Dxf export went wrong - example

The attached plate sent for CNC cutting has altered itself during the export to dxf operation and I don’t know whether the geometry or the settings has caused the corruption. Lucky for me, the operator didn’t think it looked right…

The closed curve originated from the border of an unrolled surface, then converted to arcs before exporting.
The curve was sent as a mirrored pair and it’s only the mirrored curve which has the problem.

Test - Mirrored Plate.3dm (91.7 KB) Test - Mirrored Plate.dxf (198.6 KB)

Brian, there was something wrong with the big shape inside the rectangle. I couldn’t get it to convert, so I ran curveboolean on it and that fixed it up.
Do that, then convert, then export and you’re good to go.

Thanks for that tip CarveCream, I tidied it up with a split and fillet at the time, but I’m curious to know why the curve messed up in the first place so I can look out for similar situations in the future, and catch them before the CNC - so easy to miss when just one sheet of many and this was a large part.

Brian, to help catch this stuff in the future, the workflow leading up to final export of parts to cnc needs to include, among other things, convert. This will almost always show you problem curves quite readily.

Good advice CarveCream, however, I do convert to arcs before exporting to dxf, as is the case with this curve.
I just had another look, and it turns out if this particular curve is exploded and rejoined then it exports as expected.
It also works as expected when the maximum angle setting is unchecked, which is the reason I wondered whether the problem is geometry or settings? The angle at the problem corner is 90.1, maybe a tolerance thing happening.

Hi Brian- I just exported this using the ‘CAM Metric’ scheme in dxf, and it comes back in as expected- what scheme did you use?


Hi Brian,

I believe the issue was in the settings for the scheme used. If I’m not mistaken you used the R12 Natural one but a slightly altered version from the defaults which are below…

If you disable the simplify option, the curve is not altered as in the mistake. I also found that a couple other schemes worked well for this curve as shown. The portions of the curve running horizontally from the corner are arcs and I believe the simplify option was causing them to be simplified too much. Maybe just keep this setting off for the R12 natural scheme unless it becomes necessary to use it. I’ll check with some of the Acad gurus here like @mary as well to see if there is a way to check export deviation other than importing the result again.

Thank you all, for the time checking this. The scheme settings I used are:

I’ve used these settings many times without issue, but I’ll uncheck the simplify and change polycurves to the bulge arc setting and run with it for a while and that yields a good result in this case.