Hacking A K40 Laser Cutter

The distinctive blue-and-white enclosure of the Chinese-made K40 laser cutter has become a common sight in workshops and hackerspaces, as they represent the cheapest route to a working cutter that can be found. It’s fair to say though that they are not a particularly good or safe machine when shipped, and [Archie Roques] has put together a blog post detailing the modifications to make something better of a stock K40 performed at Norwich Hackspace.

After checking that their K40 worked, and hooking up suitable cooling and ventilation for it, the first task facing the Norwich crew was to install a set of interlocks. (A stock K40 doesn’t shut off the laser when you open the lid!) A switch under the lid saw to that, along with an Arduino Nano clone to aggregate this, a key switch, and an emergency stop button. A new front panel was created to hold this, complete a temperature display and retro ammeter to replace the modern original.

Norwich’s laser cutter has further to go. For example, while we secretly approve of their adjustable bed formed from a pile of beer mats, we concede that their plans to make something more practical have merit. The K40 may not be the best in the world, indeed it’s probable we should be calling it an engraver rather than a cutter, but if that means that a small hackerspace can have a cutter and then make it useful without breaking the bank, it’s good to see how it’s done.

This isn’t the first K40 enhancement we’ve featured. Norwich might like to look at this improved controller, or even extend their cutter’s bed. Meanwhile if [Archie]’s name rings a bell, it might be because of his Raspberry Pi laptop.

Problems that Plagued an Edible Marble Machine

Prolific creator [Martin Raynsford] recently created a plus-sized edible version of his laser-cut Marble Machine for a Cake International exhibit and competition; it seemed simple to do at first but had quite a few gotchas waiting, and required some clever problem-solving.

Gears are three layers, stacked and cemented with sugar glue, and coated with a hard edible shine.

The original idea was to assemble laser-cut gingerbread parts to make the machine. Gingerbread can be laser-cut quite well, and at first all seemed to be going perfectly well for [Martin]. However, after a few days the gingerbread was sagging badly. Fiddling with the recipe and the baking was to no avail, and it was clear [Martin] needed to find something other than gingerbread to work with. After experimenting, he settled on a modified sugar paste which kept its shape and dried hard enough to work with. (While appearing to stretch most people’s definition of “cake” past the breaking point, the category [Martin] entered in the competition allows it.) The parts were cut by hand using laser-cut wood parts as a guide, then finished in a food dehydrator overnight.

The next problem was how to create the large spiral which forms the main ramp. The answer was to laser-cut a custom support structure that supported the piece while it dried out, and doubled as a way to transport the piece safely. High stress points got extra layers cemented with sugar glue, and some parts were reinforced internally with strands of uncooked spaghetti. Everything was sealed with an edible shine, which [Martin] says acts as a kind of varnish for cakes. A video demonstration is embedded below. Continue reading “Problems that Plagued an Edible Marble Machine”

Laser Levitation With Scrap Parts

After a year away from YouTube, the ever-energetic [Styropyro] has returned with whiteboard in hand to remind us just how little we actually know about lasers. In the last month he’s really hit the ground running with plenty of new content, but one video of his particularly stands out: a practical demonstration of laser levitation. Even better, unlike most of his projects, it looks like we can replicate this one without killing ourselves or burning our house down!

For those unaware, laser levitation is probably as close as we’ll get to Star Trek-style tractor beams in our lifetimes. In fact, the NASA Innovative Advanced Concepts program has been examining using the technology for capturing small particles in space, since it would allow sample collection without the risk of physical contamination. While the demonstration [Styropyro] performs lacks the “tractor” part of the equation (in other word’s, there’s no way to move the particle along the length of the beam) it does make us hopeful that this type of technology is not completely outside the reach of our home labs.

