Cleaning Galvo Mirrors


Hi all,
Been trying to see what the best way for me to clean the galvo mirrors is, I know of the air bulb for loose dust, but I’ve been having a lot of failed prints recently, and I re-leveled, checked everything then finally took a close close look at my mirrors and noticed

There is a nice little dot on the one mirror which seems like it could be causing some of the headaches I’ve seen. I have a second Moai running the same file now, I just got a second because my first one was going down mid heavy production runs a lot recently.

Whats the best cleaning method for those little mirrors, and how do I access the other one turned away from camera?

How to safely clean the galvo mirrors
Problem leveling since changing vats

unscrew the laser/galvo piece from the Moai and clean it, use an air bulb or just a little blow will do


I tried an airbulb already and whatever is on that mirror doesn’t come off with a puff from the air bulb.


Here is another picture of the area cleaned with an air bulb. This mark seems to be more of a burn or something on the mirror than a dust spec.


Here is a pic from my machine with that dot you can see easily that it is effecting anything being printed in the middle and I just did a new vat that is leveled properly. Also there is a pic from my new, second Moai unit printing the exact same file and it is totally fine.


i assume you are talking this spot right in the middle?




yea, that spot is no where on my other Moai’s galvo unit, I’m not sure if it’s debris or something else?


We don’t tell the user to do this most the time because if not careful they may do more harm than good. But since you got a spot right in the middle that will affect light, you may be as well wipe it with alcohol. Use cotton swap with alcohol (preferably ethanol) and try to clean it off and then use an air blower to blow away any residuals from the swap.


Alternatively, use a photographic lens paper wetted with undenatured ethanol (<80% is best) and LIGHTLY drag it across the face of the mirror letting the weight of the paper and the surface drag from the ethanol provide the mechanical force. Dry with air from a photographic squeeze bulb (CMOS duster). Be careful to use undenatured ethanol, as denaturants tend to be oils that will destroy first-surface silvering.

Using Ethanol of greater than 80% runs the risk of damaging the glue used to attach the mirror to the galvo.

If you look online, there is a “magic elixir” developed by Karl Zeiss for cleaning immersion lens oil off fragile coated-UV and confocal microscope optics. It is a mixture of isopropanol, ether, and ddH2O. It is likely published on a microscope forum/blog. It should be good for cleaning first surface glass nondestructively.


I just took apart my machine… found the same thing on both mirrors, but not a dot, more like a line. How did the cleaning go?



I bought a DSLR cleaning kit and some ped pad wipes then put a small bit of ipa on it. Slowly and gently wiped in one direction and poof gone like magic. I’m up and running perfectly.


I always assumed you could even touch the galvos because if they even moved slightly it would throw the whole thing off calibration. It is OK to wipe them slightly, and what happens if the Galvos rotate a few degrees to one side or th other? How do you reset them so they make the laser point up again? And how much pressure can you put on the things without damaging them… Iam afraid to do anything more than brush them with a cloth with no direct pressure on it. Is a slight press of a Q-tip too much pressure?


I mean they are goijg to rotate if you even touch them at all. I ran the circle check after I cleaned it. I was extremely gently. I actually found a PDF from the FormLabs team on the exact same issue they had with theirs. If you have doubts I’d contact @peopolysupport immediately.


So, even after moving it a few degrees during the cleaning, it maintained its calibration on the circle test? That’s good news. I was not looking forward to having to try to manually get things back in calibration. It must have some set point that can read the current position and move it to where it is supposed to be.


it will not affect your calibration if you rotate it slightly.


Well, I tried cleaning it with isopropyl alcohol and pec pads, wiping repeatedly from bottom to top with very low pressure. Without putting significant force on the mirror, which I think would be a big mistake, it seems to have made minimal difference to the area… or rather the area is smaller, but it is more intense and the edge is sharper.

After cleaning

Before cleaning:

Any thoughts on something else to try? I have some PEC12 solution for cleaning films and things, which is a mixture of ethanol and n-butyl acetate. Anyone know what that “burn” may be… is it damage to the silver, or some aerosolized resin that got stuck there? I have some acetone, as well… but I think the mirror is glued on and I don’t want to dissolve the glue.



Did you use an aerosol spray originally?


Nope. Only pec pads and isopropanol. I want to be super careful with this part as I think I recall it being about 700 dollars to replace it (but that could just be my failing memory). I had read that aerosol sprays leave deposits on the mirror. I thought maybe I scratched it, but I was going bottom to top only, so against the grain of this… I would expect any scratch to go the other way.


I am guessing it is a laser burn. The question is: why? If the material isn’t coming off easily, then it may be permanent. The last thing you want to do is scrub the mirror surface.

Try a print. See if there is a noticeable loss of resolution. If there is, then you may have to consider replacement or re-aiming the laser.


OK… adjusted both mirrors with no issues. Was much easier to do than I expected. I dropped the Y mirror down about 1 mm, readjusted the position slightly and it seems to work just fine. I still need to bend the metal tab on the build plate a bit so it doesn’t rub, and then can try it out. Unfortunately, I work every day for the next 4 so it won’t likely be until Tuesday.