Here’s an example of creating a core and cavity mold of a simple tray. Both core and cavity are 3" away from the tray. I made them semi transparent for this demonstration. The top of the tray is the parting line.
First, move the cavity to the parting line and subtract the tray. Delete that portion from inside the tray. Next, extend the core so that when it is moved 3" to meet the parting line, it is fully embedded in the cavity. Subtract the cavity from the core then subtract the tray from the core.
(Note: Instead of deleting that inner portion inside the tray, I could have left it there and after subtracting the cavity from the core, I could have done a union of the core and that portion.)
Let me know if any questions.
-Mike
