Holes In Rolled Sheet Metal Parts

[stammerde]

I am having trouble placing holes in rolled sheet metal part in Invetor 2010. I have used two different methods:
1) Creating sketch planes through the axis of the roll at the correct angle and blasting the hole through all.
2)Using the unfold command, placing the holes, and refolding.

Method 1 results in deformed holes in the flat pattern and poly-lines in the exported dxf. We have had several parts come in missing the poly-line holes.

Method 2 results in a correct flat pattern but a model that is very difficult to constrain in assemblies.

Is there a better way to create these holes without the issues I'm running into?

 

[rollupswx]

There is another trick involving a sacrificial face and Project Flat Pattern. Then Cut Across Bend.

But what is the problem with constraining in assemblies?

Can you attach your file here?

 

[stammerde]

Once you refold the part the holes are no longer circular and have no center line, so you can't locate other parts using hole centers. All your constraints become angles and tangents (constraints I try to avoid if possible). Mating to the surface can be done, but it doesn't work quite like you'd expect. Constraining these parts just becomes cumbersome and sometimes inaccurate.