Throw out some bait, see what I could reel in. No bites (yet.)
You have a valid point, of course in your above comment, but I seriously doubt even in the future we'll see anything other than single shot pistols, rifles, and shotguns printed from the home. Any repeating weapons and any weapons that fires high pressure cartridges are going to need some kind of metal reinforcement, period. Without metal of some sort a semi-automatic pistol is simply not feasible.
There was a great "fear" in the 80s and early 90s that untraceable weapons would be made and proliferate American streets with the advent of the polymer pistols such as the Glock. Well that fear was unfounded, and absurd, given that the core operating component is made out of metal.
Right now the liberator pistol is only good for a proof of concept and to ruffle some feathers. I guess if you were ballsy you could load it up, and sneak up on someone who actually had a gun on them, shoot them, and take their real gun. Oh wait...t
hat's what the Liberator pistol is for in the first place.
That said, I could build an AK type rifle at home for less money than it would take to get a decent 3D printer. And I have done that. Mine has a serial number but my friends' AKs don't. I have an AR-15 lower receiver without a serial number that I "manufactured" using a drill press. I took some shop classes in high school and that's the extent of my technical knowledge.
I guess my point is that the scary future where anyone can easily make weapons in their home is already here. It's just this time the geeks are bringing us the weapons and not the tradesmen and craftsmen.