Wax casting is a process that uses a wax pattern to create metal parts. This technique is also called the lost wax or investment casting process. Aluminum, copper, and stainless steel are among the most commonly used metals; almost any castable metal may be used including gold, titanium, and brass. Due to the smooth surface of the wax pattern that is used to create a ceramic mold, the resulting parts have a very fine finish that requires little machining.
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Wax Casting Methods
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 pre existing 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 a ceramic slurry called the investment. It is dipped multiple times in increasingly coarse mixtures 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. A liquid metal at very high temperatures is poured into the hollow shell when removed from the oven. The metal cools within minutes, and the shell can be removed, exposing the part within.
Applications of Wax Casting
Wax casting effectively produces 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.