Robotic Arm

4-Axis Robotic Arm with Browser Control

A fully working 4-axis robotic arm with a parallel-gripper end effector — driven by a NEMA 23 with a custom 5:1 planetary gearbox at the shoulder, three NEMA 17s for the base, elbow and wrist, and controlled live in a browser over USB through a custom Three.js + WebSerial app.

This upload is the **mechanical structure** — the printable parts of the arm. Wiring, firmware and the browser control app are all open-source and linked below.

> ⚠️ Build status note -  the Second Link and Link to Wrist parts in this upload are the latest design revisions and have not yet been printed and assembled at the time of this post. All other parts are printed and in active use. I'm uploading the design as-is so others can start their own builds; printability has been validated in the slicer for both unprinted parts.

| Part | Notes |
| BASE REMAKE | Dome / skirt base with bolt circle. Mounts to a flat surface with M5 bolts. |
| BOTTOM PLATE | Lower plate of the planetary gearbox housing. ×2 needed (one per gearbox: shoulder + elbow). |
| TOP PLATE | Upper plate of the planetary gearbox housing. ×2 needed. |
| First Length | Upper arm — from shoulder pivot to elbow. |
| Second Link ⚠️ | Forearm transition piece. Not yet print-validated. |
| SECOND LENGTH (V2) | Forearm horn — the long tapered cone. |
| Link to Wrist ⚠️ | Wrist tube + face plate where the gripper bolts on. Not yet print-validated. |

The planetary gears themselves (sun + planets) are deliberately not in this upload — they'll be in a separate gearbox post so people can mix-and-match gear ratios.

Print settings (recommended)

- Material: PETG or ABS for structural rigidity. PLA+ works for testing but the shoulder yoke takes real load.
- Layer height: 0.2 mm
- Walls: 4 perimeters minimum
- Infill: 35–40% gyroid for structural parts, 100% for the gearbox plates
- Supports: required under the dome flare on BASE REMAKE and overhangs > 45°
- Orientation: print everything with the smallest face down except the dome — flip that so the bolt rim is up

Hardware bill of materials

Motors & drivers
- 1× NEMA 23 stepper (shoulder)
- 3× NEMA 17 stepper (base, elbow, wrist)
- 1× DM556 standalone stepper driver (drives the NEMA 23)
- 1× Arduino UNO + CNC Shield V3 (3× onboard A4988 (or other compatible) drivers for the NEMA 17s)
- 1× 24V DC power supply (for the DM556)
- 1× 12V DC power supply (for the CNC shield)

Mechanical
- 8× planetary planet gears + 2× sun gears (printed — separate upload)
- M3 bolts, nuts, washers throughout
- 608 bearings for the rotating disc
- M5 bolts for floor mounting

Optional
- iPhone 12 Pro or newer (for LiDAR hand-tracking control)

Joint specs: 

Joint | Motor | Gearbox | Range | Microsteps |
- Base | NEMA 17 | direct (1:1) | ±180° | 1/8 |
- Shoulder | NEMA 23 | 5:1 planetary | ±90° | 1/8 (DM556) |
- Elbow | NEMA 17 | 5:1 planetary | ±140° | full step |
- Wrist | NEMA 17 | direct (1:1) | ±720° | full step |

Total reach: ~420 mm fully extended.

Software

The browser-based control app, iPhone LiDAR hand-tracking bridge, WebSocket relay, and full source for the Arduino firmware are all open-source on GitHub: 🔗 **[github.com/cambue12/Nema-motor-arm-controller](https://github.com/cambue12/Nema-motor-arm-controller)**

Features include:
- Live 3D simulation in the browser (Three.js)
- Real-time WebSerial control over USB
- Webcam hand-tracking (MediaPipe) — IK and per-finger control modes
- iPhone LiDAR hand-tracking (ARKit + Vision)
- Activity macros: Wave, Dance, Pick & Place, Showcase, EXPO Demo, etc.
- Layered safety system with confirmation modals and panic-stop

Customisable parameters

Each `.f3d` file has a `Scale` parameter exposed to MakerWorld's customizer — bump it up or down to print the arm at a different size. (Note: hardware will need to be matched accordingly.)

Print order recommendation

1. BASE REMAKE`
2. BOTTOM PLATE (×2)
3. TOP PLATE (×2)
4. First Length
5. SECOND LENGTH (V2)
6. Second Link ⚠️ unprinted reference
7. Link to Wrist ⚠️ unprinted reference

Credits & License

Designed in Fusion 360. MIT-licensed source on GitHub.

If you build one, please share photos in the print log or tag me — I'd love to see other people's takes on it. Pull requests welcome on the GitHub repo too if you find improvements.