Blender 2.8 repair mesh

Question

I am new to blender.

I am trying to render a fountain pen nib (a parametric surface given by a set of three complex formulae) .

I have imported the *obj file to blender, and then extruded along local normals using proportional editing on. This gives me a completely broken mesh.

See :

or with x ray on :

Obviously, the mesh is broken.

I have seen this question. But it seems that one has to manually correct all the faces.

Is there an automatic way to correct the mesh? I tried :

Edit mode > Mesh > Cleanup > degenerate dissolve as well as : decimate geometry and delete loose. None of them helped. What can I do now?

Thank you

Edit :

the file after importing the obj (can't directly upload an obj file) :

The file after extrusion :

Answer 1

There was some manual work to do. I don't know how useful this answer is, but my steps were:

• S.001 Bring the object to a sensible scale, and apply the scale.
• In the 3D View 'View' tab, set Near and Far Clipping to be able to see the object consistently
• Note, by enabling Face Normals in Overlays, that the object is already 2-sided
• Also note, by seeing the face-dots around the perimeter, that there are degenerate faces connecting the inside and outside.

So.

1. ShiftG select the degenerate faces by similar area (0). Delete them.
2. Using CtrlL select (linked) all the inside faces and delete them.
3. Delete the bottom half of the object and replace with a Mirror modifier in Z, 'Merge' and 'Clip' checked.
4. Assign a Solidify modifier above the Mirror with 'Rim' unchecked to allow merging, towards the inside. This leaves gaps which can be filled, but no intersecting faces, which you're trying to avoid.
5. When it looks good, apply the modifiers.
6. Enable the 'F2' shipped Add-On. and use it to run round the gaps between edges, connecting by hand, (holding down F), because 'Bridge Edge Loops' fails somewhere, and I want to see where.
7. OK, got them, fix the topology at the points by hand. About half a dozen faces.

Bevel and subdivide, if wanted.

Answer 2

This is only to add some screenshot of Robins explanation of how to get your nib ready before adding the Modifiers.

1: In Object mode, Orthographic View with the nib selected open the Properties side panel with the N key toggle, > Item tab > Transform menu we see the nib is 10,000 times to big :

2: to correct this scale the nib by 0.0001 ( S 0.0001 Enter )

3 Next we need to Apply Rotations and scale. Ctrl A to open the Apply menu and choose the rotation and Scale option:

4: If we now switch to perspective View and zoom in on the model it will look like parts are missing.

5: This can be corrected by reducing the Clip Start Distance to less than a millimeter. Properties Side panel > View tab > View menu Clip start > 0.0001m :

6: Now we are ready to start the cleanup, Tab into edit mode and with the All the model selected open the Vertex menu > Merge Vertices > By distance and set the merge distance to something like 1 tenth of a millimeter, this will remove a Line of vertices along the center which may cause problems later on when using the modifiers :

7 And finally still in edit mode with everything selected open the Mesh menu > Cleanup > Delete Loose. this will remove a couple of loose edges:

Now you are ready to use the Mirror and solidify modifiers as suggested above.