Investment Casting/Lost-Wax Casting

1.Produce A Master Pattern-An artist or mold-maker creates an original pattern from Wax,Clay,Wood, Plastic, Steel, or another material.

2.Mold Making-A mold known as the Master Die,is made of the master pattern. The master pattern may be made from a low-melting-point metal, steel or wood. If a steel pattern was created then a low-melting-point metal may be cast directly from the master pattern.

3.Produce The Wax Patterns-One method of doing this is filling the entire mold with molten wax, and let it cool, until a desired thickness has set on the surface of the mold. After this the rest of the wax is poured out again, the mold is turned upside down and the wax layer is left to cool and harden.

4.Investment-The ceramic mold, known as the investment, is produced by three repeating steps: coating, stuccoing, and hardening.

• Coating-The first step involves dipping the cluster into a slurry of fine refractory material and then letting any excess drain off, so a uniform surface is produced. This fine material is used first to give a smooth surface finish and reproduce fine details.
• Stuccoing-In the second step, the cluster is stuccoed with a coarse ceramic particle, by dipping it into a fluidised bed, placing it in a rain sander, or by applying by hand.
• Hardening-Finally, the coating is allowed to harden.

5.Dewax-The investment is then allowed to completely dry, which can take 16 to 48 hours. Drying can be enhanced by applying a vacuum or minimizing the environmental humidity.It is then turned upside-down and placed in a furnace or autoclave to melt out and/or vaporize the wax.

6.Burnout & Preheating-The mold is then subjected to a burnout, which heats the mold between 870 °C and 1095 °C to remove any moisture and residual wax, and to sinter the mold. Sintering is a method for making objects from powder, by heating the material in a sintering furnace below its melting point. Sometimes this heating is also as the preheat, but other times the mold is allowed to cool so that it can be tested. If any cracks are found they can be repaired with ceramic slurry or special cements.

7.Processing-The investment mold is the placed cup-upwards into a tub and filled with sand. The metal may be gravity poured, but if there are thin sections in the mold it may be filled by applying positive air pressure.

8.Removal-The shell is hammered, media blasting, vibrated, waterjeted, or chemically dissolved to release the casting. The casting may then be cleaned up to remove signs of the casting process, usually by grinding.