Better Stepping With 8-Bit Micros

The electronics for motion control systems, routers, and 3D printers are split into two camps. The first is 8-bit microcontrollers, usually AVRs, and are regarded as being slower and incapable of cool acceleration features. The second camp consists of 32-bit microcontrollers, and these are able to drive a lot of steppers very quickly and very smoothly. While 32-bit micros are obviously the future, there are a few very clever people squeezing the last drops out of 8-bit platforms. That’s what the Buildbotics team did with their ATxmega chip — they’re using a clever application of DMA as counters to drive steppers.

The usual way of driving steppers quickly with an ATMega or other 8-bit microcontroller is abusing the hardware timers. It’s quick, but there is a downside. It takes time for these timers to start and stop, and if you’re doing it two hundred times per second with four stepper motors, that clock jitter will ruin your CNC machine. The solution is to use a DMA channel to count down, with each count sending out a pulse to a stepper. It’s a clever abuse of the hardware, and the only drawback is the micro can’t send more than 2¹⁶ pulses per any 5ms period. That’s not really an issue because that would mean some very, very fast acceleration.

The Buildbotics team currently has a Kickstarter running for their four-axis CNC controller using this technique. It’s designed for Taig mills, 6040 routers, K40 lasers, and other various homebrew robots. It’s an interesting solution to the apparent end of the of the age of 8-bit microcontrollers in CNC machines and certainly worth checking out.

Rolling Around A 4th Axis

[Perry] was interested in adding a 4th axis to his CNC machine, but not very excited at the prospect of spending hundreds of dollars on the parts and electronics to make it work. There is a very clever and very inexpensive way to add a 4th axis to a CNC machine, though, and after a bit of fabrication, he was able to add a ‘rolling’ 4th axis to his machine.

[Bob]’s ‘rolling’ 4th axis.
The idea for this build comes from [Bob] over on the CNC Shark forums. Instead of adding a motor to rotate a work piece around, [Bob]’s build simply mounts it between two jaws, and rolls everything around against the bed of the CNC router. Don’t have a clue what that means? Check out the picture to the right, and you’ll see brilliance built in Delrin and HDPE.  By mounting two rack gears to the bed and two geared jaws to the carriage of the machine, moving the router in the Y axis also rotates the 4th axis. This is far, far too clever; it doesn’t require any additional electronics and the only software tweaks are a bit of G-code hacking.

[Perry] took one look at [Bob]’s project and decided this would be the perfect build to get him a 4th axis. The parts for this build were fabricated out of black HDPE, with the only real change to the design being a ‘variable length’ 4th axis. Instead of two rack gears mounted to the bed of the machine, [Perry]’s build only uses one rack, with the other end simply rolling on the bed.

There are a lot of clever inventions that don’t work, so what’s the verdict with this CNC hack? It actually looks pretty good. [Perry] was able to turn some square stock into round stock, and able to engrave a spiral around a cylinder. You can check out those videos below.

Continue reading “Rolling Around A 4th Axis”

Hackaday Prize Entry: A Manual, CNC Pick And Place Machine

Everyone who wants a 3D printer probably already has one, and even laser cutters and CNC machines are making their way into garages and basements ’round the world. Pick and place machines are the next great frontier of personal manufacturing, and even though that’s a long way off, [Tegwyn]’s project for this year’s Hackaday Prize is bringing us that much closer to popping down 0201 LEDs reliably.

This project is a manual pick and place machine — otherwise known as ‘tweezers’. It’s a bit more complicated than that, because the entire idea behind [Tegwyn]’s build is to decouple a human’s fine motor skills from the ability to place components on a board. To do that, this project is using an off-the-shelf, blue light special CNC machine. There’s not much to it, just a bit of aluminum extrusion and some threaded rods. However, with the addition of a vacuum pump, a hollow needle, and a few manual controls to move the axes around, the operator has very fine control over where a resistor, cap, or LED goes.

There are a few neat additions to the, ‘put a vacuum pump on a CNC machine’ idea. This is a 4 axis machine, giving the user the ability to rotate the part around a pad. There’s also a microscope hooked up to a small monitor mounted to the machine. If you’re assembling hundreds of boards, this is not the machine you want. If, however, you only need a handful, don’t mind spending a few hours placing parts, and don’t want to go insane with tiny QFN packages, this is a great build and a great entry for the Hackaday Prize.

Continue reading “Hackaday Prize Entry: A Manual, CNC Pick And Place Machine”

Turning and Burning with a CNC Pyrography Machine

With CNC machines, generally the more axes the better. Three-axis machines with a vertical quill over a rectangular workspace are de rigueur, and adding an axis or two can really step up the flexibility of a machine. But can only two axes be of any use? Sure can, as witnessed by this two-axis CNC wood burning machine.

As [tuckershannon] tells the tale, this was a newbie build aided by the local hackerspace. Axis one is a rotary table of laser-cut wood gears powered by a stepper. Axis two is just a stepper and lead screw sitting on a couple of blocks of wood. A Raspberry Pi under the hood controls the motors and cycles the pyrography pen on and off as it scans across a piece of wood on the rotary table, burning a spiral pattern that makes for some interesting art. Hats off to [tuckershannon] for figuring out the math needed to adapt to the changing speed of the pen over the wood as the diameter gets bigger.

