Exporting obj "generates/creates" intersecting faces

#1

Hi everyone, we are running in some issues here and we can’t figure out what is going on… Little background info here: Our products are 3d printed and created in 3ds Max. We check these with Magics and normally this is all fine. However, we have a software partner which needs to have obj files. Our obj files aren’t any good because they contain intersecting faces. We can’t figure out why though. They told us to check our files in blender but blender creates new intersecting faces upon exporting the obj. Even when we cleaned them with the 3d printing toolbox and export the seemingly "clean file, once we open it new intersecting faces appear… If we repeat step 9 -12 from the process, eventually, the mesh will be “clean”. This can’t be right, can it? Unfortunately I can’t include the file due it being part of our protected intellectual property.

Here’s the process:

[ol]
[li]STL import in Magics
[/li][li]Full Analysis
[/li][li]Automated / manual fix file to 0 flipped triangles, 0 bad edges, 0 bad contours,
[/li][li]Export STL from Magics
[/li][li]STL import in Blender
[/li][li]3D Toolbox -> check all
[/li][li]Manual fix file to 0 intersecting faces and 0 non-manifold edges
[/li][li]Export OBJ from Blender
[/li][li]OBJ import in Blender
[/li][li]3D Toolbox -> check all
[/li][li]Manual fix file to 0 intersecting faces and 0 non-manifold edges
[/li][li]Export OBJ from Blender
[/li][/ol]

For those who don’t know what Magics is: http://www.materialise.com/en/software/magics

#2

huh that looks like one complicated procedure to get your meshes cleaned up.

have you tried loading the file directly in blender and using the 3d printing addon to identify issues?
https://daler.github.io/blender-for-3d-printing/printing/mesh-problems.html
maybe it gives a hint if the original model has already some issues or if this Magics software creates some additional problems. i would be suspicious of any software that has the name magic in its name:D sounds like they have a make nice button as well:D (just kidding here^^)

we work a lot with cad data and scanned 3d data and i never seen blender creating new geometry that wasnt there in the first place so i would assume this happens somewhere on the way in your pipeline?

you could also use meshlab to clean up the mesh and see if it does also create this unwanted geometry.