Build your own superhero

Step 4: Start machining

Alright, it's time to get down to the business of creating body parts.  With your toolpaths ready to go and your foam clamped down to the bed of the CNC machine, you place the correct bit in the router and let it run. If you have a variable speed router you'll want to slow the router speed to the slowest setting in order to cut the foam and not melt it.  You'll also want your dust collection working well since the fine foam particles can trash not just the linear motion of your CNC machine but also the router itself.  Don't ask me how I know this.

First comes the roughing pass and then a bit change and the finishing pass.  Once the finishing pass is complete and you have the two halves of a particular part, you'll see what I mean when I say that there are limits to the CNC process.  The parts will be close but due to the orientation of the part and other factors, they won't be perfect.  Don't despair.  This is where some 80 grit sandpaper, glue and spackle come into play.  If the part is at the extremities (head, hands or feet) it's okay to glue them together and start sanding/Spackling.  If the part it anywhere else (torso, legs, arms, rocket pack), you first need to create a channel between the halves for the PVC armature to reside. 

It does take some planning on exactly how you intend to tie it all together because once glued, sanded and spackled, there's no going back.  The 1/2" PVC used for the armature has an outside diameter of approximately an inch, so I created slightly oversized channels in all the limbs, torso and rocket pack for the PVC to reside. I then used expanding spray foam insulation such as "Great Stuff" to fix it in place.