Even if it was in good faith: 3D printed guns are not a problem. Even if you made one it is going to jam up very quickly due to softening and melting, if not just explode all together.
It would be easier, faster, and more effective to build a gun from things sourced at the local hardware store.
Even then, If someone is going to commit a crime with a gun they are unlikely to build it themselves. Most guns used in crimes are actually legally purchased, purchased at a gunshow, or purchased on the black market.
Anyone 3D printing a gun is doing it as a novelty. Because of that I don't see this as a second amendment violation. This is blantantly a first and fourth violation.