Jan 312014

Ever since I saw a post about a drawbot on Hackaday I’ve been wanting to build my own.

A quick search of drawbot or plotterbot or polargraphic plotter will lead you to plenty of youtube videos and websites describing and demoing polargaphic style plotters.

I don’t expect to break any significantly new ground here. I’m planning on building a pretty standard two stepper motor, servo pen lift, monofilament on pulleys, weighted gondola polar plotter.

One thing I am doing that is possibly different, at least I haven’t seen it’s like yet, is I’m planning on using an Eggbot EiBotBoard for motion control.

If you don’t know what an Eggbot is google it, watch a couple youtube videos, visit a few websites. It is a cool toy, and fundamentally nearly identical to a polar plotter. Basically an Eggbot is a spherical plotter. It should be a short step to a polar plotter. Certainly the hardware should be a drop in. The EiBotBoard has built in two axis coordinated stepper motor control, a pen lift servo control, and open source software for control and drawing conversion.

I plan on 3D printing the motor mounts and the pen gondola. Thingiverse has multiple models for motor mounts of various sizes and multiple different gondola styles. No real rocket science there. Download the models, update as needed for my motors and pen, and print them.

The interesting part is likely to the modification of the path generation to interface to the EiBotBoard. The Eggbot community has written a plugin for inkscape to wrap a flat vector drawing to a sphere and output the motion commands to the Eggbot EiBotBoard. It seems like a reasonable launching point to start with that plugin and modify it to convert line art to polar graphics and then drive the EiBotBoard on a polar plotter.

Often my blog posts are generated after the fact, after I’ve already completed the project, or done enough to figure out what I want to say or how the project is going to go down. In this case I’m blogging as I go. I haven’t started my polargraphic plotter project yet, other than a vague idea of what hardware I want to use and some of the mechanics that I think will work.

Next steps include picking parts and getting them ordered, picking some models and getting them downloaded and printed, downloading the Eggbot interface software and figuring out what’s going on there, then hook it all up and print, easy-peasy-pie.

I’ll keep you updated as I go.

  4 Responses to “Building a Polargraphic Plotter (a Drawbot)”

  1. Hi Brad!
    I’m glad to hear you’re embarking on a drawing robot build! You may find that the Inkscape Unicorn plugin may work better for your drawing robot. It’s designed to convert an SVG file into a set of XY coordinates. It might be a lot easier for you to use a set of XY coordinates than trying to hack the EggBot Inkscape plugin “unwrap” the sphere again.
    I look forward to hearing more about your drawbot!

    • Hey !! thanks for the hit up. I’ve been reading your makerblock and plotterbot blogs and you’ve provided a ton of interesting information. Thanks for doing all that legwork. I just finished 3D printing my motor mounts and am about to print your filament spools.

      I’ll look into the Unicorn plugin. The EiBotBoard commands are pretty well documented so it might make sense to go at it from that angle.

      • You’re welcome! I love seeing other people put together drawing robots. If there’s anything I can do, definitely drop me a line.

        Oh, man – don’t print those spools. They’re finicky and can unexpectedly come apart. Once one of them popped apart – spewing monofilament line all over the place.

        Now, these spools http://www.thingiverse.com/thing:73378 are totally rock solid. (I discussed the design at length here http://makerblock.com/2013/02/overengineered-spools/ )

        If you do go the Arduino route, you should seriously consider checking out Sandy Noble’s Polargraph hardware. That’s what I use to power my own robot.

        Good luck and keep in touch!

        • Thanks for the heads up on the spools. I was just sitting down to fire up the printer for the old spools but I’ll download and take a look at your new spools. I read your blog post and your reasons for the redesign seem reasonable.

          I’m still gonna give the Eggbot board a shot. It’s not necessarily a better choice for any good reason I can come up with, but I think I’m going to try it anyhow. And if I can’t get from A to B I can always fall back.

          If I get stuck I’ll definitely call for help. Thanks again for all the hard work documenting your build. Having you break trail makes it easier for the rest of us to follow along.

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