Better Laser Cuts: Know Your Kerf

April 15, 2023 by Al Williams 19 Comments

The recent crop of laser cutters are nothing short of miraculous. For a few hundred dollars you can get a machine that can easily engrave and — subject to materials — cut well, too. [Nate] has been taking advantage of a laser to make boxes that join together using finger joinery. The problem is, the pieces have to fit exactly to get a good box. While setting dimensions in software is fine, you need to account for how much material the laser removes — something traditional woodworkers and machinists know as kerf.

You can, of course, employ trial and error to get good results. But that’s wasteful and potentially time-consuming. [Nate] built a “tolerance fence” that is quick to cut out and allows accurate measurement of kerf. You can quickly use the tolerance fence to make measurements and increase your chances of nailing your boxes on the first cut.

You have to customize the fence based on the thickness of your material. [Nate] uses Lightburn, which probably has a kerf offset already set by default in your layers. If not, you’ll need to turn it on and set an estimate of your kerf size. Then you are ready to cut the fence pieces and see how they fit together.

If the fit is too loose, you want to raise the kerf setting and try again. If it is too tight, you lower the kerf setting. As [Nate] says, “Lower equals looser.”

The results speak for themselves, as you can see in the treasure chest image [Nate] provided. Well worth the effort to get this parameter right. We do enjoy laser cutting and engraving things. If you are cutting and don’t have air assist, you really need to hack up something.

Laser And Webcam Team Up For Micron-Resolution Flatness Measurements

March 16, 2023 by Dan Maloney 36 Comments

When you want to measure the length, breadth, or depth of an object, there are plenty of instruments for the job. You can start with a tape measure, move up to calipers if you need more precision, or maybe even a micrometer if it’s a really critical dimension. But what if you want to know how flat something is? Is there something other than a straightedge and an eyeball for assessing the flatness of a surface?

As it turns out, there is: a $15 webcam and a cheap laser level will do the job, along with some homebrew software and a little bit of patience. At least that’s what [Bryan Howard] came up with to help him assess the flatness of the gantry he fabricated for a large CNC machine he’s working on.

The gantry arm is built from steel tubing, a commodity product with plenty of dimensional variability. To measure the microscopic hills and valleys over the length of the beam, [Bryan] mounted a lens-less webcam to a block of metal. A cheap laser level is set up to skim over the top of the beam and shine across the camera’s image sensor.

On a laptop, images of the beam are converted into an intensity profile whose peak is located by a Gaussian curve fit. The location of the peak on the sensor is recorded at various points along the surface, leading to a map of the microscopic hills and valleys along the beam.

As seen in the video after the break, [Bryan]’s results from such a quick-and-dirty setup are impressive. Despite some wobblies in the laser beam thanks to its auto-leveling mechanism, he was able to scan the entire length of the beam, which looks like it’s more than a meter long, and measure the flatness with a resolution of a couple of microns. Spoiler alert: the beam needs some work. But now [Bryan] knows just where to scrape and shim the surface and by how much, which is a whole lot better than guessing. Continue reading “Laser And Webcam Team Up For Micron-Resolution Flatness Measurements” →

A Hacker’s Introduction To DIY Light Guide Plates

March 13, 2023 by Sonya Vasquez 36 Comments

Last year, I found myself compelled to make a scaled-down replica of the iconic test chamber signs from the video game Portal. If you’ve played the game, you’ll remember these signs as the illuminated monoliths that postmarked the start of every test chamber. In hyperstylized video game fashion, they were also extremely thin.

https://www.thonky.com/portal-walkthrough/test-chamber-19 — Stay tuned for cake at the end of this article.

True to the original, my replica would need to be both slimmed down and backlit with a uniform, natural white glow. As fate would have it, the crux of this project was finding a way to do just that: to diffuse light coming in from the edges so that it would emit evenly from the front.

What I thought would be quick project ended up being a dive down the rabbit hole that yielded some satisfying results. Today, I’d like to share my findings and introduce you to light guide plates, one of the key building blocks inside of much of today’s backlit screen technology. I’ll dig into the some of the working principles, introduce you to my homebrew approach, and leave you with some inspirational source code to go forth and build your own. Continue reading “A Hacker’s Introduction To DIY Light Guide Plates” →

Laser Scanner Upgraded To Use PCB Motor

February 22, 2023 by Chris Lott 10 Comments

[Rik]’s Hexastorm laser scanner project originally used a discrete polygon mirror controller+motor module from Sharp to spin a prism. But the scanner head was a bit difficult to assemble and had a lot of messy wires. This has all been replaced by a single board featuring a PCB-printed motor, based on the work of [Carl Bugeja]. The results are promising so far — see video below the break.

