Metal casting using sand casting molds is one of the most prevalent processes in the casting industry. Fundamentally, a mold is produced by shaping a refractory material to form a cavity with the desired shape and then molten metal is poured into the cavity. The mold cavity needs to retain its shape until the metal has solidified and the casting is removed.

While the basic process remains the same, there are several types of sand casting processes that may be used depending upon the choice of metal, the size of the part, necessary dimensional accuracy, quantity required and other factors.

Sand Casting Examples:

Green Sand
 
Sand Casting
 
Typical dimensional ± .010″
tolerances, inches ± .030
Relative cost in quantity  
Low
Relative cost for small number  
Lowest
Permissible weight of casting  
Unlimted
Thinnest section castable, inches  
1/10″
Relative surface finish  
Fair to good
Relative ease of casting complex design  
Fair to good
Relative ease of changing design in production  
Best
 
Range of alloys that can be cast  
Unlimted

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.