The Sand Casting process includes packing sand around a pattern to form a mold. A pattern is the same form, allowing for slight shrinkage, that the final casting will be.
The mold is in two parts so the pattern can then be removed and the metal poured in to the resulting cavity. We use a synthetic sand that is mixed with a binder so it forms a smooth surface when packed.
The castings are finished by removing the parting line and gating areas. The castings are then glass bead blasted or tumbled in ceramic chips to enhance the finish.
Sand Casting has low tooling costs and the part cost is below average. Die-Casting and Permanent Molding have tooling costs that are several times that of sand casting. Also with sandcasting it is fairly easy to make design changes to the pattern without having to re-tool.
For these reasons Sand Casting is especially good for large parts and prototyping, or other short runs where tooling costs are a significant factor.