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 — http://www.javelin-tech.com/blog/2017/06/calculating-bend-allowance/
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?
Anjan,
Unless you are bending the part in your own shop then you should let the vendor do his own flat pattern calculation. K-factors or bend deductions will vary greatly from shop to shop. This is highly dependent on the tooling and technique. A lot of modern shops these days can take your fully formed part and flatten it themselves using their own method and values. A lot of these shops have SolidWorks so they can use your part file and flatten it directly using their method. If your shop is any good they will share this information with you so you can also make an accurate flat pattern for them.
If your value R is the inside bend radius of 3mm and the thickness is also 3mm then I would expect a K-factor of closer to .4 rather than the .22 you came up with. Attached is the explanation and calculation of K-factor I have used to teach others. In my experience, the biggest mistake people make in determining K-factor or bend deduction is to assume the material thickness is the nominal published value. Even your own information shows a thickness of 3mm. I'll venture to bet that if you were to measure it with a micrometer or caliper that it will be something a little less than that.