Hypothetically you could make a machine that can self-replicate, but it would be on the level of complexity of many different fully automated factories, 3d printers would be one small part of such a machine.

Some things are just much easier to do with machining and grinding, like making linear rails to the required precision and surface finish.

Some things require completely different manufacturing processes, such as the electronics components.

There's also the issue of creating all the different materials required as input. You'd basically be automating a whole economy.