I was trying to model my object for 3d-printing and faced this problem. I use 3D Printing Toolbox
in Blender v2.79
. And checking my object for manifoldness, it shows me that I have Bad Contiguous Edges
. I don't know what to do with it.
On this picture, that edges are selected. And 28 Non Manifold Edges are because I haven't used Mirroring yet.
3 Answers
In Edit mode, I pressed A to select all, then Mesh->Normals->Recalculate Inside. This fixed it for me as my problematic edges were inside a cylinder recess in my object.
Select the face, then in Face Menu / Face Data, click "Reverse UV". That generally happens when a face is made on the wrong side.
Additionally, you will need to use "Mesh / Normals / Recalculate Outside". Seen that with parts of bottom faces detected as top in STL exports (bad color seen in Cura for the example)
Just re-calculate normals(Ctrl+n with everything selected in edit mode). That fixed it for me.