Laser Smoothies At Maker Faire

This year at Maker Faire, laser cutters were all the rage. Dremel announced a 40W laser cutter, but it won’t be available for purchase until this time next year, there is no price yet, and therefore doesn’t deserve further mention. Glowforge was out in full force, but the most interesting aspect of the Glowforge — a compact filter system that sits right underneath the laser — was not to be found. It looks like lasers are the next 3D printer.

Of course, those in the know have already been using laser cutters for years, and there are options for desktop CO2 laser cutters that cost less than a kilobuck. I speak, of course, of the ubiquitous K40 laser, a machine you can get off of eBay or AliExpress for the price of a generic, off-brand 3D printer. There is a downside to the K40, though: the control electronics and software are notoriously terrible. Fix that, though, and you have something really spectacular.

The Cohesion3D Mini

This year at Maker Faire, [Ray Kholodovsky] of Cohesion3D brought out his Smoothie-derived control boards for CNC machines and laser cutters. Of note is his K40 upgrade that turns the eBay special laser cutter into a 32-bit professional machine. This is the cheapest way to start lasing in your workshop.

We saw [Ray] at the Faire last year when he was demoing his Smoothie-derived boards for 3D printers and CNC machines. These are tiny, relatively low-cost boards that use Smoothieware, an Open Source, 32-bit CNC control system that is extremely extensible and very powerful. Basically, if you’re building a normal, ordinary DIY 3D printer, a RAMPS or RAMBO will do. If you’re doing something weird, like a 3D printer with strange kinematics, a 5-axis milling machine, or you’d like awesome engraving on a laser cutter, Smoothie is the way to go.

The stock board found in a K40 (left) and the Cohesion3D Mini (right). The Cohesion3D Mini is a drop-in replacement for the stock K40 board.

The Cohesion3D board is a direct, drop-in replacement for the control board found in the K40 laser. Since all of the K40 laser cutters are the same, and they’re really only a power supply and a CNC gantry, this is the one-stop-shop of K40 upgrades. The terrible electronics are gone, you don’t have to use Corel, and for a hundred bucks, you have something resembling a professional laser cutter.

The K40 laser has been around for several years now, but only recently have a few very interesting hacks and mods come out that push this blue light special laser cutter into semi-professional territory for people willing to get their hands dirty. A few months ago [Scorch] published K40 Whisperer, a piece of software that makes the stock electronics tolerable and able to accept normal SVGs and DXFs. The K40 has also been modified for a larger bed, and LaserWeb has been handling the software side of things for about two years now. Things are looking great for the K40 hacking scene, and Hackaday already has a, ‘I just bought a K40, now what?’ series in the works. Things are looking up for cheap laser cutters, and a Smoothie upgrade is just the cherry on top.

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.

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Building Set Limitations Make for Z-Height Follies

I’m working on a small CNC mill that uses a robotics building set as a starting point. I don’t know what to expect from the process. Maybe the connections will be too wobbly for the machine to be anything but a curiosity. Maybe I’ll be able to do pen plotting and balsa carving but nothing tougher than that. My goal is to have it carve PCBs, but what ultimately is important is that I have a tool whose awesomeness justifies the expense I’ve put into the project.

So far the process has been fun and interesting. But recently the Z-axis build has been especially so. It raises a really interesting question: where does the balance between unknown finished design and known material parameters fall?

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Custom Cut Resistor Bandoliers

Through-hole resistors come on tape that we’re now calling bandoliers. Since [Spencer] is selling a boatload of his RC2014 backplane computer kits on Tindie, he’s been chopping up a lot of resistor bandoliers. It’s a boring and monotonous job.

Fortunately, a lot of people have had a bandolier cutting problem over the years, and there are some hobbyist-grade robots that will do this work for you. One of the more popular robots tasked for bandolier cutting is a laser cut robot. However, if you already have a laser cutter, why not just use the laser to cut the bandoliers? It’s brilliant in its simplicity.

[Spencer] spent a little bit of time designing a template to turn his laser cutter into a cutter for through hole resistors. No, he’s not trimming the leads — this is just a device to cut resistors into groups mini bandoliers of a handful of resistors. The tool is made out of plywood, with a smaller top piece held down with magnets to keep the resistors aligned.

The entire template is up on Thingiverse, and it’s great if you need to cut hundreds of resistors to kit dozens of projects. If you’re only doing one or two, scissors will be the way to go, but if you’re cursed with the monotony of trimming hundreds there’s no better way to get things done than to put a robot to work.

Swedish Rocket Knives

There are trends in YouTube videos among various video producers. A few weeks ago, it was all about fidget spinners until some niche tech blog ran that meme into the ground. Before that, the theme was red-hot knives cutting through stuff. The setup was simple; just heat a knife up with a blowtorch, cut through a tomato or golf ball, hit stop on the high-speed camera, and collect that sweet, sweet YouTube money.

[David] from RCExplorer.se isn’t like most YouTube stars. He actually knows what he’s doing. When the latest trend of rocket-propelled knives hit the tubes, he knew he could blow this out of the water. He succeeded with a fantastic rocket-propelled machete able to slice through watermelons and fling itself into the woods behind [David]’s house.

Unlike most of the other YouTube stars trying their hand at rocket-powered slicers, [David] is doing this one right. He’s using hobby rocket motors, yes, but they’re reloadable. [David] crafted an engine casing complete with a proper nozzle machined out of stainless for this build. The rocket sled itself is an aluminum bracket bolted to a piece of carbon fiber plate that travels down a rail with the help of four skateboard wheels. A machete is then bolted to the plate, which is propelled down the track a bit faster than 200 km/h.

When it comes to rocket-propelled knives, the word ‘professional’ really doesn’t come into play. This, however, is an amazing piece of craftsmanship that you can check out in the videos below.

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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!