Autodesk Inventor

[#1]

Inventor 2013-I'm working on a sheet metal cover using contour roll and I find when I dimension the flat pattern that radii that should be the same are not. Can someone tell me if my approach is fundamentally flawed? I  tried making this part out of one 220 degree contour roll and I found when dimensioning that the center points of the arcs are not symmetric as expected. I then used two contour rolls to create the part basing the second contour roll on the first contour roll sketches and I still have the same issues. Any thoughts would be appreciated. Thanks

[#2]

You most likely need to read up on Bend Allowance Factor. This will vary according to the type of bending procedure used. The Flat-Layout length is determined by the neutral axis through the material. Not quite the center line of the product.

The attached spread sheet might help you out.

[#3]

Check this example.

[#4]

thank you for you quick reply, I took a look at the spread sheet and  it looks like I have a lot to understand in order to properly apply all possible variables to my project. In the mean time while I try to figure this all out and understand the spread sheet, does it make sense that these variables create the problems in symmetry that I see in the flat pattern dimensions?

[#5]

thank you for you quick reply and example, your solution sure is elegant compared to my attempt. now I have to go back and see if it fits my mating part and if I can create the remaining parts to the cover in a similar fashion, thanks again.