Investment Casting denotes the mechanical manner of obtaining a mold rather than the material used. It is the process completely investing a three dimensional pattern in all of its dimensions to produce a one-piece destructible mold into which molten metal will be poured.
Extreme accuracy and flexibility of design. Useful for casting alloys that are difficult to machine. Exceptionally fine finish. Suitable for large or small quantities.
Limitation on size of casting. Casting cost make it important to take full advantage of the process to eliminate some or all machining.
|Typical dimensional tolerances, inches||± .010″|
|Relative cost in quantity|
|Relative cost for small number|
|Ounces to 100 lbs.|
|Thinnest section castable, inches|
|Relative surface finish|
|Relative ease of casting complex design|
|Relative ease of changing design in production|
|Range of alloys that can be cast|
Parting Line Influence
When Parting lines are considered, very close tolerances are difficult to obtain. A parting line absorbs fractions of inches per inch. A foundry is doing well to hold a parting line to 0.015 inch. Additional measurement is added to the casting tolerance.