Cam & Encoder Designer

Design radial (disk) cams, barrel (cylindrical) cams, and optical encoder discs (incremental & absolute) — with live SVAJ analysis, design-rule checks, manufacturing exports (CSV/DXF), and one-click solid model generation in FreeCAD.

Python 3 + tkinter + matplotlib. No cloud, no license keys. MIT.

Highlights

• Motion program editor — compose the 360° cycle from Dwell / Rise / Return segments using 8 standard motion laws (cycloidal, simple harmonic, modified trapezoidal, modified sine, 3-4-5 & 4-5-6-7 polynomials, parabolic, uniform). Peak-acceleration coefficients validated against Rothbart's Cam Design Handbook. One-click example programs.

• SVAJ diagrams — displacement, velocity, acceleration and jerk vs cam angle, scaled to real units (mm/s…) by the cam speed.

• Radial cams — profile synthesis by inversion for translating roller (offset, CW/CCW) or flat-faced followers, with a live animation of the rotating cam driving its follower.

• Barrel cams — unwrapped groove development, groove-edge geometry, and a 3D preview.

• Encoder discs — incremental (PPR, duty, index/Z track, quadrature readout info) and absolute (1–12 bit Gray or binary code tracks).

• Design-rule checks — pressure angle vs the 30° guideline, undercutting (radius of curvature vs roller), flat-follower cusp condition, encoder window manufacturability. Every warning links to a fix in the built-in guide.

• Built-in user guide — press F1 (or any ❓ Help button): seven chapters explain every option, every motion law, and every warning. Hover any field for a tooltip.

• Exports — CSV motion tables, DXF R12 (cam profile, groove development, encoder mask for laser cutting), and FreeCAD solids via the bundled workbench.

Related MCP server: FreeCAD MCP Server

Screenshots

Generated solids in FreeCAD:

Installation

Requires Python 3.10+ (tkinter included in the standard Windows/macOS installers; on Linux install python3-tk).

git clone https://github.com/Sweetkubuni/cam-encoder-designer.git
cd cam-encoder-designer
python -m venv .venv
.venv\Scripts\pip install -r requirements.txt
.venv\Scripts\python cam_designer.py

On Windows you can afterwards start it by double-clicking run.bat.

Using the designer

1. Define the motion (left panel): add Rise / Dwell / Return segments — durations must total 360° and rises must cancel returns. Pick an entry from the Example drop-down to start from a known-good program. Double-click a segment to edit it; the editor describes each motion law.

2. Check the SVAJ tab — smooth curves mean smooth running. Set the cam speed (rpm) to read peaks in real units.

3. Enter the cam geometry — base circle, roller radius, offset and follower type for the radial cam; cylinder and roller radius for the barrel cam. The Results panel shows peak values; the status bar turns green (✓ OK) or red (⚠ warnings).

4. Animate — on the Radial cam tab, drag the slider or press ▶ Play.

5. Export — File menu for CSV/DXF, or Send to FreeCAD ⚙ for solids.

The Encoder tab is a self-contained designer: choose Incremental or Absolute, set the disc geometry, then export a DXF cutting mask or send the disc + shaft to FreeCAD.

Stuck? F1 opens the user guide; the Warnings explained chapter lists every warning with its remedy.

FreeCAD integration

The bundled workbench (freecad-workbench/CamDesigner, tested with FreeCAD 1.0) turns designs into solids: an extruded radial cam with shaft bore, a barrel cam with the roller-swept groove cut into the cylinder, and encoder discs with windows cut through, assembled on a shaft.

1. Run install_workbench.bat (copies the workbench to %APPDATA%\FreeCAD\Mod), restart FreeCAD.

2. With FreeCAD running, click Send to FreeCAD in the designer — models appear immediately. Without FreeCAD running, the design is saved as JSON under exports\ and can be loaded later via the workbench command Import cam design…, which also exposes thickness, bore, outer radius and groove depth.

Automation / MCP

The workbench auto-starts a localhost XML-RPC bridge (127.0.0.1:9875). freecad_mcp_server.py exposes it as MCP tools — freecad_ping, generate_cams, freecad_exec, freecad_objects, freecad_screenshot — so an AI assistant such as Claude Code can generate and inspect models. Example MCP configuration:

{
  "mcpServers": {
    "freecad-cam": {
      "type": "stdio",
      "command": "<repo>/.venv/Scripts/python.exe",
      "args": ["<repo>/freecad_mcp_server.py"]
    }
  }
}

Security note: the bridge executes Python sent from localhost. It binds 127.0.0.1 only; don't run it where other local users shouldn't have that access.

Exports reference

Project layout

cam_designer.py                  the designer app (single file)
freecad_mcp_server.py            MCP server bridging Claude <-> FreeCAD
freecad-workbench/CamDesigner/   FreeCAD workbench (builder, bridge, GUI commands)
install_workbench.bat            copies the workbench into FreeCAD's Mod folder
docs/                            README images + generate_images.py
requirements.txt, run.bat

Conventions

Millimetres and degrees throughout. Internally velocity/acceleration/jerk are per radian of cam rotation (v = ds/dθ); plots and readouts also show time-based values at the entered rpm. Encoder discs: dark = opaque, white = transparent window; angles CCW from +x; the LSB track is outermost.

References

• mechref.org — Cam design

• METU OCW ME 301, ch. 8 (cam motion curves)

• Rothbart, Cam Design Handbook, McGraw-Hill 2004

• Quantum Devices — Incremental encoder basics

License

MIT — see LICENSE.