We love this build, can’t help but wonder if some clever gearing could eliminate the need for the second stepper. And perhaps an upgrade from the standard resistive wood burner to an arc lighter pyrography pen would improve resolution. Still, it’s hard to argue with results, and this is a great hack.

[via r/raspberrypi]

Thanks to [Liz] for the tip!

Hackaday Links: July 9, 2017

Doom is now running on the ESP32. This is some work from [Sprite_tm], and the last we heard about Doom on the ESP32 is that there was a silicon bug or something. Now we’re knee deep in the dead on a tiny WiFi and Bluetooth-enabled microcontroller.

Loading animations have a long and storied history. What originally began as an hourglass quickly turned into a hand counting to five and progress bars. There were clocks, the Great Beach Ball of Death, and now loading animations are everywhere. However, the loading animation has still not been perfected — until now, that is. This is a fidget spinner loading animation. It’s beautiful.

Just a quick reminder that a Minecraft scholarship exists. Yeah, I know what you’re thinking, but there is a scholarship from the Klingon Language Institute for studying any language, and last year’s winner built a redstone computer from scratch,

[8bit generation] recently released a documentary, about the rise of Atari. Easy to Learn, Hard to Master is about the rise of Atari under [Nolan Bushnell]. Now [8bit generation] is working on a new documentary: Firing Steve Jobs. The [Steve Jobs] story is fascinating, and no matter what you think of him, he probably knew what he was doing.

Want to build and sell some hardware? Over on Tindie, we’re taking a look at some of the most successful designers of custom crafted hardware. This time it’s [Albertas Mickėnas] of Catnip Electronics who has sold five thousand soil moisture sensors.

You can just go out and buy a CNC machine, but that doesn’t quite underscore the difficulty in getting a CNC machine running. Our ‘ol pal [Jeremy] recently picked up a Romaxx CNC machine and put together a video of its commissioning. There’s a lot of work here, from building a shelf/stand for a rather beefy machine to cutting into the bed for t-tracks, and figuring out how dust collection is going to happen.

Before there was KiCad and Eagle and a ton of web-based PCB design tools, there was Autotrax. Want to know what PCB design and GUIs look like in DOS? I did a walkthrough for designing a small PCB in the DOS version of Autotrax late last year. There are thousands of designs locked up in discontinued EDA suites, and [Erich] has a way to revive them. He’s developed an Autotrax/Easytrax layout import/export plugin for pcb-nd. Now legacy Protel designs can be imported into software released in this century. This is really cool, and you can check out some screenshots here.

A Poor-Man’s Laser CNC Engraver

What do you get when you mix the disappointment that sometimes accompanies cheap Chinese electronics with the childhood fascination of torturing insects with a magnifying glass on a sunny day? You get a solar-powered CNC etcher, that’s what.

We all remember the days of focussing the sun on a hapless insect, or perhaps less sadistically on a green plastic army man or just a hunk of dry wood. The wonder that accompanied that intense white spot instantly charring the wood and releasing wisps of smoke stayed with you forever, as seemingly did the green spots in your vision. [drum303] remembered those days and used them to assuage his buyer’s remorse when the laser module on his brand new CNC engraver crapped out after the first 10 minutes. A cheap magnifying glass mounted to the laser holder and a sunny day, and he don’t need no stinkin’ lasers! The speed needs to be set to a super slow — 100mm per minute — and there’s the problem of tracking the sun, but the results are far finer than any of our childhood solar-artistic attempts ever were.

Do we have the makings of a possible performance art piece here? A large outdoor gantry with a big Fresnel lens that could etch a design onto a large piece of plywood would be a pretty boss beachside attraction. Of course, you’d need a simple solar tracker to keep things in focus.

Continue reading “A Poor-Man’s Laser CNC Engraver”

Home Built PCB Mill Reportedly Doesn’t Suck

It’s 2017, and getting a PCB professionally made is cheaper and easier than ever. However, unless you’re lucky enough to be in Shenzhen, you might find it difficult to get them quickly, due to the vagaries of international shipping. Whether you want to iterate quickly on designs, or just have the convenience of speed, it can be useful to be able to make your own PCBs at home. [Timo Birnschein] had just such a desire and set about building a PCB mill that doesn’t suck.

It might sound obvious, but it bears thinking about — if you know you’re incapable of building a good PCB mill in a reasonable period of time, you might save yourself a lot of pain and lost weekends by just ordering PCBs elsewhere. [Timo] was fairly confident however that the build would be able to churn out some usable boards, however, and got to work.

The build is meant to be accessible to the average hacker who wants one. The laser cut & 3D printed parts are readily available these days thanks to online services that can manufacture for those who don’t have the machines at home. [Timo] uses a rotary multitool for a spindle, a common choice for a budget CNC build.

With the hardware complete, [Timo] has spent time working on optimising the software side of things. Through careful optimisation of the G-Code, [Timo] has been able to improve performance and reduce stress on the tooling. It’s not enough to just build a good mill — you’ve got to have your G-Code squared away as well.

Overall, the results speak for themselves. The boards don’t suck; the mill can do traces down to 8 mil, and even drill the holes. We’d love to have one on the workbench when busting out some quick prototypes. For another take on the home-built PCB mill, why not check out this snap-together version?