Building a 6-axis arm

A while ago I started looking at a project which would require a robot arm with a payload of up to a pound and a reach of ~2 feet. New commercial models were too expensive ($5k+) and I didn't want to mess around with surplus stuff full of proprietary systems, so I went looking for plans or build logs and couldn't find anything. So, I decided to build my own and document it as an open-source design.

I decided to use the PUMA configuration as a starting point as it seemed like the best mix of simplicity in construction and control while still being relatively capable. As an added benefit, it will be possible (I think) to re-use pieces of the arm to build other configurations such as a SCARA arm with limited or no modification.

This past weekend I was able to run a smoke test of sorts with the two sections of the arm lifting some test weights to validate my motor torque estimates. The video below shows it lifting a bag with 36 ounces of weights as well as another weight to simulate a motor I expect to attach on the end of the smaller arm. The distance from the load to the center of the first joint is 24" so I am now feeling pretty good about ending up with at least a pound of payload allowing for about a pound for the wrist and gripper which I am now designing.



(in case the video preview doesn't work, it's here: )

All design has been done so far in Alibre and parts are being made on a Tormach running LinuxCNC. I am hoping to be able to use LCNC to run the arm when it is done.

They're just ordinary deep groove bearings in 1" and .750" size. Eventually I want to run the cabling through the bores but that will require a little redesign. I'm also using pairs but one would probably be enough.