Mechatronics student Damian Lickindorf designed a 3D-printed 6DOF robotic arm for his engineering thesis, which is similar to A&R Technology’s 6DOF Industrial Robot but infinitely cheaper. Known as Atlas, the robotic arm was designed using five 3D-printed hollow shaft (for wire pass-through) cycloidal reducers, along with eight encoders, a pair of Odrive BLDC servos, four stepper motors, and five Teensy 3.2 boards connected over a single CAN network.
Lickindorf states the Atlas has a maximum load capability of almost 10 pounds (five pounds are nominal), and although the load is wrist limited, it was able to lift 20 pounds at 0.5m with the axis 1, 2, 3 assemblies. The robotic arm is outfitted with a pair of encoders per axis for ax2 and 3, as well as one encoder directly on the motor shaft used by the Odrive, and one on a belt-driven joint.
Damien explains, “Ax4, 5, 6 — long NEMA17 steppers, also 2 step reduction, 1:2 belt (adjustable between 1:1 and 1:5 if needed) plus 1:11 cycloidal, so 1:22 total. The reducer I’m using here will be open source, and it'll be called OpenCyRe. Each of these 3 wrist axes has its own encoder, driven by a dedicated belt, from the cycloidal gearbox output. The belt increaser is 1:5.25, the encoder is 512PPR, so the resolution of the joint rotation is 2688 for ax4, 5, and 6. Ax5 and ax6 run on the same teensy, and ax4 has its own Teensy.”
While four Teensy 3.2 boards are used to actuate the robot, the fifth is dedicated to controlling the arm via a pair of 3-axis joysticks, and can also connect to a PC with input commands delivered over a serial connection. Lickindorf notes the mechanical side of the Atlas is completed, and he’s currently learning ROS and Moveit! to program the robot. Those interested can follow a detailed walkthrough of Lickindorf's build on his project page.