Gavin, if you’re still looking I’ve owned several laser cutters, including 3 chinese ones (2x 1290’s, 1x k40)
For the chinese lasers, the biggest issues you’ll have with the machine itself is the bed. They are almost always built out of angle aluminum that’s pretty lightweight and will flex. I re-built my bed supports from rectangular hollow section aluminium extrusion with square hollow section mounted on top - overkill but no deflection of the bed. Deflection == out of focus == doesn’t cut.
Next up is controllers. I’m a huge fan of the Ruida controllers, particularly the RDC6332G controller - great display, great control, decent software for setup. Even cooler, you can just plug in a USB stick with your pre-prepared cut file, and run it, you can change speed/power/machine settings right from the control panel (it runs linux). The number pad makes it really quick to enter numbers in. They also support network over USB control if you want to go that way.
The Leetro controllers are awfully popular… but really bad. They require a dongle for the software, with the Ruida’s you can setup the job from anywhere. With the Leetro’s they have issues with file storage on the machine (gotta delete all files before you download your cut), they have lots of bugs, and I’ve seen more dead leetro controllers than you can poke a stick at. The PWM for the tube power control comes up as an issue a lot. The displays on them are really basic too. The most frustrating thing I find about these is you can grab a Ruida RDC6332G for the same price.
If you compare the chinese machines mechanics to Epilog or Trotec, you’ll see they are really overbuilt. The trotec’s and epilogs are super super lightweight minimal heads that can get accelerated up and down incredibly fast (trotec’s basically teleport from spot to spot) - the chinese machines are really great at cutting, the beam quality isnt quite as good as the rf excited lasers, but they are pretty good. I agree with the minimum 60W tube recommendation, an 80W would be better though, as you’ll get more servicable life out of it. However, if you’re looking at a smaller machine, the 80W tube will stick out the side. The main issue with the chinese lasers is them using stepper motors vs the very expensive lasers using servos. So with microstepping you have a realistic vertical engrave resolution of about 333lines per inch. The glass tubes can’t ignite as fast as the RF tubes, so you wont see every pixel if you engrave a dithered picture, you’ll typically only see lines that are a minimum of 3-10pixels if its a 333dpi image with a good laser tube powersupply. Cheap laser powersupplies will blow - budget for replacements. I went through 3 cheap powersupplies on my 100W laser before I switched to a genuine RECI one (with the lcd for power/temp/humidity etc).
If you look at the bed slats or honeycomb on a 1200x900 laser at most hackerspaces, and measure the area with the thickest residue you’ll find that most people use the top left (assuming it homes top left) corner for about 600x500mm. The newish 700x500 size lasers are really a perfect size, gives you just that little bit extra room over the 6040 lasers that have been popular for so long.
That being said, the $30k trotec’s are worth it… but who has that sort of spare change. The chinese lasers are very serviceable, by comparison their engravings are pretty terrible, but still look great. The spot sizes for the tubes and optics are larger, which means you need to cut slower (and get more burning on wood edges, but also more polish on acrylic). The expensive lasers ignite instantly, and if you engrave a 1000x1000 pixel checkerboard on a 1x1" square at 1000dpi, you’ll see every single pixel, with a chinese laser you wont see a single one… BUT if you have enough pixels to keep the laser on (or go greyscale and vary the laser power with the darkness of the image - as long as the power sits above 10% for the entire engrave, you’ll get every point engraved perfectly) then the quality is good.
Other costs to consider will be a water chiller - if it’s going to be a centrepiece of your hackerspace (most are) then you’ll need something to keep the laser at 100% duty cycle (ie: long cuts at full power, many sequential cuts at full power, large full power engraves), which for a 60W laser means a refrigerated chiller NOT just a fan and a radiator, or a bucket of water with a pond pump in it. So you’re looking at a CW5000, or better yet a CW5200 (the 5000 has two dissimilar metals in the coolant loop, so it will corrode after a few years, 5200’s are just a little more expensive). I have seen people modify water coolers and fridge pumps for chilling water for laser tubes if you feel you can do that reliably. If your coolant fails, your tube fails. If your coolant gets too hot, the tube’s life rapidly diminishes.
A glass tube is about 20% efficient, so a 100W tube generates 400-500W of heat. A 60W tube will give you 300-400W of heat to deal with. Think of how fast you can boil a cup of water in a microwave, well the waste heat from the laser is 1/4-1/3rd of that power - admittedly you do have a lot of thermal mass in the coolant loop, but it’s still a ton of heat to deal with.
