Sheetmetal Bending. Bending process Points: Sheet thickness (t) in range 1/64” £ t £ 1/4” If t > 1/4” then stock called plate Usually cold-worked, but warm worked if brittle material or thicker stock Tooling is punch and die Products are called stampings
A = bend angle
Bending model - springback
If R/t is small (R is punch radius), the sheet metal will stretch some, changing length of stock required to complete final shape. In effect, the neutral axis displaces from the center of the stock. The bend allowance (BA) accounts for this from the equation:
BA = 2 p A (R + Kbat)/ 360
where if R/t < 2, Kba = 0.33
R/t ³ 2, Kba = 0.50
and Kba is a stretching factor.
Examples in text show that punch forces are in the thousands of pounds rather than hundreds of thousands!
What have we learned?