Hello there !
I am an average rhino user and lately I would like to make some mini concrete items via 3dprinting and silicone molding !
When I design something in rhino (eg. attachment) , when I will cast the mold I will get the ‘‘negative’’ of what I see… is there a command to reverse this situation ? I mean, I want to get what I see , so before molding, I need to reverse it hte rhino model or something …
I believe the best approach would be that after you have designed your part and made it a closed polysurface the next step would be to design the mold body so that it completely surrounds your part except for one side which is the side you want to pull your finished part from. The mold should be just slightly short on this side (just a tiny bit more than tolerance) of the part surface. This mold box should also be a closed polysurface. Then run the boolean two objects command from the solid menu.
Be sure to account for draft when designing the part. There’s a draft analysis command which will help assure there is no negative draft (locking).