Fusion System Blocks

Draw system block diagrams right inside Autodesk Fusion.
Plan how your product fits together — without leaving your CAD environment.

---

What Is This?

Fusion System Blocks adds a diagram editor to Fusion. You draw blocks for the parts of your product — a motor, a circuit board, a sensor, a piece of firmware — and draw wires between them to show how they connect: power, data, mechanical linkages, and more.

The diagram is saved inside your Fusion design file, right next to your 3D model. Anyone who opens the design sees both the physical model and the system plan in one place — no separate Visio or PowerPoint file to keep in sync.

An example system diagram with blocks, connections, and grouping.

What you can do with it:

• Draw blocks in 8 shapes, color-coded as Electrical, Mechanical, Software, or Generic.
• Connect blocks with typed wires (power, data, signal, and more), with arrows and tidy right-angle routing.
• Link a block to a real component in your 3D model, so the diagram knows the part's name, material, and mass.
• Track progress: mark each block as Placeholder, Planned, In-Work, Implemented, or Verified.
• Run Check Rules to catch problems — unconnected blocks, voltage mismatches, power budgets that don't add up.
• Save snapshots of your diagram over time and restore any earlier version.
• Export reports: PDF, bill of materials (BOM), connection tables, diagrams as images, and more — 11 formats in total.

Heads-up: this is an early release (v0.1.1). It works well for personal and school projects, but expect some rough edges, and keep backups of important work.

---

Installation

You do not need to know anything about programming. If you can install a Fusion add-in, you can install this.

You need: Autodesk Fusion (current version) on Windows 10/11 or macOS. Nothing else — no extra software.

Step by step

1. Download the latest release ZIP from the Releases page.

2. Unzip it. You'll get a single folder named Fusion_System_Blocks. Put it somewhere permanent (like your Documents folder) — Fusion will load it from this location every time, so don't leave it in Downloads and delete it later.

3. Open Fusion. If it was already running, restart it.

4. In Fusion's top toolbar, click Utilities, then click the Add-Ins button (its icon looks like a green plus sign) and choose Scripts and Add-Ins.

5. In the window that opens, click the Add-Ins tab.

6. Click the + (plus) button next to "My Add-Ins", then browse to and select the Fusion_System_Blocks folder you unzipped in step 2.

7. Fusion System Blocks now appears in the list. Click it once to select it, check the Run on Startup box (so it loads automatically from now on), and click Run.

That's it. A System Blocks button now appears under Utilities → Add-Ins in the toolbar. Click it to open the diagram panel.

Don't see the button? Make sure you are in the Design workspace (check the workspace picker at the top-left of Fusion). Then look under Utilities → Add-Ins. If it's still missing, restart Fusion and check that the add-in shows "Running" in the Scripts and Add-Ins window.

---

Your First Diagram (2 Minutes)

1. Click the System Blocks button to open the panel.
2. Click Block in the ribbon at the top of the panel and pick a type (Electrical, Mechanical, Software, or Generic). A block appears on the canvas.
3. Type a name for it right away (the name box opens automatically), then press Enter.
4. Add a second block the same way.
5. Connect them: click the first block to select it, then press C (or click Connect in the ribbon). Small circles appear on the block edges — these are connection points. Now click the second block, and a wire appears between them.
6. Press Ctrl+S to save the diagram into your Fusion design.

Important: saving the diagram stores it inside the currently open Fusion design. Remember to also save the Fusion design itself (Fusion's own save button) so everything is kept together in the cloud.

Moving around the canvas

To do this…	Do this
Move a block	Click and drag it
Pan the view	Drag with the middle mouse button
Zoom	Scroll the mouse wheel
Fit everything in view	Press Ctrl+0
Rename a block	Double-click it
Delete something	Click it, press Delete
Undo / Redo	Ctrl+Z / Ctrl+Y

Press ? inside the panel any time to see the full list of shortcuts, or F1 for the built-in help guide.

