A New Elbow


You may remember the Arc-O-Matic, an Arduino-powered drawing robot I built back in March for Gallery Night.

Well, things have been quiet on the Arc-O-Matic front for a while, and there are reasons for that. First, while shooting a video showing how it works, It started to fall apart. This was not unexpected. The whole thing was built in a few hours, and held together with hot glue and gaff tape. Failure was just a matter of time. Second, while it was in my workshop awaiting repair, one of the cats (ChaCha!) managed to knock it off a table onto the concrete floor, which made things worse.

But an important thing happened between the destruction of the Arc-O-Matic and now… I can easily 3D print things!

Elbow (old)

Here we see the old elbow mechanism, which consists of glue and tape. Pretty sad. It held up fine for Gallery Night, but it’s no permanent solution.

So my first idea for repair was to take some of the weight off the arm via the elbow joint. I thought about buying some ball casters but then realized I could just print my own! Here is one on Thingiverse, and here’s a photo of the one I printed. My initial idea was to just glue this on to the bottom of the micro-servo.

But when you’ve got a 3D printer, why stop there? I ended up designing a part that would hold the micro-servo, and allow the dowel to attach to it. See this photo.

Now, I know some of you still don’t get Google+, so here’s how it works. I posted my progress there, and someone who follows me mentioned a post about Florian Horsch printing a servo coupler on a Ultimaker. My first thought was, “crap, can I print that on my MakerGear Prusa?” And yes, I definitely can.

Elbow (new)

So here’s the result so far. A new elbow. The bottom piece holds the larger dowel and the micro-servo, while the top piece fits snugly onto the business end of the micro-servo and holds the smaller dowel. I’ve not yet attached the ball caster (which uses a marble) in this photo, but I tested attaching it to an earlier version using acetone to weld the plastic together. (I suppose a screw could be another option there.)

I’m hoping to get this thing rebuilt and working before the end of July (hint hint!) and once I’m pleased with all the pieces, I’ll write up some instructions, toss the files on Thingiverse, and hope someone else thinks it’s cool enough to play with.

3 replies on “A New Elbow”

I am actually working on a design that I would love to leverage the electronics and software of this for!

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