Cutting Metals With A Diode Laser?

Hobbyist-grade laser cutters can be a little restrictive as to the types and thicknesses of materials that they can cut. We’re usually talking about CO2 and diode-based machines here, and if you want to cut non-plastic sheets, you’re usually going to be looking towards natural materials such as leather, fabrics, and thin wood.

But what about metals? It’s a common beginner’s question, often asked with a resigned look, that they already know the answer is going to be a hard “no. ” However, YouTuber [Chad] decided to respond to some comments about the possibility of cutting metal sheets using a high-power diode laser, with a simple experiment to actually determine what the limits actually are.

Using an XTool D1 Pro 20W as a testbed, [Chad] tried a variety of materials including mild steel, stainless, aluminium, and brass sheets at a variety of thicknesses. Steel shim sheets in thicknesses from one to eight-thousandths of an inch appeared to be perfectly cuttable, with an appropriate air assist and speed settings, with thicker sheets needing a good few passes. You can definitely see the effect of excess heat in the workpiece, resulting in some discoloration and noticeable warping, but those issues can be mitigated. Copper and aluminium weren’t touched by the beam at all, likely due to the extra reflectivity, but we do have to wonder if appropriate surface treatments could improve matters.

Obviously, we’ve seen that diode lasers can have an impact on metals, simply smearing a little mustard on the workpiece seems to make marking a snap. Whilst we’re on the subject of diode lasers, you can get a lot of mileage from just strapping such a laser module onto a desktop CNC.

34 thoughts on “Cutting Metals With A Diode Laser?

    1. Thanks. I can figure inches, feet and miles approximately, but 8 thousands of an inch means nothing to me. For the writers, when you speak of half inch plywood, we can get that it is a bit larger than a centimeter, and have some understanding of what you get.
      But with such measurements, it’s hard to make sense of it without some calculations, because we are absolutely not used to such values.

        1. When I apprenticed I learned that “thou” meant 0.001″ and “tenth” means 0.0001″. From there we go to millionths, and many operations are in the 10 to 40 millionths of an inch (go take a look at any of Dee Dee’s videos on operating a Moore Jig Borer.

          1. “thou” is fine… But when PCB people say “mil,” short for “milli-inch” (i.e, a thousandth of an inch) then THAT is confusing! I read somewhere that “thou shalt always say thous” which I have tried to adhere to.

  1. It might also be the thermal conduction. Try coating it with dry erase marker, perminent sharpie, cermark, and other absorbers. If it is refection,, then this will allow you to cut or mark. If it is therma conduction, then it might mark but not cut copper, aluminum, or brass.

      1. For different colored/translucent materials yes wavelength plays a big role, but from my understanding to cut metal there are two big factors: energy concentration (focal spot size) and total power output. For these diode lasers it usually just comes down to not having enough energy in a small enough area to blast through the metal. From what I’ve read fiber lasers are usually suggested for metal cutting over these cheaper/lower power diode lasers. The difference in power is on the order of a magnitude between the two.

        1. Metal is best cut at or near infra red wavelength as it absorbs that range well. That is why older CO2 lasers used to be the gold standard for metal cutting. Newer fiber lasers are a little higher wavelength but last longer and easier to scale up and literally stack together into modules.

          1. Well, it does depent on the alloy. While steel has a rather “good” absorption rate for CO2-Lasers 10µm infrared wave length of 10 to 15%, Aluminium absorbs about ten times less. Fiber lasers wave length of 1µm has an absorbtion rate of around 5% in Aluminium and over 30% in Steel. Laserdiods reach up to ~15% in Aluminium as its absorption rate has a local peak at around 0.85µm.

            CO2 Lasers where the standard because it was the most economic way to get that much power from a laser for a long time. It would be great to have powerfull Lasers at wavelengths with absortion rates of 80% and more… Meanwhile we have to pump way more power into the material than theoretical necessay because of our lack of appropriate lasers.

            And dont get me started on their efficiency. CO2 Lasers in itself only deliver around 15% of their input power in Laser power. Fiber and diode lasers are way better at around 50%.

        2. lol, I was still at the 6kw co2 laser source I saw several year ago at bystronic… just checked they do 20kw fiber sources now… impressive… no surprise that a poor 20w laser diode won’t get you far :)

          1. This is true, but one must remember also…. while you are dropping big stacks of cash on the high end lasers, I just bought my first diode for $491.00 delivered to my door, and it has a work area of 18 x 32 inches, with a $69 dollar upgrade taking me to 1090mm. And I’ve etched and/or cut leather, plywood, acrylic, slate, granite, mdf, etc…… I guess it really just depends what you are producing with the thing, and what it PAYS! Along with how deep your pocket goes!

          2. Interesting. If anyone tries that, also try sweeping the laser, as well as giving a random timing delay between 20 and 40KHz. Might also want to play with the on/off time.

    1. Get a cheap spark plug gapping set and try this for yourself.

      You can cut “foil” pretty easily on a laser, but the edges tend to be burnt. As the thickness goes up, the edge burning effect becomes more noticeable. In my experiments I decided that .001″ metal was the limit on our 80 watt laser, anything thicker and the edges are too burnt to be really useful.

