Ooh exciting, I’ve wanted to find someone with your knowledge! I couldn’t find a good answer when I was researching this a while back.
How powerful of a laser would I need to cut 18mm ply at a workable speed? Would I need crazy cooling setups? And what size steel or aluminium could I cut with that?
This would be a home DIY setup, but on the ‘serious business’ side of DIY.
The lasers I ran could do that but we typically cut steel and aluminum with them. They had a separate chiller that had to vent outdoors, along with forced ventilation systems to keep fumes and fine metal dust from building up.
I’m not as familiar with cutting plywood, unfortunately. But I feel like 18mm material woukd need at least 1,000 watts.
I’ve cut plywood that thickness with a CO2 laser at 150 Chinese watts (closer to 140 SI watts). It takes several passes, and you would want a lens that makes a parallel beam. Most laser cutters come with a lens that focuses the beam to a point. That’s good for thinner material, but not something this thick.
It’s not great at it. Might have a lot of char. But it’s possible.
Full disclosure, I don’t run CNC lasers for a living anymore. But I did for about ten years.
The laser is generated in a cabinet the size of a large refrigerator. Inside that cabinet is a bunch of stuff, but what we are concerned with today are the tubes and turbine. There are glass tubes with mirrors at each end, and they are filled with a mixture of helium, CO2, and nitrogen. These tubes have an electrode in the side of them where high-voltage DC (around 40k volts) is used to “pump” the laser. Some lasers are RF pumped which is nice, because you don’t have to put an electrode through the tube, and they are less prone to leaking. In addition to the laser tubes, you have at least one turbine circulating the laser gas through a heat exchanger, because lasers are only 10%-15% efficient and the extra heat has to go somewhere. There will be a chiller, a machine that makes cold water, which circulates water through the heat exchanger and the mirrors.
Once you have that juice being pumped into the laser gas, the tubes will look light purple or pink. But the beam itself is invisible, in the infrared spectrum. There is typically a small red laser, like a laser pointer, which is aimed through the optics to show where the beam is pointed.
To cut metal, you need a cutting gas in addition to the laser. For carbon steel, low-pressure oxygen is used, around 35-60 torr. (so .04 to .05 bar) To cut the steel, the laser is focused on the top surface of the material, and a nozzle is held about .035" (~0.9mm) above the material. The laser pulses at first, say around 2200 watts and 1/2 Hz, for a second if the material is more than 9mm or so thick. Once the laser has pierced the metal, the beam will switch to either continuous wave (full “on”) at 2000-2500 watts, or it will run at a frequency which can be chosen by the operator, and a duty cycle which the operator also chooses. In this case the beam will look like it’s “on” but it’s really flashing too fast to see. While the laser is running, the aforementioned low pressure oxygen is blown at the hot spot it makes, which burns the steel out of the cut.
If you are cutting aluminum or stainless steel, you need nitrogen instead of oxygen, and it needs to be higher pressure. Like 120 psi/8.2 bar. And you have to use more power, because there isn’t oxygen to help with the cutting, and because aluminum is a good heat conductor. So you run at 3600-4000 watts, and this is important, your focal point needs to be about 2/3 of the way through the material. This produces a cut that is shiny and fairly smooth on stainless, and fairly neat and clean on aluminum. A good machine with clean optics can cut steel and stainless steel with no burrs, and aluminum with a slight burr which can be easily knocked off with a file.
A 4kw laser can handle carbon steel 3/4"/19mm thick, and stainless or aluminum 1/2"/13mm thick. Speeds vary, but I could generally get any machine to cut 1/4" carbon steel (6mm) at 90-120 inches per minute, which is 2286-3050 mm per minute.
And now, everywhere I go, I spot bad laser cuts on stuff. Nothing like going to the gym and seeing focus lines in the equipment.
Well, what do you know, not boring at all after all!
Although now I’m curious as to the role of the gas being pulsed at the metal. It sounds like without gas you can’t cut metal? So… no laser cutting in a vacuum? Laser cutting really is just plasma cutting?
Laser cutters, plasma cutters, and cutting torches all use the same method to cut - a point is heated until it’s hot enough to burn, then oxygen is blown into it.
The difference is the heat source and how small of an area you can heat up.
I haven’t tried to cut anything in a vacuum, but i think it would work with adjustments. The oxygen or nitrogen is bottled for the laser anyway. (Or rather its stored as a liquid in tanks outside)
A laser doesn’t cut any more than a flashlight or a microwave. It just makes things hot.
Nope, have to keep it to myself. I know a lot about lasers. People think lasers are cool.
But I know incredibly specific boring things about CO2 lasers that are used for metal cutting. I know enough about lasers to make them boring.
Ooh exciting, I’ve wanted to find someone with your knowledge! I couldn’t find a good answer when I was researching this a while back.
How powerful of a laser would I need to cut 18mm ply at a workable speed? Would I need crazy cooling setups? And what size steel or aluminium could I cut with that?
This would be a home DIY setup, but on the ‘serious business’ side of DIY.
