negative k factor required (but not possible)

[travis]

I'm running a brand new cnc press brake with new tooling, and trying to bend a 12 ga angle with 1.25" x 1" legs.  Both the tooling company and machine manufacturer has confirmed i'm using 'middle of the road' tooling (not too sharp of punch, not to wide of die... just right)

when i set 12ga (.1046) to a k factor of 0 in fusion I get a flat pattern dimension of 2.096".  My machine states the flat pattern should be 2.053".  Based on test bends, the machine is correct..  for a single bend part I don't really care, however we do 6 bend parts and the difference adds up.  Based on this information I should be setting a negative K factor in Fusion.... but that's not possible.

any help is much appreciated

[TheCADWhisperer]

Can you File>Export and then Attach a *.f3d file here and indicate dimensions that your machine calculates (if there are also other bends than the one you have already stated.)?

[travis]

I produced a more straight forward file to show the issue I'm having.  Attached is a 14ga angle 2" x 2" x 2" long.  my press brake flat dimension is 3.78664".  The sheet metal settings in this file have a K factor set to 0 and the flat pattern dimension is 3.819".

Please let me know if you need more information... thanks!

[TheCADWhisperer]

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@travis wrote:

...my press brake flat dimension is 3.78664". 

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Can you show some sort of verification that the radius of .0747 is set.

[travis]

You mean in my press brake?  It bases it's flat pattern and back gauge equations on the tooling loaded.  My punch is .063 tip radius.  I changed that in Fusion and now my flat is 3.824"... still too big. 

I noticed that each bend seems to be roughly 1/16" over what my press brake tells me.  Could fusion be thinking that i'm coining?  I'm currently air bending and I know there is some material lost when the tooling bottoms out.