Sand Casting

Sand casting machine

Wheel hub made by sand casting

Sand casting is a process in which molten metal is poured into a non-reusable, compacted sand mold and held until solidification occurs. The mold is composed of sand mixed with small amount of binding materials. A channel called a pouring basin is provided at the top of the mold. Molten metal runs into the mold cavity. Sand casting offers low cost for medium to large size parts in low quantity. Sand casting is typically used to make simple 3D shapes.

Some applications of sand casting include engine blocks, gear blanks, crankshafts, brake drums etc. Sand casting can be used for most metals including aluminum, brass, cast iron, cast steel, etc. The process requires making a pattern (a positive replica of the final part shape). Costs of sand casting can be reduced by reducing the size and weight of the part.

Sand Casting Design Considerations

• Use rounded corners.
• Add ribs to add strength, reduce material usage and reduce distortion caused by thermal contradiction.
  
• A parting line will occur where the two halves of the casting meet.
  
• Produces rough textured surfaces that often require secondary machining steps.
• The shape of the pattern must allow for removal with disturbing the sand. Therefore a taper (draft) must be used on surfaces perpendicular to the parting line. 
• Gas pockets can cause internal voids.