Exact ARC export in DXF
Illustrator internally represents curves as Bézier paths, while CAD/CNC workflows rely on true ARC entities (constant-radius circular arcs).
At the moment, there is no reliable way to export Illustrator geometry containing circular arcs to DXF while preserving them as exact ARC entities. All curves are approximated as splines or segmented polylines, even when the geometry is mathematically circular.
This creates a serious issue for CNC workflows, where exact radii and true arcs are required for correct toolpaths, tolerances, and part fitting.
A highly valuable feature would be:
• Detection of constant-radius Bézier curves
• Optional conversion of those curves to true ARC entities during DXF export
• Or an explicit “Export arcs as ARC entities” setting
Many users create simple technical drawings in Illustrator because of its excellent drawing tools, but currently must redraw all rounded geometry in a CAD application to guarantee accuracy.
Enabling exact ARC export would significantly improve Illustrator’s usability in maker, CNC, and fabrication workflows.
stefaan van damme
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stefaan van damme
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Thanks @Egor for the thoughtful reply and the references — they’re very helpful.
I agree that Illustrator is not a CAD application, and that CAD software is often better suited to interpret Bézier geometry and convert it into true arcs. In practice, CAD-side conversion options like the ones you linked are indeed the most realistic solution today.
That said, I still hope this conversation can live on as a forward-looking consideration rather than a closed conclusion.
Illustrator does provide the data it has — Bézier curves — but in many real-world workflows those curves originate from exact primitives and constrained constructions. Once that semantic information is discarded, the handoff becomes lossy in a way that isn’t always visible to users until fabrication.
Even if the primary responsibility remains on the CAD side, any future improvement in how Illustrator preserves, exposes, or flags known constant-radius geometry before export would be greatly appreciated. Not as an attempt to turn Illustrator into CAD, but as a way to make the transition between design and fabrication more transparent and intentional.
For those of us using Illustrator as an early step in automated or CNC-oriented workflows, small improvements in this area would have a disproportionately positive impact.
Thanks again for engaging with the topic — even acknowledging these edge cases already helps move the conversation forward. -
I feel the pain... Ai is not a CAD application because of this, among other reasons.
I feel like it’s the a CAD app’s task to detect these and convert... after all, Ai honestly provides the data it actually has — Bezier approximations for arcs. I personally think that 'Import Bezier arcs as ARC entities' feels like a more realistic option — and some apps have it:
1. https://www.engview.com/online_help/2024/package_designer/en/home.htm#t=ang%2Fdraft%2Fdraft-bezier-convert-arcs.htm
2. https://docs.ledwizard8.com/doc/lw8/8.17.18.1
3. https://forum.freecad.org/viewtopic.php?t=18077
4. https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/lisp-to-convert-curves-to-true-arcs/td-p/9160419
...and some scripts exist. After all, it’s like playing by the rules you don’t know.Many users don’t realize the circles in Ai aren’t real:
http://illustrator.uservoice.com/forums/333657/suggestions/33499646And there is a hack to display a constant width of a rotated circle the team had to implement to both confuse and stop confusing people:
http://illustrator.uservoice.com/forums/601447/suggestions/34684633
