Castings - 3: Making a Sand Casting
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.
Sand castings are the most common type of castings, and are used to make brass, aluminum. cast iron, and cast steel parts. Sand castings have the largest amount of draft, radii, mismatch, and surface roughness, compared to the other types of castings.

The typical draft angle for cast iron is 6 degrees, or about 1/8” of taper for every foot of length.

The steps in making a sand casting are as follows:

1. A pattern is made in the shape of the finished part
2. The pattern is packed into boxes with wet sand on either side that has been moistened with water and/or resin
3. The boxes are split, the pattern is removed, and the sand is dried. The pattern will then be reused to make the next mold.
4. The two boxes are put together (using alignment pins) to form a mold
5. Molten metal is poured into the mold down a sprue, filling the cavity, and allowed to cool and solidify
6. The sand mold is broken and sand cleaned away from the metal part
7. The sprue, riser, and vent holes are trimmed off leaving the part ready to be machined. The riser (or group of risers) provides excess metal to compensate for shrinkage when the metal cools and hardens. Vent holes are used to allow air to escape

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label: casting, castings, sand casting, die casting, investment casting, bosses, lugs