In order to build more complicated projects such as personal robotic assistants, robotic bartenders, and more, I first needed to design a reliable low-cost robotic arm. View build log and project details at sajivshah.com
The upper base was contoured based on the KUKA KR-10 robot, as I found it visually appealing. On the outside, it features an encoder, and on the inside, there is a sun gear bolted to the face on which two planet gears from the first axis motors will drive around. This part was also printed from a 0.6mm nozzle, and in the middle, there was a slight hiccup but I solved that with some simple filler and acrylic cement, The encoder wires go into the main hole through small holes, and beneath the upper base piece is a hex axle which goes into a hole and sticks down through the bearing at the bottom of the lower base piece. On this axle is a gear, which the base motor drives using a motor hosted on the inside.
The base piece for the robotic arm is 3D printed using a 1mm nozzle and is about 8 inches wide at the max. It tapers at the base and has mounting holes to mount to a table, and also has a bearing hole in the middle, which in this image is covered by the first axis encoder. This encoder has a through bore for a hex axle, which is what I will be using as it easily indexes and does not require a set screw. The lip at the top is for a lazy Susan bearing, which will be used to attach the upper base piece. The hole towards the edge is for a DC motor, which will transfer power to the center axle using a gear.