An intro to Pen Plotters

Tobias Toft
Published in
9 min readMay 2, 2019

I originally posted this on my website back in July 2014. It seems that interest in pen plotters has picked up recently, so I decided to move the post to Medium which is arguably a much better place for it.

HP 7475A plotter — I paid $50 for it on eBay. The Delaunay triangulated Marilyn was one of my first experiments.

I’ve been fascinated with pen plotters for a long time now and I’ve owned several of them — but for some reason never posted any of my explorations or findings online. Until now, at least.

You might wonder what’s so special about pen plotters? Well, let me tell you. Pen plotters are friendly robots from a not so distant past. They’re the missing link between pencils and laser printers. They’re lovely pieces of high precision technology that nobody cares about anymore. They’re computer controlled machines that use regular pens to draw on regular paper with incredible speed and precision. They would draw blueprints for tweedy engineers and turtlenecked architects back in the 70’s and 80’s, they would draw colorful charts on transparencies for slick investment bankers to present on overhead projectors, and they probably also drew the schematics for the laser- and inkjet printers that replaced them a decade later. They were expensive, beautifully engineered, high quality machines. Which means that there are still plenty of them around, fully working and very cheap. You can, for instance, pick up an HP 7475A on eBay for roughly $50, it’s a great starter machine and I can’t recommend it enough.

They’re purely made for drawing though, so you can’t print a book with them (unless you want a certain style to it), and they would suck at printing holiday photos or boarding passes. But they excel at crisp line drawings with a wonderful analog feel.

A closeup of the 7475A’s line quality when using a slightly worn felt tip pen on rough paper. No pixels, lots of personality.

Talking to them

There is one minor problem though, and that is that you can’t just hook them up to your laptop and start plotting things from Illustrator: They speak a language that most operating systems have forgotten. Luckily it’s a pretty simple language, so with minimal coding skills you can start plotting like it’s 1984.

Here’s what you’ll (probably) need to get started:

  • A pen plotter with a serial interface