Question

How do ribosomes exit the nucleus once formed?

Answer 1

The ribosome units leave the nucleus through the nuclear pores and unite once in the cytoplasm for the purpose of protein synthesis. When protein production is not being carried out, the two subunits of a ribosome are separated.
Hopefully that was of help to you :)

Answer 2

ribosomes exit the nucleus by difussing via aquaporins (small transmembrane protein similar to those in facilitated diffusion and creating ion channels