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Fusion - the Fusion 360 Bridge

Public Made by Adom

by adom

Drive Autodesk Fusion 360 from the cloud via Adom Bridge: component libraries, IPC package generation, board layout, exports (STEP/Gerbers/BOM/CPL), fast APS cloud search, and parametric modeling.

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Closed bug report

fusion_export_gerbers detects a 4-layer board as 2-layer (detectionMethod ulp) and exports only the outer layers

Glenn Jones · 7d ago ·closed by Colby Knox

We kept a list of tool issues as we worked on a project, the 772 power module (LM251772), a 4-layer board built with AI Flow on the Fusion lane, and set them aside so they wouldn't slow the build down. Now that the project is finished, we're filing them together. Some were seen on earlier versions; where we could, we checked that they still apply.

Versions: fusion-bridge 1.13.67 (seen 2026-11-03 and again 2026-11-04).

What happens: on a 4-layer board (layerSetup (1+2*15+16), inner planes on Route2 and Route15, JLC 4-layer stack), fusion_export_gerbers without layers reported 2 layers (detectionMethod: ulp) and wrote a zip with 11 files: top and bottom copper only, no .G1 / .G2. The reply said success. Passing "layers": "4" produced the full 13-file set.

Expected: detect the layer count from the board's layer setup (or the design rules' stack), and refuse or warn when the detected count disagrees with the board.

Related: adom-aiflow's fusion export doesn't pass layers either (filed there).

No design files attached; happy to describe more on request.

1 Reply

Colby Knox marked this in progress · 7d ago
Colby Knox · 7d ago

Thanks, Glenn. Fixed in fusion-bridge 1.13.72, which is public. Update the bridge; Fusion needs one restart to load the new add-in.

The old detection counted layers that carry traces, so inner planes that are only pours looked like a 2-layer board. fusion_export_gerbers now takes the count from the board's own stack, so you don't need to pass layers.

We tested a 4-layer board whose inner layers are only pours, with no layers argument: it reported 4 layers and wrote the full 13 files, including .G1 and .G2. A 2-layer board still exports 2.

The Gerber jobs cover 2 and 4 layers, so a 6- or 8-layer board is now refused (unsupported_layer_count) rather than exported with layers missing. We tested that refusal in code, not on a real 6-layer board.

Colby Knox closed this · 7d ago

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