Fusion 360 DXF exports that other programs can actually read

Fusion 360 is the free CAD most laser and plasma people settle on, and its DXF exports cause a disproportionate share of import trouble: parts at the wrong size, curves that vanish, lines that cut twice. Those are three separate problems with three separate fixes, and none of them requires leaving Fusion.

Problem 1: the export route decides your units

There are two common ways to get a DXF out of Fusion, and they do not agree on units. Right-clicking a sketch in the browser tree and choosing "Save As DXF" writes the file in your document units, typically millimetres. Exporting the same design through the Fusion web hub writes centimetres, no matter what your document says. Autodesk's own knowledge base describes the sketch route; guides for laser cutting services recommend it for the same reason.

The symptom is unmistakable: a part designed at 100 mm imports at 10 mm, because centimetre numbers were read as millimetres. If your factor is 25.4 instead of 10, you have an inch and millimetre mix-up, which is a different problem with the same flavour. The wrong-size guide has the full table of scale factors and what each one means.

Problem 2: fillets and conics leave as splines

Fusion exports sketch fillets and conic curves as SPLINE entities by default. SPLINE is a NURBS curve, and many laser and CAM importers parse it badly or not at all: curves come in zigzagged, faceted, or missing entirely while every straight line arrives fine.

The fix inside Fusion is the free "DXF Spline to Polyline" add-in from the Autodesk App Store, which converts splines during export. The spline guide explains the failure modes and the alternatives (PEDIT in AutoCAD, the SVG route). LightBurn also maintains an official Working with Fusion 360 page that covers this pairing from the importer's side.

Problem 3: projected geometry cuts everything twice

When you project a body into a sketch, derive one sketch from another, or lay out parts that share an edge, the exported DXF can contain two identical entities stacked on top of each other. On screen you see one line. The laser cuts it twice: scorched edges, doubled cut time, and in thin material a burned-through kerf.

After importing into LightBurn: ungroup everything, then run Edit > Delete Duplicates (Alt+D). It removes objects that are identical in size, shape and position. The double-cutting guide covers the other mechanism (stroke outlines from traced artwork) and the fixes in other tools.

The export routine that avoids all three

A sequence that holds up in practice:

1. Keep the geometry you want to cut in one sketch, and only that geometry.
2. Install the DXF Spline to Polyline add-in once; it does its work at export time.
3. Right-click the sketch in the browser tree and choose "Save As DXF". Do not use the web hub export.
4. Import the DXF and measure one dimension you know, before doing anything else.
5. If the measurement is off by exactly 10 or 25.4, it is a units problem, not a geometry problem.

The measuring step is the one people skip. It takes ten seconds and catches the units problem while the fix is still one re-export away, instead of after a sheet of material.