What is lost wax casting? from jiachuan's blog

Lost wax casting is a process of creating objects ranging from simple to complex in various metals such as gold, silver, brass or bronze by casting original models or patterns.

It is one of the oldest known metal forming techniques, dating back 6,000 years, but it is still widely used to produce jewelry, dentistry and art. Its industrial form, investment casting, is a common method of making precision metal parts in engineering and manufacturing.

While traditionally associated with manual craftsmanship, creators can now transform the lost wax casting process through digital design and 3D printing to streamline workflows, save time, reduce costs and reshape 21st century processes.

The lost wax casting process can vary by industry and application, but generally consists of the following steps. Castings can be made from the wax model itself, called the direct method, or from a replica of the original wax model, called the indirect method. The direct method jumps directly from the first step to the fourth step.

Model making: The artist sculpts the design in wax. The size and complexity of the wax model is limited by the skill of the wax carver, and the capabilities of his casting equipment.

Making the mold: The caster then casts this model and polishes the casting to produce the "master" pattern. Master molds are used to make wax molds out of rubber, which are heated and "vulcanized" around the master mold to make a flexible wax mold.

Making a wax mold: Inject or sometimes pour molten wax into a rubber mold. This can replicate the original design over and over again.

Assembling the wax mold: Add gates to the wax replica and connect them to form a tree-like structure, which provides a path for molten wax to flow out and molten metal to subsequently fill the cavity.

Apply Embedding Material: Dip wax tree in a silica slurry, or place in a flask and surround with liquid embedding plaster.

Burnout: After the embedding material has dried, the flask is placed upside down in a kiln to melt the wax, leaving a negative cavity in the shape of the original model.

Pouring: The investment mold is further heated in the kiln to reduce the temperature difference with the molten metal. The metal is melted and then poured, using gravity or vacuum pressure to pull the metal into the cavity.

Demoulding: Once the molten metal cools slightly, the investment is quenched in water to dissolve the refractory gypsum and release the rough casting. . Gates are cut and recycled, while castings are cleaned to remove signs of the casting process.

Finishing: Filed, ground, machined or sandblasted castings to achieve final geometry and surface finish. When necessary, castings are also heat treated to improve the mechanical properties of the material.

A brief summary of the long history of lost wax casting

It is no exaggeration to say that lost wax casting is as old as civilization itself. Artifacts such as scepters, sculptures and furniture made from lost wax casting have been found as far away as Israel, Vietnam, Nigeria, Nicaragua and the Indus Valley. The oldest known lost wax casting is a talisman created by a society in the Indus Valley, over 6,000 years old.

After centuries of use in the production of sculptural ornaments and textile reliefs, lost wax casting began to be replaced by single-piece molding in 18th century Europe. Part of the process was adapted for investment casting to meet the needs of a growing industry in the 19th century.

In dentistry, the lost wax method is widely used to make gold crowns, inlays and onlays. Therefore, the tradition of lost wax casting is still evident today.