Pictures of Prints with Dirty vs. Clean Optics (Form 2)

In case it helps anyone, here’s an example of an identical print on a Form 2 before and after cleaning the optics (galvos, large mirror, window).

The printer had been working just fine a few days ago. After about 3 days straight of printing (mostly in Tough v5) I started getting a sloppy mess on the floor of my part. I tested in both Grey and Black, with different tanks. I think I caught the schlop as soon as it began to manifest, and interestingly, the vertical surfaces in all those prints still looked pretty good. On inspection, I noticed the main mirror and the optical window both had a thin layer of “haze” on them.

If you’re interested, here’s what the failure looked like in Black:

Fortunately a cleaning fixed everything right up.

I’ve also noticed an early sign of dirty optics can be larger “bleed” where your part (or raft) meets the build platform. One user once referred to the effect as “elephants foot”. You can see it as a thin crust at the bottom of the left part in the first two pictures above.

Here’s a more extreme example, contrasted to what it’s supposed to look like in Preform. You can see a thin pancake of resin where the rafts for the two models on the left bled right into each other.


Thanks for the detailed post. What cleaning procedure do you use for mirror and window?
I find it interesting that a dirty mirror and window creates this “elephants foot” effect. I would have assumed that dirty optics reduce the laser power that gets to the resin but it seems the laser spot just gets broader.

I suspect it’s a combination of both (impeded power diluted over a less focused spot), and perhaps others (e.g. flare / reflections / less crisp edges).

Formlabs publishes cleaning procedures. The Optical Window one is included here: Maintaining the Form 2, but for others you need to contact Support (presumably since they want to verify cleaning is neccessary - too much or improper cleaning can damage the delicate parts). Ask for “Diagnosing and Cleaning Form2 Main Mirror” and “Cleaning the Form 2 Galvo Mirrors”. They amount to PEC-PADs for the main mirror, and Q-Tips on the galvo mirrors (both with a bit of IPA), but the guides cover some important details.

The mirrors in a Form2 aren’t like the ones in your bathroom. They’re “primary mirrors”, like for optical telescopes. The reflective coating is on the front side of the glass, and it’s a very thin and delicate layer of metal.

Improper cleaning of the mirrors will scratch them, and even remove some of the reflective coating, in either case ruining the mirror. Which is why FL wants you to contact them for instructions before attempting cleaning…