Wax Casting
Wax casting is effective at producing complex and detailed parts that other manufacturing methods cannot. There are no seams, flashes or parting lines because the part is made as one whole piece. Because a wax model is created in the exact size and shape as the part, wax casting provides a highly accurate part. Castings can be fractions of an inch thick or weigh hundreds of pounds; most parts are around 15 pounds or less. Wax casting is a traditional metal part manufacturing process that has been used for jewelry making for hundreds of years. It is finding modern uses in a wide variety of applications including dental and medical tools, engines, couplings, fittings, pipes, propellers and in aerospace, automotive, dental, medical, electrical, construction, mining, food processing, telecommunication, plumbing, military, sports and other industries.
Wax casting relies heavily on wax and its properties, though the actual wax is not necessarily pure; it may contain plastic or other substances. The wax can be carved by hand or machine but may also be produced through injection molding where hot wax is poured into a metal mold. Items such as preexisting patterns made from other materials may be covered in wax that is carefully removed when hardened then reattached. When the wax model is ready, it is attached to a wax sprue using a heated metal tool. Depending on the side and shape of the part, several hundred patterns may be attached to the same sprue resulting in an assembly called a tree which is dipped in ceramic slurry called the investment. It is dipped multiple times in mixtures that are increasingly coarse until the investment shell is thick enough. Another method is to place the tree in a flask and pour investment into the container until the tree is completely covered. Once the investment has hardened, the tree is inverted and placed in an oven or furnace. It is exposed to high temperatures during the burnout stage when the wax melts and runs out; all residual moisture is baked off. When removed from the oven, a liquid metal at very high temperatures is poured into the hollow shell. The metal cools within minutes and the shell can be removed, exposing the part within.
