Sheet Metal Working

Apiwat Muttamara

Historical Note;Sheet metal stamping was developed as a mass production technology for the production of bicycles around the 1890’s. This technology played an important role in making the system of interchangeable parts economical (perhaps for the first time).

Stress Strain diagram

A

BC

Basic Sheet Forming Processes(from http://www.menet.umn.edu/~klamecki/Forming/mainforming.html)

Shearing

Bending

Drawing

Shearing of sheet metal between two cutting edges

Schematic of a Blanked Edge

Blanking & Punching(Piercing)

Shearing Operation Force Requirement

Die

SheetPunch T

D

Part or slug

F = 0.7 T L (UTS) T = Sheet ThicknessL = Total length ShearedUTS = Ultimate Tensile Strength of material

F = T L (Shear Strength)

MPa= ? 10.1 kg/cm2

Bending Force Requirement

PunchWorkpiece T

Die

L

Force

T = Sheet ThicknessW = Total Width Sheared

(into the page)L =Span lengthUTS = Ultimate Tensile Strength of material

Engineering Strain during Bending: e = 1/((2R/T) + 1)R = Bend radius

Minimum Bend radius: R = T ((50/r) – 1) r = tensile area reduction

in percent

)(2

UTSLWTF

Minimum Bend radius: R = T ((50/r) – 1)

r = tensile area reduction

in percent

Engineering Strain during Bending: e = 1/((2R/T) + 1)R = Bend radius

Bending of sheet metal;both compression and

tensile elongation