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  • Writer's pictureJohn Strope

Animatronic Chain Chomp

Updated: Aug 18, 2022

This is an animatronic Chain Chomp, best known from a number of Nintendo games and the perennial enemy of uncoordinated Mario kart players everywhere. I got to spend some time on a recent project with a full-scale version of this, and immediately wanted to build a smaller version for my desk. After a little bit of 3D printing, painting, sanding, and solder, this is what I ended up with.

Three motors run the entire mechanism. This allows for looking up/down, left/right, and opening/closing the jaws. Everything was designed in Fusion360 and printed on an Ender 3 V2, with small magnets holding most of the pieces together for ease of assembly.

I wanted everything to be extremely compact. I thought the envision board was as small as something like this could get, but I was sorely mistaken. After playing around with the Seeeduino Xiao and DFRobot Beetle, I decided to work with one of these boards.

After writing some basic code, I measured the amount of current that 3 servos consumed to be around 300mA peak. This should be a low enough draw to run the motors directly from the board, meaning we can run everything with a single USB cable and don’t need any external power inputs.

Printing the parts was a relatively straightforward affair. I initially used a grey PETG filament for prototyping, but later realized that white material would save an extra coat of paint. Parts like the teeth then became much more “realistic”-looking.

For removing the layer lines from the shells, I sanded the raw parts with 200 grit sandpaper before applying a coat of filler primer, sanding again with 200 grit, applying another coat of filler primer, sanding with 400 grit, and then applying a few thin coats of the final matte black topcoat. The teeth I masked with masking tape before spraying the mouth and jaw hinges matte red.

Painting the bricks of the base was probably my favorite part of the whole process. I used a brush to apply multiple thin coats of a terracotta color and before adding highlights/lowlights to each of the bricks’ edges/facets. It’s really hard to understate how good this looks in person. It feels like I’m staring at an object from the video game.

I ended up printing some thin eyes, but you could just as easily use 1”/25mm googly eyes for a more dynamic look.

Assembly was not as simple as I would’ve liked. After installing the motors, the cables have to be run through the bottom shell and base cap before being hidden inside the shaft, a finicky process that saw me break and reprint many a piece. Eventually I got it, but it wasn’t easy.

All in all, I’m happy with how this one came together!

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