Please check out our Titan 1 3D printer, with a patent-pending technology, which is the only versatile high-resolution professional-grade stereolithography printer in the market for different applications. The Titan 1 specs are comparable to that of $50,000 printers. All for $2999. Our rings don't require any internal supports:

We also offer a castable resin that is compared to EnvisionTEC's resin. http://www.kudo3d.com/product/castable-resin/

We printed 17 rings at the same time without internal supports. http://www.kudo3d.com/blog/portfolio...-noah-beasley/

Please let me know if you have any questions that I can answer, you can email me at catherinepark@kudo3d.com.