[HN Gopher] Pen plotters: not just output devices (2016)
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Pen plotters: not just output devices (2016)
Author : rbanffy
Score : 66 points
Date : 2021-04-30 08:10 UTC (1 days ago)
(HTM) web link (scruss.com)
(TXT) w3m dump (scruss.com)
| timonoko wrote:
| Can you make printed circuits by filling the ink cartridge with
| acid? I know it does not happen rightaway, put if you keep
| plotting same pattern and occasionally wipe the board clean.
| Eventually it would work for sure, but how long would it take? It
| would be slow but much easier than any other method.
| NegativeLatency wrote:
| Probably some kind of photo resist would work
| Animats wrote:
| There's conductive ink. There are pens that dispense an
| etchant. There's making printed circuit boards by iron-on toner
| transfer. There are little CNC routers for making boards.
|
| All these approaches are worse than the standard
| photolithography process with plated through holes. It's so
| cheap and easy to get boards made now. Upload files, pay a few
| dollars, boards come back.
| craftinator wrote:
| I've heard this so many times, but making your own is just a
| strong learning experience you don't get when you purchase
| them. You get exposure to mistakes!
| Animats wrote:
| Most of the alternative techniques are not precise enough
| for modern surface mount pin spacing. At 2.5mm pin spacing
| (0.10 inch, DIPs) they work. At 0.5mm spacing, not so much.
| It's mostly for retro projects that use through-hole
| components.
| xyzzy_plugh wrote:
| > It's mostly for retro projects that use through-hole
| components.
|
| Welp now I feel very old.
| IgorPartola wrote:
| I looked into making my own PCBs and came out with the
| impression that unless you need truly rapid prototyping JLCPCB
| is just better on all other accounts.
| scruss wrote:
| I'm always amazed when (or how) an article of mine shows up here.
| I suspect it came about through this twitter exchange regarding a
| mystery device that came with someone's Calcomp plotter:
| https://twitter.com/artandtech/status/1387838582149287939
|
| What I could never adequately explain is just how nicely made
| these digitizing sights are. They give a very bright, crisply
| magnified image of the point immediately under the pen position.
| This contrasts with how massively fiddly it is to try to operate
| exactly the right buttons on a pen plotter while squinting down a
| tiny optical sight.
|
| Even though pen plotters weren't rare in the 1980s and early
| 1990s, I've never found any software (beyond the terrible script
| I wrote for that article) that uses this capability. There's
| probably some HP BASIC code lurking on a half-forgotten
| instrumentation archive that does the job, though.
| zabzonk wrote:
| I loved our HP pen plotter, back in the early 1980s. I never used
| it for input, but one of the more useful bits of software I wrote
| back then was to take the output of a Coulter counter (see
| https://www.wikiwand.com/en/Coulter_counter ) via some strange
| sort of serial interface it had (current loop?) and store it on
| floppy disk on a CP/M machine. I then wrote another utility to
| read the disk and plot parametrised graphs of it on our HP pen
| plotter.
| GordonS wrote:
| We used to have a plotter when I was a teenager, in the 90s. My
| dad was into any kind of tech, and bought it 2nd hand, even
| though he'd never done any kind of CAD or anything like that (he
| did that with all sorts of stuff). I _think_ it was a Roland
| device, and I think it was A3 sized, but it might even have been
| A2.
|
| I got a copy of AutoCAD from a warez site (downloaded over dial-
| up, obviously!), and learned how to use it, using the plotter to
| print my masterpieces - things like floor plans and building
| elevations - yeah, I was a weird teenager, and went through a
| phase of being interested in technical drawing. I thought I'd end
| up as a draftsman or an architectural technologist.
|
| Anyway, it was absolutely _fascinating_ to watch the plotter at
| work! The pen would fly across the page at high speed to the next
| target site, then make all these incredibly quick, tiny, precise
| movements, before flying off to another part of the page. I can
| still remember the pleasing electrical whine of the motor as it
| worked. Wonderful bit of kit :)
| at_a_remove wrote:
| Around 1991 or so, I built an extraordinarily slow and deeply
| terrible scanner out of a plotter which had a simple fiber
| optical sensor instead of a pen. It was one of those "see what
| you can do with this stuff" projects that got thrown at me and I
| just coded this up with a data acquisition board and some flavor
| of BASIC. Supposedly about 1000 dpi.
