Need custom import tolerance on STEP

Hi guys,
We need the ability to set a custom STEP import tolerance!
Solid works won’t let the user set the STEP export tolerance (at least I have only found proof of that)
And we need solids to stay solid. On large assemblies it is not an option to import as unjoined and then join part by part, so PLEASE give us this option asap.

Rhino 4 used to generate nice and tight solids. I know it could generate issues, but V5 allways generates issues, so that is not a step in the right direction for me.

Ref this earlier reputation that V4 had: “I don’t usually go back into Alias, but I do remember big headaches when I did. Using Rhino as an intermediary step usually kept everything tight. I had Rhino just for this sole purpose…”


@chuck, can you please help?

Hi Holo,

Can you attach a sample Step file please that shows the difference when importing to 4 or 5? Or email it to and I’ll get it filed right away.

I’ve just finished writing a new importer for polysurfaces that seems quite a bit better than both v4 and v5. It needs a lot of testing before I would feel comfortable putting it out for general use. Any examples would be appreciated. I’m not yet convinced that allowing users to set a tolerance is a good idea. There are several places that use a tolerance in STEP import of a polysurface. By default, they all use the same tolerance. In v4, I changed one or another based on the geometry encountered during import. Just changing all of them to a bigger number would not help in general.


Hi Chuck, thanks for looking into this!
I’ll more than gladly run a preliminary test for you. (make a plugin called something like testStepImport and I’ll give it a tough test)
The files I work on can not be shared, so if I have to make a new model then it has to wait until I have time to do so. But this applies to all STEPs that comes out of SolidWorks.

Great. That would be a big help. At this point, my new stuff is the v6 step importer which of course no one can get to yet. Some of the code is in the core of Rhino and probably should not go into v5 since it effects other things besides STEP. If I can figure out a safe way to get that part into v5 without any chance of messing anything else up, I should be able to get you something. Don’t expect anything right away, though. I have another project that has to come first. Also, if we get close to putting out a v6 WIP (I have no idea if this is the case!!!) by the time I can do this, I will just wait for that.


Chuck Welsh

Hi Chuck,
I import a lot of files from Solidworks which I have to fix, edit or modify. For me, V5 STEP import is far superior to V4 import. Editing V4 STEP imports was a complete nightmare. So many of the joined edges were bogus that it was easier to reconstruct the entire model in Rhino from scratch than it was to try to make changes to the imported STEP model.

I like the option in V5 to bring the model into Rhino without joining surfaces. I can then join the model at the tolerance I need and find where there are any naked edges (if any). I hope that feature is kept in V6.


@Chuck I have sent you several examples, over the years, of the stuff I get, do you keep those or do you need more?

Don Lewis

Hi Jim,

Yes, that will be kept.

Chuck Welsh

Hi Don,

I have a bunch of them that you sent over the years and do use them for testing.

Chuck Welsh