A pen plotter is a simple kind of robot. In technical terms, it’s an XY gantry that holds a pen. The pen holder can go up and down — that would be your Z axis. Put a piece of paper underneath, move the pen around, and ink goes on the paper. This is more fun than it sounds.
The world of pen-plotting falls somewhere in the universe of "making". There are so many ways to "make" — but many creative avenues take a lot of space, like woodworking, or create quite a bit of waste or fumes, like 3D printing or laser cutting.
Pen plotting doesn’t have to take much space at all. While I have mine on the desk, I've seen people hang pen plotters on their wall (one plotter, the Makelangelo Art Robot, is expressly designed for wall mounting). The only waste you’ll be creating is easily recyclable paper. It doesn’t generate any fumes or dust, and it doesn’t use exotic consumables. You just need some pens and paper.
Pens and paper, by the way, are their own special kind of fun. I always loved stationery. There is something magical about walking through a local store and seeing all the pens and papers and inks. But I never had much use for all those wonderful pens and papers because, as you might have guessed, I tend to type more than write things by hand.
But now, with pen plotting, I can suddenly enjoy a world of pens and inks and papers and see how they interact. And yes, if you've been following along, my pen collection did grow since I wrote ZSA Loves Refillable Pens.
Another aspect of pen plotting which is quite fun is precision. There is something very satisfying about crafting something precise. A perfectly straight line on its own is nice — this is why we buy rulers. One thousand perfectly straight lines, each perfectly spaced from the next—that’s something that starts looking a little more interesting.
In technical terms, what the plotter runs off of is called G-code. That’s the same type of simple code that CNC machines and 3D printers use to work their own kinds of magic. It’s a text-based, human-readable language. This again adds to the appeal and simplicity of plotting, because I can actually read through the line-by-line machine instructions that my plotter gets and understand them. "Here's where it raises the pen, and then it moves a bit!" — thrilling stuff, as I've said.
That said, I don’t have to manually write G-code: There are mature and free tools for converting vector graphics files into G-code. And for creating those vector files, there are so many options. You can use free software such as Inkscape or traditional vector editors such as Adobe Illustrator or Affinity Designer. Or you can use more purpose-built software for creating plots, like DrawingBot or Paragraphic. You can also create beautifully artistic SVGs and line art using code with frameworks like p5.js.
Once you have an SVG you want to plot, it’s time to consider the actual plotter you'll be using. There too, you’ll find such a wide variety of options. There are DIY plotters that people make from scratch with general-purpose servomotors and aluminum extrusions. Right above that, there are plotter kits like the Michelangelo or the ACRO Openbuilds Pen Plotter. Then there are commercial, fully packaged plotters, like the ones from AxiDraw or the ones that I use from iDraw/Uunatek.
Once you have a file and a plotter, it’s time to consider the pen and the paper. I touched on this earlier, but I remain impressed by how little waste my plotting generates—especially when compared to my other hobby, which is 3D printing and 3D design. My own pens are all refillable, and fountain pen ink comes in numerous colors.
That's another difference between plotting and printing: You control the color "in hardware", by simply using whichever pen you'd like. So you can plot the same exact file and get drastically different results depending on the pen you use. You can also slightly shift the paper and then plot the same file again for an interesting offset look — again, without touching any code or software at all. It's simple and tactile.
The flip side of that tactility is that it's easy to mess up a plot. Maybe you didn't set the pen at the right initial height when you put it into the holder; maybe the paper was a bit crooked or it shifted around or lifted. And even once you know what you are doing and have a good plot, whatever you get out of a plotter has tiny inconsistencies in it. From afar it might look like a print, but as your viewer draws nearer to the image, little inconsistencies and wobbles or skips of the pen start showing. This is very much a part of the magic in pen plotting.
We all have an intuitive understanding from a young age of what happens when you put pen or brush to paper. And so there is this lightbulb moment where you see someone realize the image they’re looking at was drawn line by line using a pen. This creates an instant connection, because we all know what a pen feels like.
The Surprise
One surprising thing for me about pen plotting is how photogenic and engaging the process itself is.
We all have many machines doing things throughout our lives. It would not usually occur to us to just sit down and watch a washing machine as it works. Most of us take the running of cars, blenders and fans for granted—they just do their thing.
A pen plotter is unique within the landscape of machines in my life in that I just like watching it work. It is inherently transparent and clear. You can tell exactly what is going on by simply looking at it, and that makes it quite mesmerizing.
In that regard, a pen plotter is that rare machine in my life where it is just as much about the process as it is about the end result.
