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Project: "Eggplot" - Eggbot-based plotter
1st September 2011

A project that I've been desperate to try for a while: convert Eggbot from Evil Mad Scientist Laboratories into a plotter.

This isn't a plotter that works with X-Y axes, rather it's a plotter that works by hanging a pen assembly from a string passing over two motor spindles.  I have no idea what this kind of plotter is called if in fact it has a name...

Eggbot based plotter pen assembly

The hardware from Eggbot worked perfectly once I de-mounted it from the eggbot chassis.  I made some really rough mounting plates for the motors and the control board and a couple of iterations produced a working pen holder.

The pen holder gave me some trouble, it needs to hold the pen at constant alignment to the paper, any wobble makes the lines drawn really imprecise, so I settled on using 4 bolts as guides (with 2 heavier ones at the bottom), the suspension cotton is just run through two holes in centre of the holder.

The cotton is wrapped around the motor spindles a few times, a counterweight on each side (more bolts) keeps it in tension and reduces the load on the motor.  I was expecting some slip but I saw nothing significant, even on a really long plot.  I was also prepared for the flat spots on the spindles to make the plots wobble but I couldn't see anything on the ellipses I drew.

I had a happy accident with the mounting for the board, I put it on the Ikea painting/drawing easel the kids use and it turned out to be exactly the right height, width and angle, it should even be possible to mount the plotter directly on the easel & use it as a dedicated free-standing piece...

Theres a video (YouTube link) of the plotter in action embedded below, it's not fast so I think it might need larger spindles...

It would be very possible to make up some laser-cut mounts for the motors, control board and pen holder - in fact I'm working on that now & when I'm finished I'll make them available for download.

The next step is software, the geometry of this plotter means that the rotational movements of the motors don't neatly break down into linear X or Y movements and so the control software will need some tweaks to allow un-distorted shapes to be drawn.

I'm really excited about this project, at the moment it's small but there's no reason why it couldn't be scaled to draw on a whole wall.

Thanks have to go to Evil Mad Scientist - I've really enjoyed playing with Eggbot and I could spend entirely too much money at their shop...

fastness - Iain Banks Graphics
Fastness - Iain Banks Graphics
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An open source programming tool aimed at artists, engineers and designers.  Simple, light and Java-based with a wealth of libraries and a strong user community

3D printing for the masses - plastics and metal to your design or team up with a desigenr to personalise a design with a 'co-creator'.  Visit my Shapeways shop for some things I've designed.

MeshLab is an open source, portable, and extensible system for the processing and editing of unstructured 3D triangular meshes

Blender is the free open source 3D content creation suite, available for all major operating systems under the GNU General Public License

GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages

An Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format

Retail laser cutting outlet with centres in New Zealand, USA, Germany, Italy and the UK (if not more by now)

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