Investment castings are one of the oldest forms of creating precision parts in metal. It is also known as the lost wax method. The process involves creating a wax pattern which is essentially a replica of the desired part in steel. The pattern is encased in a ceramic material and then removed or "lost" through the introduction of heat. The mold will then have molten steel poured into the opening. Once the mold is broken away from the solid steel, the casting is available for use.
The history of this process dates back thousands of years. Originally bees wax was formed into the desired shape and then covered in clay. Metal was melted using bellows and coal fire. The process was used to form shapes such as idols, jewelry, and art. As time progressed, advancements were made in the precision of the materials and processes to the point where extremely predictable results could be achieved. Dentists were some of the first users of investment casting on a more industrial level, utilizing the process to create fillings to be used inside the mouths of patients.
Advancements in the pattern making, wax, refractories, and melting equipment have resulted in processes that can hold extremely tight dimensional properties. Modern investment castings generally hold dimensions that are measured by a few thousandths of an inch per inch. This allows components to be made that often can be used directly from the manufacturer without subsequent machining. Worst cases allow the parts to be near net shape, which minimizes the amount of handling and processing to be completed on the casting. Users of these casting processes can also deploy the process to create parts that can be poured in thousands of different materials including steel, non-ferrous materials, duplex alloys, aluminum, iron, and more.
Applications of investment casting have grown tremendously during modern times. Investment castings are used to create components in aerospace, transportation, material handling, pump and valve, food processing and more. Sculptures and original art also employ investment casting to create a metal version of an artist creation. Investment casting is also used to create medical implements and components used inside the human body.
The history of investment casting will continually be redefined through the advancement of materials employed in the process. Each passing year has shown that raw materials can be combined in such a manner that results in improvements of process and cost. Investment cast wax, ceramic, and alloys combined with improved equipment to produce castings on a high or low volume basis ensure that the process will be deployed well into the future.
Andy Miller is CEO of Pennsylvania Precision Cast Parts (PPCP), investment castings and lost wax casting foundry located in Lebanon, PA. PPCP is a non-union enterprise with 175 employees and over $16 Million in casting sales annually.