Method of modifying patterned sand molding elements through machining for producing prototype metal castings

A method of forming prototype metal castings by forming and modifying one or more sand mold elements of a sand mold assembly, the sand mold assembly having an internal cavity adapted to be filled with molten material for forming a metal casting, the method comprising:

• molding and patterning sand into shapes of the sand mold elements with at least one master pattern, the sand mold elements fitting together into a first sand mold assembly to define the internal cavity;
• forming a first metal casting by filling the internal cavity of the first sand mold assembly with molten metal material and allowing the molten metal material harden;
• evaluating the first metal casting;
• patterning sand into shapes of the sand mold elements with at least one master pattern, the sand mold elements adapted to fit together into a second sand mold assembly to define the internal cavity;
• machining at least one of the sand mold elements of the second sand mold assembly to modify the shape of the internal cavity based upon at least one change determined from evaluating the first metal casting;
• and
• forming a second metal casting by filling the modified internal cavity of the second sand mold assembly with molten metal material and allowing the molten metal material harden.