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K-Factor calculation from trial and error?

Question asked by Anjan Babu on Oct 19, 2017
Latest reply on Oct 19, 2017 by Dennis Dohogne

I did a 90 degree test bend of a mild steel sheet with a thickness of 3mm.

Calculated the K-factor of the test piece with reference to calculation mentioned here —

L1 = 27mm
L2 = 45mm
R = 3mm
T= 3mm
BA = 5.76 mm
R` = 3.6669 mm
t = 0.6669 mm
K = t/T = 0.6669/3 = 0.2223

My concern is, I’ve been reading that the K factor lies between 0 to 0.5 in most cases and I understand that a smaller K factor signifies a larger bend radius for thicker sheet thickness and such, does the K-factor value I calculated sound optimum to my sheet metal development application?

The fab shop where I do the bending owns an Amada CNC press brake, they do the bending with reference to the total length of the piece after the bend. Is that the correct method considering that I design the piece in CAD by placing the flange bend outside the material edge?