Export 3d Model Geometry Errors

I’m having a problem with exporting 3d models. I’m using 3d export to just export 2d faces I have arranged on the origin plane, but the geometry isn’t lining up. A lot of the arcs are just slightly off and leaving gaps in the part drawings. Anyone else come across this? I have the faces placed close to the origin.

From your screen shot I see two things that could be causing the problem. First, I see the negative blue axis which tells me your view is generally down toward the ground plane but it isn’t the standard top view. (The word “Top” would show in the upper left corner of the drawing window if it was.

I also wonder if you’ve set the camera to Parallel Projection. If not, you should.

Try those things: Parallel Projection and Standard Top view. Export again and see if you get better results.

And to get a more definite answer, upload your model here so people can check it for issues and also see whether they get similar problems on export.

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19000.skp (1.1 MB)

Here’s my model. I tried parallel projection top view but still had the same problem.

Hmmm… the parts that I’m having problem with were originally drawn in DraftSight and saved as a .dwg before being imported into Sketchup. Could that be causing my problem?

What format are you attempting to export?

If you export a DWG, try going into Options… and turn off everything except for surfaces and see if that yields good results.

Just tried exporting only surfaces. The geometry looked good with no open ends, but all the arcs were exported as small line segments, which I’m trying to avoid because these parts are for CNC. So exporting edges gives me clean arcs but open geometry, and exporting surfaces gives me closed geometry but bad arcs…

I’ve tried exporting using the different AutoCAD releases and as both .dxf and .dwg.

Hi @SubparFiddle

In SketchUp:
• Select all the edges
• Right Context Click on the selection > Explode Curve
• Select all the edges again > Weld … as in TIG: TIG-weld v2.0

Here’s the result:
19000_3D.dxf (785.4 KB)

19000_Welded.skp (19.4 KB)

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Simplicity has it virtues.
Try something simpler … http://www.cadstd.com/

It looks like what’s causing the problem is creating the part as a .dwg in DraftSight, importing that part into SketchUp and extruding into 3d, then modifying it in SkethUp. The modified geometry isn’t being exported the same as what was originally imported, even though it looks fine in the model… Would this be considered a bug? Or am I just making a mistake assuming that importing and exporting different file types should go smoothly? :slight_smile:

Ok, doing the same steps but with a .dxf file from the software Geo suggested worked great, so I’m gonna say it’s a problem with how I’m saving the parts with DraftSight. I’ll mark this as solved and try to figure things out on that end. Thanks for the help, guys!

As the Head Beagle around here once said, “No file conversion is lossless.”

One of the “Edges” involved in the episode was actually a 1-segment Arc entity.
Perhaps a ‘straight arc’ isn’t in every application’s vocabulary.

I closely inspected the areas around the problems, and I think that the way the outlines are joined together is confusing the 3d dwg exporter. In particular, when it sees that a sequences of edges are marked as an arc in SketchUp, the exporter uses the circle parameters of the arc in SketchUp to export a true dwg arc instead of SketchUp’s segmented representation. If you look at the attached screenshot, where I have used the line tool to expose the inference engine’s snap points for the two arcs that meet at the endpoint, you can see that the one for the arc to the right is not at the point where SketchUp’s segment representation meets the small arc. I think this is messing up the exported dwg. That is, the exporter is drawing a true arc to the same place as the inference point, not to the end of the segment representation.

Applying TIG-Weld repairs the problem by joining all the outline into a polyline, which causes SketchUp to discard all of the original circle parameters. If the resulting segmented representation is good enough for your CNC, that’s the fix.

This seems like a bug (or at least a limitation) in the 3d dwg exporter!

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One can even place a point at center of the ‘straight’ arc and measure the distance from the arc center to the problem intersection.

19000_Arc Radius Issue.skp (27.9 KB)

Yep, that’s another instance of the issue! Hard to say exactly where in the multiple export/import and edit process it happened, but in the end the SketchUp 3d dwg exporter doesn’t like that geometry.