Actually created this discussion for the poll to be more 'in the picture'.
Please go to the poll and please add comments to this discussion as well.
Provided you have set your y factor or your k factor, you can flatten bent parts if the bends are simple.
If you don't understand y factors or k factors, you need to review sheet metal fabrication techniques. A good place is SheetMetal.Me – Bend Allowance
It is very important to understand how sheetmetal parts are fabricated to get accurate results.
I'm currently using Creo 5, and my solution is next:
- use unbend instead of flat pattern to flatten the sheet metal part, because it keeps part unbend in further steps (model / unbend / unbend);
- make datum plane within thickness of a flattened sheet metal part (model / plane / offset);
- make cross section through this datum plane (view / section / planar);
- make datum curve from cross section (right click on cross section feature or: model / datum / curve / curve from cross section);
- analysis / measure / length: select x-section curve.