Watching acrylic (not quite) burn

I was cutting a pretty intricate pattern in clear acrylic, and you can see quite clearly the spark when the laser passes over the crumb tray and the sheer amount of heat/smoke that’s generated. If you’re ever wondering how acrylic catches fire…this should give you a good idea!

This did not catch fire - I was watching REALLY carefully and paused a couple times!

Plus I find seeing the lines appear in the acrylic to be fascinating :stuck_out_tongue:


Is your air assist fan running? Whenever I cut, the smoke makes a beeline for the front of my Glowforge (and then out the left rear) but that smoke seems to just be moseying wherever it feels like going…

Not sure, but that may be the smoke under the acrylic.

Easy to see where the possibility of ignition is pronounced with the flashback. A good reason to have the power dialed in, no more energy going through than necessary.


This exactly, that smoke is under the acrylic - if I had masking on you wouldn’t see it at all - or the flashes. So many people have acrylic fires and they invariably say “everything looked fine and then woosh!” Because this is clear and unmasked you can see that everything is not fine, it’s building up under there.

That my exterior fan is pulling the smoke away I think is probably helping - if that were weaker I imagine you’d see it building up even more.


D’oh! I hadn’t thought of that because mine’s usually masked…


cool video. Also, you machine sounds… labored on the downside of those cuts.

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Oh interesting, he’s always sung to me like that - of course if you’re more than a few inches away you can’t really hear it - it may seem more so because the microphone is so close?

I does the same thing when you cut wood. It’s just harder to see since wood isn’t transparent. Those flashes create flashback and show up as burnt spots on the backside of the material. That’s why we put masking on the backside of a lot of materials so it doesn’t show up. Seeing the flashes is a indicator that you are cutting through the material.

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Possible. Stepper motor music is a normal thing for people that deal with CNC/3D Printer/Laser/etc, and maybe it’s just because it was so close, but it sounded odd to my ear.

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Yup - but people don’t tend to be surprised when wood burns, just acrylic…I have to presume it’s because it seems to be a hard object, but it burns just the same!

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