Insanely kludgy pen plotter actually works

This pen plotter, held together with structural epoxy, is an amazing piece of engineering, and almost as impressive as a bridge made entirely out of Bondo.

[Brian] at the Rochester, NY hackerspace Interlock needed to build something for the BarCamp geek “unconference.” To lure BarCamp attendees over to the Interlock table, they needed a small tabletop device with whirring motors that was able to make some decent swag. Hacking together a pen plotter sounded like the perfect project.

The mechanics of the build were scavenged from old printers and scanners. [Brian] decided to use pin-feed card stock, so the take-up wheels from an old dot matrix printer was sacrificed as well. This paper feed mechanism serves as the Y axis, and the X axis rides above the paper on precision rods. The pen holder is supported by a tiny solenoid.

Things start getting crazy at the software level. grbl was loaded onto an Arduino with a stepper driver shield, and vector text drawings were printed. After a bit of live-action hackery, [Brian] figured out how to plot captured webcam images. OpenCV captures and does a trace outline. This is converted to vectors with autotrace, and from EPS to HPGL by pstoedit. A Python script then cleans up the HPGL and converts it to G code and sends it to the printer. Confused? So are we, so just check out the video of the plotter in action after the break.

Comments

  1. Alex says:

    That’s pretty damn cool. I like how he used tractor paper for the feed system. Definitely makes things simpler…

  2. Ren says:

    It’s drawing a picture of itself! It is self-aware, don’t hook it to the Internet or it will become Sky-Net!

  3. PI says:

    I wonder… how well does Sharpie ink hold up against etching chemicals?

    Seems as though you could use something like this to make circuit boards.

    • Paul says:

      My first board etching was done using permanent marker to draw over the copper that I wanted to keep, then etched the remaining copper away, then nail polished the permanent marker off. So it works (using ammonium persulphate as the etchant at least). Didn’t make the prettiest board, since I was drawing on it by hand :-)

  4. Kyle says:

    I’ve gone to the BarCamp in my area for two years now, ever since I was convinced by a few of the other folks in the Linux Users Group. BarCamp is awesome. :)

  5. svofski says:

    Having made my own pen plotter, I can appreciate this work. And I’m really curious about their pen holder/actuator, which looks too fast and precise to be a made-on-your-knee hack. Not really a reused pen holder from another plotter?

    • Beardicus says:

      #imadethis

      Fast: yes, precise: not so much. The pen bits are basically the aforementioned solenoid from adafruit, epoxied to the two linear slides. On the solenoid plunger bit, I press-fit a little chunk of hardboard (same crap the whole structure is made out of) with a second hole big enough for a sharpie to sort of wedge in there. That’s it. I later realized that the solenoid plunger rotates freely, and thus the pen wobbled back and forth along the Y axis. Some tape and luck fixed this good enough for decent drawings, but it still needs a better solution.

      • svofski says:

        Thanks for the explanation. Well, you could probably try making a less wobbly plunger from some other printer parts, or other things. I could still appreciate some closeups of the pen mechanism, maybe consider making some pictures next time you’re bored :) Cool project!

  6. Robert says:

    Is there a reason it goes back and forward rather than just rolling one direction and drawing slices so to speak? Is it so the pen can roll?

    • third says:

      Yes there is. If it would draw ‘slice by slice’ it would be called a printer, not a plotter. A plotter draws the actual vector lines in the image, rather than some rasterised representation.

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