Acrylic on Fire?

I have had my Glowforge for several years now, and cut wood and acrylic mostly. Up until the last couple of months I have NEVER had a problem with the masking paper catching on fire, but now it is happening literally any time I cut wood or acrylic (engraving is ok)–even on the materials I have had for a long time and were previously not problematic.

My lens is clean, the crumb tray is clean, the mirrors are clean. This was never a problem, and now is ALWAYS a problem. Did something change with the software? Anyone else having similar problems?

I have a Plus (circa Spring 2019), converted to an additional air assist and a 6" duct in early 2020. The fires did not start until September of this year, and very suddenly. I’m stumped.

I don’t think your problem is a change of software, although there was a glitch with saved settings. Are you using Proofgrade settings? Are you using Proofgrade material? Is your air assist fan clean? You say have an inline fan, but what about the air assist fan and printhead fan?


Likely your air assist fan is dirty. It’s what blows the flames forward and out - and what blows the smoke forward.


Here is an image of my air-assist fan after a year of MDF core material.

Have a look at yours.


I would check all the fans. The fan at the back, even with an inline fan, will get caked, esp. if you are like me and cut a lot of acrylic. I have to clean my back fan once a month. The fan underneath the carriage plate I have to blow out every other project(roughly 6-7 hours of cut time) I would check this fan first. It may be caked and not getting enough air blown to put out the flame, it could also be that the fan has stopped working.


Some of it had been proofgrade, some not. I haven’t checked the fans, that must be the case!

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I haven’t tried that yet, thank you for the link!

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This looks familiar. :wink: Guess it’s time to clean it out!

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Depending on the build up, you probably don’t need to extricate the fan, just pull the gantry forward and blow the fan clean with air from above and behind. A cloud will come off of it, so a vacuum positioned to catch it would be advised.

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I’m so sorry to hear about the trouble! It looks like there is already some great advice here from our wonderful community members. Cleaning the air assist fan is what I would recommend as the next step here too.

From the Glowforge manual page 5:

A small, candle-like flame where the laser beam strikes the material is normal. This flame should move with the laser and should not remain lit when the laser has moved past.

If the behavior you’re seeing while printing is different, the next step is cleaning the air assist fan.

You can follow the instructions here to remove the carriage plate and clean the air assist fan.

If the issue still occurs after cleaning, please post the following photos:

The carriage plate and air assist fan this like this example below:

The bottom of the printer head with the lens installed:

Please let me know how it goes after cleaning or if you have any questions!

Thanks so much for the help. I have done all that was advised, and there is still a large flame that continues along. I’ll post a video below:

It often will catch a corner of masking that continues to burn and ruins the piece. It has become so frustrating! :crazy_face:

That video is too blown out/overexposed to see what’s going on. Here, I fixed it for you:

The problem appears to me to be that your air assist fan still isn’t working correctly. You shouldn’t see any flaming like that, it should all be getting blown in a tight stream towards the front of the machine. I’d say your fan isn’t working at all, except I thought the GF sensed the tachometer signal from the fan and would refuse to lase if the fan wasn’t running fast enough…

Thanks! That’s what I’ve been wondering too. I don’t know how to tell if the fan is or isn’t working when it’s running, except maybe the flame. :rofl:

It was so sudden with the burning, maybe my fan gave out?

I’d say “yes, your fan has shit the bed” except like I said, the GF checks to make sure the fan is running fast enough and it’ll refuse to cut if it isn’t.

FYI - this is what it should look like when your fan is working correctly - there isn’t enough time for any really flame to develop. Rarely you’ll get little flashes, but they go out immediately if the fan is working correctly (Obvi there is slightly more with masking, but it’s slightly)

Hi @carly, thank you for posting the video and a shout out to @randy.cohen for the video adjusting wizardry. I definitely want to keep investigating this for you. Taking a look at air assist fan and printer head is the next step here. Once I can see the current condition of everything, I can advise if anything else needs to be cleaned or if it is time to recommend a replacement part.

Here are the photos that would be helpful for me, I look forward to seeing what you post so I can get this resolved for you.

The carriage plate and air assist fan this like this example below:

The bottom of the printer head with the lens installed:

A photo of the back of the printer head:

Let me know if you have any questions about the photos, I’m always happy to help. ​

Thanks so much! I was able to find a piece of debris lodged in the air assist fan I didn’t see previously. Now that it’s removed, it works great!


Hi @carly! Oh that’s such great news, I appreciate you updating me.

Since the issue has resolved, I’m going to close this post. If you need anything else in the future, please start a new post or email us at Happy printing!