Hi everyone,
I’m reaching out to see if anyone else has encountered a sudden, systematic failure across multiple units. We are running two Fuse 1 and one Fuse 1+ units, and all three have started exhibiting the exact same symptoms simultaneously.
The Problem:
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Rapid Optical Buildup: A brand-new, perfectly clean optical cassette becomes heavily “cloudy” with dust within just 15–20 minutes of starting a print.
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Aggressive Beadtearing: This lead to consistent beadtearing early in preprint.
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The “3rd Time’s a Charm” Pattern: Curiously, the machines usually fail 2–3 times in a row, but then suddenly start working as intended on the 3rd or 4th attempt.
What we’ve already ruled out:
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Consumables: Tested with 100% fresh, virgin powder.
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Maintenance: New filters installed, IR sensors deep-cleaned (spotless), and brand-new optical cassettes used.
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Environment: Room temp is stable at 21.5°C. We’ve tested both with and without AC/Dehumidifier to rule out low humidity and static electricity (humidity adjustments didn’t solve the immediate clouding).
The Mystery:
Since this is happening on all three machines, it feels less like a mechanical failure of a single component and more like a systemic issue. It’s as if the “Air Curtain” or the exhaust system fails to create the necessary pressure to protect the optics during the initial heating/start-up phase, but somehow “primes” itself after a few failed starts.
Has anyone experienced this “warm-up” requirement before? Could it be a specific firmware behavior, a batch issue with filters/pumps, or something hidden in the air-path that we are missing?
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On my Fuse 1+, from 7/28/2025 - 2/2/2026 I ran 58 prints and only had 2 print failures (~3% failure rate) which I attribute to insufficient part spacing resulting in layer curling. Since then, I have run 24 prints and had 5 print failures (~21% failure rate) all due to layer curling. Even though this is not the same as bed tearing, I believe it is related to bed temperature control.
I have noticed my optical cassette has been very fogged up after every print recently, but I’m not certain when this behavior started. I used to only need to clean the cassette typically every few prints. When did you first notice this problem? Curious if it lines up with my failure uptick.
I contacted FL a couple weeks ago and basically got the “clean everything again” answer. Performed all the requested cleaning steps (most of which I always do before a print) and it ran successfully, but this didn’t really address the problem. One of the extra steps I took was replacing the exhaust filter. It wasn’t even close to the due date, but it did have some gray residue built up. Unfortunately for me, it seems like you’ve ruled this out as the root cause.
Support said they could tell from the error logs that my optics were occluded. I asked for information on how to determine this so I could troubleshoot myself, but they didn’t tell me. How are you determining that your optics are getting cloudy right after starting a print?
Hi @jmasterson.
The print errors started about a week ago. Same bedtear on all three printers. I just checked the optical cassette after a detected error and noticed it was cloudy. Replaced with a brand new one and got another error, checked the cassette again and massive amount of clouding.
But, i might be on to something. If i let the printer cool for another hour after a finished print, i don´t get the error.
Atleast ive tried that on one of the printers and i did not get an error. It could be as simple as a cooldown issue. Once the chamber reaches 100 degrees celsius i remove the chamber, clean it out, in with another chamber and start printing again. So i will be trying this today aswell.
If i don´t get any errors, id say i found the issue. I will update this post if it should be the case.
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Turns out the printers dislikes being used back to back.
I let the printers cool down for 30 min between printjobs and that did the trick.
I can’t say I’ve seen this issue happen to us.
But then again, we don’t print nearly as much as you guys do 
Our Fuse currently runs once a week with batch jobs over the weekend. Of course, our Fuse cools down completely before the next print starts.
Since we rely more on achieving the highest possible dimensional accuracy for all parts, we also give each build chamber plenty of time to cool down.
We don’t remove most build chambers from the Fuse until the internal display reads around 40°C.
But it’s good to know that a slightly longer cooling period is enough to fix the issue.
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Well we really run our printers to the max currently. If they break im in for an allnighter of repairing. 
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Oh damn
But I totally get it. In a situation like that, those things just have to run, run, run.
I find it remarkable how you run multiple printers at such a high capacity.
We rarely find ourselves in a situation with that kind of workload, but when we do, there’s no more testing, playing around, or experimenting during that time.
Instead, we document the “current state” once and then don’t change any software or hardware in any way.
But it still gives me a good feeling to hear that the Fuse can be run as such a workhorse. Right now, we’re simply playing the speed card, where customers receive a handful of parts from the Fuse within a few days. Our printer doesn’t run much, but when it does, it has to run reliably. So far, that’s been working out pretty well 
Lets just say there is no room for errors right now.
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A glance at your profile and the dots become connected what the big rush is for
Best of luck to you guys!
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haha, thank you @StackCore 