So with my recent knowledge of Stepper Motors it was time to try them on my next robot arm.

Steppers are much heavier than RC Servos so I knew I needed some kind of counter-balancing for at least the shoulder and elbow joints. So why not use the motor itself as a counter-weight? This required a few things:
So each motor is part of its arm segment and swings with it.
V Click thumbnails for full size V

I also wanted to try using the 80/20 Aluminum Extrusion T-Slot hardware for this arm. I thought black would look cool.

So I found some used right-angle gearheads on Ebay and went to work. I used thin lazy-susan bearings for the pivot points.

With this arm section working I built an MDF base with an aluminum turntable also driven by stepper motor. The aluminum disc sits on a large 13-inch lazy susan bearing.

The gearheads were "loose" and had a lot of backlash. Plus, just these two sections were very heavy. So this partial arm's movement was sloppy and jerky. I decided to chop it in half by removing one side of each section. Still, it was very sloppy mostly due to the used gearheads ... typical for Ebay :|

Although it somewhat worked, it was very bulky and heavy and way too much machining had to be done to the 80/20 hardware. To be a sellable product I needed to reduce the labor a great deal and use as much off-the-shelf hardware as I could find, yet still have decent precision.

Maybe with a better design I'll come back to using the 80/20 hardware. But for now, it's back to MDF for more prototyping and the MDF Arm ...