Damage to window of printer head

What is happening here? The window on the side of my printer head is lighting up then smoking and it now has damage to it.

Turn the machine off and inspect all of the optics - especially the lens and mirror. Send photos to Glowforge support. Order a new window.

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What is happening is that there was residue on the window. Infrared is just light until it touches something - then it’s heat. If the energy isn’t transmitted it’s deposited. Enough film on the window gives a surface to deposit the energy on and it will burn it. The laser is burning that window, not your work.
That’s why the first rule of lasers is clean optics! That includes the lens and mirror. If you can see any film on any of the optics they need to be cleaned.


I am amazed it was cutting up to now to get that much crud on it.


In no way to argue, but if you can see a film, it’s too late.

By the time it’s visible to the naked eye, the laser has been cooking it and destroying the optical coating, which affects transmission and therefore the cuts. At that point, even what appears to be clean can significantly impact how much laser power passes thru if the coating has been damaged. I could refer you to the science but it’s easy enough to find, “anti-reflective” coatings significantly improve transmission.

Cleaning the optics takes a minute, literally. It needs to be done regularly.


I had a bit of “not cutting through” and discovered this as the cause just a few cuts after previous cleaning. It can build up like that in just one cut if a wisp of smoke happens to be near as it is cutting. However, not cutting through should alert you to the need long before burning out that window. Fortunately this wiped off with no damage or observable losses.


A cheap fix
Printer Head Window (Black) – Glowforge Shop


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