The lasers I ran could do that but we typically cut steel and aluminum with them. They had a separate chiller that had to vent outdoors, along with forced ventilation systems to keep fumes and fine metal dust from building up.
I’m not as familiar with cutting plywood, unfortunately. But I feel like 18mm material woukd need at least 1,000 watts.
Cool!
… Speaking of, what’s the cooling like on a 1kW laser?
You two are fun. U sense there’s a drinking game just around the corner
With a slight possibility of blindness
I wish to make an insight check
I feel like the guys that run our plasma may not have the best ventilation.
I’ve cut plywood that thickness with a CO2 laser at 150 Chinese watts (closer to 140 SI watts). It takes several passes, and you would want a lens that makes a parallel beam. Most laser cutters come with a lens that focuses the beam to a point. That’s good for thinner material, but not something this thick.
It’s not great at it. Might have a lot of char. But it’s possible.
Go on…
So, you were talking about CO2 lasers…
Well… we’re waiting…
You had me at “lasers”.
I know ArF lasers lol. So the CO2 is used to generate your lasers or what?
Full disclosure, I don’t run CNC lasers for a living anymore. But I did for about ten years.
The laser is generated in a cabinet the size of a large refrigerator. Inside that cabinet is a bunch of stuff, but what we are concerned with today are the tubes and turbine. There are glass tubes with mirrors at each end, and they are filled with a mixture of helium, CO2, and nitrogen. These tubes have an electrode in the side of them where high-voltage DC (around 40k volts) is used to “pump” the laser. Some lasers are RF pumped which is nice, because you don’t have to put an electrode through the tube, and they are less prone to leaking. In addition to the laser tubes, you have at least one turbine circulating the laser gas through a heat exchanger, because lasers are only 10%-15% efficient and the extra heat has to go somewhere. There will be a chiller, a machine that makes cold water, which circulates water through the heat exchanger and the mirrors.
Once you have that juice being pumped into the laser gas, the tubes will look light purple or pink. But the beam itself is invisible, in the infrared spectrum. There is typically a small red laser, like a laser pointer, which is aimed through the optics to show where the beam is pointed.
To cut metal, you need a cutting gas in addition to the laser. For carbon steel, low-pressure oxygen is used, around 35-60 torr. (so .04 to .05 bar) To cut the steel, the laser is focused on the top surface of the material, and a nozzle is held about .035" (~0.9mm) above the material. The laser pulses at first, say around 2200 watts and 1/2 Hz, for a second if the material is more than 9mm or so thick. Once the laser has pierced the metal, the beam will switch to either continuous wave (full “on”) at 2000-2500 watts, or it will run at a frequency which can be chosen by the operator, and a duty cycle which the operator also chooses. In this case the beam will look like it’s “on” but it’s really flashing too fast to see. While the laser is running, the aforementioned low pressure oxygen is blown at the hot spot it makes, which burns the steel out of the cut.
If you are cutting aluminum or stainless steel, you need nitrogen instead of oxygen, and it needs to be higher pressure. Like 120 psi/8.2 bar. And you have to use more power, because there isn’t oxygen to help with the cutting, and because aluminum is a good heat conductor. So you run at 3600-4000 watts, and this is important, your focal point needs to be about 2/3 of the way through the material. This produces a cut that is shiny and fairly smooth on stainless, and fairly neat and clean on aluminum. A good machine with clean optics can cut steel and stainless steel with no burrs, and aluminum with a slight burr which can be easily knocked off with a file.
A 4kw laser can handle carbon steel 3/4"/19mm thick, and stainless or aluminum 1/2"/13mm thick. Speeds vary, but I could generally get any machine to cut 1/4" carbon steel (6mm) at 90-120 inches per minute, which is 2286-3050 mm per minute.
And now, everywhere I go, I spot bad laser cuts on stuff. Nothing like going to the gym and seeing focus lines in the equipment.
Man, that’s a lot more in depth than I expected, thank you. Ours pulse at 6 kHz but operate in generally the same way as far as I know.
I used different pulse frequencies and duty cycles depending on the material.
Cool that makes sense. Ours max out at the 6 kHz but the customer does vary the range and duty cycle a bit for their uses.
I loved this
Well, what do you know, not boring at all after all! Although now I’m curious as to the role of the gas being pulsed at the metal. It sounds like without gas you can’t cut metal? So… no laser cutting in a vacuum? Laser cutting really is just plasma cutting?
Laser cutters, plasma cutters, and cutting torches all use the same method to cut - a point is heated until it’s hot enough to burn, then oxygen is blown into it.
The difference is the heat source and how small of an area you can heat up.
I haven’t tried to cut anything in a vacuum, but i think it would work with adjustments. The oxygen or nitrogen is bottled for the laser anyway. (Or rather its stored as a liquid in tanks outside)
A laser doesn’t cut any more than a flashlight or a microwave. It just makes things hot.
What do you think of the youtuber styropyro?
I went and looked that one up. Im a little surprised he doesn’t have an eyepatch.