How to Pour Cast Aluminum

Aluminum is a popular material for creating cast parts because it is lightweight, strong and resistant to corrosion. Aluminum casting can be performed by hobbyists on a small scale or by industrial manufacturing methods on huge scales. Like many manufacturing process, success in aluminum casting is based on planning, quality of the process and safety precautions.

Things You'll Need

• Polystyrene foam
• Knife or wire foam cutter
• Hot glue
• Sheetrock mud
• Casting box
• Sand
• Tamping rod
• Metal rod for venting
• Casting pressure tool
• Aluminum scraps
• Crucible
• Wire brush

Instructions

Casting Aluminum

1. Make a mold of the part out of foam. Cut the foam to shape with the knife and glue pieces together as needed to create a composite shape. Aluminum does shrink slightly when it cools, so the mold should be slightly oversized. Once the basic shape is complete, add a pouring sprue shaped like a funnel to the top of the mold.

2. Cover the completed mold with sheetrock mud. By adding the mud coat, the outer surface of the cast part will have a smoother surface.

3. Fill the bottom of the casting box with sand and pack down tightly. Place the mold into the box and pack sand around it. Use the tamping rod to pack the sand tightly around the mold and gradually fill the box. Create a vent channel by inserting the metal rod into the sand until it contacts the mold.

4. Pack the sand in the box until the level of the sand is flush with the sprue surface. Tamp the sand firmly and add more sand as needed. Remove the rod from the vent channel. Put the casting pressure tool over the sprue. This tool will allow the molten aluminum to pool over the sprue rather than spilling over the sand.

5. Put the scrap aluminum into the crucible and heat it until it has melted. Pour the metal into the sprue of the mold. The metal will melt the foam on contact and fill the void where the foam was. The vent channel allows gasses to escape from the mold.

6. Leave the assembly alone for several minutes so that the aluminum can cool and solidify. After several minutes, begin to dig the sand away from the cast part. The part will be extremely hot, so wear leather gloves.

7. Remove the cast part from the sand and remove excess sand with the wire brush. The cast part can then be finished by grinding away excess aluminum or machine finishing the part.

References

• Materials and Processes in Manufacturing (9th ed.); E. Degarmo, J.T. Black and R.A. Kohser; 2003.
• Casting Aluminum