The trick seems to be with the focus of the laser beam itself. Your average laser pointer just doesn’t have the appropriate beam for this kind of work, but with a diode pulled from a DVD burner and a driver circuit made from parts out of the junk bin, the effect can be demonstrated very easily as long as you can keep the air in the room extremely still. Of course, what you’re trying to pick up is also very important, [Styropyro] has found that synthetic diamond powder works exceptionally well for this experiment. At about $1.60 a gram, it won’t break the bank either.

So how does it work? With a few trips to the aforementioned white board, Professor Pyro explains that the effect we’re seeing is actually electromagnetic. If the particle you want to levitate is small enough it will become polarized by the light, which is in itself an electromagnetic wave. Once you’ve got your mind wrapped around that, it logically follows that the levitating particle will experience the Lorentz force. Long story short, the particle is suspended in the air for the same reason that a projectile is ejected from a rail gun: if you’ve got enough power and the mass of the object is low enough, there will be an observable force.

We’ve been covering the work of [Styropyro] for years now, and are glad to see him back on YouTube creating new content and terrifying a new generation of viewers. Between this and the return of [Jeri Ellsworth], it’s like we’re experiencing a YouTube hacker Renaissance.

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Homebuilt Laser Engraver Using Salvaged Parts

Now that anyone can go online and get a fairly decent 3D printer for around $200, they’ve officially fallen out of the “Elite Hacker” arsenal and are now normal, if perhaps highly specialized, tools. That’s great for the 3D printing community as a whole, but what about those who want to be on the fringe of technology? Telling people you have a 3D printer at home doesn’t get that wide-eyed response like it used to. What’s a “l33t” hacker to do?

Enter the laser engraver/cutter: it’s like a 3D printer, but easier to build and has a higher capacity for bodily harm! While there are a couple good options for kits and turn-key setups out there, just like the early days of 3D printers, some of the best machines are still home built. In his latest video, YouTuber [MakerMan] takes us through his build which features an impressively low part count.

To start his build, [MakerMan] strips down four printers and salvages seven high quality 8 mm linear rods; a huge cost saving tip in itself. We’ll certainly be picking up any printers we see in the trash for the next couple months hoping to score some rods. With the addition of some cheap LM8UU bearings and 3D printed holders for them, [MakerMan] has a smooth 2D motion platform for just a couple bucks. The frame of the machine is built out of type of aluminum square tubing you can find at the hardware store, no expensive extrusion here.

For the laser itself, [MakerMan] is using a six watt PLH3D-6W-XF from Opt Lasers. This module features integrated driver and cooling, so all you need to do is provide it power and a stable means of moving it over the work piece. They even offer a magnetic “dock” which allows you to remove the laser from the mount without any tools for servicing or tool changes. [MakerMan] reports he’s been able to engrave stainless steel with this laser module, and cut thin wood.

This isn’t the first laser engraver we’ve seen built out of scrap parts, though if you want to save some work you could just upgrade a cheap commercial model.

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Interference Scanner with Clear Instructions

Meticulous. Thorough. Exacting. These are all words we’d use to describe this video by [BrendaEM] about her Homemade 3D Optical Interference Scanner which can be seen after the break. The scanner uses 3D-printed parts and repurposed materials you might find lying around in your spare parts bin. An old optical drive tray acts to move the laser-wielding sled while a stripped-out webcam is an optical sensor. Links to relevant files such as 3D models and Arduino sketches will be found in the video’s author section.

The principle of operation is demonstrated with a water analog in the video at 2:00 with waves in a plastic container. By creating two small apertures between a light source and a sensor, it’s possible to measure the light waves which make it through. [BrendaEM] uses some powerful visualization software to convert her samples into 3D models which look really cool and simultaneously demonstrate the wave nature of light.

On the left side of her device are the control electronics which don’t need any special coatings since light won’t pass over this area. For the right side, where coherent light is measured, to borrow a Rolling Stones lyric: no colors anymore, I want them to turn black. Even the brass strips with apertures are chemically darkened.

Most of the laser hacks here use lasers rather than measure them, like this Laser Clock and a Laser Projector.

