I deep read this forum and found many kinds of Laser to use, but still need some advise, I want to be able to cut plastic/acrylic 7mm, and write text very small in size like the size of this font here in my request, of course cutting and engraving in wood would be nice as well.
My place is small I am using a bathroom and not too much ventilation. My MPCNC work size of 480x390mm.
So which Laser are you guys suggest for 2020. 
7mm acrylic is pretty thick for a small laser. I have a 40 watt C02and it does a great job in one pass on some 5mm acrylic I have. I can make it through 7mm going slower, but the kerf isn’t as nice or you can do two passes.
The lasers that folks use for the MPCNC are diode lasers that have relatively low power. Fine for engraving acrylic and wood, but not good for cutting thicker materials. Then you also need to think about air assist to ensure there are no fires. Venting to is important.
Have you watched the videos on YouTube from Making Stuff and Some Old Guy Coding?
I’m interested in this question too because I have seen folks talk more of the problems with the lasers rather than showing cool stuff that works.
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You’ll need co2 for cutting clear acrylic. Diode lasers just pass through.
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thanks I will take a look …
Thanks David seems that is not too easy and will be bigger than I thought.
Is your 40 watt CO2 laser mounted on your MPCNC or another machine?
Like @manolo I am also interested in a more capable laser.
Thanks!
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It’s a totally separate machine.
Have you come across MPCNC owners who have successfully mounted a 40 watt or larger CO2 laser to their rig?
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I haven’t seen that here. It definitely would be a test of accuracy and stability getting the mirrors aligned. Would be interesting to set a long tube over the gantry with its mounts fastened on either end. Getting the the beam from horizontal to vertical in the Z axis would be critical here. Then the whole safety thing of needing a full enclosure.
Well, lookie here:
I keep thinking about doing it. What keeps me from it is trying to figure out how to mount the last mirror. It needs to be a fixed mount so that it aligns with the X-axis, but then the focusing mirror needs to move with the Z-axis to change height from what you’re cutting. I’m sure I could design some type of mount to come off of the top of the gantry, but I haven’t gotten that far.
It’s about $500 worth of materials to get a 60W laser, power supply, mirrors, and mounts.
At that point, I decided to just buy a cheap diode laser from banggood. I bought one of the 50cm x 65cm engravers. It’s only a 3.3kW. It doesn’t cut, but it’s a good start for engraving.
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There was one that was successfully built, but I don’t think he kept it that way. It requires mirrors to bend the beam around the machine, and it’s not the smoothest motion system. It worked, but took a lot of work.
Found it! Sorry, it’s a 100w co2 laser, but same idea, just a smaller tube for 40w.
Yeah. I read that post last night. It looks like he scrapped the MPCNC in the end.
using the mpcnc linear motion for even a 40w tube, I would not recommend. I am currently building a 60 watt machine using extrusions, so it’s pretty inexpensive for the xy.
Also, because the X and Y are separate motors, if one skips a step, the results could be instantly disastrous as the mirrors become misaligned. On my 40 watt, I engrave at 300mm/s, which is about the speed limit of the smoothie board at 32 bit with clustering, I don’t think the mpcnc gantry can move that fast reliably, IMO.
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Hi,
The hardest part are the mirrors. If they do not align 100% you will understand that 1 mm will reflect at the end at 10cm …
We had it working and it was pretty smooth but the board couldn’t calculate it all and de motors were skipping parts. Took a lot of time to figure out how to get past that.
I ordered a smoothie board and converted the project.
Then we still had a little problem with the alignment of the mirrors…
Then we decided to build old the parts from aluminum with metal parts, perfectly drilled.
So you can do it but your projects won’t be perfect.
If you want I can post some of our first projects, then you can see why we converted it. (project is a bit wobbly around the edges)
Don’t forget if you are going to use a laser, create extraction for the air. If you are going to cut or engrave acrylic the gas is heavier than air. You need to suck the air from below your project.
If you need any help or have any question. now you know i’m still here
I agree a bit on this.
Look at my project haha, we use a smoothie board as well. And yes you need to. Else it will skip steps and your project is messed up. have plenty of picture of that 
Forgive my ignorance because I am still new to this.
Why can’t a relatively low, CO2 30 watt laser tube be mounted on the centre with appropriate cooling. Especially on the revised burly MPCNC. Would this not remove the problems of aligning mirrors altogether?
Thank you for the other advice though. I had not thought about the air being denser.
Where would you mount the tube? The center also moves left and right. Do you mean mounting it on the opposite sides/y axis motors mounts?
If one of the x axis skips a step it can twist the 3rd mirror away, even though the first two are attached to the y axis motors. If anything, a corexy or maybe a beefed up zenxy might be a better option.
If anyone is interested, I am also building an 80 wat laser, I wouldn’t mind doing a build log.
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I mean mounting it as you would a diode laser. (Or spindle motor etc). From my understanding the CO2 tube gets hot so you have it off your mpcnc in order to cool it properly and use mirrors to reflect it to the centre. Could one not cool a 30 watt adequately enough with it in situ?
So if either axis skips a step your burn is just messed up but you haven’t shone your beam off mirror.
Leverage will be an issue I think. If you are mounting it directly in the center you have the water lines pulling it down. The glowforge has the tube on the back of the gantry, but there’s no moving parts there. Also, a 30 watt tube is about 635mm long, and still need watercooling lines.