What if robots start self-replicating using 3D printing?

They won't,, indeed can't, do that alone.

Whilst it's perfectly possible to use 3D printing for some of the components (others, and of course the printing materials, would need be bought from elsewhere) , both the machines and products have to be designed and set into operation by people.

Ultimately the so-called "robots" are only machine-tools.

https://en.m.wikipedia.org/wiki/Gray_goo

Good, maybe they can fix the supply chain shortage...then they'll eat us...

Can't you print a 3D printer with a 3D printer?

The guy robots will only put in a huge hard drive and send pics of it