This was a great intro! Makes me want to get a pen plotter while I can, and it's cheap to do.

I love pen plotters. In the 80's, and actually a ways into the 90's, I used them in tandem with CAD systems to do a variety of manufacturing and detail drawing related tasks. The drawings part is what you would imagine. It's a ton of vectors that add up to an engineering or architectural drawing.

The precision of these machines is actually quite good. When used with vellum paper, one can make overlays or underlays for inspection, layout and other tasks. An X,Y plotter will be more uniform than a roll plotter, but the roll plotters can handle very large sheets in one axis. Usually, a small factor can be used to compensate for whatever difference there is between the roller and the other linear axis. I remember it being small, fraction of a percent.

Over / underlay drawings, along with check drawings of various kinds were the daily driver use case. For the check drawings, ordinary paper worked fine. Vellum, has better characteristics for precision work. It won't stretch and can be handled and tolerate some shop grease and grime in a pinch when thicker grades are used. I recommend it for archives and or just that serious tech look. If you want a very seriously sharp drawing, a fine pen can produce amazing line art! There is almost no ink bleed.

Once, I ended up on a contract to make parts for Boeing and the shop I was in at the time had no real certifications, so Boeing sent me a 1:1 camera produced image of the part. And it was from a CAD system! Had I been able to get the file, I would have produced the part for them quick and easy. Just use the CAD data to drive a laser and one and done, but no.

So, I ended up taping the 1:1 scale image to a large inspection table, taking points, using a pen plotter, with compensation factors to get max precision, vellum paper, and laboriously recreated the shape and overlaid it to insure accuracy. This took a very long time, but it was actually very satisfying to do.

Another odd use popped up one time too.

There was a group of parts that formed an assembly. This was before nesting and optimization software was common for sheet metal turret punch and laser machines.

I used a plotter to produce all the flat shapes of all the parts, and abused a pen by drawing over profile edges enough times that the paper would tear / cut easily. Sat down at a table and shuffled them, until they would just fit into the largest possible sheet. That was kind of amazing. Do it once, save X square inches. Do it again, lose Y square inches. Again, Save, save, lose, save... eventually finding an arrangement that saved a ton! The software and computing systems really were not up to doing this at the time. Or, were but the applications were ultra expensive. So it took an hour to do it old school.

Used a Polaroid camera to capture that layout and reproduce it in the CAD system with precision to allow for optimal shared profile edge cuts and such.

Then came punching it out of the metal! Several thousand punch operations were needed, and that was another optimization problem and it was useful to do the same kind of iterative process, but machine time was expensive, so I used a pen plotter. Pen changes mapped to tool changes reasonably, and double drawing some entities mapped to other machine attributes. All in all, after a few basic constructs were mapped out, I had a very representative simulator that did produce useful visual output and the motion could be evaluated for other purposes, like sheet snagging and or just potential cosmetic issues.

Spent a few days sorting and plotting. Got 10 minutes of machine time down to a little under 4 minutes.

A year or two later, after I had left a friend saw the company buy the high end nesting and optimizing software. It was able to get another minute out of that job, and was able to do so in 10 to 15 minutes of computing. I think this was called SigmaNest and I forget what the tool path optimizer was called...

The work I did took about 4 days!

All that aside, I find pen plots, the noises, watching the paper move, all of it really satisfying. The better plotters are just wonderful machines that nail their purpose. Fun to see. Good tech, if sort of useless now.

If you want, you can use an old 3D printer as a pen plotter!

I have done this on mine, and it works very well. The accuracy is comparable, but paper sizes may be limited by the printer build area.

All one needs is Z dimensions to handle PU and PD, and G0, G1, G2, G3 to handle the basic lines, moves, arcs.

You won't get any of the fancy fills that way, but Inkscape can generate those as a combination of lines and arcs, and the overall effect is the same, only the plotters are generally much quicker than the 3D printers can be.

Overall look, with a good pen, vellum paper, is comparable as well.