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Making the Best Plywood for Laser Cut Puzzles

Plywood laser-cuts fairly well but has drawbacks when used in serious production runs, as [Marie] explains in a blog post about a quest for the ultimate laser-cutting plywood. One of the things [Nervous System] makes and sells is generative jigsaw puzzles, and they shared their experience with the challenges in producing them. The biggest issue was the wood itself. They ended up getting a custom plywood made to fit their exact needs, a process that turned out neither as complex nor as unusual as it may sound.

An example of how a dense knot hidden in one of the plywood layers caused the laser to not cut all the way through.

Plywood is great because it’s readily available, but there are some drawbacks that cause problems when trying to do serious production of laser-cut plywood pieces. Laser cutting works best when the material being cut is consistent, but there can be areas of inconsistent density in plywood. If the laser encounters an unexpected knot somewhere in the wood, there is no way to slow down or to increase power to compensate. The result is a small area where the laser perhaps doesn’t quite make it through. A picture of an example from my workshop shows what this looks like.

When doing basic project work or prototyping, this kind of issue is inconvenient but usually some trimming and sanding will sort things out. When doing a production run for puzzles like [Nervous System] was doing, the issue is more serious:

  1. A jigsaw puzzle with a large number of cuts in a relatively small area has a higher chance of running into any problem spots in the material. If they exist, the laser will probably encounter them.
  2. Trouble spots in plywood can be on the inside layers, meaning they can’t be detected visually and are only discovered after they cause an incomplete cut.
  3. Increasing laser power for the whole job is an incomplete solution, as excessive laser power tends to make the cuts uglier due to increased scorching and charring.
  4. An inspection process becomes needed to check each puzzle piece for problems, which adds time and effort.
  5. A puzzle that had even one piece that did not cut properly will probably be scrapped because rework is not practical. That material (and any time and money that went into getting the nice artwork onto it) becomes waste.

Plywood is great stuff and can look gorgeous, but [Marie] says they struggled with its issues for a long time and eventually realized they had gone as far as they could with off-the-shelf plywoods, even specialty ones. They knew exactly what they needed, and it was time for something custom-made to serve those specific needs.

Having your own plywood custom-made may sound a little extreme, but [Marie] assures us it’s not particularly difficult or unreasonable. They contacted a small manufacturer who specialized in custom aircraft plywoods and was able to provide their laser-cut plywood holy grail: a 3-ply sheet, with high quality basswood core with birch veneers, and a melamine-based glue. It cuts better than anything else they have used, and [Marie] says that after four years they had certainly tried just about everything.

Milling a Flow Sensor to Safeguard a Laser Tube

Powerful lasers get powerfully hot and if you don’t keep them cool you’ll pay the price. After two such experiences [NixieGuy] got smart and milled this flow sensor as a failsafe.

Laser cutters are awesome. But acquiring one can be expensive, and keeping them in working order is no small feat. From the gunk that builds up as a byproduct of vaporizing the cutting stock, to keeping the optics focused correctly, it’s a game that forces you to become a laser cutter operator and not merely a user. One of the worst things to deal with is having to replace a burnt out laser tube. They do have a life to them but in this case the filter on the water cooling system clogged and the tube cooked itself. Twice.

Flow sensor shown in the upper right.

This flow sensor now acts as an interconnect with the laser enable line. Starting with an acrylic rod, [NixieGuy] machined out a center hole for a magnetic stopper, then milled three channels for water to pass around it. Each end of the rod was turned on a lathe to interface with plastic tubing of the water cooling system, and a slot was milled on the outside for a reed switch.

The demo video is below. You can see that when water flows it pushes the magnetic stop up (against gravity) where it engages the reed switch, allowing the laser to operate. If something impedes the flow of water (even if the pump still runs) the laser will be disabled and (hopefully) prevent future tube loss.

Want to see some of the oops moments faced by many a laser cutter operator? Check our guide on how to fail at laser cutting.

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