A Polar Coordinate CNC Plotter Even Descartes Could Love

Take apart a few old DVD drives, stitch them together with cable ties, add a pen and paper, and you’ve got a simple CNC plotter. They’re quick and easy projects that are fun, but they do tend to be a little on the “plug and chug” side. But a CNC plotter that uses polar coordinates? That takes a little more effort.

The vast majority of CNC projects, from simple two-axis plotters to big CNC routers, all tend to use Cartesian coordinate systems, where points on a plane are described by their distances from an origin point on two perpendicular axes. Everything is nice and square, measurements are straightforward, and the math is easy. [davidatfsg] decided to level up his CNC plotter a bit by choosing a polar coordinate system, with points described as a vector extending a certain distance from the origin at a specified angle. Most of the plotter is built from FischerTechnik parts, with a single linear axis intersecting the center point of a rotary drawing platform. Standard G-code is translated to polar coordinates by a Java applet before being sent to a custom Arduino controller to execute the moves. Check out the video below; it’s pretty mesmerizing to watch, and we can’t help but wonder how a polar 3D-printer would work out.

Have polar coordinates got you stumped? It can be a bit of an adjustment from Cartesian space for sure. It can be worth it, though, showing up in everything from cable plotters to POV fidget spinners and even to color space models.

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Junk Build Printer Uses Pencil To Print

Sometimes, it is interesting to see what you can build from the bits that you have in your junk drawer. [Dr West] decided to build a printer with spare parts including a hard drive, a scanner base and an Arduino. The result is a rather cool printer that prints out the image using a pencil, tapping the image out one dot at a time. The software converts the image into an array, with 0 representing white and 1 representing black. The printer itself works a bit like an old-school CRT TV: the scanner array moves the printer along a horizontal line, then moves it vertically and along another horizontal line. It then triggers the hard drive actuator to create a mark on the paper if there is a 1 in the array at that point.

We’ve seen a few drawing printers before, but most use a plotter or CNC approach, where the motors move the pencil on an X-Y . This type of dot matrix printer (sometimes called a dotter) isn’t as efficient, but it’s a lot of fun and shows what can be achieved with  a few bits of junk and a some ingenuity.

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Extracting A Vector Font From A Vintage Plotter

There is a huge variety of hardware out there with a font of some form or other baked into the ROM. If it’s got a display it needs a font, and invariably that font is stored as a raster. Finding these fonts is trivial – dump the ROM, render it as a bitmap, and voilà – there’s your font. However, what if you’re trying to dump the font from a vintage Apple 410 Color Plotter? It’s stored in a vector format, and your job just got a whole lot harder.

The problem with a vector font is that the letters aren’t stored as individual images, but as a series of instructions that, when parsed correctly, draw the character. This has many benefits for generating characters in all manner of different sizes, but makes the font itself much harder to find in a ROM dump. You’re looking for both the instructions that generate the characters, as well as the code used to draw them, if you want a full representation of the font.

The project begins by looking at what’s known about the plotter. The first part of any such job is always knowing where to look, of course. It’s quickly determined that the font is definitely stored in the main ROM, and that there is no other special vector drawing chip or ROMs on board. The article then steps through the search process, beginning with plaintext searches of the binary dump, before progressing to a full disassembly of the plotter firmware. After testing out various assumptions and working methodically, the vector data is found and eventually converted into a modern TrueType font.

In the end, the project is successful, and it’s a great guide on how to approach similar projects. The key is to lay out everything you know at the start, and use that to guide your search step by step, testing and discarding assumptions until you hit paydirt. We’ve seen similar works before, like this project to dump the voice from an ancient Chrysler Electronic Voice Alert.

New Life For An Obscure Apple Plotter

We’ve all at some point or other seen something done online by somebody else, and thought “I’d like to have a go at that!”. When [Phooky] saw the artwork on the #PlotterTwitter hashtag, he remembered a past donation of a plotter to the NYC Resistor hackerspace. Some searching through the loft revealed a dusty cardboard box containing not the lovely Hewlett-Packard he’d hoped for, but instead an Apple 410 Color Plotter. This proved to be such an obscure part of the legacy Apple product line that almost no information was available for it save for a few diagrams showing DIP switch settings for the serial port.

Undeterred, he took a look inside and found a straightforward enough control board featuring a Z80 processor and support chips with 1983 date codes. The ROMs were conveniently socketed, so after dumping their contents, he was able to identify the routine for the plotter’s test program, and thus work from there to deduce its command set.  A small matter of the plotter using hardware handshaking lines to signal a full buffer later, and he was able to use it to produce beautiful plots. Should you be one of the lucky few remaining Apple 410 owners, you may find his software library for it to be of some use.

If you’d like to see some more aged plotter action on these pages, we’ve had an analog Hewlett Packard here in the past, as well as a vintage drum plotter.

Thanks [Sophi] for the tip.

A Case for the Desktop Vinyl Cutter

As far as desktop workbench fab tools go, it’s too easy to let 3D printers keep stealing the spotlight. I mean, who doesn’t appreciate that mechatronic “buzz” as our printer squirts a 3D CAD model into plastic life? While the 3D printer can take up a corner of my workbench, there’s still plenty of room for other desktop rapid-prototyping gadgets.

Today, I’d like to shed some light on vinyl cutters. Sure, we can start with stickers and perhaps even jumpstart an after-hours Etsy-mart, but there’s a host of other benefits besides just vinyl cutting. In fact, vinyl cutters might just be the unsung heroes of research in folding and papercraft.

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Make a Plotter Out of Rulers

Instructables user [lingib] made a clever and inexpensive pen arm plotter that uses plastic rulers for arms. An inspiring sight for anyone without a bunch of robot parts lying around,

The electronics are straightforward, with an Arduino UNO and a pair of Easy Drivers to control NEMA17 stepper motors connected to robot wheels, which serve as hubs for the rulers. At the end of the arms, an SG90 micro servo raises and lowers the pen as commanded, shoving the whole pen assembly off the paper with its horn—an elegant solution to an age-old drawbot problem. He even wrote wrote a custom Processing program that allows him to control the plotter from his desktop

[lingib]’s experimented with different kinds of drawing machines, including a drum plotter (video after the break), a V-plotter, as well as a rolling drawbot.

You’ll find tons of Hackaday posts about all types of drawing machines, including vintage plotters, plotters for making circuit boards, and even one built out of cardboard.

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Vintage Plotter Handles Chaos With Ease

No lab in almost any discipline was complete in the 70s and 80s without an X-Y plotter. The height of data acquisition chic, these simple devices were connected to almost anything that produced an analog output worth saving. Digital data acquisition pushed these devices to the curb, but they’re easily found, cheap, and it’s worth a look under the hood to see what made these things tick.

The HP-7044A that [Kerry Wong] scored off eBay is in remarkably good shape four decades after leaving the factory. While the accessory pack that came with it shows its age with dried up pens and disintegrating foam, the plotter betrays itself only by the yellowish cast to its original beige case. Inside, the plotter looks pristine. Completely analog with the only chips being some op-amps in TO-5 cans, everything is in great shape, even the high-voltage power supply used to electrostatically hold the paper to the plotter’s bed. Anyone hoping for at least a re-capping will be disappointed; H-P built things to last back in the day.

[Kerry] puts the plotter through its paces by programming an Arduino to generate a Lorenz attractor, a set of differential equations with chaotic solutions that’s perfect for an X-Y plotter. The video below shows the mesmerizing butterfly taking shape. Given the plotter’s similarity to an oscilloscope, we wonder if some SDR-based Lissajous patterns might be a fun test as well, or how it would handle musical mushrooms.

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