Here are two examples and guides on how to cast pewter metal parts in 3d printed molds.
The first detailed guide is on Instructables and involves Lumi Pocket DLP printed mold:
Detailed guide is at:
http://www.instructables.com/id/3D-Printing-with-metals-at-home/?ALLSTEPS
Here is a different method presented in video by Ian Garrett who made a powder based mold on z-corp 350 3d printer: