Newbie questions about laser cutters

So, I'm currently working on building a CNC router and I like the idea of making it so that I can also use it as a laser cutter / engraver. I saw some jTech kits for lower wattage diode lasers. As I understand those would work fine for engraving non clear acrylic, and other materials, and some very light duty cutting.. but that is a little under powered for my taste, especially considering the cost of the kits.

Thus I started reading about CO2 lasers. And while building my own CO2 laser from scratch does sound like a fun project, it's also a very tedious and hard to get right project from the looks of it. Looking on ebay, I found this:

40W USB CO2 Laser Engraving Cutting Carving Machine Engraver Cutter 350mm/s

This looks very appealing. It is cheaper than many of the low powered diode lasers that jTech sales, and looks like it has the majority of the components I would need. So basically I'd be buying this just to strip out all the parts I want for the laser to retrofit onto my CNC when I finish it.

The question I'm unsure about is just what would a 40w CO2 laser be capable of? As I understand, it should be able to cut clear acrylic, which is one thing I'd like to be able to do with clear plexiglass and such. Would this be powerful enough to cut very thin sheet metal? Something that you might would use for a metal face plate or something like that.

Also on this unit, what is the point of the blue round thing? You can see it outside the box in one picture, and in another it's in the top back of the box and has the silver piece on the head depressing a section of it.

This thing seems really cheap for what it supposedly is. Next step up for 50w CO2 I only see things costing 1300+ dollars. Also though, from all the DIY stuff I've looked at, they all have a way to add CO2 to it, these things don't seem to. Is it a sealed system already pressurized with CO2 or something? That could make removing the parts to place them onto my own CNC more difficult. But, if I did buy one of these, I'd probably initially just use it as is, but I'd eventually want to move the parts out to go beyond the 12" x 8" work space restriction.

 

After doing some more research after posting this I got a few answers myself. Putting them here in case anyone else reads this and has the same questions.

It is a sealed system, so the CO2 and possibly some Helium is already sealed inside the tube and does not have to be added. My earlier concern about it being difficult to remove due to this I don't think is really a concern. After looking at some videos of the unit, it looks like it would actually be a fairly simple process to transfer the laser parts onto another machine.

Also again, after watching some video for this specific unit, I have a better idea of what it is capable of. It looks like it can do 3 - 4mm acrylic without to much trouble. I've seen videos of people using it to cut and engrave window glass even (doesn't fully cut through the glass but scores it much like a hand held glass cutter so that the glass snaps on that score). I think if I transferred this to a CNC machine with Z-Axis movement capability then it will probably be able to cut thicker stuff, since all this is being done with just one or two passes at the same height.

I have not been able to find out if this would be able to cut thin sheet metal. But I can experiment with that cause I'm probably going to end up ordering one of these. It seems to do enough of what I want at a good enough quality to satisfy what I want to do with it for now. One of the biggest things being that I want to be able to cut clear acrylic and a diode from jTech can't do that.

Another question I have, if I understand it correctly based on my limited research on how to build a CO2 laser... the power of the laser is directly proportional to the power you feed it, correct? So if I got a bigger power supply driver, I could increase the power of this laser using the same tube, yes? I imagine there are some consequences to this, perhaps shortened life of the CO2 tube due to additional heat build up or something? Maybe the CO2 gas over time looses it's effectiveness at creating the photons needed to generate the laser light? I haven't read much about the science behind it just a little that has been mentioned in how to build it lol.

EDIT: Oh and that blue thing I'm pretty sure is just an exhaust tube that is just inside the machine in some pictures for storage. It connects to the exhaust fan to pipe the fumes somewhere safe.

 

I did order the laser. Will get it in some time next week. One of the CNC projects I'm working on (yes I have multiple lol) is an Ox like CNC build, and it is the one I will most likely transfer the laser onto. My design has a beam behind and a little above the y axis rail, it's purpose for added rigidity and for a cable snake to lay on (don't know what the proper term for those things are lol. I could mount the laser tube on it, and use the mirrors to bounce the laser around to the front of the z axis. Then use the z gantry to hold the lens in order to be able to change the focus height of the laser. And the y axis / x axis would work just like it does on this machine.

It will probably be a little bit before I get to the point of transferring it to the CNC, since I have to finish build the CNC first lol... but it will definitely get done at some point And like I said, I think with the z-axis allowing focus change, it should be able to cut much thicker stuff in multiple passes. It can do 3 - 4mm acrylic as it is supposedly (I've seen videos of it doing it), I think with a z-axis focus change it will probably be able to at least double or tripe the thickness. Biggest worry there would probably be melting issues, or the non straight cuts due to beam focal length. The second could be controlled some with a longer focal length lens though.

Oh, and yeah I had already planned on enclosing this CNC. To prevent dust and all from getting everywhere when I use it. I had planned to have plexiglass doors on the front. If I add a laser to it, I'll change that to some of the OD4 acrylic or something (like the sheet on the lid of the laser I linked). And maybe I'll beef up the ventilation I had planned to have on it a little in case I'm cutting plastic to make sure I get the fumes out faster.

 

I'm just starting out as well, so I only know what I've done research on so far.

I'd only be moving the lens up and down. So basically there are 3 mirrors involved. One right at the end of the tube at a 45 to bounce it out, another in line with that one and in line with the z axis mirror (this is also referred to as the head), that bounces it over to the head mirror. Then that mirror bounces it down to the lens. All 3 mirrors in the design I'm thinking of would be stationary relative to each other (they'd all ride on the y axis so to speak). Well, the Z (head) mirror would get closer to the one mirror, but it would still be in line with it.

The biggest thing I'd worry about is vibrations or any sway from the weight moving around throwing the alignment off while it's moving to cut. That could make precision on subsequent cuts more difficult.

I honestly don't know how the bigger lasers are done. Haven't researched that so much cause I like trying to come up with ways to do things myself first hehe.

I also don't know if you can use fiber optics instead of a mirror. I do not know how fiber optics work really. I just know it's a light based transmission of some form lol

 

Well I got the laser cutter in last week, but finally got a chance to finish setting it up and play around with it tonight. I have to say initially, I'm fairly impressed with it. I mean it's obviously not extremely powerful took about 80% power to cut 1/8" plexiglass. But out of the box everything worked. The mirrors seemed to be aligned and everything. I didn't see any of the problems I read about with this machine of bad wiring or things like that. All the wiring looked good, didn't see any dangerous potential shorting spots. Now there are of course some things that could use improvement. The exhaust port is woefully small and the fan doesn't seal at all in the back to create any real suction. Plus nothing about the laser cutter area is sealed so the exhaust is only minimally effective anyway. My entire house stinks atm even though I had the exhaust piped outside lol. That needs to be reworked a bit, and I think this thing might have to live in the garage as soon as I can clear a spot out for it in there. A safety switch on the lid to disable the laser would be a good idea as well. I'm also not even sure if this piece of colored plexi glass on the door is safety glass or just colored plexi glass lol.

But for a 300 dollar laser cutter / engraver, it is not bad. Attaching an image of some of the things I messed around with tonight, yeah I just used my name, I know boring I was just testing lol.