Create new object from selected faces in mesh


I am a newbie at Blender and am trying to modify some stl files for use in 3D printing. I think there is probably a simple solution to my issue, maybe someone can help me.

I have a surface model of some patient anatomy (could be a skull surface, etc) in an stl file. In order to 3D print an area of that surface in a different color (I have a cubex trio 3 color printer), my printer software requires that I load that area as a separate stl file. So, what I would like to do is:

  1. Select a region of the surface. This is easy, I can do this manually but maybe in the future I can find a way to use some other technique that uses some other outside information to decide which faces in the mesh to select.

  2. Duplicate that region, and create a new object from it, without moving it. I see how to duplicate (shift D), but the result is still a part of the original object. I REALLY don’t want to move this new object, the surface may be a complex curved shape and getting the new object back to its original location seems tricky.

  3. Give the new object some thickess so that the printer software will be ok with it. It only needs to be 1mm or so. I could extrude the object, maybe? Otherwise I saw an online tutorial that showed how to add the thickness modifier to an object, that looks like a good way to go. I would like the extrusion to be towards the interior of the surface, so that the final printed object doesn’t have a bump-out where the different color is.

  4. Having created the new object, I would then add a boolean modifier to cut the new object out of the original surface. Then I would have two objects, where the new one is a ‘plug’ in the surface of the original object. Presumably I would have no problems exporting them separately as two stl files.

Any suggestions highly appreciated!

Kent Ogden

Separate selected faces to make a new object with shortcut P in edit mode.

Add thickness with a solidify modifier


Thanks for the tips. That is what I finally figured out how to do, but first I had to duplicate the selected faces. After duplication, I left click being careful not to move the new mesh, the duplicate, then solidify. I then verify that the created object doesn’t have any funky parts that should be smoothed out (the original surface has a lot of curvature in places and weird things seem to happen sometimes when solidifying. Finally, I add a boolean difference modifier to the original to make a hole for the new object to fit into. Works great.:slight_smile: