CNC Etch-a-Sketch

by BenJackson, published

CNC Etch-a-Sketch by BenJackson Mar 6, 2011

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What can I say? I've never been able to draw anything with an Etch-a-Sketch. I won this one in a Christmas gift exchange some years ago and hung onto it with the idea that someday I'd CNC it.

The stepper motors are 7.5 degree Airpax steppers I got surplus many years ago. It turns out those mounting ears are actually NEMA 23 compatible so this should work unmodified with "square" steppers as well. The 7.5 degree steps led me to make the most aggressive gear reduction I could fit in the available space. They take me to about 0.15mm (6 mil) steps with half-stepping.

The stepper drivers are L297+L298 almost straight out of the appnote. They're built on a piece of copper clad with a combination of dead-bug and Manhattan prototyping. I bought all the parts years ago and never got around to etching PCBs. Those flyback diodes are ridiculously oversized because I didn't know better.

I chose http://reprap.org/wiki/Teacup_Firmware because of the builtin gcode interpreter. That saved me from having to integrate with any desktop software. I ported it to the AT90USBKEY you see in the picture and added support for LUFA-based serial right in the AVR. (I already had the AT90USBKEY or I would have just bought an Arduino!)

It easily goes 8000mm/min (which is how fast the pictured spiral was drawn). Given the torque and the large step size I suspect it could go fast enough to melt the stylus if you cared to.

The gears (as printed and uploaded) have slightly too much backlash. The "exact" fit was too tight so I backed off by 1mm which was way too much. They're derived from http://www.thingiverse.com/thing:5505 .

The spiral was drawn in Inkscape and converted to gcode for Unicorn with http://www.thingiverse.com/thing:5986 . I plan to modify that to make more Etch-a-Sketch friendly output.

Video: http://www.youtube.com/watch?v=6UV05jmrK7k


Print one of the mounting plates, then mirror along the long axis and print again for the other side.

Print two each of the stepper gear and the Etch-a-Sketch gear.

Remove the original knobs from the Etch-a-Sketch (they're just press-fit).

The mounting plates are designed to closely follow the contour of the Etch-a-Sketch. I attached mine by applying substantial amount of hot glue (quickly!) to the plate and pressing it into place. The plate is attached very solidly but I'm hopeful it would peel off with some effort.

Mount NEMA 23 steppers to the plates.

Press the large gears onto the Etch-a-Sketch ensuring that the hub faces inward. Make sure the gear clears the mounting screw for the stepper.

Press the small gears onto the stepper shafts with the hubs facing outwards. Align the teeth with the large gears.

Print two feet for it: http://www.thingiverse.com/thing:6872

Connect the steppers to stepper drivers and some kind of controller. Standard gen3, gen5, pololu, etc would all work fine. Find some 2D gcode (such as you might generate for the Unicorn!) and go!

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Really nice Build! I'm assuming the squaring off on the "x"
is due to the slop on the internal cables?
but the "y" seems smoother for some reason anyone Know?
I took mine apart 2 days after I got it, like all my other toys, Made a mess...

That is a very cool driverboard indeed!

I love it. Just need to make it leave messages from the internet on the fridge and automatically wipe out. Maybe even a screen saver that slowly draws until the message expires.... the possibilites are endless....

An amazing idea very well executed. Love it! :-D

This is awesome. Not only the design of the gears and the mounting is good but also the electronic board looks fantastic. The diodes may be oversized but they look amazing in there :D

Looks like it could be hacked into a 3d printer by using it as the x and y stages in a simple box and something like twotimes z-rider as the z stage. Using a bowden extruder and a small heater nozzle like the one Adrian designed recently.

Inside an etch-a-sketch looks like this http://www.howstuffworks.com/question317.htmhttp://www.howstuffworks.com/q...

With the cover off you could lay it down on some carbon paper and print on anything you want. Provided the moving stylus can stand the necessary amount of pressure.

Who knew! It's UltiSketchMaker!

I have added a video! It's at http://www.youtube.com/watch?v=6UV05jmrK7khttp://www.youtube.com/watch?v... but the spiral has actually turned into a bit of a test for the video CODEC. When I get the Unicorn Inkscape plugin working better for Etch-a-Sketch purposes I'll try another.

Huzzah! Oh, please, oh please post a video?!!!!

Beautiful! Could we perhaps have a video of it sketching at 8000mm/sec? That would be awesome!

I love this for several reasons.

  1. The design is elegant.

  2. The documentation is complete.

  3. Your choice of blue plastic contrasting with the red etch a sketch is excellent.

  4. Your prototyping board is beautiful, almost a work of art in itself.

  5. The combination of the etch with the new technology is nostalgic yet cutting edge.

Very nice.

I made one of these a few years ago with a basic stamp. It was hideous. Yours is awesome. Thank you so much for posting this.

Awesome work! Now if you could just make all this internal and make a truly "magic" Etch-a-Sketch!

Mount it up to the wall and you would have a retro picture frame!

The Unicorn plotter just got upstaged. Seriously nice job. Video, video, VIDEO, VIDEO (etc.)

Very nice, I too would like a video. I want to get an eyeball on this 8000mm/s. I've never seen an Etch-a-sketch scream and burst into flames before. :)

that is pretty awesome do you have any videos of it in action?

Clever design. Really liked it:)