Science olympiad is coming up! This year one of my events is called “Robot Arm”. The rules say you must construct an arm that can drop various objects (D batteries, nails, other things the judges had sitting on their desks when writing the problem) into specific bins. To control the full sized arm, I designed and built a smaller model out of 1/8″ acrylic. Potentiometers act as the fulcra, allowing me to run them through a microcontroller and later transpose these signals into larger actions by the servo motors. I think this is a pretty cool way to control a larger arm. Also, rapid prototyping working gears on the laser is really, really satisfying. Lasers really do make everything better.
The first video above shows the process of cutting out all the parts, while the second is a time-lapse of assembly. Of course, you can download the design here, for your own laser-cutting/CNC router pleasure: Source.
The design is very specific to these slotted potentiometers. It’s a really tight fit, and that’s intentional. I didn’t want to have to use glue on the joints. These 10k potentiometers from Sparkfun should do the trick. You could probably get them cheaper from Digi-key, if you could find them.
Join all the non-moveable joints with superglue, and you’re good to go! Now, making the arm actually do something is up to your discretion. I’m going to get around to building the larger arm as we get closer to the competition… it’s a slightly bigger task.
I’ve been working on building the full sized arm (a pretty big job) with my friend Ben, and we’ve made some progress assembling it. Instead of glue and slotted joints, we’re using slots that nuts fit into, with bolts driving everything together. It’s coming out really well so far! Things go a lot faster with two pairs of hands!
We had some problems with flare ups on the laser while cutting the acrylic. I wasn’t using the air assist (which blows 30psi air on the work surface while cutting) because I need to go pick up some oil for the compressor, but we effectively eliminated the flame issue by taking off the acrylic’s protective paper ahead of time.
Cutting acrylic on the laser is fantastic, because it beautifully polishes the edges while being cut.