Sorry Jeffeb3 replied to wrong person all those things can go wrong on a k40 why is it worse on a MPCNC?
Because the k40, the y rails are tied together on one motor. Because on the K40, the tube is not attached vertically to the laserhead on the gantry. on the k40 the tube is in the back and enclosed almost completely separately. When a tube fails, the electricity can arc from the attachment points, and then it goes to the case because it’s the closest. If you attach it to the gantry, it will arc to the nearest piece of metal, so the motors or the pipes. No good.
The y1200 from further fabrication also has separate Y motors, also bad idea.
I thought about it more, and if you can encase the tube itself while on the gantry I think it might be okay, but the downside still exists that if your only using it for cutting, you’re giving up a major use of the laser.
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Doing more thinking, I would recommend keeping the mpcnc frame and replace the gantry with vslot extrusion or 2020 and cheap hgr20 rail. This would relieve a lot of weight. Then mount the tube normally.
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Mount the laser fixed, pointing up, with an absorbing target above. Then mount the workpiece to the tool mount and cut inverted.
Juat be careful your waste pieces don’t fall down onto the laser, and try to avoid slicing the center assembly in half…
Definitely worth looking into changing up the gantry.
Is there just too much slop in the belts we use to control both sides with pulleys to a single stepper? I still don’t think it would deflect enough to be a concern but it’s a complete non concern if it could be driven with a single stepper. I can lift the print bed to clear anything “down below”.
Here’s the build thread for the double-decker:
I can see how it would be sort of a natural fit for a huge laser, but jeez it’s so heavy already it would probably need a counterweight to prevent skipping steps in Z. And plus keep everything super super slow.
I’m not in any way shape or form some kind of official. Yes, I talk a lot here, but the point of this forum is discussion. I really appreciate your input, experience and perspective. I would really like to see your participation continue.
You’re probably right, and although I am imagining it in a way that doesn’t feel dangerous, I have never used a CO2 tube, so I have much to learn.
I really just like solving the problems. There was a video posted not that long ago with a CO2 laser mounted to the gantry of another type of CNC machine. I believe they still used the laser diode for engraving. I have seen that, and Jamie’s double decker, and I would like to explore the space between them. I care about Kelly, and I would hate for something bad to happen to him.
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This is the video I was thinking of, with the vertically mounted co2 laser:
It seems to be very much a prototype.
I don’t have the vertical space for a setup like that (luckily I think 
Am I missing a conversation about a higher power diode laser somewhere here? How strong do they go? Will they cut?
Holy crap! That thing is impressive! No more lining up mirrors! Definitely no way it could run the speeds my k40 hits in engraving, though.
I believe that’s the build your own CNC guys. I’ve seen it before and while it works these are also the guys that build and sell desktop laser cutters and a wall mounted 80 watt cutter… Out of MDF. The thought of constantly taking that tube on and off and getting the bubbles out seems like a lot of work too. I wouldn’t risk leaving it on and some debris damaging it.
At the end of the tube itself is a lens, which can fail/crack and send the beam in another direction, and you won’t see it because the beam is invisible. Also, imagine a crack or leak in the tube and water coming down on your work area + high voltage.
Gantry mounted horizontal would be better, that’s how the big bed lasers work, but still dangerous, but you would get fast engraving speeds though. I think running a single extrusion or linear rail for X and then the rest of the mpcnc frame would be much more reasonable.
Nick E, @nellson, in the FB group has/had a Co2 on his MPCNC. I don’t remember if he switched to a faster frame or not. He would have some good answers for you.
Thanks Ryan. You are correct, he did. But has now switched to the Y-1200. He said he ran the CO2 for several months on the MPCNC but also offered that he’s very accustomed to working with lasers and dangers. This all stems from missing out on a job for some 1/8 cutout work that would have carried me through a good year or two of decent income. I missed the boat by taking too long to decide if I could make the laser upgrade or not. The customer went ahead and ordered a Glowforge last weekend. Lucky for me she wants to get going so has hired me to do a first run using my spindle MPCNC. That’s where the cost half-offset income is coming for for this.
Hi ya!
Yup I sold my whole add-on kit to another from the FB group in Gresham Or so they could learn with it. 
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Tell her she can contact me at marmak3261 on the Glowforge forum if she needs any help. Hope her initial experience goes well. The Glowforge is a great machine, but support can be a bit slow even though they always make it right.
I think the dangers and the setup can all be overcome for the MPCNC handling a CO2. However, cutting would be fine but engraving would need some serious work to get speed. It definitely would require an good built get get the resolution you’d like on an engrave.
All in all, if you have an MPCNC frame, know about power supplies and laser control. Are willing to do the setup with mirrors, it would work. I think only the return on investment would really depend on how good you are at scrounging the mirrors and lens assembly and the tube itself. I’d say if you want something that is going to serve you well in the long run, build something with linear rails and extruded profile. But it would a a great project just because.
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Just throwing this out there, but a zenxy with beefy 17’s would probably be a better choice for a co2 laser. Less moving mass for the mirrors. I could be completely wrong, but in my mind it makes sense.
beefy 17’s https://www.filastruder.com/collections/electronics/products/super-whopper-motor
LOL…that’s what I needed…another project bubbled to the surface that maybe I should build up first (it’s all printed - just need the tube).
I wish I was in the US. Best price I can find up here on those big 17’s is over $100 a pop.
I think I’ve mentioned this in the last thread that asked about vertically mounting the tube as well, corexy might be better, and less motors too. Do skipped steps on a corexy motion system skew the gantry?
No, the tension is what keeps it square.
If I’m still thinking this through and paying attention to all of the above (appreciated) comments I should start asking some other important questions.
The K40s as far as I can tell are housed in a “tin box” just like the Glowforge is. The Further Fab Y-1200 was/is just clad in acrylic or plexi yet I do believe in one of his videos he mentioned something like “you could use wood or even cardboard” or something to that effect. Of course with safety in mind cardboard would be an absolute NO. But the question then becomes - what’s best? I’d be inclined to isolate the tube much like the K40s do so that if a break occurs I can attempt to control the repercussions.
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