Investment Casting History Investment casting among the most ancient of metal-crafting arts, conversely, it is among the most modern. The process of investment casting can be traced back to the early dynasties of china where artisans cast intricately detailed boxes from bronze to contain the master’s treasures. The “lost wax” investment casting method was used by an Italian monk some 900 years ago to craft large statues. The monk’s process was very similar to those used in investment casting today; the original model was sculpted in wax then coated with successive layers of plaster. After the plaster hardened, the wax was melted out and molten metal was cast into the void. A short time later, after the metal cooled and hardened, the plaster was broken away and there stood the statue; an exact replica of the original wax sculpture. For many centuries, jewelers used rubber molds to cast quantities of rings and bracelets, and during the late 19th Century, dentists were using investment casting processes to manufacture dental fillings and inlays. Industry realized the need for investment castings at the beginning of World War II with the sudden increase in demand for large quantities of intricately machined armament and aircraft parts. Manufacturers found that the “lost wax” process of casting these parts virtually eliminated all but the closest machining operations; thereby increasing their ability to produce critical items such as turbine blades, gun parts, etc. at the fraction of their original costs. Knowledge gained from the dental trade was combined with the permanent die techniques perfected by jewelers to produce critical items in unbelievable quantities. Investment castings are utilized today in virtually every industry where production quantities of metal parts are required. Furthermore, investment castings are now obtainable for prototype quantities of complex devices such as electronic housings, microwave components and subassemblies; without the necessity of producing the permanent dies to cast these devices. What is a metal casting? A casting is a metal part formed by pouring molten metal into a sand mold or metal die. The mold or die is comprised of two halves that, when mated together, form a cavity into which the molten metal is poured. The mold or die form the external surface of the casting. If an internal cavity is required in the casting, a core is placed inside the mold cavity. After the metal solidifies, the mold is broken, the cores removed and the part is readied for finishing operations. The sand is then remolded and used again. When a metal die is used, the two halves of the die are separated and the solidified casting is removed. The die is then reused. What metals can be cast? Virtually any metal that can be melted can and is being cast in foundries today. The most common alloys used in metal casting are shown below. Metals are most commonly categorized as ferrous or nonferrous.
What are castings used for? Metal casting are used in virtually any application you can think of More than 90% of all manufactured goods and capital equipment use castings as engineered components or rely on castings for their manufacture. All sectors of the military are reliant on metal castings for tank, truck, jet engine and other vital components. ADVANTAGES OF " LOST WAX " INVESTMENT CASTING OVER CONVENTIONAL CASTINGS
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