How to calculate unfolded length of a bend in a sheet metal part?
The formula for working out the developed length (unfolded length) of a bend where material tends to stretch or compress during the forming process.
To achieve accurate results please perform practical test to confirm results as material can stretch based on the forming process.
Developed length = Circumference at Neutral Axis (L) + Straight length
L = (Rad + C) x 2Piθ
Where θ = bend angle in degrees
t = material thickness
R = internal radius
Value of C
For R < 2 x t C = 0.33t
For R = 2~4 x t C = 0.4t
For R > 4 x t C = 0.5t