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A burndown chart or burn-down chart is a graphical representation of work left to do versus time. [1] The outstanding work (or backlog) is often on the vertical axis, with time along the horizontal. A burndown chart is a run chart of remaining work. It is useful for predicting when all of the work will be completed.
Lost-wax casting – also called investment casting, precision casting, or cire perdue (French: [siʁ pɛʁdy]; borrowed from French) [1] – is the process by which a duplicate sculpture (often a metal, such as silver, gold, brass, or bronze) is cast from an original sculpture. Intricate works can be achieved by this method.
The fragile wax patterns must withstand forces encountered during the mould making. Much of the wax used in investment casting can be reclaimed and reused. [2] Lost-foam casting is a modern form of investment casting that eliminates certain steps in the process.
Wax patterns are used in an alternative casting process called investment casting. A combination of paraffin wax, bees wax and carnauba wax is used for this purpose. In this case the wax "pattern" is melted out from the mould cavity which is normally a rigid plaster like material rather than sand, so the wax "pattern" can only be used once. [5]
The lost wax process originated in ancient Mesopotamia. The earliest known record of lost-wax casting is a clay tablet written in cuneiform in the ancient city of Sparta, Babylon, which specifically records how much wax is needed to cast a key. [6] The earliest-known castings in the global archaeological record were made in open stone molds. [7]
One key in casting metal cores is to make sure they do not contain any porosity as it will induce flaws into the molded part. In order to minimize porosity the metal may be gravity cast or the molding cavity may be pressurized. Another system slowly rocks the casting dies as the molding cavity fills to "shake" the air bubbles out. [9]
Evaporative-pattern casting is a type of casting process that uses a pattern made from a material that will evaporate when the molten metal is poured into the molding cavity. The most common evaporative-pattern material used is polystyrene foam. [1] The two major evaporative-pattern casting processes are: [1] Lost-foam casting; Full-mold casting
Wax carving is the shaping of wax using tools usually associated with machining: rotary tools, saws, files and burins or gravers. Actual knives can be used and most certainly are, but the hardness of the material is such that they are not the ideal tool, generally.