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Trouble modeling undercut form block to compensate for springback on aircraft rib flange

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asdFletcher

Mechanical
Oct 5, 2012
11
NX 8.5, Windows 7 64 bit

We are looking at hydroforming some aircraft ribs. The ribs follow the outside shape of the aircraft skin so the web does not have straight edges and the rib flange angle is variable along the length of the flange, including joggles. The question I have is regarding the form blocks - the solid piece that will be used to form the parts. Modeling a block that fits the inside of the sheet metal rib "exactly" is easy enough, however, if I want to over-bend the flange to account for springback the form block will have a different shape than the rib. The desired shape is going to be the local flange angle + X. Where X is a constant that we'll play around with on some test parts. But must be the same for all parts in the family.

I don't think there's an NX feature that can detect the local angle between two faces and then do a "relative" draft...

I've tried offsetting my face back into the part and then drafting the top edge out (close but not precise, works for straight flanges), and I've tried using the Synchronous Modeling feature Angular Dimension (doesn't recognize flange face, but does work on any straight flanges).

Does anyone know how to do this? Is there a module that has a magic "relative-draft-angle" feature? The closest I've been able to come is doing an Offset Curve in Face on the bottom of the form block, then re-building the flange surface with a Thru Curve Mesh using this new line as an edge. Again, close but A.) not quick and B.) not entirely precise.

Would the 'Aerospace Sheet Metal' module have something like this? Or one of the Tooling Modules?

See attached picture for a general idea of the flange

NX 8.5, Windows 7 64 bit

Regards


The tool and target do not form a complete intersection.
 
 http://files.engineering.com/getfile.aspx?folder=658c8beb-9371-4f5b-9099-fe6428297980&file=hydroform_flange.png
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