|
| I eventually came up with routines to speed up the scanning (left
| to right, move up, right to left, move up ...) and even hit upon
| using the "judder" from the repositioning of the pen to, properly
| timed, grab a point. This saved me from having to fully stop, I
| could just vibrate the pen forward. This ... probably did not do
| much for the lifetime of the plotter.
|
| Man, that was a hot mess.
| neilv wrote:
| I think that's an improvement upon Forrest M. Mims III's
| plotter scanner. (He's the one who hand-drew some of the books
| at Radio Shack, like Getting Started in Electronics, and the
| 555 timer application notes circuits.) IIRC, for an article for
| Computers & Electronics magazine, he rigged up a flatbed X-Y
| plotter with an optical sensor (maybe one of the cadium sulfide
| photoresistors that RS sold?), and the resolution was very low,
| but it was pretty inspiring to kids. (It also gave you another
| reason to crave a plotter, which you now saw was really a robot
| module.)
| bluenose69 wrote:
| When I was a grad student, some code for drawing axes would draw
| a tick on one side, go all the way to the other side and then
| swing all the way back. The motor was strong enough to make the
| table sway back and forth, and of course this method was slow. I
| remember writing code to draw a tick, come back on the tick, and
| then draw along the axis to the next tick. Presto, much faster!
|
| We also had an HP plotter connected to one of those large
| (typewriter-sized) HP calculators, and I also wrote code to graph
| on that, too.
|
| All of this was pretty low-level stuff, but not difficult, and
| the rewards were high for a grad student trying to get science
| done.
|
| Fun times. And a step up from summer work preceding it, when I
| had to boot my machine by toggling binary switches for certain
| binary sequence that had to be loaded before it would start to
| read paper tape.
|
| I think I'm old.
| rbanffy wrote:
| > I think I'm old.
|
| No. We're vintage.
| neilv wrote:
| > _some code for drawing axes would draw a tick on one side, go
| all the way to the other side and then swing all the way back._
|
| Things like that were a weird combination of cool and
| hilarious, but in some cases you could turn it doubly cool.
|
| When I was an intern, there was an old poster-size (D?) HP X-Y
| color pen plotter. Probably someone got for EDA/ECAD by our in-
| circuit emulator business, but someone had made a tool to make
| it work with CASE platform.
|
| Being able to put a poster-size view of your system in team's
| area was pretty cool. (Though a Gantt diagram on the wall, of
| your team's entire project, to projected completion, was even
| cooler.)
|
| The problem, like with those axis ticks, was that the HP-GL
| from our software wasn't very aware of the implications of a
| pen plotter, especially not the usual kind, which had to return
| home to change pens. Which made it almost comically slow to
| watch printing (though still impressive that it could draw one
| color for a few seconds, go change a pen for a few seconds, and
| then possibly return to approximately the same place, and
| repeat).
|
| So, as one of my energetic intern midnight unofficial projects
| was to write an optimizer that read in that HP-GL and spit out
| HP-GL that would print faster. Rather than solve hard
| optimization problems, IIRC, I tried this very simple approach:
|
| 1. Do all the drawing for a single pen color in one go, before
| you switch pens. (Even with a rolling plotter, rather than a
| bed plotter, the mechanics of the pen change seemed to make it
| the most expensive operation.)
|
| 2. When you're done with one drawing operation, pick the next
| operation based on which has the nearest start point to the
| current pen position. (Greatly reduce the duration of pen-up
| movements that are not due to pen changes.)
|
| The speedup from that very simple approach was dramatic, as you
| might be able to imagine, even if you've never seen a pen
| plotter work.
|
| (If it hadn't worked so well, I'd have had to be smarter about
| optimization, like looking ahead multiple steps in a plan
| rather than just looking for the nearest start point, and
| getting more flexibility, like being able to reverse the
| direction that a pen-down movement is drawn. Or maybe you'd
| even even sometimes break up an atomic movement, for a really
| big win, like in the hypothetical of a few-foot border segment
| drawn along a page, and near midpoint of that border axis has a
| little adornment drawn. In that hypothetical, you could draw
| the half the border, pick up the adornment, and then resume the
| border, gaining speed at the cost of your border looking
| slightly less perfect.)