---

Everyday Tasks

Saving and opening diagrams

• Ctrl+S saves your work into the open Fusion design.
• Save As (Ctrl+Shift+S) stores the diagram under a name of your choice — useful for keeping variants like "Concept A" and "Concept B" in the same design file.
• Open Named (Ctrl+Shift+O) lists your named diagrams so you can switch between them.

Linking a block to a real part

1. Click a block to select it.
2. Click Link to CAD in the ribbon.
3. The panel steps aside so you can click a component in your 3D model.
4. Done — the block now shows a blue banner with the component's name, so you can always see which part of the 3D model it represents.

Checking your design

Click Check Rules to scan the diagram for common problems: blocks with no connections, mismatched voltage levels, more power drawn than supplied, blocks still using their default names, and more. Click any result to highlight the offending blocks on the canvas.

Tip: for power checks, give your blocks attributes like current (e.g. 200mA) and voltage (e.g. 5V) in the properties panel, and give your power supply an output_current or power_supply_mw attribute.

Snapshots (version history)

Think of snapshots as save points. From the History tab you can:

• Create a snapshot with a short note ("before motor redesign").
• Restore any earlier snapshot — your whole diagram returns to that state.
• Compare two snapshots to see what was added, removed, or changed.

Exporting reports

Click Export, tick the formats you want (PDF report, bill of materials, connection matrix, SVG image, and more), optionally click Browse to pick a destination folder, and confirm. If you don't pick a folder, files go to an exports folder inside the add-in's folder — the confirmation message shows the exact location.

Bigger diagrams

• Pages: use the tabs at the bottom of the canvas to split a large system across several pages (for example "Power" and "Controls").
• Nested diagrams: select a block and click Create Child to open a diagram inside that block — great for breaking a complex subsystem into its own sheet. Use Drill Down and Go Up to move between levels.
• Groups: select several blocks (drag a box around them) and press Ctrl+G to group them with a labeled boundary.
• Net labels: instead of dragging a long wire across the canvas, drop a connection on empty space and give it a name like 5V — every block with the same label counts as connected, just like in electronics schematics.

---

Troubleshooting

The System Blocks button disappeared. Switch to the Design workspace and look under Utilities → Add-Ins. Restart Fusion if needed. The button re-adds itself whenever you switch back to the Design workspace.

My diagram was gone when I reopened the file. The diagram lives inside the Fusion design, so two saves matter: Ctrl+S in the System Blocks panel and saving the Fusion design itself. If Fusion wasn't saved, the diagram from that session is not in the cloud copy.

Something looks broken. Go to Utilities → Add-Ins and click Run Diagnostics. It runs 30 built-in self-checks and tells you exactly what passed and failed — without touching your design.

Reporting a bug. The add-in writes log files to a FusionSystemBlocks/logs folder inside your user folder (C:\Users\<you>\FusionSystemBlocks\logs on Windows, ~/FusionSystemBlocks/logs on Mac). Attach the newest log file when you open an issue — it makes problems much easier to track down.

---

For Developers

Everything below is only relevant if you want to work on the add-in's code — regular users can stop reading here.

• The Python core (fsb_core/, src/diagram/) is pure Python with no Fusion dependencies; the Fusion-specific layer lives in fusion_addin/ and Fusion_System_Blocks.py. The panel UI is plain HTML/JS in src/.

• Run the automated test suites:

  # Python (requires the test extras: pytest, hypothesis, jsonschema)
  pip install -e .[test]
  pytest -q
  
  # JavaScript (requires Node.js 18+, no npm dependencies)
  npm test

• Current baseline: 775 passing Python tests, 24 JS harness tests, and 30 in-app diagnostics checks.

• Manual regression plan: docs/FUSION_MANUAL_TEST_PLAN.md

• Full release validation plan: docs/DETAILED_TESTING_DOCUMENTATION.md

• Verbose logging for debugging: set the SYSTEM_BLOCKS_LOG_LEVEL environment variable to debug before starting Fusion.

---

License

The source code is available under the Fusion System Blocks Community License for personal, academic, and non-commercial use. Commercial use requires a paid license — open an issue to discuss.