Hi Matadem, MoI does not have a general developable surface unwrapper. Check out Rhino for that.
But for the case of a cylinder you can try doing it in MoI using using curve to curve flow.
You will need to create a line that is the same length as the circle circumference. You can do this either by getting the length of the circle using Details... > Curve properties > "Length" and then create a line of that length or also the UnwrapCurve plugin mentioned by Brian above can do it. UnwrapCurve is here: http://moi3d.com/forum/index.php?webtag=MOI&msg=5136.1
Place the line at the bottom point of the circle like this:
Now select the curve you want to flatten. And run Transform > Deform > Flow. When the prompt says "Select base curve or surface", select the circle as the base curve. The next prompt will say "select target curve near matching end". Click on the line.
I do not have Rhino.
But I did find a quick solution
Export as 3d stl from Moi to Pepakura designer - unfold, export as dwg/svg back to Moi edit as needed then send to cut.
Hi Matadem, with that method watch out for gaps between pieces. Pepakura designer is more meant to handle low polygon output where you are going to fold paper along poly edges.
But it looks like it's handling your case as a larger developable surface ok.
As Michael mentioned Rhino is great for very accurately unwrapping surfaces. I've designed complex tube notched structures, unrolled the tubes, and used a cricket cutter to create full size templates. Everything fit perfectly in the real world and welded up nicely. It's amazing to have the ability to create a complete set of templates and jigs in moi3d that translates into a perfect fit in steel.
fl2.3dm