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:
Mounting the motor inside each arm segment behind the pivot point.
Using a right-angle gearhead with its shaft fixed to the "parent's" segment.
Passing cables through a hollow bearing.
So each motor is part of its arm segment and swings with it.
V Click thumbnails for full size V
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 ...