IT'S ALIVE! Mirrors Cleaned, Printing Fine!


After one good-night sleep, I woke up wondering why such a well-built machine could be brought down to it’s knees by a simple speck of dust… If you read my sad and dramatic post, Print Fail… With Kick-Ass Mirrors! you will see what I went through - and what a lot of us are going through, when it comes to having a print “explode” on you and not knowing why it happened, what you did and what you can do to solve it!..

So I will try to explain it with pictures…

The Problem

When my first “explosion” occurred I had no idea what I did wrong. Up to that moment I did everything correctly, followed Thomas Roussel’s workflow to the letter, washed my hands and ate my veggies. So I contacted Support - by opening a ticket, and got two fantastic PDFs from Hubbard on how to clean the big mirror and the Galvanometers’ Mirrors…

So I tried to print again and BOOM! Another “explosions”… At this point, and after begin up for three days, I decided that the best thing was to go home and to get some sleep…

The next day ((12 hours ago,) I came to my studio and decided to investigate what else could I have missed. Did I clean the mirrors thouroughly enough? Could there bee some other “culprits”? I checked the big mirror and it looked fine. Then I decided to empty the Resin Tank via a Paint Strainer with 190-Mesh:

After all the resin was transferred, this is what I saw:

So I had a new Resin Tank laying around:

I was going to set aside as the clear resin tank. I double-checked it for flaws and found a small scratch:

This was not a problem, since I was able to fix it using Novus 1 Plastic cleaner. I then decided just to double-check the mirrors from my first clean up attempt:

It looked great, just some small specs of dust here and there.

On Cleaning Mirrors (Three Days Ago…)

If you have “exploding” prints, one of the first things you should check are the mirrors, specially the BIG mirror. Check the Help Pages on how check the mirror for dust and Resin, because when you first look at the big mirror… it looks fine, right? Then place a light (as they demonstrate on the Help Pages,) and your jaw will drop!

Here’s what mine looked like the first time:

That, my friends, is residue from the DustGun air-can! Yes, the “Dust remover” left all that residue, and that’s what messed-up my mirror! This is a sample between a clean area and one covered with residue from the air-can:

(left-side clean Vs. right-side residue)

So I popped open my cleaning kit:

I used the PEC-PAC lint-free pads soaked in 90% - 99% proof isopropyl Alcohol for the bulk of the clean up as for the instructions from the instruction-PDFs Hubbard sent me:

I also bought these sensor cleaning swabs from the same company, since the instructions requires you to build “lollipops” using sticks and folded PEC-PADS, and because these sensor swabs are made from the same material the PEC-PADS…I thought “when in Rome?!”…

The rest of the tools are from my i**Fixit repair kit**, one of the best things anyone should have!

And you get other great tools to repair anything mechanical, electrical and gun-wounds!

It has a the 2.5 hex bit you will need to take the six screws to open the back plate in order to get to the Galvanometer mirrors:

I started by removing the screws. The side ones, which have a round-top:

The top ones, which have a flat-top and are short:

BEWARE!: the instructions failed to mention that the are two screws in the bottom!:

Keep the screws in the iFixit tool-cover:

Next, the instructions show you - in pictures, where the two Galvanometers and the laser’s connectors are:

You label the connectors:

Then you proceed to unscrew the Galvanometer assembly and to clean the mirrors - ONLY if needed:

(Looking good…)

So this was my first attempt at cleaning the mirrors… I decided to try to print “something” I knew had succeeded prior to all these fails. I picked this guy:

And this is what I got:

Yes, you guessed it; BOOM!… Not only that: when I checked the NEW Resin Tray for debris… I noticed that it already has new ghosting! WTF? Ho strong is that laser?

This Morning: A New Start

With some sleep under my belt and with a new “damaged” Resin Tank, I decided to double-check the mirrors. I went back, checked the big mirror… all was clear “in the Western Front…” Then < I decided to check the Galvanometer mirrors… and to my AMAZEMENT!.. this is what I discovered using a 10X magnifying lens:

And here’s another close-up:

I used one of the Sensor Swabs to clean the speck. Make sure you ONLY use 90% - 99% proof isopropyl Alcohol with these Sensor Swabs and the PEC*PAD wipes! The Sensor Swabs are sold in three sizes: #1, #2 & #3. #1 has a width of 17mm, then #2, at 20mm and #3 at 24mm - great for the bigger mirror of the Galvanometer assembly and the BIG mirror. So, because the #1 was still too big to clean the tinny mirrors of the Y and the X Galvanometer, I had to make a “hand-made” swab! Before closing the printer, I gave the BIG mirror another clean up:

As for the dust particles, which are ALWAYS going to fall back, DON’T USE COMPRESSED AIR! Again, it leaves a residue. Use a hand tool like this amazing Giotto Air Blaster:

And presto! The culprit specs and their friends where out… for now!