| vidanay wrote:
| Pen plotters were fascinating to watch. I wish I knew what the
| motion optimization algorithms looked like. It would do stuff
| like draw the tail of an "R" but then wouldn't come back and draw
| the remainder of the letter until two minutes later.
| joshu wrote:
| the plotters themselves don't have any, really. i do an
| optimization step before sending anything to the plotter.
| zabzonk wrote:
| HP pen plotters were/are highly intelligent devices - for
| example you could tell them to draw a pie-chart, provide the
| data and the labels, and they would go off and do it. If they
| were not intelligent, and you had to plot all graphs by
| individual pen movements, no business would have used them.
| They also optimised things like pen changes and paper
| movement.
| rahimnathwani wrote:
| Do you send the data and the labels to the plotter, or to
| the driver software running on your computer? I always
| imagined HP-GL would be a list of lines/curves, and that
| the plotter would plot them in whatever order they came in.
| zabzonk wrote:
| I was using a CP/M computer - there was no driver
| architecture. You sent HP-GL instructions and data as
| text via the RS232 interface. The plotter obviously had a
| limited buffer size, which would prevent certain
| optimisations, but then so did the CP/M computer!
| rahimnathwani wrote:
| So interesting!
|
| In the most recent reference guide I found just now, it
| seems you can draw a segment of a pie chart using a
| single EW (Edge Wedge) instruction but, for a complete
| pie chart, this method would require you to calculate the
| angles of each segment yourself. And of course to add the
| labels yourself. Perhaps I'm looking in the wrong place
| or perhaps the instruction to draw a whole pie chart has
| been deprecated.
| zabzonk wrote:
| You may be right - this was a looong time ago.
| Calculating the angles from the data is not difficult
| though, so I may have forgot that I did it. I can't
| really imagine calculating and placing the labels myself
| though, but perhaps I was cleverer then!
|
| Anyway, the HP pen plotter we had in the early 1980s was
| a very impressive device, when what we had were Z80 based
| computers driving them.
| scruss wrote:
| HP-GL was always able to plot text labels and make graph
| data markers: it was meant for scientific graphs, after
| all. Later plotters added arc sectors and filled
| (hatched) polygons. All the clever optimization was
| handled by the host computer: a plotter will just output
| what you tell it.
|
| There is a feature in HP-GL that does make certain types
| of XY plotting simpler. While it's not a programming
| language like PostScript, you can scale, rotate and
| offset the plot by arbitrary amounts. HP instrumentation
| manuals claimed it was possible to directly plot
| experimental data by feeding it straight to the plotter
| after setting the scale. I feel this was a highly
| aspirational statement, and one not seeing much real use.
| bitwize wrote:
| A basic desktop plotter that spoke HP-GL couldn't do that.
| You couldn't tell it to just go plot a pie chart. It did
| have an arc primitive, but you had to specify the radius,
| color, start and end angles, and whether the arc was
| filled. You could build a basic pie chart out of several
| such arcs. There was also a label primitive, but only one
| font (variable sizes though). So if you had a fancy font
| you had to tell the plotter to draw it with simple line
| segments and arcs.
|
| That said, most professional graphics software knew how to
| break down their elaborate output into HP-GL primitives
| with an appropriate output driver for the plotter. So few
| users actually had to do this unless they were talking to
| the plotter directly through a BASIC program or something.
| gnufx wrote:
| I wonder how many implementations there were of that sort of
| thing. I wrote one for an HP flatbed plotter sometime in the 80s
| to digitize plots from papers, but I never heard of another. I
| don't remember the implementation, but it must have been cheaper
| hardware than the one shown, and only had a plastic lens as the
| sight. (Nowadays you have
| http://markummitchell.github.io/engauge-digitizer for instance.)
| I mainly used the plotter for acetate slides for talks when I'd
| only seen hand-written ones.
|
| Some related history of input/output in physics: At the time, the
| "Bubblies" (bubble chamber particle physicists) used "flying spot
| digitizers" on their photos; I don't know how they worked, and to
| what degree they were automated. In contrast to that
| sophisticated input, HEP output was mainly histograms on line
| printer paper, stacked high, occasionally the grotty Tektronix
| 401x storage tube. Fortunately, nuclear physics had fast direct
| manipulation vector graphics and Benson roll pen plotters -- from
| whose song you could recognize types of plot across the room.
