There is already FUD about 3D printing being used to create untraceable weapons for criminals.
Look, I get the point - excessive regulation is silly. But the idea of a 3D printed gun is without comparison in today's society.
Anyway, that said, I think you're wrong factually too -- 5-axis milling machines have existed for a long time and they can create practically anything a 3d printer can (with much, much higher resolution if you've got the money).
Now, either everyone should be allowed a gun without background checks etc., or lathes/3D printers/whatever that can manufacture a gun are a problem.
With computers, prices dropped and the learning curve wasn't much of an issue anymore. CNC Mills and lathes still require a much greater skill and up-front cost than a 3D printer needs. With CNC machines, there's usually still an additional necessary step required to turn a model into a tool path, based on your machines. So you still have a learning curve no matter which way you cut it (pun intended).
I don't think 3D printing will be a viable way to distributively mass-produce weapons, it's the fact that somebody already has been able to produce functional weapons with 3D printing, and it's comparatively much easier buying a $10K mill and generating tool paths.
I think you're not up to date with recent developments in this space. What you say is no longer true with things like Carbide3d and Carvey. With this new line of "Desktop CNC milling" machines, it's as easy as 3dprinting (if not easier). And the price is comparable (if not cheaper). E.g., compare the Carvey with a Makerbot... or an Ultimaker. It's cheaper than both. If you're willing to be brave and buy a kit, it's even cheaper. Heck, even before this wave you could get a CNC router for very cheap. You could be under the 4 figure range -- with 3d printing it's hard to go below 4 figures and get a decent and reliable machine (though admittedly it very much is possible).
When it's accessible to everybody it's accessible to the people we forgot were also included in "everybody", those with bad intentions -- or simply different ones, such as maximising their personal profit from an apartment rather than living there and being part of the neighbourhood. If we start seeing mainstream magazines talk about desktop CNC milling machines and classes pop up to teach kids how to use them -- and you know, with the Maker movement that's certainly possible and is probably already happening somewhere -- then these technologies become just as "dangerous" as 3D printers.
Systems can be abused through many mediums. If hobby CNC machining had gotten big like 3d printing earlier, certainly we would have seen exactly the same kind of rebuke as some in the 3d printing circles are receiving now. I think now it's particularly hard to come up with good answers. Regulating 3d printers seems difficult. After all, building one yourself from scratch isn't that hard (indeed, many do do this). So you don't know if and when the bad actors with intent to harm are making weapons. I'm an anti-gun person, so I think the answer is having no regulations of 3d printers, but coming down hard on people who misuse 3d printers in making very dangerous things.
You can't make a handgun with a lathe, though.
different tools for different jobs.
They're to mass-produced firearms what cheap bathtub hooch is to Jim Beam.
Wikipedia mentions them along with much more sophisticated designs:
... if you invest a lot in the proper materials, tooling, and skill set.
Not to mention, the results you'd see from a mill are much safer, reliable, effective, etc.
Well, you'd need a ball end mill, but you can definitely convert an 80% handgun to a 100% handgun in your garage, and it is 100% legal to do so.
I can personally 3D print one, turn one on a mill (CNC or not), drill-out an 80% AR lower with a drill press, purchase one, be gifted one.
A 3D printer is a poor, poor device among most of those options (and mostlikely more expensive).
You'll also notice that none of the above manufacturing devices are outlawed or regulated in any form.Why do 3D printers need to be called out?
The firearm itself serves no commercial purpose.
That is what I meant by "personal use."
Both activities are protected by the Constitution of the United States of America.