Sand molds are used to create the space that is filled with molten metal to form the casting upon solidification.
Two molding processes are used, this page covers green sand molding:
Green Sand Molding: Green sand is predominately used in the foundry and it has the advantage of being continually recycled. After each use, the sand is screened, mulled in a Ringmuller and then water added to bring it back to the correct moisture consistency. Smaller castings are molded on numerous lines using BMM Molding Machines. Large castings are molded on the ground and are termed “floor molds”.