The Neutral Zone is the line inside of the material where the metal neither compress or expands in the bend.

#3, Neutral Zones for different metals as follows, #2, Outside Radius on Bends equals inside radius plus material thickness. #1, Inside Radius on bends equals material thickness. I follow these few simple rules and usually get parts within 0.3mm Tol over 1000mm 6 to 8 bends. Laying out your profiles in third angle projection will give you granular control over the K-factors for bend allowances as you can draw single lines down from the middle of the radius to the bend line on the flat development.(Neutral Zone, Bend Arc Radius, Plastic Zone Length are different names for the same thing) An added bonus is I can easily add material to allow for shrinkage from welding.

If you are already using and are familiar with AutoCad, I recommend drawing your sheetmetal part (AutoCad not Inventor), I daily create complex sheetmetal parts including flat developments for CNC Punch / Laser then onto CNC Press Brakes all on the one drawing.

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