Over Christmas, I was mentioning to my brother that I purchased a CO2 laser cutter and was in the process of upgrading it. He mentioned that he would love to use it to cut airbrush stencils (he does auto detailing.) The stencil material is about 3 mil to 10 mil thick in various materials including mylar.
Anyway, I said the CO2 laser cutter was probably overkill for something like this and claimed that I could make a laser cutter in an aluminum briefcase for less than $300 using a laser diode. So, he took me up on the challenge and here we are now.
Looking around at options, I couldn't find any good sources for laser power vs. cutting capability. So, I looked for what what the most powerful I could get for a reasonable price. I settled on a 2W 445nm laser diode with a GaAs lens, copper host, and a built in driver (as I understand this diode can go up to 3W if an appropriate driver is made and the laser is pulsed) for simplicity. $125 shipped. I also picked up an aluminum heatsink to fit the laser.
I received the items today, so the build has officially started.
Before I get too far into it, I wanted to mention this: I set up the laser with a momentary pushbutton just to make sure it was working. Knowing how powerful these are (and not having the proper safety glasses yet) I set up a black target, looked it the opposite direction of the beam and pressed the button. It freaked me out how bright this diode is. So, now I am quite paranoid about the safety of this laser and know I need to do a lot more research before calling the build finished. These things are no joke! It may have been misinformation, but I had been reading that at about 3W, these 445nm laser diodes are as powerful (cutting ability) as my 40W laser. I am skeptical of that, but that was what I stumbled on in several forums.
On to the build...
So we start with a typical aluminum equipment case. Dimensions are 17.5x12.5x6 inches. The stencil material is found in either 8.5x11 or 8x10 sizes. I decided on a 12x12 cutting area since the electronics will take up very little room. I am basing the XY stage on the CoreXY design which is very compact and takes up only a little more room than the cutting area itself.
I decided that I wanted to use parts that I could find in a typical hardware store as much as possible. I also have a 3D printer which will assist me in a great deal to get just the right design.
The corexy platform consists of two steppers with gears/pulleys and 8 idlers. The motors are mounted parallel to each other and both are driven at the same time to produce the motion. Since the carriage will only be carrying the diode with heatsink, I am able to get away with a very lightweight system. Instead of timing belts and gears, I will be using Spectra 100lb braided fishing line and custom 3D printed pulleys. The Y axis rods are standard 1/4" steel rods you can find in just about any hardware store and 1/4" brass bushings. The X axis consists 1/2" aluminum C channel.
Attachment 263112 All the parts with the C channel and laser heatsink for clarity
Attachment 263114
The laser carriage up close with details shown
Attachment 263116
And the guides for the Y axis. The other parts shown are the motor pulley, idler pulley, spacer, and the stepper mount
Attachment 263118The laser mounted in the carriage. That is actually a prior iteration. But the new iteration is just beefier and a better fit.
Attachment 263120 The gist of the mechanism. I need to cut the metal rods and C channel drill and rivet the guides to the C Channel, and polish the rods to ensure uniform thickness.
The aluminum case will serve as the majority of the structure. The rods will be mounted to the walls of the case. The rear pulleys will be mounted on a bracket that will also attach to the back wall. Same with the steppers on the front wall. I tore out the felt lining from the case mainly for static reasons. I haven't decided what I will re-line it with yet.
Attachment 263122Cheap 5V geared steppers common on Ebay (2 for $6, I think) with the gearing, they achieve a step angle just under 0.9 degrees. The gearing is very strong, I can barely turn the pulleys with my fingers. I will be using these same motors, but I ordered another set with a more friendly mounting arrangement.
For the electronics, I will be using an Arduino Uno with CNC shield and DRV8825 stepper drivers capable of 1/32 microstepping. A customized GRBL firmware will be loaded and many g-code sender programs are capable of supporting GRBL. This may get a customized open-source treatment, though.
I started to cut a window in the aluminum case, but realized after seeing how bright that laser is, that standard anti-glare plexi isn't going to cut it. I am trying to research what I can use that would be relatively safe. Transparent red acrylic might work with a UV protection film applied.
The case has the combination locks on it, and I will be interfacing interlock switches to these that will only allow the laser to operate when the case is latched shut. The case will be decorated with brass hardware and the build area lined (and stiffened) with anodized sheet metal.