N-DOF: The Modular Robotic Arm

This project uses connectors that are compatible with Modular Mounting System (MMS) and GoPro to join motorized robotic modules.

Features

• Modular: Ideal for flexible use and re-use. Try different arm designs without having to re-print parts. Disassemble and reassemble with ease.
• Limitless: Print the same part multiple times and chain them together. N-DOF = "N Degrees Of Freedom".
• Extensible: Have a motor or actuator you want to use in your own robot? Design a joint with GoPro mounts separated by 30 mm... Now it is N-DOF compatible!
• Compatible: There are a huge number of mounts for various objects that are already compatible with N-DOF. Search for "Modular Mounting System" or "GoPro".

Included Modules

• The included modules use print-in-place joints to keep part count low. They require supports when printing and a little force to move for the first time.
• Included modules use NEMA 17 stepping motors.
• The only non-printed parts required are M3 bolts to mount the motors.

If you are thinking of designing a module that is compatible with N-DOF, these features are not a requirement.

Base

• Gear ratio = 6:1
• Support blockers when slicing may help support removal.
• If greater stability is required, print some MMS arms to spread the legs out further.
• 2 x M3 bolts required to mount NEMA 17.
• 6 x legs.
• 1 x motor gear (with 12 teeth).

Gear Joint

• Gear ratio = 4:1
• Support blockers when slicing may help support removal.
• This joint has an asymmetric range of motion: -60 deg to 150 deg.
• 3 x M3 bolts required to mount NEMA 17.
• 1 x motor gear (with 12 teeth).

Swivel Joint

• No gearing.
• This could be improved using planetary gears.
• 4 x M3 bolts required to mount NEMA 17.

Notes

• Regular PLA might not be strong enough for the M5 bolts. I used PolyMax PLA and have had no issues.
• If extending the arm to great lengths, be sure to attach the base to a desk with a clamp so it doesn't tip over.
• OpenSCAD code can be found at https://github.com/keeeal/n-dof