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Tuesday, 12 November 2013

Cold-Working Processes - Cold-pressing and Deep-drawing

Cold-pressing and Deep-drawing
Points : Cold-pressing and Deep-drawing, Definition Definition These processes of cold pressing and deep drawing are so closely allied to each other that it is very difficult to define each separately. The operations range from making a suitable pressing in one stage to coupling followed by a number of re drawings. In each case the components are produced from sheet stock, and range from mild-steel motor-car bodies to cartridge cases (70-30brass), bullet envelopes (cupro-nickel) and aluminum milk churns.

Deep-drawing demands very high ductility in the sheet stock, and only a limited range of alloys are, therefore, available for the process. The best known are 70-30 brass, cupro-nickel, pure copper, pure aluminum and some of its alloys, and some of the high-nickel alloys. Mild steel can be presses and, to a limited extent, deep-drawn. It is used in the manufacture of innumerable motorcar and cycle parts by these methods. Typical stages in a deep-drawing process but it should be noted those wall thinning may or may not take place in such a process. If wall-thinning is necessary, then one of the more ductile alloys must be used. Though the processes of shearing and primary’ cupping as being effected in different machines, usually a combination tool is used, so that both processes taken place in one machine. Cold-pressing is very widely used, and alloys which are not quite sufficiently ductile for deep-drawing are generally suitable for shaping by simple press-work. Of recent years high-energy rate forming by the use of high explosive has also been developed.

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