Most 3D printing technologies create a rough surface. It cannot even be polished without leaving porosities. This is anti-hygienic. The surface has then to be coated with silicone or epoxy gel. The difficulty is to find a reliable inner skin contact safe coating.
Stereolitography create a way softer surface. However I find the materials to be too fragile for a sextoy use. Another point is that I'm not sure that it is safe for inner skin contact.
I know that CLIP can use PU. This is a more reliable material. I'm quite insure about the inner skin contact part too.
One can make silicone molds. This seems to be quite safe but also quite time consuming.
What can you say about it ?