Error exporting STEP from Inventor to COMSOL 5.1

[Anonymous]

Hi, I'm relatively new to Inventor, but have managed to make multiple 3D drawings which could be imported in the STEP format to COMSOL 5.1. However, as of today, it seems that my Inventor has lost its ability to do so for drawings of small dimensions.

Previously, I could draw a 500 micron radius quarter-circle and then extrude it by a few microns to generate a 3D solid. This could then be saved as a STEP file, which could be imported into COMSOL with no issues.

Now, I have tried multiple solids of small dimensions, but they all resulted in COMSOL giving me an Internal error code: 900 during import. A solid with big dimensions, such as a 0.125" x 0.188" rectangle extruded by 1", would have no such issue.

To check if this problem arose because of COMSOL, I tried to import my previously drawn solids, and there were no issues. I also could modify the dimensions within my previously drawn solids, and save it as another STEP file. This way, COMSOL would be able to import it with no problems.

Based on what I did, I believe this to be an issue with COMSOL, most likely with an automatic update or patch in September. I have tried this with both Inventor 2017 and Inventor 2016, but the same problems appeared for both cases. Does anyone know of a way to rectify this issue, or is anyone else facing the same problem?

Thank you.

[TheCADWhisperer · Accepted solution]

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@Anonymous wrote:

Hi, I'm relatively new to Inventor,...3D drawings 

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We usually refer to 2D as "drawings" and 3D as "models", bodies, parts or assemblies.

Can you attach a 2017 *.ipt file that exhibits this behavior when save as STEP format?

How far is the geometry from the Origin?

Is the correct Units set in export  Options?

[Anonymous]

Hi, TheCADWhisperer.

Noted on the conventions, I'll edit my main post in awhile to reflect those. (Edit: I couldn't edit my original post apparently)

Attached are two ipt files done with Inventor 2017. Testing07 is a small model, which could not be imported into COMSOL. Testing05 is a large model, which could be imported into COMSOL with no issues.

I'm not sure what you mean by how far is the geometry from the origin, but the geometry has a vertex at the origin.

I didn't see an option to set the units in the Export options though.

[JDMather · Accepted solution]

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@Anonymous wrote:

.... Testing07 is a small model, which could not be imported into COMSOL. ...., but the geometry has a vertex at the origin.

I didn't see an option to set the units in the Export options though.

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The 07 geometry was not at the origin.  For really large or really small geometry I would center around the origin.

For some software you might need to ensure that all of the geometry is within the positive octant.

[Anonymous]

I have managed to resolve this issue. Thank you, both of you, for asking about the units.

For STEP file, the export options do not have a way to choose the units. It only asks for Application Protocol and Spline Fit Accuracy. However, by going into Tools >> Document Settings to adjust the units to m instead of micron, and checking that COMSOL's import is taking m as its unit, and then saving a STEP file based on the set units, the import would be successful. Similarly, if I adjust the ipt file's units to micron, and change COMSOL's import units to be micron as well, it would work.

Ultimately, a mismatch between the units of the STEP (or IPT) file and the COMSOL import units has been causing this issue.