custom Investment casting service

Step 1: Pattern Creation

Investment casting begins with creating a pattern of the desired part. This pattern is typically made from wax or a similar material that can be melted away later. The pattern is an exact replica of the final metal part, accounting for shrinkage factors that occur during the casting process.

Step 2: Pattern Assembly

Multiple wax patterns are attached to a central wax sprue, creating what’s called a “tree” or “assembly.” The sprue forms the main channel through which molten metal will later flow to reach each individual pattern. This assembly method allows for the efficient production of multiple parts in a single casting.

Step 3: Shell Building

The pattern assembly is dipped into a ceramic slurry coating, then covered with a stucco layer of fine ceramic particles. This process is repeated multiple times, with each layer being allowed to dry before the next application. The ceramic layers gradually build up to form a hard, heat-resistant shell around the wax patterns.

Step 4: Dewaxing

The ceramic-coated assembly is placed in an oven or autoclave where high temperature melts the wax, which then flows out of the shell through the sprue opening. This creates a hollow ceramic mold with internal cavities in the exact shape of the desired metal parts. This step gives investment casting its alternative name: the “lost wax” process.

Step 5: Shell Firing

The hollow ceramic shell is fired at high temperatures to burn out any remaining wax residue and to strengthen the ceramic material. This firing process ensures the mold can withstand the extreme temperatures of molten metal without cracking or deforming.

Step 6: Metal Pouring

Molten metal is poured into the preheated ceramic shell. The metal flows through the sprue system and fills all the cavities previously occupied by the wax patterns. Various metals and alloys can be used, including steel, aluminum, brass, and many specialty alloys.

Step 7: Cooling and Solidification

The filled mold is allowed to cool under controlled conditions until the metal solidifies completely. The cooling rate is often carefully managed as it affects the microstructure and properties of the final casting.

Step 8: Shell Removal

After the metal has solidified, the ceramic shell is removed from around the metal casting. This is typically done through mechanical means such as vibration or water blasting, which breaks away the brittle ceramic material without damaging the metal parts.

Step 9: Finishing Operations

The individual metal parts are cut from the sprue system. Various finishing operations may then be performed, such as grinding, machining, heat treatment, or surface finishing, depending on the specific requirements of the final product.