It's already being done, using very interesting technology. The printers are attached to multi-ton blocks of granite (IIRC) to counter vibrations. They're used

It's already being done, using very interesting technology. The printers are attached to multi-ton blocks of granite (IIRC) to counter vibrations. They're used to print out uncommon spectacle glasses. Several in use in North America. https://www.luxexcel.com/ophthalmic-technology https://www.luxexcel.com/ophthalmic-technology