ME 250November 13, 2007Sheet Metal WorkingCourse pack: All sections except 20.4HW 9, Problem 3 (CES)Tolerance = 0.01 and NOT 0.1Can manufacturingThe typical aluminum can weighs less than half an ounce. Its thin walls withstand approx a pressure of 90 psi (exerted by the carbon dioxide in beer and soft drinks)Aluminum's shiny finish also facilitates decorative printing, important for a product that must grab the attention of consumers in a competitive market100 billion aluminum beverage cans produced / year in the U.S.Why sheet metal parts?•High strength•Good dimensional accuracy•Good surface finish•Relatively low cost •Economical mass production for large quantities Sheet metalworkingCutting and forming operations performed on relatively thin sheets of metal Thickness of sheet metal = 0.4 mm to 6mm (1/64 in to 1/4 in)Operations usually performed as cold working (room temperature)TerminologyPunch-and-die: the tooling to perform cutting, bending, and drawingStamping press: the machine tool that performs most sheet metal operationsStampings: sheet metal products
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Sheet metal cuttingShearingto make large sheets into smaller onesBlankingto cut part perimeters out of sheet metalPunchingto make holes in sheet metalCutting action (Fig 20.1)Cutting sheet metal by shearing actionSheared edge (Fig 20.2)Appearance of the cut edgeBlanking & punching (Fig 20.4)blankingpunchingClearanceClean separation Æmeeting of fracture linesGood clearanceClearance (Fig 20.5)clearance too smallclearance too large