How to build AR4 (Annin Robotics)
6-DoF desktop robot arm · Intermediate
Build Chris Annin's AR4 MK5, a 6-axis stepper desktop arm from Annin Robotics: 629 mm reach, 1.9 kg payload, Teensy 4.1 control, free software and ROS 2.
Some soldering, calibration and Linux comfort needed.
Our estimate, part-time
Annin's MK5 combo kit (aluminum, hardware, electrical) starts at $1,189, plus the $699 StepperOnline motor, driver and power supply package; printed covers and a gripper are extra
Annin Robotics Open Source Non-Commercial License 1.1 · non-commercial
What is AR4 (Annin Robotics)?
The AR4 is Chris Annin's six-axis desktop industrial arm, sold by Annin Robotics in Emmett, Idaho, as kits, with free build manuals, software and 3D print files on anninrobotics.com. It's built like a scaled-down industrial manipulator: closed-loop stepper gearmotors on every joint and a machined aluminum structure.
It follows the AR2 and AR3, and the AR4 itself has gone through MK1 to MK5 revisions. The current MK5 adds Hall-effect homing on J1 to J3 and ships with a new build manual and full DH kinematic sheets.
Annin's software and CAD files use the Annin Robotics Open Source Non-Commercial License, so personal and classroom builds are welcome, but selling robots, parts or software based on the work needs Annin's written permission.
Versions and forks
- AR4 MK1–MK5 revisions, with upgrade kits for earlier arms
- Servo and pneumatic gripper options
- ROS 2 add-ons such as hand-eye calibration and Xbox teleop
AR4 (Annin Robotics) specifications
- Axes
- 6 DOF (plus optional servo or pneumatic gripper)
- Reach
- 629 mm (24.75 in), J1 center to flange
- Payload
- 1.9 kg (4.15 lb) rated
- Repeatability
- 0.25 mm
- Mass
- 12.25 kg (27 lb), aluminum structure
- Power
- 24 VDC, 198 W (8.25 A) max
- Actuators
- Closed-loop stepper gearmotors with integrated encoders
- Drivers
- DM332T (J1–J3), DM320T (J4–J6)
- Controllers
- Teensy 4.1 (kinematics and motion) + Arduino Nano or Mega (grippers, I/O)
- Revisions
- AR4 MK1, MK2, MK3, MK4, MK5 (current)
- Software
- Annin AR4 Python HMI; Annin AR4 ROS 2 driver (Jazzy, Humble branch)
Figures as published by the project. See Sources below.
Bill of materials
| Part | Qty | Notes |
|---|---|---|
| AR4 MK5 aluminum parts kit | 1 | 26 machined aluminum pieces (Annin) |
| AR4 MK5 hardware kit | 1 | Bearings, HTD belts and pulleys, shafts, pins, screws (Annin) |
| AR4 MK5 electrical parts kit | 1 | Teensy 4.1 path, wiring and base electronics (Annin) |
| Stepper gearmotors | 6 | In the StepperOnline motor, driver and power supply package for MK3–MK5, $699 via Annin |
| Stepper drivers | 6 | 3 × DM332T, 3 × DM320T, in the same package |
| 24 VDC power supply | 1 | In the same package |
| 3D-printed covers | — | Print yourself or order from Annin's licensed print service |
| Gripper (optional) | — | Annin servo or pneumatic gripper parts kit |
Where's the full bill of materials?
The full BOM, with exact quantities and vendors, lives in the project's own files. Prices change often, so treat Not published as a ballpark. Start at the project repository.
Tools you'll need
- Metric hex keys
- Soldering iron
- Crimper
- Multimeter
- PC for the AR4 software
Step-by-step build overview
Electronics & wiring overview
The Teensy 4.1 sends step and direction signals to the six stepper drivers, reads the encoders and homing sensors (Hall-effect on J1–J3 and microswitches on J4–J6 on the MK5), and runs the kinematics. An Arduino Nano or Mega handles 5 V grippers and solenoids. Both connect to the PC over USB serial.
Software
Annin's free Python HMI (the ar4-hmi repository) covers joint and Cartesian jogging, calibration, teach-and-repeat programs, an offline digital twin, Xbox controller jogging, Modbus, G-code streaming and OpenCV vision. For ROS 2, Annin's ar4_ros_driver (developed with Yifei Cheng) adds ros2_control, MoveIt 2 and Gazebo for the MK1–MK4 and the servo gripper. It's tested on ROS 2 Jazzy, has a Humble branch, and includes its own Teensy and Nano firmware.
Tips from the bench
- ☕ Prove the arm in Annin's software before trying ROS; it makes wiring faults easier to find.
- ☕ Check the driver DIP switches against your revision and software version.
- ☕ On Linux, add yourself to the dialout group so the ROS driver can open the serial ports.
- ☕ Wrist cables that are too tight cause most later faults.
AR4 (Annin Robotics) FAQ
Can I sell AR4 robots I build?
Not without permission. Annin's license prohibits selling robots, parts or software based on the AR4 without Annin's express written permission.
What are the AR4's specs?
Annin rates the AR4 at 6 axes, 629 mm reach, 1.9 kg payload and 0.25 mm repeatability, with a 12.25 kg arm running on 24 VDC.
How much does an AR4 kit cost?
Annin's MK5 combo kit starts at $1,189. Motors, drivers and the power supply come in a separate $699 StepperOnline package that Annin links to.
Does the AR4 support ROS 2?
Yes, through Annin's ar4_ros_driver, with MoveIt 2 and Gazebo support on Jazzy and a Humble branch.
What controls the AR4?
A Teensy 4.1 runs the kinematics and joints, and an Arduino Nano or Mega handles grippers and I/O.
Sources
- Annin Robotics (official AR4 site)
- Annin Robotics: AR4 MK5 robot combo kit
- Annin Robotics: AR4 kits and parts
- Annin Robotics: downloads (manual, software, print files)
- AR4 software: Annin-Robotics/ar4-hmi
- AR4 ROS 2 driver: Annin-Robotics/ar4_ros_driver
Written by Bots n' Beans from the project's own documentation. Check the sources for the latest revision before you buy parts.
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