Fail Of The Week: Did My Laser Cutter Tube Really Burn Out?

All the cool kids are doing it these days, or more like for many years now: you can get a laser cutter for a song if you don’t mind doing your own repairs and upgrades — you know, being a hacker. The downside is that some failures can really ruin your day. This is what [Erich Styger] encountered with his cutter that is just a bit more than a year old. This Fail of the Week looks at the mysterious death of a CO2 laser tube.

This is the infamous K40 laser cutter. Our own [Adam Fabio] just took one on a couple of months back and [Erich] even references Hackaday coverage of the K40 Whisperer project as what pushed him over the edge to make the purchase. We’ve followed his blog as he acquired the cutter and made upgrades along the way, but after an estimated 500 hours of use, a horrible teeth-gnashing screech sprung forth from the machine. [Erich’s] reaction was to hit the e-stop; that’s certainly why it’s there.

Chasing down the problem is a story well-told, but as is often the case with these FotW articles, in the end what caused the failure is not entirely known. We’d love to hear what you think about it in the comments below.

The investigation began at the power supply for the laser, but that didn’t yield any answers. Next he moved to the tube itself, noticing that the wire connection to the tube’s anode wasn’t soldered. The anode is an unknown material he suspects to be graphite and he found a video showing the “soldering” process for connecting a wire. (We added quotes to that as the video he linked doesn’t actually solder anything but the wrapped wire strands themselves.) The solution he found is a great tip to take away from the story. It’s a socket by TE Connectivity to which he soldered the wire. Assuming it’s power rated for the task, and won’t fall off during normal operation, this is a great way to do it.

But we digress. Even with the connection made, the old tube had to be replaced with a new one. It’s also notable that the portion of that anode inside the bad tube is orange in color when a new tube would be black like the part on the outside. Does this hint at why that tube died, and could this have been avoided? If you have insight, help us learn from this failure by leaving a comment below.

Scratch-Building A Supersized Laser Cutter

Now that 3D printers have more or less hit the mass market, hackers need a new “elite” tool to spend their time designing and fiddling with. Judging by the last couple of years, it looks like laser cutters will be taking over as the hacker tool du jour; as we’re starting to see more and more custom builds and modifications of entry-level commercial models. Usually these are limited to relatively small and low powered diode lasers, but as the following project shows, that’s not always the case.

This large format laser cutter designed and built by [Rob Chesney] is meticulously detailed on his blog, as well as in the in the video after the break. It’s made up of aluminium profile and a splattering of ABS 3D printed parts, and lives in an acrylic enclosure that’s uniquely isolated from the laser’s internal gantry. All told it cost about $2,000 USD to build, but considering the volume and features of this cutter that’s still a very fair price.

[Rob] carefully planned every aspect of this build, modeling the entire machine in CAD before actually purchasing any hardware. Interestingly enough his primary design constraint was the door to his shed: he wanted to build the largest possible laser cutter that could still be carried through it. That led to the final machine’s long and relatively shallow final dimensions. The design was also guided by a desire to minimize material waste, so when possible parts were designed to maximize how many could be cut from a one meter length of aluminum extrusion.

The laser features a movable Z axis that’s similar in design to what you might see in a Prusa-style 3D printer, with each corner of the gantry getting an 8 mm lead screw and smooth rod which are used in conjunction to lift and guide. All of the lead screws are connected to each other via pulleys and standard GT2 belt, but as of this version, [Rob] notes the Z axis must be manually operated. In the future he’ll be able to add in a stepper motor and automate it easily, but it wasn’t critical to get the machine running.

He used 3D printed parts for objects which had a relatively complex geometry, such as the laser tube holders and Z axis components, but more simplistic brackets were made out of cut acrylic. In some components, [Rob] used welding cement to bond two pieces of acrylic and thereby double the thickness. Large acrylic panels were also used for the laser’s outer enclosure, which was intentionally designed as a separate entity from the laser itself. He reasoned that this would make assembly easier and faster, as the enclosure would not have to be held to the same dimensional tolerances as it would have been if it was integrated into the machine.

[Rob] gives plenty of detail about all the finer points of water cooling, laser control electronics, aligning the mirrors, and really anything else you could possibly want to know about building your own serious laser cutter. If you’ve been considering building your own laser and have anything you’re curious or unsure about, there’s a good chance he addresses it in this build.

Short of having the fantastically good luck to find a laser cutter in the trash that you can refurbish, building your own machine may still be the best upgrade path if you outgrow your eBay K40.

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Video Shows Power Isn’t Everything In Laser Engraving

When it comes to power tools, generally speaking more watts is better. But as laser maestro [Martin Raynsford] shows, watts aren’t everything. He shares a brief video showing his older 100 W laser being handily outperformed by a newer 30 W machine. Shouldn’t the higher power laser be able to do the same job in less time? One might think so, but wattage isn’t everything. The 30 W laser engraves and cuts a wooden tile in just under half the time it takes the 100 W machine to do the same job, and with a nicer end result, to boot.

Why such a difference? Part of the answer to that question lies in that the newer machine has better motion control and can handle higher speeds, but the rest is due to the tubes themselves. The older 100 W machine uses a DC-excited (big glass water-cooled tube) CO2 laser, and the newer 30 W machine uses an RF-excited laser that looks a bit like a big metal heat sink instead of oversized lab glassware. Both tubes output what is essentially the same beam, but the RF tube is overall capable of a more refined, more stable, and more finely focused point than that of the glass tube. Since engraving uses only a small fraction of even the 30 W laser’s power, the finer control that the RF laser has over the low end of the power scale results in a much higher quality engraving.

