The Practical Approach To Keeping Your Laser In Focus

You could be forgiven for thinking that laser cutters and engravers are purely two dimensional affairs. After all, when compared to something like your average desktop 3D printer, most don’t have much in the way of a Z axis: the head moves around at a fixed height over the workpiece. It’s not as if they need a leadscrew to push the photons down to the surface.

But it’s actually a bit more complicated than that. As [Martin Raynsford] explains in a recent post on his blog, getting peak performance out of your laser cutter requires the same sort of careful adjustment of the Z axis that you’d expect with a 3D printer. Unfortunately, the development of automated methods for adjusting this critical variable on lasers hasn’t benefited from the same kind of attention that’s been given to the problem on their three dimensional counterparts.

Ultimately, it’s a matter of focus. The laser is at its most powerful when its energy is concentrated into the smallest dot possible. That means there’s a “sweet spot” in front of the lens where cutting and engraving will be the most efficient; anything closer or farther away than that won’t be as effective. As an example, [Martin] says that distance is exactly 50.3 mm on his machine.

The problem comes when you start cutting materials of different thicknesses. Just a few extra millimeters between the laser and your target material can have a big difference on how well it cuts or engraves. So the trick is maintaining that perfect distance every time you fire up the laser. But how?

One way to automate this process is a touch probe, which works much the same as it does on a 3D printer. The probe is used to find where the top of the material is, and the ideal distance can be calculated from that point. But in his experience, [Martin] has found these systems leave something to be desired. Not only do they add unnecessary weight to the head of the laser, but the smoke residue that collects on the touch probe seems to invariably mar whatever surface you’re working on with its greasy taps.

In his experience, [Martin] says the best solution is actually the simplest. Just cut yourself a little height tool that’s precisely as long as your laser’s focal length. Before each job, stick the tool in between the laser head and the target to make sure you’re at the optimal height.

On entry level lasers, adjusting the Z height is likely to involve turning some screws by hand. But you can always add a motorized Z table to speed things up a bit. Of course, you’ll still need to make sure your X and Y alignment is correct. Luckily, [Martin] has some tips for that as well.

Play Dough Simplifies Interferometer Build

An interferometer sounds like something complicated, and in a way, it is. But it is also pretty easy to build one with some common materials. [Let’s Innovate] has instructions for how to make an interferometer using a green laser pointer, some mirrors, and a CD case. one of the most mundane parts, though, might be the most important: Play Dough.

The very sensitive device needs very precise alignment of the mirrors that reflect the beam. Using Play Dough it is easy to adjust the mirrors to the spot that is just right and then have it stay there.

For the best result, the mirrors really need to be first surface mirrors and not the more common kind with the reflective part on the back. Apparently, a green laser gives better results than a red one, too. If you don’t want to hack up a CD jewel case, a DVD player may give up a beam splitter.

So what do you use it for? Well, most of us use it to see the pretty patterns. But the instrument actually has wide-ranging applications to measure very small distances in fields as diverse as astronomy, optics, and photomicroscopy. To do anything really practical, you might need to add a detector of some sort.

If you want a more robust build, this one is similar. If you have a well-stocked test bench, you might be able to get by with even less.

Building A Mag Lev Optical Table

When you’re talking about optics, things are often happening on a nanometer scale. This means that even the slightest amount of vibration can spoil delicate work. [The Thought Emporium] is working on a long-scale project to produce chocolate holograms, and needed a stable surface to set up some optical components. Thus, he decided to build a magnetically levitated laser table.

The build starts with a series of eight machined delrin bushings, each mounting a strong neodymium ring magnet. Four are placed on the base, with a thin steel rod protruding upwards. The other four bushings are then placed such that the poles of the magnets are opposite one another, causing them to levitate. An acrylic plate is then lowered on top, being supported by the levitating magnets.

It’s a very simple way to create a magnetically levitated table, and in a basic interferometry test, appears to do a decent job of isolating the table from vibrations. We also wonder if there’s scope for further improvement through the use of some kind of eddy current damper. It should make an excellent platform for further experiments, and we look forward to seeing some chocolate holograms in the near future.

It turns out that [The Thought Emporium] was inspired by an earlier chocolate optics project. Video after the break.

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Exquisite Craftsmanship Elevate Vic’s Creations Above The Rest

This booth was easy to miss at Maker Faire Bay Area 2019 amidst tall professional conference signage erected by adjacent exhibitors. It showcased the work of [Dr. Victor Chaney] who enjoys his day job as a dentist and thus feels no desire to commercialize his inventions — he’s building fun projects for the sake of personal enjoyment which he simply calls Vic’s Creations. Each project is built to his own standards, which are evidently quite high judging by the perfect glossy finish on every custom wood enclosure.

