Sheet Metal Working

These processes are forming and related operations are performed on sheets, strips and coils. Press working is the term often applied to sheet metal operations. A part produced in a sheet metal operation is generally called as stamp.

Contd… Sheet metal includes cutting and forming operations performed on sheets of thickness ranging between 0.4 mm and 6 mm. Sheet or plate are produced by rolling for sheet metal working/operations. Note : Thickness > 6 mm…..referred as plate.

Contd… Commercial and industrial aplications : 1)Automobile and truck bodies 2)Airplanes 3)Railway cars 4)Locomotives 5)Farm and construction equipment 6)Office furniture and many more.

Contd… Sheet metal parts are generally characterized by 1)High strength 2)Good dimensional accuracy 3)Good surface finish 4)Relatively low cost (bulk deformation products)

Contd… Sheet metal working is performed at room temperature. In special cases; stock is thick, metal is brittle, or deformation is significant; working of these is usually warm rather than hot.

Categories of Sheet Metal Working a)Cutting : used to separate larger sheets into smaller pieces. b)Bending c)Drawing b) & c) are used to form sheet metal parts into required shape.

Cutting operation/s Accomplished by shearing action between two sharp cutting edges.

Steps in cutting operation 1)Upper cutting edge (punch) sweeps down past a stationary lower cutting edge (die) 2)Plastic deformation starts as the puch pushes into workpart. 3)Penetration occurs as the punch moves downward, compresses the sheet and cuts into the metal. 4)Fracture initiated at the two cutting edge as the punch continues to travel into the work.

Characteristic feature of product

Contd… Rollover : Topmost region of the cut surface. This corresponds to the depression made by the punch in the work prior to cutting. Burnish : Just below rollover region. This results from penetration of punch into the work before fracture began.

Contd… Fractured zone : relatively rough surface beneath the burnish. Burr : sharp corner on the edge caused by elongation of the metal during final separation of the two pieces.