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Comment by thot_experiment | Hacker News Reader

That is one EXTREMELY overbuilt plotter, you love to see it.

For a properly extremely overbuilt plotter, you could do what I've done: tape a pen to a 3D printer. It's a bit like building a back massager by putting a cell phone on vibrate and texting it continuously, but it's also a dang good plotter once you figure out a set of G-Code instructions that don't destroy the pen by accident.

I've been thinking of taking advantage of the ability to raise the pen really high to do something crazy like use a quill and an inkwell, but I use a bed slinger printer, so figuring out an inkwell that doesn't splosh ink around everywhere or floats just over the bed is probably more work than the idea is worth.

I have a custom built plotter that paints in watercolor, I don't have a lot of good media depicting it yet, but if you're local to the Bay Area I'll have a booth at Maker Faire showing it off!

I'll look for you!

That is really, really cool! I'm not but I look forwards to hearing more about it in the future. Really curious about how you move the brush. Pointillism? Filling polygonal regions with lines? Some sort of interesting "imitate real brushwork" algorithm?

Do you do color change by swishing the brush in water? Ooo, does it mix colors? Because that'd be super fun if probably impractical.

Here is a simple commercial product (designed by EMS who also makes the axidraw plotter) https://watercolorbot.com/

I take a bunch of different approaches so the short answer is "Yes" but I'll try get a little more in depth.

I mostly use something akin to a "imitate real brushwork" algorithm, but it's more a "mess with the code until it looks right to me" algorithm.

> Do you do color change by swishing the brush in water?

Sort of, this aspect of definitely has some physical bugs (flooding my work area occasionally) but I am using an automated water pot that works using a pythagorean siphon and is controlled using the coolant flood commands in GRBL (used to cool bits when cutting with a CNC ordinarily)

> Ooo, does it mix colors?

This is what I'm currently working on, but it's very much a non-trivial thing to solve. Luckily you don't have to be precise to make good art, there's a lot of opportunity for happy accidents.

self promo: While I haven't been very good at producing compelling media about my plotter, I do have a patreon where for $7/mo I mail you a postcard-sized plot every month demonstrating whatever thing I'm working on at the moment. https://www.patreon.com/thot_experiment

here are a few examples of last month's plots, these are colored by hand https://thiic.cc/heavy/bb_plot.jpg https://thiic.cc/heavy/crank_plot.jpg https://thiic.cc/heavy/pedal_plot.jpg

and here's a few that are pure robot https://thiic.cc/heavy/abstract_plot.jpg https://thiic.cc/heavy/other_plots.jpg

Really cool! Thanks for sharing.

A sponge is the inkwell you want :) micro-baffles

> figuring out an inkwell that doesn't splosh ink around everywhere or floats just over the bed is probably more work than the idea is worth

What if...

- cut a custom bed out of a piece of plywood or something, letter-shaped so there's a few cm of open space along one side

- position an ink well directly under the Z gantry

- set your Z offset such that the tip of the quill is 0 and set your min-z to -5cm or something

Refilling the quill would then be homing the X axis and dipping the quill down to negative Z.

I bolted a linear rail to my 3D printer next to the nozzle and clamped a pen to it, so it applies constant pressure (due to gravity) and there's less risk of destroying the pen/paper. The downside is that lifting the pen is very slow, since it's a lead screw Z axis and there are a couple mm of travel in the rail before the pen carriage hits its stop and actually lifts from the paper.

I agree that the instructions were the tricky part - lots of messing around in Inkscape and Python and manually editing GCode.

Very over built. A lot of the times you just see two beams that advance their respective axis because there's so little force applied by a pen.

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