| Later the colour plots were sacrificed to faster monochrome
| Versatec electrostatics. (The Versatec printed my thesis, the
| first I knew produced electronically locally, long before we had
| an implementation of TeX.)
| AlexanderDhoore wrote:
| To this day HP still sells "plotters". They are just mostly used
| for cutting but you can definitely put a pen in there. And they
| have an optical eye to read markers on the printed media.
|
| See HP Latex cutter: https://www8.hp.com/us/en/printers/large-
| format/latex-plus-c...
|
| EDIT Oh, and they still speak HP-GL!
| brtkdotse wrote:
| The HP Latex cutter is a rebranded Summa cutter. AFAIK HP
| doesn't produce plotters/cutters anymore, they do however
| produce large format printers (which operate on a totally
| different paradigm)
| scruss wrote:
| You can still make many HP and compatible laser printers speak
| HP-GL (well, HP-GL/2) through some arcane PJL commands.
|
| Fun fact: HP-GL is equally compatible with metric and US
| customary measure as it uses 1/40 mm as its base unit. This
| just happens to be 1/1016 inches: not a tremendously useful
| integer factor, but every bit of integer goodness mattered back
| when peripherals were 8-bit.
| rbanffy wrote:
| > Fun fact: HP-GL is equally compatible with metric and US
| customary measure as it uses 1/40 mm as its base unit. This
| just happens to be 1/1016 inches
|
| That's a brilliant hack.
| joshu wrote:
| here is my HP DraftPro DXL going full tilt:
| https://www.instagram.com/p/CF048Zlpu2u/?igshid=1xsl4wmrcx2f...
|
| Here is my CNC router with a paint pen also zooming along:
| https://www.instagram.com/p/CMT56JwA9sA/?igshid=15p9mru3f5ug...
|
| if you want to get into this, the way to go is the Axidraw from
| Evil Mad Scientist Labs
| tekstar wrote:
| I was going to get an axidraw but on a whim I checked locally
| and scored a HP7475a for $60 and got it working.
|
| So definitely worth looking around a bit before going with new!
| tejtm wrote:
| warning: images are not shown, just a social media login page
| frosted-flakes wrote:
| On mobile you can watch the videos without logging in.
| walshemj wrote:
| Interesting mention of Ferranti back when I was young we had a
| state of the art A0 Ferranti digitizer delivered (serial no 7)
|
| My boss said "interesting project for you - hook this up to the
| PDP 11 make it work and then go and talk to Dave so he can use it
| to digitize the droplet cloud from an experimental rig"
|
| First order of business was to get my soldering iron out and make
| up a suitable cable
| zabzonk wrote:
| I must admit I didn't realise that Ferranti did things like
| digitisers. I used to work at the Western General Hospital in
| Edinburgh, just down the road from the Ferranti site on Crewe
| Toll, where a couple of my flatmates were radar engineers.
| Don't know if that's where they produced the digitisers though.
| scruss wrote:
| the mailing address for Ferranti-Cetec was at Crewe Toll. I
| have a vague memory of the Ferranti-Cetec office being
| further west, though, but I could be wrong
| DaiPlusPlus wrote:
| I grew up with books about technology and computers and whatnot
| which always seemed to include plotters in their sections about
| output devices (along with laser printers, CRTs, etc) and even
| contemporaneous books in the mid-1990s still talked of plotters
| as present-day output devices, yet I still haven't ever seen one
| in-person (but plenty of HP's large-format inkjet printers which
| still look-like plotters from a distance).
| Stratoscope wrote:
| Related folklore: Thunderscan - turning a dot matrix printer into
| a scanner.
|
| https://www.folklore.org/StoryView.py?project=Macintosh&stor...
| myself248 wrote:
| Ooooo.
|
| Yet more reason to get my Draftmaster II up and running.
|
| I wonder, is this command also what's used by vinyl cutters with
| the laser-sight for doing contour-cuts around vinyl printed in a
| different machine?
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(page generated 2021-05-01 23:01 UTC)