We ran a story about a wall-mounted plotter bot this week, Mural. It’s a simple, but very well implemented, take on a theme that we’ve seen over and over again in various forms. Two lines, or in this case timing belts, hang the bot on a wall, and two motors drive it around. Maybe a servo pulls the pen in and out, but that’s about it. The rest is motor driving and code.
We were thinking about the first such bot we’ve ever seen, and couldn’t come up with anything earlier than Hektor, a spray-painting version of this idea by [Juerg Lehni]. And since then, it’s reappeared in numerous variations.
Some implementations mount the motors on the wall, some on the bot. There are various geometries and refinements to try to make the system behave more like a simple Cartesian one, but in the end, you always have to deal with a little bit of geometry, or just relish the not-quite-straight lines. (We have yet to see an implementation that maps out the nonlinearities using a webcam, for instance, but that would be cool.) If you’re feeling particularly reductionist, you can even do away with the pen-lifter entirely and simply draw everything as a connected line, Etch-a-Sketch style. Maslow CNC swaps out the pen for a router, and cuts wood.
What I love about this family of wall-plotter bots is that none of them are identical, but they all clearly share the same fundamental idea. You certainly wouldn’t call any one of them a “copy” of another, but they’re all related, like riffing off of the same piece of music, or painting the same haystack in different lighting conditions: robot jazz, or a study in various mechanical implementations of the same core concept. The collection of all wall bots is more than the sum of its parts, and you can learn something from each one. Have you made yours yet?
(Fantastic plotter-bot art by [Sarah Petkus] from her write-up ten years ago!)
There was a guy making these, huge ones, in the mid 1980’s West of Palo Alto (along San Gregorio creek? Pescadero?). IIRC he had commercial customers who would do entire walls for places like auto dealerships. Or basically anything.
Links! Would love to see.
I have pictures of some guys using the same basic mechanism with three spray cans on a concrete wall in San Francisco in 2018. We even had at least one wall size pen plotter at my college that worked this way in the early 70s. The tech world loves to reinvent things.
By the way, my guess would be this type of pen plotting technology dates back to some military project in the 50s , if not earlier.
Wall plotters are boring.
Inkjet wall printers are where its at.
https://youtu.be/6wj1VeNsv4k?si=B8i1xcZUx2NKYEED
The guy I mentioned above used ink-ket / air-brushes.
I have a very similar hack on my wall at the moment, with two line-producing lasers creating an “X” instead of a pen, and various maps of the world instead of a blank canvas! One day I’ll sit down and do the maths to have it accurately point at a provided lat/long — I’m so close!
After reading the article seen last week here about this wall plotters, I have added another project to my todo list.
One thing I would like to explore is replacing the pen with a Inkjet head such as the HP45. Carriers for these cartridges and cheap replacements are plenty as well as documentation for how to drive them.
Now I just need time to work on it.