So, as those of you who follow me elsewhere may know, I’ve been getting into CNC recently, with the help of this sweet little desktop machine:
The Genmitsu Cubiko, from SainSmart via Kickstarter. And since it has arrived here, I’ve been having a merry old time designing little widgets in Fusion 360 and milling them out of assorted bits of scrap lumber hereabouts as I learn and practice on my way to larger projects.
As of yesterday, however, the laser module I got along with the machine in the Kickstarter arrived, so I’ve been getting started with some laser engraving. This module, as it turns out, is the already-existing Genmitsu CFL55-33 laser module, a nice 5.5W violet diode laser that works very nicely indeed.
But for one eensy issue.
Connecting it up and configuring it (using LightBurn for now, at least) was simple, as was using it. But where physical installation is concerned - well, the Cubiko uses a 42 mm spindle, which you take out and replace with the laser module. There are four corners neatly cut into the otherwise circular interior of the spindle clamp to let you do just this. But unfortunately, it turns out that in practice - at least on mine - when you put the laser in the spindle clamp and tighten its bolt as far as it will go, the laser (at 33 mm each side) is just too small to stay fixed. Close enough that it will stay where you put it, even, but that’s not quite tight enough for me to trust it when it’s moving back and forth at laser-engraving speeds.
At first I was able to shim it with a thin piece of wood I had handy, and move on. Which worked fine for my initial runs, but isn’t what you might call a permanent solution.
So I turned to 3D printing for a solution, but printing a round holder for the laser was out: a 33 mm square won’t fit into a 44.5 mm (the interior diameter of the clamp) circle, period. So instead I experimented by making a thin, square belt for the laser, to slip on over it and clamp down.
That worked, but even a very thin “belt” - one that came out on the printer as a single wall, and that alone - was too much. While it would hold the laser in place, it bowed out between the corners in use, and also placed what I deemed to be excessive strain on the clamp.
Which led me to my eventual solution.
This, if you will, is a laser wearing suspenders.
My eventual 3D print job (which you can download here as the .STL to print, or here as the original Fusion archive) consists of two small right-angled “suspenders”, each one printed wall thick, which widen the laser for 18 mm of its height at the appropriate spot, just enough to let the spindle clamp grip tightly.
To make sure I installed them at the right spot (just below the vents, as seen in the below picture), I used the following procedure:
Dialed the laser in, while placed in the clamp, for a job on very thin material. For me, this meant positioning the Z axis at -38 mm (machine coordinates), and positioning the laser thereafter with the built-in focus widget on a 2 mm wood blank over my spoilboard.
Using a thin Sharpie, make a small mark on each side of the laser where it emerges from the bottom of the spindle clamp.
After removing the laser, place a drop or two of cyanoacrylate adhesive on the inside of each “suspender”, and apply them to the front corners of the laser as seen in these pictures, lining up the bottom of the suspender with your mark.
Let the cyanoacrylate cure. I don’t recommend putting the laser back in the clamp until it does.
As long as you’re installing it at a height where the “suspenders” are within the clamp, from now on, your laser should fasten there securely.
You’ll note that by setting the default position for them where I did - i.e., dialing in the laser on very thin material - there’s plenty of room to adjust the position of the laser for different jobs - there’s only a small distance further down you can go before reaching the bed, and with 18 mm of “suspender” inside the clamp in the original position, there’ll still be plenty available to hold the laser in position.
Going up, you’ve got 18 mm in which you can raise the laser inside the spindle clamp before the top of the “suspender” reaches the top of the clamp, not to mention a whole 38 mm of Z axis to play with.
And that’s how to make your laser stop slipping!