The How and Why of Laser Cutter Aiming

Laser aficionado [Martin Raynsford] has built up experience with various laser cutters over the years and felt he should write up a blog post detailing his first-hand findings with an often overlooked aspect of the machines: aiming them. Cheap diode laser cutters and engravers operate in the visible part of the spectrum, but when you get into more powerful carbon dioxide lasers such as the one used in the popular K40 machines, the infrared beam is invisible to the naked eye. A secondary low-power laser helps to visualize the main laser’s alignment without actually cutting the target. There are a couple of ways to install an aiming system like this, but which way works better?

[Martin] explains that there are basically two schools of thought: a head-mounted laser, or a beam combiner. In both cases, a small red diode laser (the kind used in laser pointers) is used to indicate where the primary laser will hit. This allows the user to see exactly what the laser cutter will do when activated, critically important if you’re doing something like engraving a device and only have one chance to get it right. Running a “simulation” with the red laser removes any doubt before firing up the primary laser.

That’s the idea, anyway. In his experience, both methods have their issues. Head-mounted lasers are easier to install and maintain, but their accuracy changes with movement of the machine’s Z-axis: as the head goes up and down, the red laser dot moves horizontally and quickly comes out of alignment. Using the beam combiner method should, in theory, be more accurate, but [Martin] notes he’s had quite a bit of trouble getting both the red and IR lasers to follow the same course through the machine’s mirrors. Not only is it tricky to adjust, but it’s also much more complex to implement and may even rob the laser of power due to the additional optics involved.

In the end, [Martin] doesn’t think there is really a clear winner. Neither method gives 100% accurate results, and both are finicky, though in different scenarios. He suggests you just use whatever method your laser cutter comes with from the factory, as trying to change it probably isn’t worth the effort. But if your machine doesn’t have anything currently, the head-mounted laser is certainly the easier one to retrofit.

In the past, we’ve covered a third and slightly unconventional way of aiming the K40, as well as a general primer for anyone looking to pick up eBay’s favorite laser cutter.

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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Drop-in Laser Cutter Alignment Beam Works like a Charm

Every laser cutter enthusiast eventually pops the question: how on earth do I align an invisible beam that’s more-than-happy to zap my eyeballs, not to mention torch everything else in its path? We hate to admit it, but laser cutter beam alignment is no easy task. To greatly assist in this endeavor, though, some folks tend to mix a red diode laser into the path of the beam. Others temporarily fixture that diode laser directly in the beam path and then remove it once aligned.

One deviant has taken diode laser mixing to the next level! [Travis Reese] has added a servo-driven diode laser that dynamically drops into the path of the laser tube when the lid pops up, and then tilts comfortably out of the laser path when the lid closes again.
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