Investment castings are normally not competitive with die casting where parts are being manufactured in very high production runs, and where piece part strength and other properties, as die cast, are considered adequate.
However, where parts have more complicated design features; or where they may require superior strength; or when quantities of parts required are relatively low, investment castings become more attractive. They can be produced with the superior qualities required with less expensive tooling in quantities compatible with your needs at a cost saving over die-casting.
CONVERTED FROM MACHINED FORGINGS
Forgings are satisfactory when requirements call for high quantities of medium-to-large parts with simple designs including plenty of draft. Where forgings require machining operations to finish the part, or where stronger, tougher materials should be used, conversion to the investment casting process should be considered.
Complex details can be cast eliminating the machining requirement. Tolerances can be held much closer. In most cases, no draft is required. In case of lower quantity runs, a considerable cost saving over forgings can be realized by the investment casting process.
CONVERTED FROM SAND CASTINGS-SHELL MOLDING
Sand castings are most useful for medium-to-very large parts when surface finish and close tolerances are relatively unimportant, when a rough part can be used with few secondary finishing operations, and when cost per pound is one of the major factors.
Shell molding and permanent mold casting have many of the same advantages of sand casting with the added advantage of finish. Tooling costs are normally higher than in sand casting.
Plaster mold castings (non-ferrous only) achieve a very good surface finish and can be relatively complex in design compared to sand castings.
Investment casting is the most versatile of all casting processes. Some of its prime advantages are: closer tolerances, especially across parting lines; superior surface finish; and the ability to cast extremely complex designs in almost unlimited number of alloys.
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