Cutting Balsa Wood With Air (Oh, And A Laser)

[DIY3DTech] likes using his Ortur laser cutter for balsa wood and decided to add an air assist system to it. Some people told him it wasn’t worth the trouble, so in the video below, he compares the results of cutting both with and without the air assist.

The air assist helped clear the cut parts and reduced charring in the wood. The air system clears residue and fumes that can reduce the effectiveness of the laser. It can also reduce the risk of the workpiece catching on fire.

In addition, the video shows the results of cutting wood using different speeds and number of passes. So the holes marked 5/10, for example, are cut at 5mm/second and ten passes.

Although air assist might help if you are engraving, the real benefit, according to the video, is when you are trying to do cuts. However, removing the fumes is probably a good idea even when engraving.

The video doesn’t go into much detail about the air system, but there are links in the video description to pages that have more information about how to add something like this to your laser cutting setup. There’s also a more recent video specifically about how the air assist system works.

If you need more on laser cutter basics, we read a great post about it last year. Like 3D printers, it used to be fashionable to build your own cutter, but now it is cheap enough to buy one if you’d rather not mess with it.

33 thoughts on “Cutting Balsa Wood With Air (Oh, And A Laser)

  1. It seems a lot of people are using quite weak pumps, like aquarium air pumps, for the air assist. A little bit of airflow certainly helps a lot compared to no airflow, but has anyone tried out at what point there is diminishing returns? As in litres per minute of air flow or similar metrics.

    I’ve been having trouble cutting >3mm plywood (the kind meant for laser cutting), and I wonder if beefing up the air assist would help.

    1. Here I thought blowing on charred wood would create a fire, but the opposite happened. I wonder if instead of air, someone hooked up a pressurized oxygen tank? Would that make cleaner cuts? Or would it be better to go anoxic with a nitrogen tank? In a zero oxygen environment, would the wood char at all?

      1. charring does not require oxygen. Think of the production process for charcoal: In the classic pile you have just enough oxygen to burn just enough wood (or wood gases) to produce the necessary heat. You can also place an airtight ( not completely sealed to avoid pressure build up) reaction vessel in an external heat source like a camp fire.

    1. It takes a bit of looking around, but there are many gcode creation opinions.
      The main issue our group encountered was most apps were only mostly-done for a specific use, but hardly a complete generic CAD/CAM workflow (FreeCAD is slowly changing this with plugins). Also, LinuxCNC is a bit overwhelming for the uninitiated, but realistically it is the only real precision CNC option. Note nativeCAM generates stuff like simple lathe operation gcode directly, but other tool-path-generators are better at contoured surfaces etc.

      For belt-drive + PWM-laser cutters… where speed is more desirable, one usually uses inkscape plugins to vectorize graphical images, clean up 2D CAD exports, and convert the drawing lines/dots into gcode. A tool like bCNC with grbl (not all builds support the pwm on all arduino hardware) interprets the gcode to execute the rapid position and PWM duty cycle updates.

      We attempted to collect as many _verified_working/stable_ FOSS tools for our needs in one place to explore. And more importantly, provided a consistent standard install image for the groups equipment with the RT ARM kernel.
      Our conclusion was people who build their own equipment are usually solving for their specific needs, and thus by nature all tool-suite designs naturally fragment after ones own needs are met.

  2. For cutting nothing beats the CO2 laser not wimpy little diode. For the cost of diode module small tube and lens can be bought – rest is doable with drill press and healthy remaining eye, and it cuts thru balsa, pmma, pc like butter.

      1. $70 diode + ttl driver? ( 10W )

        $68 tube ( 40W )
        $41 driver
        $18 focus lens
        3x$8 mirrors

        frame you already have

        some alu L-brackets, bolts for kinematic mount

        $151 (40W) vs 70$ (10W?)
        cuts 4X more materials at 8X depth

        cost of elbow grease not included

        1. – Probably just unfounded / uneducated / unexperienced concerns, but I have a significantly higher ‘you’ll shoot your eye out, kid’ concerns about setting up a 40W and bouncing it off multiple mirrors, than with a diode mounted to a spindle mount facing directly down. Of course either is dangerous and demands safety gear/respect/etc, but at least for DIY, seems diode is a safer entry point if you don’t need CO2, or maybe as stepping stone to it.

