Resurrecting an Old Plotter (2019)

Those old pen plotters are beautiful to watch. I used to use them many, many years ago, and it was great fun.

You'd get annoyed sometimes because you'd watch it draw half of something, zip waaaay over to the other end of the 30x42 in sheet, draw half of something else, and then zip back and finish. I mean, that's neat and all, but really inefficient.

They also made a lot of architecture firms change their logos. If you had a logo with a big, solid black shape somewhere, the plotter trying to fill it in would often just tear through the paper.

This was also back in the days when Ethernet was some weird thing only found in Dennis Ritchie's office. So if you had a lot of CAD stations who all needed to use the plotter, you'd have a whole shelf of serial switchboxes and a baroque and byzantine process to select who gets to plot. And woe unto the poor serf who messed with the switch boxes and cut a plot short. At upwards of 20 minutes a sheet sometimes, you might find yourself hurled into the void.

auto-upvote for anything plotter-related... they're so much fun.

be sure to check out #plottertwitter on the twitter tubes (oops, totally missed that this was called out in the very first sentence), and i've also been collecting useful plotter-related links here:

https://github.com/beardicus/awesome-plotters

(one last edit / promo: if you get the nostalgia fuzzies for plotters, be sure to check out the "Manuals and Ephemera" section of the above repo, where i've linked up a bunch of plotter-related manuals and brochures and advertisements from the internet archive)

A few little comments:

1) The HP 7440A does support hardware flow control (RTS/CTS) so no need for the OA trick. You might sometimes need a better serial controller.

2) HPGL is simple enough you don't totally need it, but Chiplotle is a Python library for generating HPGL that will save you some work: http://sites.music.columbia.edu/cmc/chiplotle/

3) What the author calls a "DB-22 to DB-9 adapter" should be called a "DB-25 to DE-9 adapter." The shell size is kind of pedantic but the pin count confused me, because DB-25 is the spec standard RS-232 connector while a DB-22 is very much not! Actually if you get a USB serial adapter that's already a DB-25 it's more likely not to have issues with hardware flow control. Some of these plotters used HPIB instead which is a little annoying because the controllers are not so easy to find but they are out there and as a bonus you can use them with your old CRT storage oscilloscope too.

4) NOS pens for these plotters are stupid expensive, but I've had good success with using a lathe to produce some adapters to get it to grip Microliners. You will need a "case mod" of cutting out the section of the case between the carousel and the work area so the taller pens don't hit it. There are also 3D printed adapters you can find online but I've found the plotter is very sensitive about the diameter or it will fail to detect it has picked up the pen and retry a few times before going into error. My experience has been that 3D printed adapters aren't precise enough to avoid this issue but if you have a good printer or like a resin printer you might avoid this problem.

5) The plotter is very slow at linearizing curves internally even if you have the feature board, so you're better off doing that on the host and sending line segments than using the HPGL curve primitives. It's a print quality issue too because it keeps the pen down while calculating the next segment which tends to leave noticeable bleed at every node.

One of my favorite "dead tech" memories is from when I worked as a CAD operator for an engineering firm in the late 1980s, where we had a half-dozen AutoCAD workstations and a Roland pen plotter that used a large roll (several hundred feet long) of feed paper. In AutoCAD, you could sometimes fat-finger your work and kick a drawn entity way out into coordinate space without noticing it. As such you always needed to do a zoom extents every so often (and definitely before plotting it) to make sure you didn't have your own little Nemesis object lurking out in the dark.

My co-worker neglected to do this one time and casually sent the document to the plotter to be drawn. When the plotter reached the entity way out in coordinate space, you heard the click-thunk of switching pens and then a high pitched whine as the plotter started rapidly spooling out paper to draw it. I've never seen anyone move so fast as he dove to reach the plotter power switch before all the paper scrolled off the spool and onto the floor.

Plotters were state of the art back then but they have pretty much disappeared without a trace. I think the technology has been somewhat repurposed to make vinyl sign cutters, they are basically a plotter with a cutting blade attached instead of a pen.

"affordable" = $1295 at launch in 1985.

I am pretty sure I used one of these, or a closely related HP plotter, in one of my internships to make charts for a presentation, using Harvard Graphics on a DOS machine. I remember they looked much better than I expected. It's probably hard to get a sense of the quality of either the plotter's output or, say, the quality of programs like Harvard Graphics without using them together.

I built a partial HP-GL importer to our small CAD visualization startup's internal vector data structure ~20 years ago. I remember thinking HP-GL was quite elegantly designed, especially for being so old (1977).

Always wanted one of these plotters, just because they were amazing pieces of machinery, moving so insanely quickly.

One thing, there is no such thing as "DB-9". It is DE-9. The "E" is the size of the shell. (The B shell has room for 25 pins on 1/10 inch spacing, an E shell room for 9; or 15 with pins closer, as in a VGA connector.)

That fact doesn't stop retailers from listing DE-9 hardware as "DB-9" to attract confused customers, who then remain confused.

My favorite thing about these old plotters is that you can get knife pens, meant for cutting ruby-lith to send out to a circuit board fab. You would peel off the red part wherever you didn't want copper on the board. The board shop would photo-reduce your mask to actual size, often a 10x reduction for manually produced designs. Which existed!

I wonder if you can still get ruby-lith.

I worked at an engineering office which had a monstrously big plotter; the paper was draped over a single large roller, the pen only moved in one dimension along the axis and the roller rotated clockwise and anticlockwise to move the paper in the second dimension. That thing absolutely flew, and it was mesmerising watching the paper zipping around driven by that roller.

See also https://www.buildlog.net/blog/2019/10/ I use Bart's controllers all the time.

After somewhat obsessing over the old plotters I bought one, and now I find I don’t have much I want to do with it? I’ve been playing with a few things in Inkscape and some js I wrote but that’s it. Any suggestions on where to go next?