      You can cut through thicker metals – and even PCB copper – by putting a piece of kapton tape over the surface. The tape absorbs the heat, and with enough power and a slow enough speed you can cut completely through copper clad PCB material…

      But again, the edges are very burnt. I wasn’t able to get this process to work to any degree of usefulness, but perhaps someone with more time and creativity can figure out a mode that works.

      You can also spray-paint a piece of PCB and use the laser to blast away the paint, then etch the board as normal. You can make PCBs this way, but the kerf of the laser – the minimum spot size that the laser has – will limit what you can do. A 0.002″ spot size (typical near-focus lens) will barely allow a trace between 2 pads, for instance.

      If you want to try this, it helps to bake the PCB for an hour after painting, to ensure all the paint has dried.

      1. Out of curiosity, have you tried using oxygen assist (not just air, but oxygen), or maybe using an inert gas like argon or CO2? Maybe if you have some welder friends, maybe they can hook up a bottle of their metal map gas to see if that will keep it from burning.

    2. definitely! it’s reflective, just like glass does not effect the beam! So you paint it and etch on the back side! paint gives the diode a spot to focus on.. which it may need on a reflective surface

  2. Just a random thought… instead of trying to cut room-temperature metal, why not heat the metal piece to slightly less than the melting (or deforming) point, and use the laser to add enough energy to cut. Perhaps you could heat the metal from underneath, or apply local heating (flame from a torch hitting the piece at the cutting location.

    1. First, yo would need a lot of heating. Second, things might just catch on fire in your machine.
      And then third, you would warp your plate with this heat. It would also oxydize considerably. Some metal would garden, other loose there hardening/tempering…

    2. Well, then comes the problem of what you’re metal sheet is standing on that can withstand that heat. Also, what rods or rails is the laser on that it can share this heated chamber with the heated workpiece, etc. They’d have to all be ceramics which are brittle and expensive.

  3. If copper and aluminum were untouched, that was almost certainly thermal conduction being the limiting factor, not reflection. Those are two of the best thermal conductors among commonly used metals. Iron and steel are terrible at conducting heat, that’s why you can hold a piece of steel in your bare hand when the other end is literally white hot (blacksmithing is wild).

    1. Well… we COULD add a Q-switch to the little 20w laser ;-) What would THAT cost 8-0

      A Nd:YAG emission wavelength is 1064 nm, which is smack in the middle of the infrared spectrum. So, yea. pump the heat in.

  4. Nice to see that all those people who flat out say diode lasers cannot cut metal are wrong. People have even told me (hobby) CO2 lasers aren’t powerful enough to cut steel (not even at 180 watt).
    I was beginning to doubt myself.

    They say it’s because of the wavelength or because of the reflectivity, but that doesn’t make much sense.
    You’re not evaporating the metal you’re burning it.

    Just like most materials you just need the laser to burn trough it. The difference with metals is that they conduct heat really well, so you need enough power to punch a hole. If you can punch a hole you can burn trough it with additional air (or oxigen). Multiple passes won’t help much if the laser doesn’t burn trough in the first place because you’ll end up heating the surrounding material too much. (Steel will warp from as low as 250°C, for copper and aluminum this temperature is even lower.)

    The video proves that with a decent wattage and air assist you can cut steel, all be it very thin sheets. And please keep in mind that 20 watts is not the maximum for diode lasers and the air assist needs to be optimised to cut the material cleanly, without taking away too much heat.

    Anyway, stainless steel will be the easiest to cut because the thermal conductivity is the lowest of the metals.

        1. They are available up to ~20W of actual laser light power. You do have to pay attention to the details though. Some manufacturers quote the amount of electrical power the diode laser consumes, some quote the actual amount of laser power they emit, while others quote the power “equivalent” as they feel it should be compared with. Diodes are typically limited to 4-6W per diode emitter, so the recent trend is to gang up 1, 2, 3 or even 4 diode laser modules inside the laser head and combine their beams into a single beam for increased power.

  5. Thank you for writing and sharing this article it is an honor. I clearly have so much to learn but I appreciate everyone watching and offering up great ideas on things to try in the future.

  6. It would be interesting to try cutting titanium foil and especially with air assist, because titanium has a low heat conductivity and also burns away easily so at the right speed and with air or oxygen I think it might work. It would have to be watched carefully though as it burns fiercly if a larger piece of it catches fire. What do you guys think?

  7. have you tried melting metal wire together to do diode laser welding this way?
    maybe it would make for a good 3D printer?

    Also, what about modulating the laser diode array in pulses at ~20-40 KHz, to generate optoacoustic ultrasound the metal to reduce its yield strength and make it easier to deform and or cut?

  8. There were some recent comments, and it got me to look back into this.

    Here is a chart of the absorption of a few common metals by wavelength:

    Also, recently Creality released their Falcon-2 laser cutter (which come in a 20W and 40W laser diode modules – see ). These have a 455 +/-5nm laser diodes. From the above absorption chart, you will find it is blue and smack in the published maximum absorption range.

    I also found a resent video where someone got one of these lasers to weld 2 stainless steel sheets together So, yea, these 20 and 40W modules can do a LOT

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