I’m trying to do an imprint of one object within another.
But this is what happens:
It always happens after I use the “spin” tool. How can I fix it? I already tried to “remove doubles”, it didn’t help.
have you tried flipping the normals after the spin operation?
Looks like the spin tool creates geometry with flipped normals in this case, causing the boolean modifier to invert inside/outside. You can tell the normals are flipped by the slightly darker shading. Select all your faces and hit CTRL+N to recalculate the normals.
You can try reporting this is as a bug, but I’m not sure the spin tool is even supposed to be used like that. Maybe it’s not meant to be used on a solid shape and this “works” only by accident. You’d normally use it on a profile (a couple of edges without faces) to sweep out a shape.
Recalculating the normals did the trick, thanks a lot 