Question about flames

Should i be halting my print as soon as i see a small flame spark up on the material or is a small trailing flame quite normal every now and again? Im having issues with my machine and the only way i seem to be able to cut materials consistently is at a speed that also seems to encourage a flame every now and again

We’re not allowed to address safety concerns, specifically. So you’ll want to wait for an official response.

But I’ll tell you what I’ve experienced…
I believe you should never expect to see flame when using :proofgrade: materials at their respective :proofgrade: settings.
I believe you should expect to see “flame” here and there depending on your materials/settings, but you should really never see “fire.” In other words, I’d be concerned if I saw anything more than a small, brief flame.

I do hope that helps.

Yeah thats what i thought. Im seeing a flame that ingites and then follows the cut around until flips on and off. I never had this issue previously so i believe its all to do with other issues in the machine. Not PG materials but othewise materials that cut perfectly until recently

Different materials act differently. You’re obviously using non-PG materials but we are having to guess at what, and then if a flame is normal for the materials guess we made, with settings that we are also guessing at.

Check the the air assist fan under the head is still working. That normally blows out any flames. Without it you will get a flame following the cut.

The fan is driven from the head by four contacts underneath. It is worth checking they are clean and the head is seated properly.

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Also, without air assist the laser will not cut as well because it removes smoke from the cut which otherwise blocks the beam.

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@palmercr thanks! I’ll give that a check. I know that fan seems to get quite dirty but I remember the contacts being clean last time. You’re right though you’d think that would blow it out. Now I think about it the flame doesn’t look to be pushed in the direction you would think it would be by the fan.

Should the fan run when the machine is on but idle?

No it only runs while a job is running.

Ok. Its tough to see ill try run a cut near the front so i can peek over.

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Yep. You’re a genius. Not spinning.

When you say its driven by the head do you mean the print head and the four golden nubs?

Thanks so much for your help. This might be the answer to my issues!


Yep. Cleaned those all down and reseated. No luck. To support it is then! Thank you though this is likely the root cause of my issues.

High five good sir!


Well support just got in touch. Replacement unit needed. Problem solved for now. Thanks for the help!


Just curious, are they replacing the head or the whole Glowforge?

FWIW, I use a “rocket blower” to just blow debris out of that fan to keep it clean. You might also just give it a little bit of a free spin with your finger (while the unit is off). It may be lodged against a piece of debris, etc. It’s not a high-torque fan and that could very possibly fix it without having to box up and get a replacement unit.

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Whole forge although i have had alignment issues as well so it could be a mixture of issues that has made them take that route.

Yeah ive tried a spin and a clean of it with a air can and a blower. No luck sadly. Theyve taken a look remotely and decided its a replacement job.

Disaster to be without a unit for a while but…thats life i guess!


I actually find this concerning.

The air assist fan has a tachometer, and the device should alarm if the fan (or any fan, for that matter) is not running at the target RPM.

There have been a number of reports of the unit happily churning along with fans inoperable. This seems to be a safety issue.

If they can’t easily change the firmware to stop the unit if the fans are malfunctioning, they should (at the very least) be combing the steady stream of data uploaded by the devices to try and proactively spot defective fans.

I wonder how many other people are having this problem and do not know it.


I did think this exact thing myself.

When i think back I did notice a change in the tone the machine made while it was running a good few weeks ago. I just never really dwelled on it. Its likely that was the fan dying. My partner even commented that the machine “seemed quieter” last week.

It is odd that you are not warned that fan has died. Ive been sat struggling with materials that flame and inconsistent cuts for a few weeks now. I had the lens replaced as the initial one clouded (likely due to soot build up as the fan died)

Im glad its being replaced but its kinda crazy it took a chance mention from someone one a forum for me to check that. That particular fan isnt even mentioned in the cleaning instructions, unless i’m mistaken?

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The hardware certainly supports it. It seems it is not something that is being enforced in software. Out of curiosity - maybe take a peek at your log files and see if it was generating any error messages.

If they do provide an update to the firmware that alarms and halts operation, we may suddenly see a large influx of people with inoperable fans.

It would suck if they waited until after most people’s warranties expired before doing so…

The information missing from the instructions far outweighs the content they do contain.