Thor Robotic Arm
B✓ Links verified May 19, 2026
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1,450 stars on GitHub.
Thor is a fully open-source, 3D-printable 6-degree-of-freedom robotic arm designed for education, makers, and robotics research. Standing 625mm tall and capable of lifting up to 750g, Thor brings industrial-style robot kinematics within reach of any builder with a 3D printer and around 350 euros in parts.
Source: https://github.com/AngelLM/Thor
Architecture
Thor uses a yaw-roll-roll-yaw-roll-yaw joint configuration — the same kinematic arrangement found in many industrial manipulators. Each of the six joints is driven by a stepper motor through 3D-printed gears and GT2 belt-and-pulley transmissions. The arm includes an integrated gripper as a seventh axis, actuated by a servo. All structural parts are designed in FreeCAD and printable on standard FDM printers.
Electronics and Firmware
The control board is a custom PCB shield built on the Arduino Mega, combining six stepper drivers with limit switch inputs and fan outputs. The firmware is GRBL-based, accepting standard G-code commands over USB serial — the same protocol used by 3D printers and CNC routers. Thor also ships with full ROS2 integration via Docker, including MoveIt2 configuration for motion planning.
Printed Parts
The repository contains 49 STL files covering all six arm articulations (Art1 through Art6), the gripper assembly (GripperArm, GripperFinger, GripperTop, GripperActiveArm, GripperPassiveArm, GripperBot), base components (BaseBot, BaseTop, BaseBoxBody, BaseBoxCover, BaseBearingFix), and shared hardware like bearing fixtures and motor gear interfaces. Print time is estimated at 60-80 hours total on a standard 0.4mm nozzle at 0.2mm layer height.
Software
The official control application, Asgard, provides a graphical interface for direct joint control, G-code execution, and trajectory recording. For advanced users, the Thor-ROS repository provides ROS2/MoveIt2 packages that enable full motion planning, collision avoidance, and programmatic control via the ROS2 action server interface.
Community
Thor has been deployed in university robotics courses and research labs worldwide, with an active community on Discord and official forums at thor.angel-lm.com. The project is released under Creative Commons Attribution-ShareAlike 4.0 by Angel LM.
🖨 Print Files (49)
Art1OptoFix.stl
Art1FanHolder.stl
Art1Top.stl
Art2BodyAWindow.stl
Art1GearMotor.stl
Art2BodyACover1.stl
| Item | Qty | Unit Cost (USD) | Total (USD) | Notes |
|---|---|---|---|---|
| NEMA 17 Stepper Motor — 40mm body, 39.22 N·cm holding torque | 1 | $14 | $14 | Joint 1 (base) — Amazon search / StepperOnline |
| NEMA 17 Stepper Motor — 34mm body, 121.2 N·cm high-torque | 3 | $20 | $60 | Joints 2–3 with 5:1 reduction — Amazon search |
| NEMA 17 Stepper Motor — 34mm body, 21.57 N·cm | 3 | $13 | $39 | Joints 4–6 — Amazon search |
| Arduino Mega 2560 R3 | 1 | $25 | $25 | Main controller — Amazon search |
| A4988 Stepper Driver (with heatsink) | 8 | $2 | $16 | One per stepper + spare — Amazon search |
| 12V 10A Power Supply (DC barrel) | 1 | $20 | $20 | Drives all motors — Amazon search |
| Optical Endstop Module (3.3–5V) | 4 | $3 | $12 | Joint homing — Amazon search |
| Mechanical Micro Endstop | 1 | $2 | $2 | Limit switch — Amazon search |
| 40×40×10mm 12V Cooling Fan | 7 | $4 | $28 | Driver/motor cooling — Amazon search |
| GT2 Closed Belt — 208mm (104 teeth), 6mm wide | 2 | $5 | $10 | Amazon search |
| GT2 Open Belt — 1m, 6mm wide | 1 | $7 | $7 | Amazon search |
| GT2 Pulley — 20 teeth, 5mm bore | 3 | $3 | $9 | Amazon search |
| GT2 Pulley — 40 teeth, 5mm bore | 2 | $5 | $10 | Amazon search |
| Bearing 16014ZZ (70×110×13) | 1 | $10 | $10 | Base slewing bearing — Amazon search |
| Bearing 625ZZ (5×16×5) | 11 | $1 | $11 | Amazon search |
| Bearing MF84ZZ (4×8×3 flanged) | 2 | $1 | $2 | Amazon search |
| 6mm steel balls (loose, ~30 ct) | 1 | $5 | $5 | Slewing ring — Amazon search |
| Steel rod 4mm × 14mm | 2 | $1 | $2 | Cut from longer rod — Amazon search |