A sheet metal fabrication shop needed flat blank dimensions for a 4"×6" box enclosure in 14ga mild steel — four 90° bends, each with a 0.125" inside radius. Instead of estimating, the estimator ran all four bends through IronKit's Bend Deduction Calculator and got a precise flat blank length of 14.372" (the sum of 5 leg sections minus four BD values). The part was nested on a 4'×8' sheet with 0.062" cut allowance per blank, gaining an extra 2 parts per sheet over the previous guess-and-check method.
Frequently Asked Questions
Why do I need 5 leg lengths for a 4-bend box?
A box opened from the top has 4 bends connecting 5 flat sections: end panel → side → bottom → side → end panel. The last section (leg 5) is the other end panel. You enter a Leg A and Leg B for each bend row, but Leg B of bend N is the same as Leg A of bend N+1. IronKit handles the chain automatically — just enter each bend's legs and it sums correctly.
How does K-factor affect nesting efficiency?
If you use the wrong K-factor, your blank length is off by K-error × thickness × angle (rad). For this box with 4 bends, using K=0.50 instead of K=0.38 adds 0.009" error per bend — 0.036" across all four. That seems small, but at 14ga material on a 4'×8' sheet with 0.062" cut allowance, it can cost you 1–2 parts per sheet. On production volumes of 500 parts, that's waste that adds up fast.
What if not all bends are 90°?
Enter each bend with its actual angle. IronKit computes BA and BD per bend using (π/180) × angle × (radius + K × thickness) and 2 × tan(angle/2) × (radius + thickness) − BA. A 90° and a 120° bend on the same part each get their own calculation — the K-factor lookup uses the r/t ratio for each bend separately.
How does IronKit calculate flat blank length?
Flat blank = sum of all leg lengths − total BD. For this 4-bend box: 18.000" − 0.628" = 17.372". Each bend deducts its own BD independently. K=0.38 is the Machinery's Handbook air-bend value for mild steel at r/t = 1.67. Override K per bend if your tooling has been measured differently.