I bought some plywood specifically for laser cutters, and have experienced the same disappointment - it takes multiple passes to cut through it, much more so than solid timber twice as thick. The other problem with it is even if you cut through it, it is more difficult to clean up - it soaks up the soot and the top veneer is so thin that even a light sanding will cut through to the glue layer.
Solid wood and mdf for me, and I only resort to using plywood if I have nothing else and if I’m going to paint it.
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I would definitely go CO2 if I was doing this for a business. But my attention span on hobbies is short. I built my machine which was the most fun for me. Tried to get my wife interested in doing projects with it so I can build something else.
I can’t recognize that, up to 4mm Aeroplan interior glue, I have absolutely no problems apart from 50% more in the price 
What thickness are you working with?, with your 100 Watt you should also be able to easily burn through standard 5-6mm plywood.
The plywood I have in stock is 1.5, 3 and 6mm. And I also have a 20w diode laser as well as the CO2 (not updated my profile yet). But with either laser, it takes more power and more passes to cut through plywood - cutting a small box out of 1.5mm the other day on the diode laser I was running it at 25mm/sec at 80% and it was barely making it through after 3 passes (and yes, the lens is clean, and air assist on). I can cut 4mm oak, holly, chestnut and cherry with the same settings. I have the same comparative experience on the CO2, though obviously the cut settings are different.
It is mainly the glue that causes problems, especially if it is exterior glue.
On my diode I run at 200 mm/min to cut 4.5mm underlayment in one pass (when it doesnt hit glue ornfiller) which is…way below that in seconds 
approx. factor 10 (60Watt CO2)
Slow your speed to 320 or so with 90% power. 3 passes max with a 5w sculpfun s6 pro…
But some great information on youtube lahobbyguy…Rich is awesome to learn from…
Hello, Sadas. I have the LM3 10 watt.
My cut settings for 3mm Baltic birch ply are 1 pass @ 350mm/min 100% power and a second pass 500 and 90%. 90% of the time the second pass isn’t needed, but I do a clean up pass especially in intricate patterns.
Yes, ply density can vary due to grain and glue. This setting cuts virtually any plywood I’ve used.
Are you using an air assist pump? If not you need to get one. Air assist keeps the lens clean and stops the burning. The air assist built in is not enough. I bought the Ortur pump but you can get cheaper ones.
You can also do a quick material cut test.
One thing I noticed about your example is it appears you can see the honeycomb bed marks on the backside of the material. I SUSPEND all of my material off of the bed in order to have clean cuts on the bottom side, otherwise I get charring wherever the bed is touching the material… Not sure if that is what is happening on the ‘not cut’ sections.
When I cut wood I have learned to tape (6" wide masking tape) the cut path to keep the soot off of the wood and limit the charring surface area. I also use taping when I’m engraving on softer wood for the same reason. If you do this you can go 100% power and slow it down. Also, if you do use masking tape be sure to scrape it with something like a credit card to get all the bubbles out and make sure it is adhered to the wood. Hope this helps a little. Good luck!
Clean laser lenses
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PieceMaker:
I have tried this method but found that when the tape is peeled off, it will bring with it a small amount of the top veneer making it “furry” and rough. I use blue masking tape which is supposed to be gentle but not enough apparently. This might not be an issue if you use hardwood but with cheap plywood, which usually have a thin veneer, it makes it hard to get the surface nice afterwards since you can’t sand enough without going through the veneer.
Do you use a special tape or do I just need to find a better supplier(both plywood and tape)?
Also, when engraving with tape, do you have issues with uneven engraving? I assume that my tape has a bit of structure which makes it hard to dial in the correct settings without burning through the top veneer. On solid wood or thick veneered you don’t have the issue with needing a narrow engraving depth.
You might try using a sanding sealer or similar (stain first, if desired), and then any soot will wipe away easily without the hassle of tape. I also find it easier to finish the panels before engraving anyway. Depending on what you’re after, you may still want to finish again (in the engraved areas), so plan accordingly.
Do you mean that the sanding sealer should be sanded away after cutting?
I otherwise you would see the sealer in the finished product I assume.
The Minwax sanding sealer I use dries clear. It reminds of thin acrylic clear. Probably is, actually, with some other magic added in. Supposedly zinc stearate to aid sanding without clogging the paper. It will most definitely seal the wood pores, so if you intend to stain or oil the wood, it must be done prior to sealing. My thinking with this suggestion is that it creates a thin “washable” surface that would resist smoke staining and allow wiping it clean with a damp cloth. I like the sealer for things I intend to paint or clear, but I don’t use it on cutting boards, which is where the vast majority of my smoky engraving experience lies.
I’m still learning best practices for my cutting boards. I haven’t yet found a “perfect” sealer or process for those. Most recommend masking, then engraving. I don’t much like that approach myself. Best I’ve done so far is to pre-oil, engrave, then use masking film to lift off any soot…or literally wash the board with alcohol if the tape doesn’t get it. Trials continue.
I liberally apply mineral oil to my cutting boards (over 100 and counting) before engraving, and then use Isopropyl Alcohol on a cotton rag to wipe of the “schmutz” that remains. Done quickly it doesn’t seem to hurt the finish, and I do put one more thin coat of oil on when I’m finished. I am cheating a little, in that I’m able to use Russ Sadler’s compound lens system on my CO2 laser. It creates a lot less crud.
I had no idea that there existed a clear sanding sealer. I couldn’t find any locally so I might need to import some to test it out.
I was thinking of trying with a coat of polyurethane or something but hadn’t gotten around to it. I haven’t done any research so I’m worried that the coat might catch fire. Probably not an issue.
Thanks for the tip on the clear sanding sealer!
Rich (LA Hobby Guy) says he uses sanding sealer on almost every wood piece he put thru his lasers, so fire doesn’t seem to be a concern. I have seen no evidence of any myself, but my volume of experience is a tiny fraction of Rich’s.
I have personally run into the same problem.
I “think” it is flashback.
i put a 2mm magnet in multiple places between the material and the honeycomb to permit the smoke etc to vent out easier