It’s probably asked many times before but I can’t find the answer right away. What is better, cutting with one pass and 100% power or 2 passes with less power?
Sometimes I use more speed with less power to get cleaner cuts but is cutting with less power better for the laser-life?
Pushing anything at 100% will shorten life. Heat will kill it, so 100% for short periods is not as bad as 100% for long periods.
The general rule of thumb is 1 pass. Maximum comfortable power that you can run and 1 pass.
This may not be possible.
Imagine what the beam is doing to the material… if it takes multiple passes, then the debris or char is restricting the beam power at the bottom of the cut.
Reducing the effective power and causing material damage where it isn’t wanted.
Good luck
Thanks, and the option of lowering the Z axis after each pass?
I don’t have a Z control, so I can’t advise you on how to lower it a bit for each pass. I would think it would be in the layer somewhere.
If it takes 100% power to cut through, I’ll reduce to 70% and take multiple passes. Air Assist is key. You need enough air to blow the debris out of the cut.
When I had programmable Z control on a laser, I didn’t find it all that useful for cutting. Probably best to set your focus at halfway through your material.
Don’t own a diode laser but in CO2 if you can’t get thru it in one pass, cutting slower gives me poor results. It tends to char and burn the wood. Not sure about other materials. So multiple passes with a higher power allows it to cut without burning. I would be surprised if a diode laser works different.
Z offset for defocus engraves etc. Z step per pass for cutting.
Yes, I have tested that today, works great btw for thicker materials. Thanks!
Yep, the diode works kind of the same I guess. Going too slow, even with air, gives burnmarks. Regarding the focus, U usually use the auto focus option and so far it works good.
To me these diode lasers are modern day K40’s
Only better quality and less power. I’ve been at this for a while and hobby CO2’s have trended higher wattage over the years. Looking at the cost of high wattage diode I’m not sure that’s going to work. Point is everyone wants power and I think a lot of folks are going to give up on diode and switch to CO2. Good luck with your project
For better results see my post LightBurn Super Trick
Change z with sub-layers also.
Fernando
I spent all my money on a 3D Printer, my diode laser will just have to do for the time being. As already mentioned, air works for me with 100% power on 3mm plywood. If you are showing surface burn, bump the speed up and/or use more air. I can adjust the focus easily, but I use the recomended 4mm focus block. (Distance from the shield, not the lens.) Diodes are cheap when compared to CO2.
Nice observation, but I think you cannot compare them.
The co2 laser has been around since the 60’s and how it works hasn’t changed in 60 years. It’s not evolving. This is not so with the dpssl (diode).
Much like comparing tube computers with solid state computers.
DC excited tubes have an advantage in that the excitation, hence power output of the tube can be controlled with current flow. This isn’t the case with solid state devices which are either on or off.
I’ve been doing this for a few years, the only reason for higher power is to engrave deeper or cut. I do most of my project down around 10% power with my 40W. 10% power is about 4W out to do a good job. If I had an 80W, then that 10% would be 8W. So you lose bottom end of your power.
What you do the most is probably what you should look for in a tube.
We’ve seen some incredible advances in dpssl machines and I expect it to get more powerful. The limiting area I think is going to be with getting the heat away from the laser chip. You can already see the module size increasing as the power levels go up…
Could see something like the MR20 fiber for visible light gantry machines. All the power is not on the machine, just a fiber cable to the head/lens.
Good luck
that’s right. but after 2 years of engraving and cutting with diode lasers (last one: ortur 20w / lu3-20) i can say one simple thing to all folks out there, cutting material with a diode laser: you are wasting your god damn time.
really. i feel like a stupid child when i compare the power of my new co2 laser to my 20w diode laser with all the marketing like “whoaahh, 20w diode - thats the power of 80w co2, now you can cut eeeeverryythinggg! we compared a quadrillion diodes to one powerbeam!!1”. you can’t. projects that lastet around 40 mins with the diode, the co2 cuts in under 6 minutes. it’s insane. i wish i had made this invest earlier.
yes, the diodes are good for engraving.
but another thing i have to say is this: why the hell comes every china-tech company with a full enclosured co2-machine, but the diode ones are, let me say… like rubbish. no enclosure, mostly poor air assist, a totaly crappy height adjustment, bolts and strings like it is a kids toy. i could understand it, if they hadn’t become so expensive over the last two years. for the money of two of these childish diode lasers, you can get a co2-machine (yes, china - but it’s not like the diode comes from premiumtech24…).
I’m comparing diode with K40 not in a technical way at all Jack. They market K40 for $750 and sucker folks into buying complete crap. Only technical folks can get them to perform thru modifications.
Diode lasers aren’t that bad but kind if the same thing. Sell it cheap and hope to attract the cricket buyer.
It’s impressive that you still use a 40w laser. I quickly overpowered mine, went to 55 and now have a 90. That’s my other point. Everyone wants more power (for cutting mostly) but does that make sense with a diode?
I wouldn’t say diode is a complete fad, however most who really want a wood cutting and engraving machine will go back to CO2.
Btw Jack, sure CO2 has been around forever and there are better systems like Epilog uses, they are at a much higher cost then most can justify. Also I can energize my tube down to 3 ma. It’s cutting thru 6mm pine at 8ma and 20mm/sec.
The open diode machine concept baffles me. If I don’t have full exhaust on for a minute while cutting, the whole, fairly large, room smells of smoke. My guess is that folks just tend to deal with it… because they don’t want to admit how dumb this design it?
Sorry about the side topics/ranting to who ever started the thread.
Don’t get me started on eye protection, you know how I get. 
I follow that… they do fill a nitche.
They haven’t changed since they were created. You have to generate a high voltage across them in order to lase.
That’s pretty incredible. What I usually see is that the higher the power the higher the percentage of where it will lase. I can’t get down below around 9%. It just won’t lase.
Cheap
The cabinet would cost more than the machine. I got a pair of these a couple years ago, only 500mw, but for ~$80 US, I couldn’t pass them up. Ended up mounting a much larger laser on the chassis.
So in Lightburn the power is set to 100%. Then the 100w power supply I bought has a potentiometer that adjusts power from zero to 18 ma. I can see when the beam comes on at 3ma. Works great for line engraving
I thought that in the US laser equipment is regulated by the FDA. So they consider it a medical device. I don’t think you can ship into the US a working device without proper safeties. This doesn’t apply to components
It’s very possible that diode based devices are not under the same rules as CO2 based lasers. So the reason they can ship theses open machines is simply because they can? Just like those high power lasers that idiots shine on aircraft.
