Add Slots and Tabs to Your Boxes in FreeCAD

FreeCAD is a fairly sophisticated, open-source, parametric 3D modeler. The open-source part means that you can bend it to your will. [Alexandre] is working on a module that lets him easily add tabs, finger joints, and t-slots to models (YouTube link, embedded down under).

Right now the plugin is still experimental, but it looks usable. In the video demo, [Alexandre] builds up a simple box, and then adds all manner of physical connective pieces to it. You’ll note that the tabs look like they’re pieces added on to the main face — that’s because they are! He then exports the outlines to SVG and erases the lines that separate the tabs from the sides, and hands these files off to his laser cutter. Voilà! A perfect tab-and-t-slot box, with only a little bit of hand-work. ([Alexandre] mentions that it’s all still very experimental and that you should check out your design before sending it to the laser.)

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200W Laser Bazooka Is Just Silly

We weren’t going to run this one, because, well, it’s just ridiculous. But enough of you have browbeat us by sending in tips to the tipline that we’re going to capitulate. We’re not going to name you all by name, because really, you should be ashamed of yourselves. But you know who you are!

[Styropyro] does a lot of crazy things on YouTube. We really liked his “stuff in a microwave oven” series. He’s also obsessed with lasers and popping black balloons. So he took the laser heads out of four DLP computer projectors (the ones with 24 of those 1.5W Nichia diodes) and combined them. Yup, 200W of 405 445nm blue.

Then he just straps them together and passes them through a lens. It’s not a tight beam, but this thing is really bright. Even though the beam is very loosely focused, it burns stuff. That’s about all you can say. Lots of laser. Boy Howdy!

OK, there, we ran it. Don’t do this at home. It doesn’t require much finesse, and it’s going to get someone blind. Much better to expend your efforts on something more civilized like a projector. At least then you can play vector games on the wall. And stay off my lawn!!! (Kids these days…)

For those that do want to burn stuff, [Joshua Vasquez] published an article yesterday about building a safe laser cutter… much more worth your energy than anything billed as a laser bazooka.

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Taming the Beast: Pro-Tips for Designing a Safe Homebrew Laser Cutter

Homebrew laser cutters are nifty devices, but scorching your pals, burning the house down, or smelling up the neighborhood isn’t anyone’s idea of a great time. Lets face it. A 60-watt laser that can cut plastics offers far more trouble than even the crankiest 3D-printers (unless, of course, our 3D printed spaghetti comes to life and decides to terrorize the neighborhood). Sure, a laser’s focused beam is usually pointed in the right direction while cutting, but even an unfocused beam that reflects off a shiny material can start fires. What’s more, since most materials burn, rather than simply melt, a host of awful fumes spew from every cut.

Despite the danger, the temptation to build one is irresistible. With tubes, power supplies, and water coolers now in abundance from overseas re-sellers, the parts are just a PayPal-push away from landing on our doorsteps. We’ve also seen a host of exciting builds come together on the dining room table. Our table could be riddled with laser parts too! After combing through countless laser build logs, I’ve yet to encounter the definitive guide that tells us how to take the proper first steps forward in keeping ourselves safe while building our own laser cutter. Perhaps that knowledge is implicit to the community, scattered on forums; or perhaps it’s learned by each brave designer on their own from one-too-many close calls. Neither of these options seems fair to the laser newb, so I decided to lay down the law here.

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How Lasers Actually Work

Lasers are optical amplifiers, optical oscillators, and in a way, the most sophisticated light source ever invented. Not only are lasers extremely useful, but they are also champions of magnitude: While different laser types cover the electromagnetic spectrum from radiation (<10 nm) over the visible spectrum to far infrared light (699 μm), their individual output band can be as narrow as a few µHz. Their high temporal and spatial coherence lets them cover hundreds of meters in a tight beam of lowest divergence as a perfectly sinusoidal, electromagnetic wave. Some lasers reach peak power outputs of several exawatts, while their beams can be focused down to the smallest spot sizes in the hundreds and even tens of nanometers. Laser is the acronym for Light Amplification by Stimulated Emission Of Radiation, which suggests that it makes use of a phenomenon called stimulated emission, but well, how exactly do they do that? It’s time to look the laser in the eye (Disclaimer: don’t!).

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Mouse Brains Plus Line Laser Equals Rangefinder

[Neumi] wrote in with a sweet robotics hack. It’s a 2D laser distance sensor (YouTube) made with a cheap line laser and an optical mouse’s flow-sensor chip used as a low-resolution camera. In one sense, it’s a standard laser-distance-sensor project. But it is clever for a whole bunch of reasons.

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For one, using a mouse sensor as a low-res camera is awesome. It’s designed to read from a standard red LED, so the sensitivity is in just the right ballpark for use with a line laser. It returns a 30×30 pixel greyscale image, which is just about the right amount of data for a low-end microcontroller to handle and keep up with the framerate without resorting to coding tricks.

It’s also no coincidence that these sensors are available with lenses built in, for relatively cheap, on eBay. Apparently the quadcopter gurus use them as if they were mice to visually track their quad’s motion. Hacker spillover!

Detecting the laser line as it reflects off of whatever objects are lying on [Neumi]’s floor could also possibly prove difficult, and might produce false readings in the presence of background illumination. So [Neumi] takes two readings with the camera — one with the laser on and one with it off — and differences them. Done fast enough, this should reduce any non-laser sources down to the sensor’s noise floor. Finally, there’s some thresholding and averaging going on behind the scenes that help make everything work out right. The code is up on GitHub.

Not a bad build for a 2D laser distance system on a budget. If you want to shell out a bit more money, and are into a seriously involved build, this is probably the slickest we’ve seen in a long time. And if you’re thinking that you’ve heard of [Neumi] before, you’re right: we featured this 405mm laser PCB exposer / burner CNC machine just a few months ago.

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Low Cost Optics Bench Project – Now with Lasercut Optics

[PWalsh] has a clever idea for learning and experimenting with basic optics: instead of using actual lenses, he’s using clear pieces of laser-cut acrylic cut into lens profiles instead. They are much easier to make, mount, adjust, and handle while still bending light in the same basic ways. It allows for simple hands-on experimentation with plenty of visual feedback – perfect for beginners.

Optical Group

This idea is part of [PWalsh]’s low-cost optics bench project, which uses laser-cut plastic to create adjustable optics bench components. We’ve covered this project before, but [PWalsh] expanded the idea with the concept of these simple laser-cut optics for basic experimentation; an addition that requires no additional tools and only a small amount of material. Features and value added for nearly zero cost is something we always love to see!

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How to Fail at Laser Cutting

Laser cutters are CNC power tools, which means an operator uploads a job digitally and then pushes START to let the machine do all the work while they lie back in a hammock sipping a margarita, occasionally leaping out in a panic because the sound coming from the machine changed slightly.

Like other power tools, laser cutters are built around doing one thing very well, but they require an operator’s full attention and support. The operator needs to handle all the other things that go on before, during, and after the job. It’s not too hard to get adequate results, but to get truly professional and repeatable ones takes work and experience and an attention to detail.

People often focus on success stories, but learning from failures is much more educational. In the spirit of exploring that idea, here are my favorite ways to fail at laser cutting and engraving. Not all of these are my own personal experience, but they are all someone’s personal experience.

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