Sheet Metal Bending

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 – materials selection

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

Shearing

Bending

Drawing

Shear and corner press

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

Shearing of sheet metal between two cutting edges

Schematic of a Blanked Edge

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

UTSL

WTF

Bending of sheet metal;both compression and

tensile elongation

Springback

• Over-bend• Bottom• Stretch

tension

compression

Pure Bending

Bending & Stretching

Springback