ProjectAutoParams: Fusion 360 Add-In

A tiny Autodesk Fusion 360 add-in that automatically adds your favorite user parameters (layer height, nozzle width, wall thickness, etc.) to every new design, so you don't have to type them in by hand each time.

What it does

• The moment you activate a document (new or existing), the add-in checks the active design's user parameters and adds any that are missing, using the values from a small params.json file.
• Ships with sensible defaults for FDM 3D printing: layer height, nozzle width, wall/top/bottom thickness, and fit clearance. Several are expressions derived from the others (e.g. wall = nozzle_width * 3), so changing one value cascades automatically.
• Adds an Edit Auto Params button that opens a dialog for adding, removing, and editing parameters in a table, no JSON editing or restart required.
• Never overwrites a parameter that already exists in the design; it only fills in what's missing.

Installation

Download the latest ProjectAutoParams.zip from the Releases page and unzip it. You'll get a ProjectAutoParams folder (containing ProjectAutoParams.py, ProjectAutoParams.manifest, AddInIcon.svg, LICENSE, params.json, the resources/ icons, and this README.md), already named exactly as Fusion requires. Then install it with either method below.

Option A: from Fusion's Scripts and Add-Ins dialog (easiest, no folder-hunting)

If you don't know (or don't want to know) where Fusion keeps its add-ins, let Fusion copy the folder in for you:

1. In Fusion: Utilities tab → ADD-INS panel → Scripts and Add-Ins (or press Shift+S).
2. Click the + dropdown at the top-left of the dialog → Script or add-in from device.
3. Browse to and select the ProjectAutoParams folder (the one that contains the .manifest file) and confirm. Fusion copies it into the correct add-ins directory automatically.
4. It now shows up in the Add-Ins tab of the list. Select ProjectAutoParams and click Run, and tick Run on Startup so it's always active (the whole point of this add-in is that it runs quietly in the background).

Option B: manual copy

1. Copy the entire ProjectAutoParams/ folder into your Fusion add-ins directory:

   • macOS: ~/Library/Application Support/Autodesk/Autodesk Fusion 360/API/AddIns/
   • Windows: %APPDATA%\Autodesk\Autodesk Fusion 360\API\AddIns\

   The folder, the .py, and the .manifest must all share the base name ProjectAutoParams.

2. In Fusion: Utilities tab → ADD-INS → Scripts and Add-Ins (Shift+S) → Add-Ins tab → select ProjectAutoParams → Run → tick Run on Startup.

Either way, an AUTO PARAMS panel (with an Edit Auto Params button) appears at the end of the Utilities tab's toolbar.

How to use

1. Just start or open a design. The add-in silently adds any missing parameters from params.json to the design's user parameters as soon as the document becomes active. No dialog, no button press needed for this part.
2. To change which parameters get added, or their values, click Edit Auto Params. A dialog opens with one row per parameter:
   • Type in any cell (Name, Value, Unit, Comment) to edit it.
   • Click Add in the dialog's toolbar to append a new blank row.
   • Click the minus icon at the right of a row to delete it.
   • Click OK to save. The next document you activate will pick up the new values.
3. Existing parameters are never touched: if a design already has a parameter with the same name, the add-in leaves it alone. That means you can freely override any auto-added value per-design without it getting reset.

The parameters file

The Edit Auto Params dialog is the recommended way to change parameters, but under the hood it just reads and writes params.json, a plain JSON array next to ProjectAutoParams.py. You can also edit it by hand if you prefer. Each entry becomes one user parameter:

{
  "name": "wall",
  "value": "nozzle_width*3",
  "unit": "mm",
  "comment": "Wall thickness"
}

• name: the parameter name as it will appear in Fusion's parameters dialog.
• value: anything Fusion's expression parser accepts: a plain number, a number with a unit, or an expression referencing another parameter (evaluated in file order, so a parameter can only reference ones defined earlier in the list).
• unit: the unit to associate with the parameter (e.g. mm).
• comment: shown as the parameter's description/comment in Fusion.

Ships with these FDM printing defaults:

Name	Value	Comment
layer_height	0.2mm	Slicing layer height
nozzle_width	0.4mm	Nozzle diameter
wall	nozzle_width*3	Wall thickness
top	layer_height*5	Top shell thickness
bottom	layer_height*3	Bottom shell thickness
clearance	0.05mm	Fit tolerance

If params.json is ever missing (first run, or you deleted it), it's recreated with these same defaults.

Notes & limits

• Parameters are added on document activation: opening a design, switching tabs back to it, or creating a new one all count. If you add a brand-new parameter to params.json while a design is already open and active, switch away and back (or reopen the file) to trigger the check again.
• The add-in only ever adds parameters. It never deletes or renames ones you remove from params.json, and it never overwrites a value you've changed by hand in an existing design.
• params.json lives next to ProjectAutoParams.py inside the add-in folder, so it's shared across every design on your machine; it's not per-project.

License

This add-in's own code (ProjectAutoParams.py, ProjectAutoParams.manifest, this README) is licensed under the GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later). The full text is in LICENSE.