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Extrusion is a metal forming process to form parts with constant cross-section along its length. This process uses a metal billet or ingot which is inserted in a chamber. One side of this contains a die to produce the desired cross section and the other side a hydraulic ram is present to push the metal billet or ingot. Metal flows around the profile of the die and after solidification takes the desired shape. Extrusion process can be done with the material hot or cold, but most of the metals are heated before the process, if high surface finish and tight tolerances are required then the material is not heated. DFM stands for design for manufacturing, so as the name suggest the design is manufacturing friendly, in simple terms design that can be manufactured easily and cheaply. DFM guidelines define a set of rules for a person designing a product to ease the manufacturing process, reduce cost and time. For example, if a hole is to be drilled, if the designer specifies a standard hole size then it reduces the cost because the drill bits of unusual sizes are not readily available they have to be custom made. ==Material based guidelines== Nowadays, quite a wide variety of metals are currently extruded commercially, the most common are (in order of decreasing extudability): Aluminium, Magnesium and their alloys, Copper and Copper alloys, low-carbon and medium-carbon steels, low-alloy steels and stainless steels.〔George E. Dieter, Howard A. Kuhn, S. Lee Semiatin (2003) 'Extrusion', in (ed.) Handbook of Workability and Process Design. : , pp. 291-292.〕 So obviously as the extrudability decrease the cost of production increases # For an extruded part a material should be selected from the top side of the series given above i.e. from Aluminium and Magnesium side but without changing the functionality because high extrudability properties also mean less strength. So as explained above, considering this guideline while designing leads to ease in the manufacturing process of the parts which in turn leads to cost savings. # This point generally applies when the quantity of parts required is small. So generally when you put an order for extruded parts there is customarily a minimum weight for each order of a special cross section.For example, the minimum quantity may be 1000 kg for carbon steel, 500 kg for stainless, and 80 kg for aluminum. The net result is that the most economical operation takes place at moderately low production quantities or higher. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DFM Guidelines for Hot Metal Extrusion Process」の詳細全文を読む スポンサード リンク
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