Flaming while cutting

I am getting a horrible flame whenever I cut and it is ruining my pieces.

I have cleaned the exhaust fan.
I have cleaned the fan on the print head.
I have cleaned the fan below the carriage plate.

The flame blows forwards towards the front of the machine, no matter which way the laser head is travelling.

Flames blowing forward suggest your fans are doing their job.
The point of masking is to avoid those flames from marring the project. Are you using masking?

Another issue is you may be running a tad hot or too slow. No mention of if using Proofgrade materials or not. If not, some experimentation may reduce the flames.


all of my mats are masked. I use the suggested cut settings for thick clear acrylic for 1/4" and medium for 1/8" acrylic. I just tested my 1/8" and it cuts without flaming. I also tested medium baltic birch and also no flaming. So for some reason its only flaming on 1/4" acrylic.
I use the machine settings so 115 speed, full power

oh and as for temp. my ambient temp is 63 degrees and it happens as soon as I turn the machine on and cut something.

You still never said if it was Glowforge Proofgrade acrylic.

If not, you will need to test to find settings that work for what you have, possibly making two passes to reduce the concentrated heat from a single pass. Support won’t be able to help with non-Proofgrade materials.

Acrylic is to the best of my recollection the material most often responsible for fires.

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My suggestion is to increase the speed and probably do two passes, if you aren’t using Proofgrade acrylic.

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I have used proof grade settings for Acrylic since 2019, on proof grade and non PG mats.

Something change in the last 24 hrs that I don’t know about?

I am not aware of any changes to Proofgrade settings. I have the pro and my setting for thick acrylic is 125.

I just ran the good measurements test on pg 1/8" acrylic, pg medium draftboard and pg 1/4" acrylic, because I know tech will ask me to anyway and everything ran smooth except pg 1/4" acrylic.
I got the same flame up on 1/4" acrylic as I did last night. Settings were the same, PG cut thick acrylic
I’m really puzzled by this.

If it’s doing it with Proofgrade then I don’t know what to say.

I just cut a 0.42" square from a scrap of Proofgrade clear acrylic on my 4-yr-old machine and there was no flame at all. Came out just fine, except for one edge didn’t cut all the way thru but I haven’t cleaned my optics in a few months - so I sanded that one side (furthest edge here…) That’s the “C” key on my MacBook keyboard for scale.

I test before I commit to any job, so based on this I would, for example, slow it down a little if I was using this material. Default was 125/full, so I’d probably go 115/full.

The key here is, however, there was no flame. I even took a video and there’s no point sharing it. Nothing to see.

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(This is “thick” material, which measured 0.2215")

Is the 1/4" acrylic Proofgrade?

What I have noticed is that some of the manufacturers’ paper masking tends to flame up more than others. What your video shows is what I have seen in thick acrylic (6mm) with paper masking from several vendors. The brown paper seems to flame up like that more than the white paper on Proofgrade.
This is one reason I watch every cut and anything with acrylic like a hawk.

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Make sure to use set focus … and that it hits an area without a big hole in the material.

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I would try removing the masking on a small area and do a tiny test cut with a shape. Make sure the settings are right for the thickness of the material. I have used quote a bit of non-PG acrylic and always use the PG settings. I use the medium acrylic settings for 1/8" acrylic and thick PG settings for 1/4" acrylic.


That is my next test when I try it again. I’m think the masking might be the issue since it’s only happening with one thickness and started to happen out of the blue

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I didnt think about that, it typically sets focus where I have a SVG placed, but I will double check that it’s hitting the material when it focuses.

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I bought a bunch of acrylic that wasn’t Proofgrade. Came masked. The mask material flames significantly more than the masking on Proofgrade.


Ok just did a bunch of tests… please read before responding, that way you dont assume what the issue is. I’m looking for troubleshooting based on the facts of what is happening.

  1. The flame up is only happening on 1/4" acrylic, PG and non PG.
  2. All acrylic is masked.
  3. I set up some basic shapes to cut out. I used Cut speed 115(PG setting for GF Basic), I also used 105 speed and 100 speed. They all cut without flaming.
  4. Because the basic shapes cut at all tests speeds without flaming, I tested an engraved and cut piece again, once again, it flamed.
  5. I ran a test where I cut the shape before the engrave and no flames.

Could it be the remaining dust that isnt getting blown off the acrylic during etching, is causing the flame ups ?

I read it carefully and went back to your earlier posts.

You initially said you were getting flaming when cutting. Now you are not. What changed? The fact you are now engraving first? Or were you engraving all the time, just failed to mention it?

Yes, engraving deposits sticky debris forwards, that might make a difference. What size are your pieces? I might try to replicate.

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