Makes me think a better idea would be to 3d print something like a ceramic outer shell and just fill the void with casting grain. I assume there's some reason you can't print thin layers of clay and then bake them under the print head.
Hobby level clay 3d printing is still in its infancy. Current nozzles are >1.0mm, which are too big to create parts like this. Works for creating vases/decorative stuff though.
