooling, the ceramic is vibrated and blasted off the metal parts and discarded.  The balance of the cleaning operations (cut-off, grind, heat treat, straightening, blast) are straight forward and quite similar to the other casting processes.

Investment Casting Advantages

Great flexibility in design is offered by the investment casting process.  Surface finish is excellent, and parts can be designed to close tolerances.  Parts designed for the investment cast process may assist in reducing machining, and in many cases result in the casting of intricate shapes that may have otherwise required machining.

Investment Casting Disadvantages

The investment casting process generally requires numerous operations to complete the casting, which makes the cost per casting greater than that of castings made by other processes.  Investment casting requires an individual pattern for each casting to be made.  High volume production is not normally associated with the investment casting process.

Alloys

Nearly all ferrous and non-ferrous alloys may be poured in the investment casting process.  On the ferrous side, carbon, tool and alloy steel along with the 300, 400, 15-5PH and 17-4PH stainless steels are the most commonly poured.  Most aluminum, copper and other non-ferrous materials can be cast.

Tooling

Typically, a split cavity aluminum die is manufactured that is the "female" mold from which the "male"wax patterns are produced.  Depending on the complexity of the casting, various combinations of aluminum, ceramic, or soluable cores may be employed to yield the desired configuration.  Most tooling for investment casting falls in the $3,000 - $15,000 category.

Design and Technical Information