Exporting Rhino to Solidworks 2010

Hi,

I use .STEP file extensions to export to solidworks. It seems to open well. After it asks me if I want to run import diagnostics and I say yes, it shows me any surfaces that need to be fixed. I use the automatic healer in solidworks to fix the issue. When I try to make 2D drawings using solidworks or when I try to dimension a specific feature on the 3D model, solidworks gives me an error message and tells me “the selected entity could not be converted into a line or a circular arc.”

Also when I dimension an angle in Rhino on my model it tells me it is 90.0000°. Then when I dimension the same angle in solidworks it shows me the angle is 90.0024°.

All this becomes a problem when I send a part to a manufacturer and he opens it using solidworks and tells me he has to fix up the model to get it right.

Are there settings in Rhino I can fix to help mitigate this issue?

Thanks!

Hi bingbang - can you post, or send me via private message, a simple Rhino file and the resulting Step file that shows this problem?

thanks,

-Pascal

Hi,
These problems are most of the time not problematic geometry but how SolidWorks queries the geometry:
When it says “the selected entity could not be converted into a line or a circular arc.” it’s because the surface intersection with the current workplane does not create an arc. The model could be in a slightly different orientation than standard SolidWorks planes or the surface is not a simple fillet (or other surface with a circular section). The same with the angle measurement, SolidWorks projects the surfaces edges to the current view workplane.
The best would be to post an example here.

Hi @pascal, I sent you some models. Thanks for your help!

This makes sense. Is this a translation issue? Is it a tolerance issue?

I’m seeing more than one location in the Rhino file where the nominally 90 degree angles are not quite 90. 90.026, 89.992, etc.

-Pascal

Yes that’s probably true. I know that when I’m making the models in Rhino, I’m making them the exact measurements that I need. Over time, when exploding and joining the model or just extracting a specific surface and rejoining it to the model, is it possible that the tolerances depreciate? If so, how can I guarantee that my models are ever exact, even before exporting them to other programs?

In themselves, no, these operations would not change the angles between planes, which is what I was checking. (I did not measure angles between edges)

-Pascal

Occasionally, when performing a boolean command, I’ll receive a message that tells me the tolerance had to be doubled in order for it to work. Could this have something to do with it? I can’t recall specifically if any booleans were used in the making of the part I sent you. Just trying to add information and give you as many facts as I can to help you out.

That is also unlikely - but apart from that, that message should encourage you to Undo and check things - see what the curves of intersection (Intersect command) look like between inputs - are they clean? Are there coincident or near-coincident surfaces or edges in the inputs?

-Pascal

Good to know. Will do that going forward. Any advice regarding the original issue?

See if DivideAlongCreases > SplitAtTangents-Yes before exporting makes any difference. It will not help any inaccuracies but it might allow SW to find more arcs and lines in the geometry.

-Pascal