Void Material is a special-purpose material that is primarily useful in the investment casting process. Using Void Material, you can remove some material from one shape without replacing it with another type of material. This is useful for investment casting because the shell is then meshed around the net shape.
As an example, consider the following vertical cylinder. Four shapes made of Void Material have been added around the top of this cylinder to remove material and make four notches:
Note that it is necessary for the Void Material to have a SMALLER PRIORITY NUMBER (closer to 1) than the casting material.
The result of meshing this model is as follows:
It can be seen that the notches are removed from the cylinder, and no other material fills these features. When the shell is meshed, then the shell will be meshed around the net shape.