Hi All,
MPCNC built and very operational. Stumbled across MPCNC a while ago and out came the 3d printer. Haven’t looked back since. I’ve learned so much and thanks to all who have offered help here. I want to take advantage of the MPCNC and RAMPS 1.4 and add a laser to the build. I’ve looked through the JTech 2.8W laser tutorial and again fund it very useful. Has anyone any experience of adding a larger laser to the build. Looking at the usual EBAY sources there are plenty of higher power lasers out there. I want to cut Balsa and 3mm laser ply with the RAMPS board but I’m struggling with what kit to buy and how I can integrate that into RAMPS. I would be looking at 10w for this if possible, could anyone please advise on their experiences, any help is much appreciated.
You should be able to cut balsa and 3mm ply with the 2.8W setup. I’m using the 2.8w $100 setup and was able to cut up to 3/16" balsa in one pass fairly easily (IIRC around 100mm/min) Adding air assist (just a pressurized air stream blowing at the point the laser hits the work) greatly improves the cutting ability. I’ve been testing air assist this weekend and was able to cut 5mm ply about 98% through in one 100mm/min pass with air assist, 2 passes went through perfect and with the air assist the cut is just as clean with 2 passes as with one.
Without air assist multiple passes result in a bigger sloppier cut - but with air my tests of up to 5 passes look just as good as a single pass.
It even helps on “easier” materials. Some cardboard I’ve been trying to cut kept catching fire and burning up at slower rates. I was having to cut it at 700mm/min with 7 passes to get clean cuts - but was getting a big sloppy kerf from that. With air I can cut it better in one pass at 150mm/min.
In the attached photo both cuts were made with the same gcode. But the version on the left I followed the laser with my air nozzle. You can’t see but the burned version on the right didn’t even go through the bottom of the cardboard while the air version on the left went mostly through the bottom layer - it still had a few bits hanging in so it stayed in place but was easily popped out with a little pressure.
The big problem with the higher power lasers is that you get a bigger spot so less accuracy. Plus they cost more. Air assist just requires a source of air like a small air brush compressor. Based on how well my tests this weekend did I’m working on rigging up a more permanent air assist nozzle on my laser - just plumbed to my big air compressor for now but I’d like to pick up a smaller quieter one to dedicate to the laser.
Whoops, my photo was too big…here it is resized.
And a sample of feed speeds with and with out air. These are 1000mm/min (lowest line) to 100mm/min (top line) with air on the right without on the left.
And a sample of multiple passes at 100mm/min - 1 throught 5. Looking at the edge you can see 1 pass ALMOST went through this 5mm ply, 2-5 passes all went through no problem. I have to do some more testing to see if 2 passes or just slowing it down a bit more will give better/faster results.
Also - for those tests I was just using a standard air nozzle (like this one: http://www.harborfreight.com/safety-tip-air-blow-gun-with-hook-68263.html Only with a rubber tip that gives a bit more directed air flow) at about 25-30psi. But following it around manually with the nozzle isn’t a great option, and that nozzle/hose are way too heavy to attach to the machine.
A few people I know with this setup are using a ball inflation needle on a vinyl line - but I don’t like vinyl lines and hose clamps for pressure. So I picked up a $8 air brush hose at HF and found that by cutting the threads off an inflation needle I could use the airbrush adapter to hold it into the hose. Light, flexible and highly directed! Now I just need to make something that will let it mount to my laser mount.
Hi Jason,
Wow!, thanks for the detailed reply, very much appreciated. A 2.8W laser it is then, those look like great cuts, I’ll see what I can replicate with the air assist here in the UK and post my results once the laser is up and running.Really looking forward to it. Thanks again…
I assume its easier enough to focus the laser without it being on full power. I guess I could use Gcode to power the laser at very low power to focus the beam.
I’m still experimenting to figure out the best solution for air assist. Most of my research has found people doing it on big 40w CO2 lasers not a lot on diode lasers.
That said it sounds like air volume is more important than air pressure. Apparently a lot of people are using $30 high volume (~900gph) aquarium air pumps like this one: https://www.amazon.com/Elemental-Commercial-Air-Pump-951/dp/B00I84NKA2 with their 30w CO2 lasers. I’m thinking about doing some tests with my air bed inflator as an air source to see how it does.
I also found this setup which uses a little 50mm blower fan right on the laser:
I know a few people who’ve experimented with using a smaller aquarium air pump but without much success.
It sounds like the big thing is enough air volume to blow the smoke out of the way, though there may be some additional benefit from higher pressure/volume blowing embers and ash away as well.
For focusing - yes I followed the $100 laser instructions and modified my version of marlin so the cooling fan output now controls my laser. I 3D printed a little 55mm tall measuring block I use to set the Z so the bottom of the laser heat sink is 55mm above my work. Then I just use my LCD panel to turn the “fan” on at the lowest setting that gives me a laser dot and then WITH GOGGLES (always, always wear my goggles around this thing…and I have decent goggles that cost almost as much as the laser.) I adjust the focus for the smallest dot I can get. Once that’s done I used Ryan’s laser focus script to fine tune the focus: https://www.v1engineering.com/forum/topic/laser-focus-script/
Good focus helps a LOT with getting a good cut.
I’ve also experimented with lowering the Z height as I cut multiple passes but with the air assist it doesn’t seem necessary. Without it I found that doing 2-3 passes at higher speed and then lowering the Z about 2mm and doing a final pass worked almost as well as 7 passes at that same speed. But with the air I can get a better cut in one pass so why bother now 
I use a 120mm high cfm fan 252 CFM mounted about 16" from where work area. I instantly noticed the quality of my engraves go up. Keeps fumes, smoke and debris off the work surface. Loud as hell but my work area is fairly well sound proofed.
Also serves a second purpose cooling the laser diode too. Does a great job at that.
Nice! I have a 40mm fan right over my diode for cooling, but using the mount from leo69: http://www.thingiverse.com/thing:1301138 it doesn’t act much like a duct so that little 40mm fan doesn’t help blow much smoke away.
One friend is using Ryan’s laser mount: http://www.thingiverse.com/thing:1636811 and reports getting some benefit from the way it ducts the airflow. But he still sees more benefit from additional higher pressure air. He was also the one to try a small fish pump without much noticeable difference.
I’d really like to figure out what the cheapest/quietest option is that gives the biggest benefit. But going to take some time to experiment more to figure that out!
Hi Jason, I need to cut a 5mm acrylic, is there any diode laser to do that?
Thanks
I don’t know of any diode lasers that will cut 5mm acrylic. Due to their wavelength they just aren’t effective at cutting acrylic. My 40w CO2 laser has no problem with 5mm acrylic…but that’s a different beast all together that operates at a different wavelength.
Thanks CO2 is out of question here. Thanks
I just finished rigging up a mister system for cutting alum with the router. When I get my diode I will try it with air from that nozzle. I run it at 25psi and it blows lots of chips, but it can go to 120psi if needed to clear charred wood. It doesn’t surprise me that air helps so much… lasers are nice and delicate which means the charred wood is left to block the light from getting deeper.
At speeds that you are using… I would be fine with needing to do another pass or two to get some more delicate items cut well.