09 sheet metal
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SHEET
METALWORKING
Desember 2012
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Sheet Metal Working
Sheet metal working includes cutting and forming
operations performed on relatively thin sheets of
metal.
Typical sheet-metal thicknesses are between 0.4
mm (1/64 in) and 6 mm(1/4 in).
When thickness exceeds about 6 mm, the stock is
usually referred to as plate rather than sheet. The sheet or plate stock used in sheet
metalworking is produced by flat rolling.
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Sheet Metal Working
The most commonly used sheet metal is low
carbon steel (0.06%0.15% C typical).
Its low cost and good formability, combined
with sufficient strength for most product
applications, make it ideal as a starting
material.
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CUTTING OPERATIONS
Shearing of sheet metal between two cutting edges: (1) just before the punchcontacts work; (2) punch begins to push into work, causing plastic
deformation; (3) punch compresses and penetrates into work causing a
smooth cut surface; and (4) fracture is initiated at the opposing cutting edges
that separate the sheet.
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shearing
(a) side view of the shearing operation;
(b) front view of power shears equipped with inclined upper cutting blade.
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Effect of clearance:
(a) clearance too small causes less-than optimal fracture and excessive forces; and
(b) clearance too large causes over sized burr. (a) Blanking and (b) punching
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Blanking and Punching
(a) Blanking and (b) punching.
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(a) Slotting,
(b) perforating,
(c) notching and seminotching.
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BENDING OPERATIONS
(a) Bending of sheet metal;
(b) both compression and tensile elongation of the metal occur in bending.
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Two common bending methods:
(a) V-bending and
(b) (b) edge bending; (1) before and (2) after bending.
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Flanging: (a) straight flanging, (b) stretch
flanging, and(c) shrink flanging.
(a) Hemming, (b) seaming, and (c) curling.
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Drawing
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Lancing in several forms:(a) cutting and bending;
(b) and (c) two types of cutting and forming.
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Components of a punch and die for a blanking operation.
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(a) Progressive die and
(b) associated strip
development.
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SPINNING
Conventional spinning:
(1) setup at start of process; (2) during spinning; and
(3) completion of process.
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Shear spinning:
Shear spinning:
(1) setup and (2) completion of process.
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Tube Spinning
Tube spinning: (a) external; (b) internal; and (c) profiling.
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HIGH-ENERGY-RATE FORMING
Explosive forming: (1) setup, (2) explosive is detonated, and
(3) shock wave forms part and plume escapes water surface.
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HIGH-ENERGY-RATE FORMING
Electromagnetic forming:
(1) setup in which coil is inserted
into tubular work part surrounded
by die; (2) formed part.
Electro hydraulic forming setup
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BENDING OF TUBE STOCK
Dimensions and terms for a bent tube: D = outside diameter of tube, R
= bend radius, t = wall thickness.
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Tube bending methods:
(a) stretch bending, (b) draw
bending, and (c) compression
bending. For each method:
(1) start of process, and (2)during bending. Symbols v
and F indicate motion and
applied force, respectively.