Cracked lens with hole burnt into it

Hey all,

I just followed the cleaning instructions/tutorial and taken the lens out for the first time using the lens tool. It has a hole burnt in it and a cracked lens.

Anyone know why this might have happened, if its covered by warranty, how to prevent this from happening when i get a replacement and tips on best/fasted way to ship the part to australia?

The best way to keep this from happening is regular, frequent cleaning.


Clean the optics per instructions. Any idea how many hours you’ve had on the machine until you first cleaned it?

You might want to check the rest of them (two windows, one mirror, and of course your destroyed lens).


I doubt it would be much more then 50h. i rarely use it.

They recommend 40hrs but most people clean the optics more often than that, especially if cutting “dirty” material like draftboard or medium plywood. It only takes a couple of minutes.


There are some materials, notably copper, that are good reflectors of the laser beam in a CO2 laser. If you have ever put such a material in your machine, it’s possible that the beam reflected back up into the lens and damaged it. That’s why copper should never be used in a laser of this type.

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mirror acrylic i assume would do this too?

No, mirror acrylic doesn’t reflect the beam.

:thinking: I wonder what happens if you double a laser back on itself. The lens doesn’t necessarily care what direction the beam is coming from. You can run it backwards with the only ill effect being very out of focus. But maybe a polarization issue…

So the lens is highly transmissible to the laser wavelength - 99+% of the light goes through it. But, any dirt, debris, oils from skin, water, condensation etc. all lower the transmissibility. What doesn’t pass through (due to those things mentioned above), turns into heat, and that’s what will destroy the lens.



Copper doesn’t magically reflect a perfectly focused spot back into the optics. The beam came thru there to begin with. Even if it was polished to a perfect mirror finish it would still be defocused.

CO2 lasers are used in industry to cut copper sheet, although fiber-based systems are more common due to efficiency.

I’ve engraved large pieces on painted, cheap copper sheet. No issues.

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My name is Mercedes and I’m part of the Technical team here at Glowforge.

I’m so sorry this has happened to you! I would be happy to continue this over email so I could order you a replacement if you would like?

Just let me know what you would like to do.

Hey, Thanks for getting in touch, I have already ordered a replacement and had to get it sent to me through a 3rd party shipping company as I can’t shop to Australia directly from the glowforge website. Hoping it will arrive soon so I can keep working. Still not too sure why it got so damaged though.

Thank you for following up with us @lani.angele.

Your Glowforge unit’s laser is powerful, yet it can be stopped by a tiny amount of dirt or damage to the lens or windows

As per our manual, after every 40 hours of printing, use ZEISS lens cleaning wipes (available on Amazon and many other stores) to clean the cameras, laser lens, and windows. This will keep your printer working properly and help prevent damage.

Let us know how the replacement lens goes!

Hi Jeremy, I received my package the other day and just opened it up. The lens was not inside, only the acrylic. Is it possible that my order was shipped in 2 separate parcels?

Hi @lani.angele. Oh no, I’m sorry to hear that the printer head lens was not received yet with that recent order. I saw you have an open email ticket for this, and is currently in review with our team that handles any issues with orders. They will be following up with you next to resolve this.

Also, to avoid any potential confusion with multiple threads, I’ll close out this Community thread so we can continue working with you in that email thread. Thank you!