Copper investment casting is the process where parts are manufactured through the metallic replication of wax models. The process of investment casting uses liquid copper to manufacture parts that have a very fine, smooth finish and are intricately detailed. There are no seams or flash lines and many different alloys may be used including brass and titanium.
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Aluminum, steel and copper are among the most common materials used in investment casting. Another benefit is the high dimensional accuracy of the resulting part; that is, the wax model used is practically the exact size and shape of the part that is created. However, investment casting or lost wax casting is relatively expensive though the equipment costs are low and little finishing or machining is required because of the smooth one-piece results. For very complex parts that would be difficult or impossible for other methods, precision investment casting is a good option. Castings can range from less than a sixteenth of an inch thick to weighing 1,000 pounds. Typically they are 15 pounds or less and are moderately sized. Copper castings are lightweight, strong and are widely used in many different capabilities such as pipe fittings, machine tools, mixing equipment, lock parts and jewelry. They can be found in the chemical, food processing, electrical, railroad, mechanical, marine, electronic, textile and engineering industries.
Investment casting requires a wax pattern called the master die that is an exact replica of the part being manufactured. This die can be hand or machine carved or produced by injection molding. The die is attached to a sprue which is a wax rod. Several hundred wax patterns may be attached to a sprue at once. The assembly or tree is then dipped in a ceramic slurry called the investment multiple times. Each time it is dipped in a coarser mix until it is thick enough to withstand the next steps of the process. Another method is to affix the tree in a flask and pour in the investment. Vibrations help eliminate air bubbles which could ruin the part. The investment is then dried; air or vacuum drying are viable options or a fan could also help. When it is completely dry, the assembly is placed in an oven or furnace upside down to allow the wax to drip out. The shell is heated even more to make sure that all moisture or wax is gone. Liquid copper is poured into the shell, filling the space created by the wax. Once the metal is cooled, the investment is removed. It can be hammered, vibrated, dissolved or media-blasted off in order to release the copper part inside.