Printing “Around” The Ghost…

Because I noticed the weird “ghost image” burnt in my new Resin Tank, I decided to place some “test” objects around the damaged area, to see if cleaning the Galvanometers did the trick or not. I place multiple copies of a model that I got from the internet (can’t tell you from who, burt if anyone knows who built this, let me credit the individual,0 around the center of the Resin Tank:

I went on with the print, and after two hours… BEHOLD THE MAGNIFICENCE OF IT ALL!:

So far, so good. I removed them from the Build Platform and placed them on the stringer:

And I proceeded to the cleaning process. First, a two-minute “shaking” in the first bath:

Followed by a ten-minute rest:

During that time, I carefully clean the Build Platform, with paper towels and without any alcohol what so ever! Only use alcohol if you know you can leave the Build Platform out to dry for a while, like overnight. The last thing you need is contamination of the Resin Tank with alcohol!:

Then I switch the prints to the second bath, which has cleaner isopropyl alcohol:

And gave it the second two-minute “shake” bath:

Followed by the second ten-minute rest and an o.k. song!:

At this time I could clearly see that the print was a success! So, out of the frying pan… and clean the excess Isopropyl Alcohol wit a little-bit of compressed air:

The last part of my personal pipeline is to “bake” the prints for two hours in my Tabletop Ultraviolet Sterilizing cabinet:

And last - but not least, after the two-hour bake-off, I place the prints back for a two/ten Isopropyl Alcohol finishing bath, as I learned from Robert Vignone’s AMAZING website, Mold3D TV. And here’s what the test-prints look like:

(Printed with Grey Resin at 0.1mm Resolution. Duration: 1 h 28 min, and four cups of coffee)

I think this adventure went well after all! I hope someone will learn and use something from this long and interesting experience.

Good luck with your projects!

Frank J. Guthrie

P.s.: As I just finished writing this post, it started raining in Los Angeles! How weird is this: two miracles in one day!


I had to deal with a lot of the red swirls too… glad you are seeing results again. Me too. I didn’t go check the galvo stuff sicne that seemed like a huge process.

I wonder if Form Labs can make a clear protective glass so the mirror can’t get any dust/crap on. That might mess with the optics but there has to be a way. There are just too many issues with dirty mirrors that lead to lots of wasted time and supplies.

I agree Bill, at least for the Galvanometer assembly: the back should be covered by a mesh of some sort. If its open for heat, add a mesh, with a screen small enough to prevent the dust from flying on to the mirrors…

As for the front part of the Galvanometer assembly, perhaps a small piece of glass would create refraction of the laser beam (why do I think of ***Austin power***s when I say “Laser Beams?!”…)

Besides, the machine has holes all over the place, so maybe fans creating a negative pressure inside the box would do the trick?

I’m about to finish another prints. I’ll post the results in 30 minutes, but so far (knock on wood)… so good!

Frank J. Guthrie


I just printed two-more objects: the FormLab’s Funnel and a small part of a scapula bone. Check these out:

much better that this, you will agree?!:

What I’ve Learned

1 - Never, EVER!use compressed air to remove dust from the mirrors. Use a manual air-blaster, like this Giotto Rocket Air Blaster:

2 - Open a ticket with Support if your prints begin to explode. There is a 99% possibility (not scientifically proven,) that your mirrors are dirty, that’s all!..

3 - ALWAYS get a good-night’s sleep before you begin to cry and act all dramatic, refusing to eat dinner and throwing a tantrum in front of your girlfriend, as she laughs while you wonder, (sobbing, more likely) if buying your Form # 1 was a good decision or not: like Mom said “everything looks better the next day!”… and buying true Form # 1 WAS a good decision!..

Good luck and patience!

Frank J. Guthrie


Thanks for the insight. I too have invested in the air blower you have and its saved the day as few times.
I still need to clean my mirrors - they are dirty from shipping assembly regardless of their “controlled assembly environment”.

Great write-up Frank, glad to see you got to the bottom of the problem in the end!

I use a compressed air blower to clean my mirror and i haven’t seen any particulates as of yet, not sure if i got a time-bomb or if its the brand of compressed air. Its specifically meant for electronics and lenses.
Here it is,

Also to combat dust particles from dropping back down, i use my vacuum cleaner tube close by to maintain a airflow away from the large mirror. So far its worked, but be careful in case you have a dusty vacuum, I had to really wipe mine down thoroughly before i dared bring it near the printer.

And i just ordered paint filters myself, basically the same model as you! great to hear that is working good too!

In the Ag Industry keeping dust out of the cab has come a long way. In modern equipment it is accomplished by 1- Sealing the area to perfection with silicone seals, rubber seals, or sealant… depending on the area. 2- pressurizing the area with positive air pressure drawn in by a fan through a very expensive filter. Of course #2 doesn’t really apply to a Form1, but #1 sure does.

great tutorial to see how to solve a problem!! how many time or how many print do you made with the printer before had problems? thx very much for the tutorial!!

