i have been using sketchup (and it’s predecessors) for 15 year or so. i am currently using Make 2015 pro on a mac os x system. i am trying to make a cylinder with another cylinder running down the center; when i try to modify the inner wall of the outer cylinder by deleting a segment, the center hole keeps “healing”. what is causing this and how can i keep it from happening…? i have searched and searched for an answer and am getting desperate.
a worse problem is that when i create a model for 3d printing, export it to .stl it will look fine in meshlab and then when i submit it to shapeways the “holes” often heal up. the sketchup model looks fine, the .stl model looks fine in meshlab, but the shapeways rendering is “broken”…?