Functional Design Using Design Accelerators - Autodesk Inventor 2010: No Experience Required - page 359

Unfold and Refold are arguably the same tool, but they need to be calculated
independently because you may need to create more than one unfold and refold
or a different set of unfold features at once. Even the dialog boxes for the two are
the same except the name at the top.
The dialog requires a stationary reference to get started. This can be a fl at face
or an edge. Most often it'll be a fl at face, unless you have a bent part without a
fl at portion. I select the stationary reference as though it were the portion of the
part I would hold on the table while fl attening the bend(s) that I wanted to
fl atten.
You can unfold as many bends as you like; there's even an Add All Bends
option to speed things up. As you select bends to be unfolded, give Inventor a
moment; it will calculate a preview of how the part will look.
If there are 2D sketches on a face or hanging over a bend from a face, you can
include them in the Unfold feature as well.
You'll use the Unfold tool to see what your cut needs to be. Then, you'll refold
your part after you make the cut.
Making the Cut
When you unfold a part, you're in essence re-creating the fl at pattern. On a
complex part like this, I sometimes clear the fl at pattern before using Unfold:
1. In the Browser, locate and delete the fl at pattern for the duct.
2. Start the Unfold tool, which is in the Modify panel of the Sheet
Metal tab.
3. The dialog needs a stationary reference. Pick the fl at, vertical face to
the left of the bend that you split. See Figure 7.52.