We're going to do all of this using Blender, a very powerful free tool for 3D modeling. getting the scaling right, adding some detail, and then cutting everything up into pieces small enough for printing.
I'm going to cover cleaning up the models, giving them thickness. I didn't find any really thorough guides already, so I collected all the information on the problems I've run into and the techniques I learned to solve them, and put them in this tutorial. It turns out that 3D printing pep files is a lot harder than just converting them to STL and hitting print. I've been working on 3D printing a Mark III Iron Man suit based on DancinFool's Pepakura files.
