Ablations on main mirror after cleaning with pec pads

after a long time printing successful except for some minor imperfections I am back with a damaged mirror. Today I had some dust on my mirror that my rocket air blower could not remove at all. So I took my nitrile gloves with a NEW Pec Pad ( without alcohol ) and wiped the leftover dust particles extremly careful and without any pressure over my main mirror. I inspected it and noticed that I have ablations on it like I had it before already. I don’t even know why I report this here. It doesn’t look like this problems will take an end some day. Anyway I sent a mail to the support. But even if I get a new mirror how long will it last? Its the first time I cleaned my mirror with a pec pad since I got it back from repair.
It might sound silly but can the voltage power in europe make the laser stronger and burn the mirror? I am out of any ideas that can prevent my mirror from damages like this.

It might sound silly but can the voltage power in europe make the laser stronger and burn the mirror?

It’s not possible, sorry. The switching power supply (the “power brick”) regulates the output DC voltage regardless of the input AC voltage, then comes the controller board inside the printer, with its own voltage regulator that keeps the output voltage stable, then there’s the laser driver, which keeps the laser output power constant via a feedback loop.

It is my understanding that the laser inside Form1 has a photo-diode that the driver uses to regulate the output power. Therefore, even if all the previous links in the chain were faulty, that last one would’ve kept things in check.

Also, despite what you might have heard, abrading a first surface mirror by cleaning it is actually not that easy and takes some effort. The aluminium layer evaporated onto the backing is (usually) protected with a thin layer of quartz, which has surface hardness comparable to glass.

I’ve got three hypotheses on what causes the ablation:

  1. bad mirror - simple as that, the silvering was sub-par and degrades over time, regardless of use

  2. laser interacting with something on the mirror - oil, dirt, protective coating leftovers that weren’t removed completely

  3. heat - first surface mirrors are “notorious” for being prone to damage under thermal shock, because the silvering layer tends to have a different thermal coefficient than the backing (i.e. stretches differently)

Out of curiosity - do you ever use water to clean the mirror?

thanks for the explanation @Ante_Vukorepa !

I never cleaned my mirror with water and as I cleaned my mirror yesterday it was the first time I cleaned it by direct contact with a pec pad! Before I never touched it. I just used the air blower. My prints suddenly started to get a little bit worse so I decided it had something to do with dust and in fact it looked like that. Now after cleaning I noticed the ablations and my two prints since then are very bad.

to 1.: is there a better mirror I can get to replace it?

2.: I cannot be sure 100 percent if there was an interacting but I did what I can to prevent it from any oil or dirt. At least for the oil I am sure there is no!

3.: I use an LED light to make pictures of the mirror so this can’t be a reason. There is no heat around my desktop.

  1. I think someone here recommended a place to get a replacement first surface mirror from, but i’d recommend contacting Formlabs support - they should be able to provide an original replacement part (which is probably a better choice). I’m guessing ablation-prone mirrors are a fluke, or there’d be way way more reports of them by now.

  2. Didn’t mean from you, i meant that maybe there’s some point during the manufacture that might be leaving some kind of residue by accident (like a protective foil’s adhesive?).

  3. If this were a more widespread thing, i’d hazard guessing that there might be a source of heat somewhere inside the case (PCB, for example) causing uneven heating.

I’ve looked through some of the photos on the forum and i must admit that i’ve only seen a few cases that don’t look like mechanical damage (the cases that start with yellowing and other similar changes in surface appearance, then gradually evolve into pitting). Others look more like mechanical damage.

All of this is pure speculation, of course, coming from someone still waiting on a printer (so no first-hand experience). So take everything i say with a grain of salt, but to me, your case (and other similar ones) look like mechanical damage (chips). I’m not saying you caused it, but something had to have, and there are only two options here - either it came like that from Formlabs, or some process in the printer caused it in operation (perhaps the peel process chipped off a sliver of metal and shot it into the mirror? long shot, i know).

well its my second defect mirror. Even if its a fluke formlabs did not make a statement officialy that this can happen. We always have to make our experiences on our own until we get an explanation by the support maybe. If I buy a seperate mirror by another supplier after my warranty will be gone I can possibly blame the manufacturer and get exact information what kind of mirror it is and how to prevent it from getting defect. And maybe someone here knows which kind of mirror is used in the form1+ so I get one or possibly another one which works even better! Gold plated dielectric or whatever. One that possibly costs more but at least I don’t have any problems anymore.

I had a look at this seller and am wondering if there is a better mirror that could be used:

any suggestions? :slight_smile:

I’m sure someone more experienced will chime in with better info, but if you decide to go that route once your warranty is out, check here: http://form1printer.pbworks.com/w/page/73582883/Replacement%20Components (under Mirror).

DO NOT buy a gold plated mirror, as gold is used for IR lasers (it doesn’t have very good reflectivity at blue/violet/ultraviolet wavelengths). Aluminium plated mirrors are the way to go.

A quick note — we don’t encourage people to do their own repairs on their machine.

As some consolation, we do make replacement primary mirrors available on a case-by-case basis. Please contact our support team. They’ve seen a lot of mirrors, and can take a look at your case and see what’s appropriate.

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