me_350_-_lect_18_-_ch_20.20091022.4ae1187e4f02f5.95679377

me_350_-_lect_18_-_ch_20.20091022.4ae1187e4f02f5.95679377 -...

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ME 350 – Lecture 18 – Chapter 20 SHEET METALWORKING Cutting Operations Bending Operations Drawing Other Sheet Metal Forming Operations
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Advantages of Sheet Metal Parts High strength Good dimensional accuracy Good surface finish Relatively low cost Economical mass production for large quantities
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Basic Types of Sheet Metal Processes 1. Cutting Shearing to separate large sheets Blanking to cut part perimeters out of sheet metal Punching to make holes in sheet metal 2. Bending Straining sheet around a straight axis 3. Drawing Forming of sheet into convex or concave shapes
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(1) punch before contact, clearance ‘ c ’ between punch and die (2) punch causes material to plastically deform (3) smooth cut surface is formed (4) fracture initiated at the opposing cutting edges which separates the sheet. Sheet Metal Cutting Sheet metal cutting examples: Shearing, Blanking, & Punching
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1. Shearing Sheet metal cutting operation along a straight line between two cutting edges Typically used to cut large sheets (a) side view of the shearing operation; (b) front view of power shears equipped with inclined upper cutting blade.
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2. Blanking and Punching Blanking - sheet metal cutting to separate piece (called a blank ) from surrounding stock Punching - similar to blanking except cut piece is scrap, called a slug (a) Blanking and (b) punching.
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Clearance in Sheet Metal Cutting Distance between punch cutting edge and die cutting edge (typically 4 - 8% of thickness) If too small (a), fracture lines pass each other, causing double burnishing and larger force If too large (b), metal is pinched between cutting edges and excessive burr results
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me_350_-_lect_18_-_ch_20.20091022.4ae1187e4f02f5.95679377 -...

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