          1. I’d not say safer, just easier to build and setup – Any lasing operation requires a suitable cover to be safe. As you say treat all lasers with the proper degree of respect as they are dangerous, but with that caution in mind there isn’t really any laser safety reason to pick one over the other IMO.

            That said I’d probably pick diode as a good DIY starting point because you can easily use a 3d printer kit as a core element of the build – cheap and effective CNC platform capable of the zero cutting forces and high movement speeds a laser can want. Then you just have to deal with the laser power and safety aspects – so a nice (sheet metal?) enclosure, which can easily be bolted to the frame with the right style of 3dprinter kit. Then the safety cut off so the laser has no power with the lid open.

            While I’d not call CO2 and mirrors more dangerous (unless you are a fool) its a more costly and tricky build process.

      2. I just recently purchased a CO2 cutter, and had to deal with exactly this problem.

        New lasers from US vendors are pricey, but guaranteed to be working and have tech support. New lasers from China are *much* cheaper, but can arrive broken, use shitty parts, take a bunch of time to realign and get working, and so on.

        I opted to get one used on craigslist where the original owner went the Chinese route: received a broken unit (broken tube) and had to ship it back, worked through all the issues and purchased good equipment to replace the tote of water with a real chiller and compressor for aquarium pump.

        In short, I purchased one used on craigslist that was known to be working, and it was a *little* more expensive than the chinese versions but I also got an actual chiller and compressor.

        The air assist prevents “cast off” from getting up into the laser tube and coating the optics and ruining the coatings. If you’re using a CO2 laser, only enough air assist is needed to prevent this sort of blowback. An aquarium bubbler is *probably* powerful enough to do this, but only if the ventilation system is powerful enough to suck the smoke out before it lands on the optics. If you’re directly using a laser with an uncoated lens, this may not be as much of a problem.

        I looked up the optimal pressure online, and one site said “85 psi” in no uncertain terms for a CO2 laser.

        1. I have twice bought an 80 W CO2 tube from sellers on AliExpress. Both were packed in a very sturdy cardboard box inside a wooden box, and arrived entirely without damage. One of the three laser PSU’s I have bought did get damages during shipping, but the seller sent a new one without any discussion.

  3. I wonder what effect you’d see if you filled the laser enclosure with a good portion of CO² and then pulled a partial vacuum whilst cutting. Less gas so the dust wouldn’t float around as much, no [less] fire risk due to the absence of oxygen.

  4. Great article. I have one of the far-east tinkertoy diode-laser engravers. Took a while to get everything optimized and running LaserWeb… but it’s good fun for the low price, and it’s now working pretty good.

    This spring I engraved a logo on each of 50 little wooden plant markers (batches of 5 at a time), and by the end of the run there was a sticky residue on the backing card. So laser engraving does generate all sorts of fumes and evaporate. I’m definitely going to add air to the engraver head, as well as some sort of hood and fume-exhaust system.

  5. This is genius! Thank you! Thank you! Thank you!
    I have 1m x 1m laser cutter in my garage with 40 W (15W optical output) diode-laser. It cuts 2-3mm plywood Ok, but I gave up on cutting 5mm read oak plywood. After reading this article, I wen to my garage, found there an old cheap car tire compressor and medical plastic IV pipe. I heated up the pipe with heat gun and pulled it, which thinned it, and cut it. I have got a nice nozzle. I cut off the tire connector and attached hose to the pipe using some bronze connector. There is no super-high pressure, so no extreme measures are required. Then I feed the pipe through the cable track and mounted the nozzle near the laser, and plugged the compressor to 12V power supply. That all was pretty quick. Observations:
    – I monitor laser cutting via WiFi camera. Without compressor, it looks like a rock show or a battle field due to smoke. With compressor it looks pretty clean.
    – One of a sudden, laser cuts much better! It cut through 5mm plywood like a champ!
    – The cut is much cleaner on the top side! (but the bottom side of the plywood looks like epoxy melted and leaked. I guess, I am using wrong type of plywood)
    – I was concerned that vibrating air produced by tire compressor would cause all kind of problems. But it works just fine. You can buy that airbrush compressor if you want to, but it is not necessary.

    Wow! This is must-have upgrade for a laser cutter! It makes your laser cut 1.5x better for next to nothing.

          1. If you could coat the underside with carbon, maybe it could cut from the bottom side up to top side. As the bottom gets vaporized, it adds more carbon to the new bottom. Eventually the bottom reaches the top?

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