Video: https://www.youtube.com/watch?v=q0eZf5LdW8s

This is an open-source robotic arm I made as a hobby project. It's flexible, similar in size to a human arm, and relatively inexpensive. Besides a 3D printer and a computer, no expensive tools (>$50) are required to build it. Feel free to build and use this robot however you like, as long as it's safe. I sincerely hope that someone besides me can find some use or enjoyment out of this project.

Features:

• This robot is substantially cheaper than all commercial robotic arms (that I know of) with similar size and torque capabilities.
• This arm is made entirely with 3D-printed components and mass-produced parts you can find online. If you have a 3D printer, some cheap hobby tools, and money for parts, you can build it.
• There are 7 motors: 6 degrees of freedom + a gripper.
• 4 out of 6 joints (waist + 3 wrist joints) can turn more than 360 degrees.
• Wrist joints allow the gripper to rotate completely in all 3 axes when unobstructed. The gripper can point forward, backward, up, down, left, right, and anywhere inbetween only by moving the wrist.
• The arm as I designed it reaches 860 mm from shoulder to gripper tip. That's similar in length to a human arm. You can change the length by using shorter or longer T-slot extrusions (mine are 300 mm each). A shorter arm will vibrate less or be able to lift more.
• Using the length that I used, the arm can hold a 1 kg payload when extended.
• All motors are from the Dynamixel X series from Robotis. Robotis has excellent documentation and code resources, so it is fairly straightforward to control the joints with any of their SDKs written in Python, C++, Java, C#, and more. Linux, Windows, and Mac are all supported, and you can connect the robot to a computer with USB.
• All motors are backdrivable.
• All 3D-printed components can be printed with standard PLA filament. For many 3D printers such as my Bambu Lab A1, no supports are needed.
• All components can be removed and replaced. No glue is used anywhere. Most plastic components are connected with M3 screws and heat set inserts.
• Cables are well organized. If you follow the recommended cable lengths, you shouldn't have any annoying dangling wires. Of course you will have to adjust the cable lengths if you choose extrusions that are not 300 mm.

• I recommend putting a maximum acceleration of "10" on all motors using the profile acceleration setting. Acceleration that is too high will cause joints to vibrate, and you won't get good accuracy. You can later adjust this as you see fit.
• I use 0.2mm Standard 3D printer settings for all parts except for the gears. For the gears, I increase the wall loops to 4 to try to fill all of the teeth completely.
• Some of the printed components have a small overhang inside the screw hole where the screw meets the plastic. My printer can do some overhangs, but often it leaves plastic threads sticking around, and the hole is often too small. You can fix this by taking a small allen wrench and forcing it through the hole. Then take a bigger one and do it again. Eventually you'll be able to fit the screw in there.

• Any computer with a USB port
• 3D printer that can print PLA; bed size should be at least 17 cm x 17 cm
• Soldering iron
• Crimping tool that can crimp JST SEH-001T-P0.6
• Wire stripper
• 2mm Phillips screwdriver
• Hex drivers / allen wrenches, sizes 1.5mm, 2.0mm, 2.5mm, and 4mm
• Pliers
• Flathead screwdriver
• Table clamps

Taxes and shipping are not included. These prices will vary depending on where you live.

For any JST components, I recommend you get at least double the minimum indicated above. They are only a few cents apiece, and they are very easy to mess up if you don't have much experience crimping.

Here is a list of all electronics and the lengths of cables between them, from base to tip. Every cable is written of the form "X-N-X", where "N" indicates the cable length in cm, and "X" indicates the type of connector:

• FEH: Female JST EH (JST EHR-03)
• FSM: Female JST-SM (SMP-03V-BC)
• MSM: Male JST-SM (SMR-03V-B)

Note that many Dynamixel motors come with an 18 cm female-female JST-EH cable included, so if you see "FEH-18-FEH" in the list, you don't need to make it yourself.

All cables consist of 3 wires. All F/M connectors are 3-pin JST EH connectors.

1. U2D2 USB connector
2. FEH-18-FSM
3. MSM-10-FEH
4. XM430-W350-T (waist)
5. FEH-13-MSM
6. FSM-12-FEH
7. XM540-W270-T (shoulder)
8. FEH-40-FSM (change length if you used a different extrusion length)
9. MSM-17-FEH
10. XM540-W270-T (elbow)
11. FEH-32-MSM
12. FSM-18-FEH (change length if you used a different extrusion length)
13. XM430-W350-T (wrist 1)
14. FEH-18-FEH
15. XM430-W350-T (wrist 2)
16. FEH-21-FEH
17. XL430-W350-T (wrist 3)
18. FEH-15-FEH
19. XL430-W350-T (gripper)