Fine, resin coated sand is invested over a heated metal pattern.  The heat of the pattern causes the resin to bond, producing a thin shell.  The shell is cured to the required hardness and ejected from the pattern.  The halves are assembled with cores if necessary, joined together and poured.

This process can be used for iron, steel, aluminum and copper based castings.  There are size and weight limitations and quantities are medium to high.    

Shell molding is excellent for producing small to medium sized parts requiring better accuracy and near net shape.  Tolerances generally start at +/-.015”; Surface finish can be as low as 125 RMS and wall thickness can be .100” depending on the material being cast.

The tooling cost is medium to high while piece price is medium.