Well I just screwed up. My mirror was a little dusty and my wife had a can of compressed air sitting next to the printer. I figured a little puff wouldn’t hurt. BAD IDEA. All of the compressed air you buy these contains a bitterant to prevent abuse, but I figured no big deal. But there is A LOT in there! It spit all over my mirror! My mirror is WAY WORSE. I have requested the secret pec-pad instructions from FormLabs and am waiting…

Hi Luis & Josh,


I had three good prints at the beginning, the butterfly-clip-test, at 0.10mm, 0.05mm and 0.025mm, to see the resolutions in action. I have to say, they came out amazing! Then I had about three failed prints in a row - all my bad due to my experimentation with the alignment of the models. Once I decided to trust the auto-layout, I had two good ones and then my World Tour of disasters… thank you dust!!

Once I cleaned the mirrors and placed the models around the scared-areas on the resin tank that came with the printer and on the brand-new one I bought separately, well, I got four good prints.

So right now I just received a Sylgard 184 kit, and I’m going to re-finish the silicon-side of both resin tanks, which I will then compare with the two-new resin tanks I should get by this week’s end from FormLabs, so I’m out-of-comission for the next two days! But I will post on the re-finishing of the resin tanks and the comparison tests once I’m up and running…


The instructions are not that complicated, you’ll see, or a secret, they just want you to follow certain steps, and speaking of steps, one is missing! in the instructions for cleaning the Galvanometers, they forget to mention that there are TWO SCREWS at the bottom-back-side of the printer (for removing the back-pannel.) CAREFUL: DON’T FORGET TO REMOVE THE TWO BOTTOM SCREWS BEFORE ATTEMPTING TO REMOVE THE BACK-PLATE! (I hate to sound like I’m screaming, but is very important, since I almost bent the back-plate trying to remove it!

So the thin layer of residue are bitterants?!.. it makes sense!..

Good luck and patience!

Frank J Guthrie

Watch it Pedram: “…Contains a bitterant to help discourage inhalant abuse!..” It leaves a thin layer atop the mirrors… a thin ORANGE layer… now that makes sense, look at the picture of my mirror and you can see the ORANGE bitterant! So, the more you dust, the thicker it gets! That’s what happened to me! Check it out:

So careful, good luck and patience!

Frank J Guthrie

Thanks @Frank_Guthrie, I will stay away from the galvos during this go around. Much thanks for the rocket air blaster idea as an alternative. Incredible idea! I took the bitterant warning to a new topic and used your picture with credit to you when Sam commented on it. I hope you don’t mind. Your posts are awesome Frank.


I had the same problem: HUGE print fails (over ten in a row.) 1) Contacted Support by opening a ticket, 2) got the instructions and cleaned the BIG mirror first, 3) ran another print and got another fail, 4) cleaned the Galvanometers ’ mirrors and voila! I had three great prints back-to-back!

The Galvanometers’ assembly is held by two 2.5 Hex bolts** (like the rest of the machine,) and it only took me 5 to 10 minutes max to remove both the back-plate and the assembly, the easiest thing in the world, trust me! When you put the assembly back, you realize how well-designed this printer is. It takes less that 5 minutes, piece of cake!

So good luck and patience!

Frank J Guthrie

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Frank… Thank you so much for your post. We love helping our customers get back to printing but what I love most is having your guys help each other.
You were right to suggest that Josh (and all others) open a ticket with us at as there can be a few issues that can cause blowouts or print failure beyond dirty mirrors.

I look forward to seeing what you guys print in the future.

Hubbard at FormLabs

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I’m starting to see this happening to my printer. 10+ perfect prints and all of a sudden, prints failing in exactly the same way.

Seems to me that the mirrors need more maintenance than all the other expendables.

What a great tutorial ! I’m interested in your desktop ultraviolet oven - can you share make & model please ?

how often are you intended to disassemble your machine and clean the galvanometers. they should add that process to the video…

or better yet the cleaning method described by joshk

"“but what I did last time there was dust on the mirror was get a cotton
swab and look at it to find a loose thread. Then I carefully used the
loose thread like a hook to insert between the mirror and one of the
arches on the dust particle. That way I can remove dust without
touching the mirror or blowing it around. But I have slightly better
than 20/20 vision, a very steady hand, and lots of patience.”

id love to see someone try this on the 35.000 dust particles currently sitting on my mirror.

Haha, I remember the days when I was that ambitious. now I just use the rocket air blaster and hope for the best.

does the rocket blaster have the most air pressure of the squeeze dusters? I was thinking about getting one of those air brush compressors, and maybe a computer vac

The rocket air blaster is just a squeeze duster. It doesn’t have a lot of pressure because its hole is fairly large, but it works just fine. Lots of pressure sounds like a good thing, but I really hate to stir up a bigger dust storm than necessary. Remember everything in there is as dusty or more than the mirror. The mirror gets attention, everything else just keeps collecting.