Black spot on lenses

Started having a problem with my laser not cutting all the way through. Took things apart to clean/inspect and found a bit of debris on the inside of the lenses. Was a bit surprised because I just cleaned everything really well several days earlier. Proceeded to wipe it off / clean it back up and most of it came off. However, there is a tiny black spot that will not come off. I’m thinking it’s a burnt or damaged spot on the lenses now.

I ordered a new one from gf last night. Anyone have any idea how long it typically takes to receive parts?

Also, now that most of the debris was cleaned off is it ok to use it with this tiny spot? Anyone know if it will cut all the way through wood like that? More importantly, will it damage my machine if I use it with the tiny lenses spot? Has anyone had this experience?

Guessing this happened from the cleaning several days earlier. I used caned air to blow off the super tiny fan directly behind the lenses. Thought I got all of the dust out but there must have been a bit left that blew around and landed on the inside, bowl part of the lenses when I started it all back up. Definitely frustrated with myself. Is there a better way to clean that little bitty fan?

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Yikes! This is the stuff that’s scaring the bejeebers out of me. I hope I can take things apart without breaking them, and understand what I’m doing, as I do it.

I’m really sorry for your frustration, and unexpected expense, but I admire your skill and ability to troubleshoot the problem. Thanks for posting. I’m trying to learn from everyone else as much as I can.

Welcome to the forum.
You can try soaking the lens in some alcohol and then rubbing gently to see if you can get the black spot off. You can also continue to use the Glowforge while waiting for your replacement lens. In my experience, replacement parts are shipped pretty quickly, and I received a tracking number soon after the order was processed.


Ok thank you! Glad to hear it’s a quick turnaround time. I have an event on Monday and wasn’t sure if I needed to postpone.

Just to be clear, you’re saying I can submerge the lenses in alcohol for a couple of minutes? I have only ever used the wipes on the lenses. If so I will definitely try it.

Thank you…
No need to be scared although I understand. I was no nervous the first few times my hand were shaking. You will see in no time it’s really not bad. I’ve had my machine for about a year and a half now and this is the first problem I’ve had. Just one of those things I guess.

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Soak the lens for an hour or so, then see if you can rub off the black spot. Cracks and scratches can’t be fixed, but spots usually come off.


Ok I give it a shot, thanks for the tip!

There is a good outline on maintenance here.

A single use can have buildup on the various windows and lenses. It is also possible that the laser can burn that build-up damaging the lens. Usually, before that the quality of the cut will degrade suggesting to the observant that the windows and lenses be checked. Just under the left side is a window where the laser beam jumps to the head. A very slight film on that lens can blur the beam enough that the machine will cut much better on the left where the distance jump is slight than on the right where the blur is most spread out. That is a big clue to check that window.


Quick update…
Soaked the lenses but the tiny black spot did not come off. On the plus side I have already gotten notification from Glowforge that they shipped out my part. It should be here Friday!


You still had to wipe it with a Zeiss lens wipe after soaking, might even take a little rubbing - did you do that?

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Yes, of course… the spot is definitely on/in the lenses. Not coming off unfortunately.

I think that is what happened. There is a lot of energy going through those windows, and if the build-up gets enough of it, that build-up will burn itself in.

I wonder if there is a formula that could do that deliberately on glass or tile?

Yep, I think that is exactly what happened. Looking back there were some very subtle clues something was off but since I haven’t had any problems with my machine (other than just needing standard cleaning) I didn’t realize it. When it REALLY started not cutting through is when I started trying to figure out what the problem was. By that point the damage was done. Lesson learned! On the bright side, I ordered my new lens on Wednesday and it was here by Friday! I plan on running her for a little bit today so I will get a chance to test everything out.

Do you know of a better way to clean the tiny little fan that is directly behind the lens? Blowing it with canned air didn’t seem to be the greatest option. Maybe I just need to do a better job making sure all the loose dust is gone.

I have had little problems with that one or for that matter the mirror and lens inside the head. The most common Issue I see is the two windows from the laser to the head as smoke will waft past them on the best of conditions and if it is in the way while the beam is active it will leave a smudge that needs wiping off.

I run a Vivo external fan assisting the standard exhaust fan and there is noticeably less smoke hanging around that when either are running alone. If the smoke leaves quickly enough it has less chance of getting up in the head and messing those areas.

Except for cleaning lenses I use a lot of hand sanitizer as it works very well on crud and removes most adhesives (even the MDF glue, which is why not to use it there) and it drys out fairly quickly.

On the gantry fan I was able to do an amazing job by putting a vacuum hose on the outflow and just pouring the sanitizer through the fan, leaving the vacuum a half hour or more to completely dry it out before putting everything back together.

Now with no magnets stopping that fan and the external and exhaust working together I do not have problems like that.

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