Best practices for Importing STP files to R7

I’m hoping to find a “Best practices for Importing STP files to R7” specifically including Unit conversions from mm to in. and tolerance settings.

My workflow includes importing STP files to 3DM and then converting to DWG. Unfortunately many pcs of the product are missing on open of the DWG file.

Any help with this would be greatly appreciated.

Unfortunately, you have no control over the Units or Tolerance setting in a file created by others.
Many exporting applications, those are just values in a table and not tied to the actual modeling process that was used.
Rhino does not allow this disconnect when exporting to STEP.

First check the length of a known feature. This will tell you if the Units are correct.

As to Tolerance, the best option is to Open a sample file and look at those settings in the file.
Then isolate and Explode a representative polysurface, RebuildEdges to default tolerances, and Join again.

If you get a closed, solid polysurface, you’re all set and the settings in the STEP file were good.

If you get a partial Join and an open polysurface, Explode and RebuildEdges again. Then use the reviled JoinEdge command on a pair of surface edges that did not Join before.
Read the command line to see how far apart the edges are.

To Join, Rhino needs the tolerance to be slightly more than 1/2 of that gap distance.
Cancel out of JoinEdge, change your tolerance to the new value, and test Join again.

You’ll quickly zero in on what was actually used when the imported file was built.

Thank you John. The objects are showing as solid in R7 (after the explode and rebuildedges/join) however on save to DWG format they do not show up in the subsequent open in Rhino as DWG. I’m assuming that Rhino is finding some error and just deciding to not show the entire object?

If I go back to the provider what would be the best export method to ask them to use for importing into Rhino using the STP format?

If they are closed, solid polysurfaces in Rhino, then when you export to DWG, use the “2007 Solids” export scheme, so they are exported as ACIS solids.

Test that and open the resulting DWGs in Rhino to make sure they are as expected.

Thanks John, those are the settings im using. After I correct all the naked edges and the object is showing in Rhino as solid, once i save as a DWG and reopen it’s no longer solid in Rhino.

will you post a file so we can take a look at it?

I’d like to Kyle but its new product and I don’t have permission to share it. If I could figure out how to save it to DWG without it becoming an open poly or disappearing on me I’d be back in business. Its solid and visible in 3DM.

any chance you can send us a piece of it or a sample file that is not under NDA that we can try to diagnose?

Do you have a private address I can send the 3DM file to? I have permission to share as long as it is not public. This file has the same issue. The 3DM is mostly closed solid polysurfaces but become open polysurfaces when saved to DWG format. Even the repairs I make in Rhino remain solid as 3DM but break when saved to DWG.

There’s a link on the Support page to upload files to tech support.
Please include a link back to this conversation so we can associate the details to the file.


Thanks John. Sent via the Support page.