This servo arm has 2 degrees of freedom, is made from standard hobby servos, PVC tube, and 3D prints. It has been tested with SCUTTLE and works with manipulating light loads. The joints are double-supported, utilizing the same low cost 608 bearings in the SCUTTLE wheels.
More Info (2023)
This was one of our earliest (and swiftly made) addons, and we have come a long way in design methodologies. If you are considering using this design, consider the following:
The good
- 3D Prints are printable without supports
- simple 608 bearing and a few cheap screws makes a joint complete
- Modular, to make servos into actuators cheaply
- Dual-supported – while servos have one bearing, this has two so twisting forces are handled, giving access to the full torque of the servo and peripheral loads are handled by the second bearing.
- wireways planned – it allows you to pass cables throughout the assembly for a neat, unobstructed motion.
- It uses hockey pucks – and that’s cool.
- Servos target a location all by themself. No need for PID loops and kinematics is optional. We expect at the user level of this device, most users want to perform a pick-and-place while the software follows a simple routine rather than planning its own path in realtime.
The Bad
- The counterweight bracket is flimsy. Consider using the counterweight concept but establish your own attachment.
- The end-effector cannot support much weight (as is true for most servo arms) and our next iteration will have something more similar to SCARA to move pick up much higher payloads.
- Inconsistent torque throughout range of motion – this is the same as most servo bots, once again. When we move all joints into the horizontal plane in v2, you can have a consistent torque and less planning is necessary.
- Kinematics are not solved – the concept is for you to choose your own diameters and lengths of tube to configure the joints as you wish – but that also means kinematics are a mystery unless you write them up.
- Materials are suuuper cheap but admittedly it’s rare that people have PVC just lying around in small segments. In 2020, PVC pipes went up in price by 3 or 4x, and it makes this design less desirable.
See an Example project using this design on a SCUTTLE!
