Acrylic is flaming

I have been cutting acrylic with no problems, no flames, nothing. Then suddenly I put my second piece of acrylic in and flames are coming out and the paper is really scorching. . I have the settings at 160 speed and full power. I cleaned my air assist and the other fan, cleaned lenses and emptied crumb tray. Still cause flames…any ideas?


Is it Proofgrade acrylic? Cast or extruded? 3rd party formulations can vary from batch to batch. If you haven’t done so email, as they don’t monitor the forum.


It’s happening with proofgrade and other. I have used the acrylic many other times from CMB Acrylic and it didn’t flare. It’s so weird.


that is odd. not sure what you mean by “ever since the software update.” but i haven’t had any issues with acrylic, i don’t think it’s a software thing.

i’m wondering if there’s something wrong with your air assist. if it’s not blowing strong enough, that could encourage flames.


The last firmware update was months ago, and didn’t change anything about how the machine works, it just preloaded code for a future app update. Acrylic tends to flare up for two reasons:

  1. The air assist fan isn’t blowing hard enough to blow acrylic vapor away before it ignites, or to snuff out the flames when they start. The air assist fan needs a deeper cleaning on occasion than simply blowing out like the manual suggests. You need to unscrew it from the carriage plate to clean off the back side of the fan, otherwise buildup will restrict airflow.

  2. The acrylic from CMB and most other third party stores comes with a brown paper masking that has wax in the temporary adhesive. That wax likes to ignite into a candle-like flame when vaporized. That’s generally fine as long as your air assist fan is very clean, but you can always remove the masking and use some dawn dish soap or your own masking instead.


I’m sorry I thought maybe they update to dashboard software might have done something but I realize that’s not it. It’s not doing it with the wood just acrylic. Should I take the air assist fan out and check it again ?


Updating the dashboard interface is not something that changes the performance of the machine. As stated previously, there have not been any firmware changes recently. Yes, you should remove the air assist fan and give it another clean.


what @dklgood said, clean that air assist. no firmware updates in a while that i’ve seen, either.


Ok, thank you for your help


If you remove the fan from the carriage plate be sure to install it blowing the right way. Stranger things have happened.


Imagine a software update that made the slightest difference in downgrading the way the Glowforge cut a common material. There would be thousands of upset folks within the first day! For this reason, they are very careful about any changes they make.

If you are having an issue and there is no tsunami of complaints, then it is not about any software update.


FWIW, acrylic is a lot more “flamey” than wood to begin with. It would definitely be your first sign that something is amiss.

Hope you figured it out!


Ok, I get it. My mistake lol I thought there was a update. Thanks


Reading through the comments, I though it would be helpful to point out that there are two fans on the Glowforge – the big one in the back the air exhaust tube attaches to, and the tiny one that blows directly at the cutting point. You can’t see it unless you take the black box laser head off.

  • Make sure the small fan is all cleaned out
  • Make sure that the “hood scoop” that directs where that little fan blows to, and is attached under the black box laser head, and stays on the metal plate when you take off the box.

I’ve found that that “hood scoop” can get really gross and backed up, and jamming a 1"wide paint brush in there a couple of times to knock the ash crust out really helps. Be aware that when you turn the GF back on, it will blow all the knocked off crusty ash out, and all over your material if it is already in place!


There are 4 fans in the Glowforge, although only the two you mention would have any impact on the OP’s issue.

This discussion belongs in community support, not beyond the manual.


What happens if a software issue somewhere…

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