Sand Casting

Sand casting is a common and simple way to produce metal parts.

  • Pattern
    • Draft Angle
    • Types of patterns
  • Mold
    • Sand
    • Binders
    • Cores

  • Sand casting is the most common and versatile form of casting
  • Granular material is mixed with clay and water
  • Packed around a pattern
  • Gravity flow is the most common method of inserting the liquid metal into the mold
  • Metal is allowed to solidify and then the mold is removed
Sand Casting Terminology
Draft on a pattern allows easy removal from the mold

Process

The process begins with a pattern. Patterns should be:

  • Made of a stable material
  • Oversized to accommodate shrinkage
  • Include draft angles
  • Include generous fillets and rounds (avoid sharp corners)

Here, a split pattern is used. The two halves of the split pattern nest together.

The split pattern shown with cutaway of flask.

The pattern is covered with parting compound and sand is rammed into the flask to form the drag. Excess sand is removed by a process known as strickling.

Cutaway view of a drag half that has been rammed and strickled.
The drag half of the mold after it has been inverted.

When the drag has been rammed and strickled, it is inverted and the cope half of the pattern is placed.

The cope half of the pattern and flask are installed.

Parting compound is added on top of the cope half of the pattern and the cope is rammed with sand.

With the cope rammed, sprue and risers are cut.

Sprue and riser being cut.

The mold is then disassembled and runners are cut from the sprue and riser. If cores are used, they are inserted into the core prints at this time.

Disassembled mold with core installed.

The mold is then re-assembled and is ready to be poured.

Cutaway view of a re-assembled mold showing the pouring basin, runners, and core in place.

The mold is poured and allowed to cool.

Cutaway showing poured mold.

When the part has cooled it is removed from the sand.

Gates and runners must then be removed. This process is known as fettling.

A completed casting, with rough casting and pattern halves shown.