Casting a Mold using a 3D Print
"3D printing is also used to make tooling, such as molds and dies, as well as patterns for castings. Either the actual mold or the model to make the mold can be produced more quickly and less costly than with conventional methods."
"The mold from the 3D printer is relatively stiff and brittle, so a positive mold was created, followed by curing ST-1060 polyurethane to form a flexible negative mold for casting silicone."
-- Multi-Scale Compliant Foot Designs and Fabrication for Use with a Spider-Inspired Climbing Robot by Dan Sameotoa, Yasong Lia and Carlo Menon (Download the article)
-- Wow, is it surprisingly hard to find things on positive/negative molds for 3D prints...