Some of these creations were aligned with his musical interests. The Backpacking Banjo was built around a (well cleaned) cat food can to satisfy the desire for a lightweight instrument he can take camping. His Musical Laser Rainbow Machine (fully documented in Nuts & Volts) was created so little bands formed by independent artists like himself can have a visual light show to go with their live performances. The Music Kaleidoscope is another execution along similar lines, with an LED array whose colors are dictated by music. Venturing outside the world of music, we see a magnetically levitated Castle In The Clouds which also receives power wirelessly to illuminate LEDs

The largest and most complex work on display is an epic electromechanical masterpiece. Par One is a rolling ball sculpture featuring the most convoluted golf course ever. Several more rolling ball sculptures (also called marble machines or marble runs) are on display at Dr. Chaney’s office which must make it the coolest dentist’s lobby ever. The lifelike motions he was able to get from the automatons he built into the sculpture are breathtaking, as you can see below.

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Creating A Laser Cutter From A 3D Printer

The average FDM 3D printer is not so different from your garden variety laser cutter. They’re often both Cartesian-coordinate based machines, but with different numbers of axes and mounting different tools. As [Gosse Adema] shows, turning a 3D printer into a laser cutter can actually be a remarkably easy job.

The build starts with an Anet A8 3D printer. It’s an affordable model at the lower end of the FDM printer market, making it accessible to a broad range of makers. With the help of some 3D printed brackets, it’s possible to replace the extruder assembly with a laser instead, allowing the device to cut and engrave various materials.

[Gosse] went with a 5500 mW diode laser, which allows for the cutting and engraving of wood, some plastics and even fabrics. Unlike a dedicated laser cutter there are no safety interlocks and no enclosure, so it’s important to wear goggles when the device is operating. Some tinkering with G-Code is required to get things up and running, but it’s a small price to pay to get a laser cutter on your workbench.

We’ve seen [Gosse]’s 3D printer experiments before, with the Anet A8 serving well as a PCB milling machine.

A Laser Aiming Module For First Person Hacking

You’ve perhaps noticed that [Jeremy Cook]  is rather prolific on YouTube, regularly putting out videos on his latest and greatest creations. He wanted to add a head-mounted GoPro to his video production bag of tricks, but found it was a little trickier than expected to get the camera to point where he was actually looking. The solution? A 3D printed laser “sight” for the GoPro that let’s him zero it in while creating videos.

The idea here is very simple: put a small laser module on the same mount as the GoPro itself so you’ll have a handy red dot showing more or less where the camera is looking. The position of the red dot relative to the center-point of the camera’s field of view is going to vary slightly with range, but with something like a GoPro that’s shooting a very wide area to begin with, it’s not really a problem in practice.

Sounds like a good idea, but won’t that leave a weird red dot in all the videos? [Jeremy] is already ahead of you there, and added a small push button switch to the front of the module so he can quickly and easily turn the laser on and off. The idea is that he turns the laser on, gets the dot roughly where he wants the camera pointed, and then turns it back off.

[Jeremy] has put the STL files for the single-piece 3D printed module up on his GitHub for anyone who might find them useful. Besides the printed part, you just need to provide a suitably sized 3.7 V LiPo battery and the laser diode itself. If you need to find a good supply of cheap lasers, you might want to check the clearance rack at the big box store.

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We Were Really Overdue For Laser Jackets

Depending on who you talk to, everything is either fine, or we’re living in an oppressive cyberpunk dystopia in which we forgot to drench everything in colored neon lighting. There’s little to be done about the digital surveillance panopticon that stalks our every move, but as far as the aesthetic goes, [abetusk] is bringing the goods. The latest is a laser jacket, to give you that 2087 look in 2019.

The build starts with a leather jacket, which is festooned with 128 individual red laser diodes. These are ganged up in groups of 4, and controlled with 32 individual PWM channels using two PCA9685 controllers. An Arduino Nano acts as the brains of the operation, receiving input from a joystick and a microphone. This allows the user to control lighting effects and set the jacket to respond to sounds and music.

[abetusk] does a great job of conveying the tricks needed to successfully pull this off. The instructions should allow any curious maker to replicate the build at home, and code is available on Github to help run the show. There’s lots of detail on proper enclosures, connectors, and cabling techniques to avoid the wearer inadvertently pulling everything to bits when wearing the garment to the club. Remember, there’s nothing more punk than educating your friends.

It’s an eye-catching build that would be an excellent addition to any Neo-Chicago street gang wardrobe. It’s not the first time [abetusk] has graced these pages, either – there are electroluminescent looks, too. Video after the break.

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