Imported STL is broken


I import mm STLs at Meter setting. This one gets broken, The others, from the same source, do not. If I look at the original STL it is fine to print. After importing, I check it with SuSolid Pro and SolidInspector2 and it is broken. Without trying to fix it, I resize it and export the STL and it is not printable. Why is SU breaking this? The broken part is a ~9000mm hole on the side that has a mound around it on the outside. I have no idea how the STLs were created.
front1-front.stl (1.4 MB)


it imports as a 738641564753181440 mm³ solid group for me…

but, I use jim’s Mesh Importer rather than the STL importer…



@john_drivenupthewall That’s odd. I do not get a solid using either STL importer or the Mesh importer. Did you make any changes to your version of the mesh importer?

There were 2 minor issues, but Thom’s Solid Inspector picked them up and I now have a solid.


it was a simple import, zero tweaking…

it create a 4.7 MB .stl.skp and imported it fine…

this is it zipped… (1.2 MB)



I imported it with the latest revision of the STL importer and units set to meters so as to minimize small geometry issues. Selected all and made a component. Model Info reported it as solid with no other changes. Then I scaled it by 0.001 to get mm. All looks ok to me (of course, the curves have way too many segments!).


I do get a solid when I use the “Merge coplanar faces” option of the STL importer. I did not have it selected at first.


I imported directly to netfabb and it repots as solid.
The stl format is numeric but the SU importer does some conversion. Its been log time since looking at the plugin so would have to go back and check before quoting a value.
STL files do not contain the original reference geometry to reconstruct the solid and will at the very best result in an approximation. It is basically triangles for approximation to model
What happens is the resulting surfaces have many control points (both along and across) that are exponentially more complex and degraded. As a number of these surfaces are used to construct your model process get time consuming, inaccurate and unstable.
Bottom line:do not repetitively convert from stl to su. Limited Su to stl ok.


Attempted to open your original file above in my 2017 and SU froze; opened in 2016 Jim Foltz’s Importer
reported STL Binary file ; 29784 triangles Rhino Binary STL Jun 9 2014
Jims importer repaired geometry but the solid inspector reported many errors , no solid. it would not repair. I would not want to comment what issue is without much more test.


I imported it using the stl plugin with merge faces ticked and set to cm.
Imported no problem as a solid group.


I just updated the STL importer and ticked merge faces. It gave me something that had issues but SuSolid fixed them with 2 clicks. I could not fix it b4. Maybe there was a problem with the importer, but I would have expected it would have shown on all the imports I did.
It is weird that people get different outcomes, one being what I got.
thx for your time and input.