Embedded below is a short video showing both machines engraving and cutting the same tile, side by side. You may wish to consider watching this one full screen, to better see the fine details.

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Arduino Revives Junkyard Laser Cutter

Some people have all the luck. [MakerMan] writes in to gloat tell us about a recent trip to the junkyard where he scored a rather serious looking laser cutter. This is no desktop-sized K40 we’re talking about here; it weighs in at just under 800 pounds (350 Kg), and took a crane to deliver the beast to his house. But his luck only took him so far, as closer inspection of the machine revealed it was missing nearly all of its internal components. Still, he had the frame, working motors, and laser optics, which is a lot more than we’ve ever found in the garbage.

After a whirlwind session with his wire cutters, [MakerMan] stripped away most of the existing wiring and the original control board inside the electronics bay. Replacing the original controller is an Arduino Nano running Grbl, likely giving this revived laser cutter better compatibility with popular open source tools than it had originally. Even though the laser cutter was missing a significant amount of hardware, he did luck out that both the motor drivers were still there (and working) as well as the dual power supplies to run everything.

After a successful motion test, [MakerMan] then goes on to install a new 90W laser tube. Supporting the tube is a rigged up water cooling system using a plastic jug and a cheap bilge pump. He also added an air assist system, complete with side mounted compressor. This pushes air over the laser aperture, helping to keep smoke and debris away from the beam. Finally, a blower was installed in the bottom of the machine with flexible ducting leading outside to vent out the smoke and fumes that are produced when the laser is in operation.

This machine is a considerable upgrade from the previous laser [MakerMan] built, and as impressive as this rebuild is so far, we’re interested in seeing where it goes from here. If you ask us, this thing is begging for an embedded LaserWeb server.

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Drop-in Controller For EBay K40 Laser Engraver Gets Results

[Paul de Groot] wrote in to let us know about a drop-in controller replacement he designed for those economical K40 laser engravers that are everywhere on eBay. With the replacement controller, greatly improved engraving results are possible along with a simplified toolchain. Trade in the proprietary software and that clunky security dongle for Inkscape and a couple of plugins! [Paul] felt that the work he accomplished was too good to keep to himself, and is considering a small production run.

Laser engravers are in many ways not particularly complex devices; a motion controller moves the head in x and y, and the laser is turned on or off when needed. But of course, the devil is in the details and there can be a surprising amount of stuff between having a design on your screen and getting it cut or engraved in the machine. Designing in Inkscape, exporting to DXF, importing the DXF to proprietary software (which requires a USB security dongle to run), cleaning up any DXF import glitches, then finally cutting the job isn’t unusual. And engraving an image with varying shades and complex dithering? The hardware may be capable, but the stock software and controller? Not so much. It’s easy to see why projects to replace the proprietary controllers and software with open-source solutions have grown.

Cheap laser engravers may come with proprietary controllers and software, but they don’t need to stay that way. Other efforts we have seen in this area include LaserWeb, which provides a browser-based interface to a variety of open-source motion controllers like Grbl or Smoothieware. And if you’re considering a laser engraver, take a few minutes to learn from the mistakes of other people.

Laser Surgery: Expanding The Bed Of A Cheap Chinese Laser Cutter

Don’t you just hate it when you spend less than $400 on a 40-watt laser cutter and it turns out to have a work area the size of a sheet of copy paper? [Kostas Filosofou] sure did, but rather than stick with that limited work envelope, he modified his cheap K40 laser cutter so it has almost five times the original space.

The K40 doesn’t make any pretenses — it’s a cheap laser cutter and engraver from China. But with new units going for $344 on eBay now, it’s almost a no-brainer. Even with its limitations, you’re still getting a 40-watt CO2 laser and decent motion control hardware to play with. [Kostas] began the embiggening by removing the high-voltage power supply from its original space-hogging home to the right of the work area. With that living in a new outboard enclosure, a new X-Y gantry of extruded aluminum rails and 3D-printed parts was built, and a better exhaust fan was installed. Custom mirror assemblies were turned, better fans were added to the radiator, and oh yeah — he added a Z-axis to the bed too.

We’re sure [Kostas] ran the tab up a little on this build, but when you’re spending so little to start with, it’s easy to get carried away. Speaking of which, if you feel the need for an even bigger cutter, an enormous 100-watt unit might be more your style.

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Aligning Invisible Lasers On-the-cheap

Lining up the beam from your homebrew (or retrofitted) laser cutter doesn’t come without its challenges. For instance, how do I use my remaining eye to align an invisible beam that has enough power to burn through some objects in its path? Some of us will go through the extra hassle and expense of mixing in a visible guide that traces the path of the CO2 laser. For the penny-pinchers out there, though, [Stephen] has us covered with an inexpensive technique that will cut you down by only a few strips of masking tape.

Stephan’s technique is simple, but elegant. He covers each mirror with tape, fires the laser, and leaves a burn mark, working his way from the last mirror that the laser hits to the first. With a burn mark on each mirror, and one through a guide made from a sheet of plywood, [Stephen] has a pretty good idea where the native direction of the beam is headed. He then swaps a red dot laser in to line up with the burn marks, and then aligns the mirrors using visible, and safe, light. Phew! Now that’s a lot easier than iteratively firing the beam and replacing the tape on the mirror each time we want to tweak the mirror alignment.

With all that burnt masking tape, the process can get a bit smelly. Nevertheless, we’ve filed this one away for later when we start getting that itching, burning sensation that kicks us into building our own homebrew laser cutter.

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