Jewelry casting, most commonly using the lost wax process, involves creating a metal replica of an original design, typically a wax model. Here's a breakdown of the process:
1. Creating the Wax Model:
- The process begins with a wax model of the desired jewelry piece. This model can be created in several ways:
- Wax Carving: Manually carving the design from a block of wax.
- Wax Injection: Injecting molten wax into a mold.
- 3D Printing (Wax or Resin): Using a 3D printer to create a wax or resin model. Resin models are often used for direct investment casting.
- Wax Growing: Using a specialized machine to "grow" a wax model.
2. Investing the Wax Model:
- The wax model is attached to a sprue (a wax rod or system of rods) and then encased in a plaster-like substance called investment. The sprue provides a channel for molten metal to flow into the mold after the wax is removed.
- The investment is mixed as a slurry and poured into a flask or container surrounding the wax model and sprue.
- The investment hardens, creating a solid mold around the wax.
3. Burnout (Wax Removal):
- The flask containing the investment mold is placed in a burnout oven.
- The oven heats the investment to extremely high temperatures (e.g., 1350°F / 730°C).
- The heat melts and incinerates the wax model, leaving a hollow cavity inside the investment mold in the exact shape of the original wax. This is where the "lost wax" name comes from.
4. Casting the Metal:
- Molten metal (gold, silver, platinum, etc.) is poured or injected into the hollow cavity within the investment mold.
- There are several casting methods:
- Centrifugal Casting: The flask is spun rapidly as the metal solidifies, forcing the metal into the intricate details of the mold.
- Vacuum Casting: A vacuum is used to draw the molten metal into the mold, ensuring complete filling.
- Pressure Casting: Pressure is applied to force the molten metal into the mold.
- Gravity Casting: Simply pouring the molten metal into the mold and letting gravity do the work.
5. Quenching:
- After the metal has cooled and solidified, the flask is quenched in water.
- The rapid temperature change cracks the investment, making it easier to remove the cast metal piece.
6. Finishing:
- The cast piece is removed from the remnants of the investment.
- The sprue is cut off.
- The jewelry piece undergoes various finishing processes, including:
- Pickling: Cleaning the metal to remove oxides.
- Grinding and Polishing: Smoothing and refining the surface.
- Setting: Adding gemstones or other embellishments.
In short, jewelry casting leverages a sacrificial wax model, creates a heat-resistant mold from it, burns out the wax, and then fills the resulting cavity with molten metal to create the final jewelry piece.
