A co2 laser will cut through acrylic, but not instantly, and it’s not focused until the last set of lenses at the cut area. That’s why he said you could use plywood or cardboard, though straight from the tube, it will eventually catch those on fire, just not instantly like at the focused cut area. Co2 can’t cut metal, wrong wavelength of light, it just reflects off. If I were making one, I’d put the tube in a metal box, then put metal shields behind the mirrors, just in case. Though if I were building a laser system, I wouldn’t use the mpcnc platform. This is where 2020 style aluminum extrusion excels. You can get reasonably good linear rails from china(well, probably not at the moment) and build a really light core xy motion system that will be waaaay faster than the mpcnc system for not a lot more than the mpcnc system.
Agreed, etching with one another of those takes crazy speed and accels. As light of a final head as possible and make that puppy move! Cutting…any platform.
just ordered a laser chiller last week, got here in 2 days, and HGR20 rails (waaay cheaper than MGN) in 2 days too, so supply is coming back.
cloudray has a very lightweight head if you’re using a 700mm (30 ish watts) tube, since the beam is smaller, you can get the 12mm lens one with adjustable focus and not have to worry too much about an adjustable bed. Large tubes will have a larger beamwidth and require the bigger heads.
Why not use linear rails for both the X and y?
I guess it begs the discussion about maybe a 15w diode instead?
15w diodes have a larger spot, so you can’t get super fine detail. I think they’re about a 2mm focused dot.
And the usable etching range (for the speed we can move at) is very limited so grey scale is severely limited.
How do the dot sizes compare to CO2 focusing? And what kinds of speeds are we talking a CO2 “could” reach with the optimal platform?
Well… part of the problem is that at 2mm, it’s not a tight focus, either. That fuzzy edge will burn and char the workpiece. As far as speeds go, search for ‘K40 laser’ on YouTube, and you should find more videos than you can shake a pair of protective eyewear at.
Here’s the result of 2h 50min. The sheet size is 12"x12". 15 passes at 4mm/s. 2.8w JTech diode at 100%
Probably not a sustainable duty cycle 
But it did it. Pretty proud of that little laser however impractical it may be.
Do you have air assist? If so, what kind?
Depends on the wattage. Bigger wattage means you can/have to go faster. I cut 1/8" Birch ply and acrylic at 12mm/s in one pass on my K40. At 11ma, and my tube is catalyzed so I have more room to go if I need to go faster. 1/4" Birch needs 2 passes at same speed. Test cut on my 90 watt tube is about 20mm/s at 22ma for 1/4" Birch ply.
I do. I’ve got a big ass compressor in my shop so I run it through a regulator down to a good stream of air focused on the dot. I doubt it’d have cut without that.
I wonder how ‘upset’ I’d have been to start a cut only to find I had to slow to 2mm/s with a big laser tube. Good to keep perspective that all materials burn / cut differently.
I’m still impressed by the cut this little laser gave me here today. It does have me wanting more power but also content that in a pinch I might be able to get by with this on one offs. At 16 hour days this project I just finished with the spindle would have taken 7.5 days to cut the 40 pieces I’m delivering tomorrow morning. The MPCNC cut them in eight minutes flat (and I likely could have pushed that).
I ordered up a bunch of belt and some pulleys and idlers today so I can rough together the ZenXY and wrap my head around how the single stepper (CoreXY I guess) works.
Sorry not 2mm/s, that was a typo. 20mm/s for 1/4" material
Core xy actually has 2 steppers, not 1
Indeed, conjectures and theories are fine, but let’s just have a look at reality here:
Nice, isn’t it? 
Hell yeah!
Would be much better if the pictures were still here though… They all disappeared from your thread except this one…
BTW, did you burn down your house with this machine yet?