Since the prism is not attached to anything, currently it will fall off if mounted in the intended vertical orientation. One of [Rik]’s next steps is to improve the mount’s design to constrain the spinning prism. The previous Sharp motor was specified to 21000 RPM, but was only driven to 2400 RPM in [Rik]’s first version. This new PCB motor spins at 2000 RPM in these tests, comparable to his previous experiments ( we’re not sure about the maximum RPM ).

See our original writeup from 2019 to review the goals of this project, and be sure to checkout details and documentation on the Hexastorm project page. To learn more about PCB motors, read our article about [Carl]’s first design and visit his Hackaday.io page. Thanks to [Jonathan Beri] for the tip.

Continue reading “Laser Scanner Upgraded To Use PCB Motor” →

Drilling Glass With Femtosecond Lasers Just Got Even Better

February 16, 2023 by Lewin Day 48 Comments

Glass! It’s a finicky thing. Strong as hell, yet chip it and glance at it the wrong way, and you’re left with a bunch of sharp rubbish. It’s at once adored for its clarity and smoothness, and decried for how temperamental it can be in the case of shock, whether mechanical, thermal, or otherwise.

If you’ve ever tried to drill glass, you’ll know it’s a tough errand. To do so without cracking it is about as likely as winning the lottery on Mars. Even lasers aren’t great at it. However, a research team from France has developed a new technique that uses femtosecond lasers to drill microscopic holes in glass with a minimum of tapering and no cracking! Brilliant, no?
Continue reading “Drilling Glass With Femtosecond Lasers Just Got Even Better” →

Two goniometers sit on a table. One is an open wooden box with a long piece of plywood along the bottom. A laser distance finder rests on the front edge and a printed angle scale has been attached to the back side of the box. To the right of this box is a much smaller goniometer made from an orange pipe cap with a small strip of paper serving as the angle scale inside the interior edge. It is attached to a wooden handle that looks vaguely like a V. A laser pointer can be inserted from the bottom where a hole has been drilled through the wood.

Goniometer Gives You An Edge At Knife Sharpening

February 9, 2023 by Navarre Bartz 11 Comments

Sometimes you absolutely, positively need to know the angle of the cutting edge on a knife. When you do, the best tool for the job is a laser goniometer, and [Felix Immler] shows us three different ways to build one. (YouTube)

The underlying principle of all three of these builds is to project reflected laser light off a knife blade onto a scale going from 0-45˚. [Immler] shows a basic demonstration of this concept with a hinge toward the beginning of the video (after the break). Blades with multiple bevels will reflect light to each of the appropriate points on the scale.

The simplest version of the tool is a printed PDF scale attached to a wooden box with a hole for the blade to pass through. The next uses a large pipe end cap and a drilled-out piece of wood to create a more manageable measuring tool. Finally, [Immler] worked with a friend to design a 3D printed goniometer with differently-sized adapters to fit a variety of laser pointers.

Now that you’re ready to precisely sharpen your blades, why not sharpen this guacamole bot or try making your own knife from raw ore?

Continue reading “Goniometer Gives You An Edge At Knife Sharpening” →

Turns Out, Lightning Can Strike Twice, With A Little Help

January 17, 2023 by Al Williams 19 Comments

Few things are more impressive than a lighting strike. Lightning can carry millions of volts and while it can be amazing to watch, it is somewhat less amazing to be hit by lightning. Rockets and antennas often have complex lightning protection systems to try to coax the electricity to avoid striking where you don’t want it. However, a European consortium has announced they’ve used a very strong laser to redirect lightning in Switzerland. You can see a video below, but you might want to turn on the English closed captions.

Lightning accounts for as many as 24,000 deaths a year worldwide and untold amounts of property and equipment damage. Traditionally, your best bet for protection was not to be the tallest thing around. If the tallest thing around is a pointy metal rod in the ground, that’s even better. But this new technique could guide lightning to a specific ground point to have it avoid causing problems. Since lightning rods protect a circular area roughly the radius of their height, having a laser that can redirect beams to the area of a lightning rod would allow shorter rods to protect larger areas.

Continue reading “Turns Out, Lightning Can Strike Twice, With A Little Help” →