The SLS laser window sits between the laser and the powder bed, and any film on it weakens the beam. On the Formlabs forum, a production shop with a Fuse 1+ noticed softer features at about 500 hours. At 750+ hours, a “rash” appeared across every part in the stack and hurt dimensional tolerances.
How often should you clean the SLS laser window?
Formlabs recommends cleaning the Fuse 1’s upper laser window after 1,000 hours of printing, but many operators clean it sooner. The shop above found film on the window before reaching 1,000 hours. After cleaning it, they said their parts were back to new-printer quality.
What do other operators do?
- One operator cleans the upper window once a month. They said a Formlabs field tech warned them that cleaning it after every print could damage it.
- Another cleans the optical cassette every 50 to 80 print hours and keeps a spare cassette in rotation.
- A third cleans the cassette after every print and checks the upper window for contamination every 300 to 400 hours.
A Formlabs rep replied that 1,000 hours is a general average. The right interval depends on print frequency and length, powder type, environment and filter cleanliness. If you need cleaning far more often, contact support, because an underperforming fan or clogged exhaust can be the cause. One operator also reported an early Fuse 1 whose window seal leaked a clear liquid onto the glass, which required a full window replacement.
How do you clean it?
Formlabs says to inspect the optical cassette after every print and to expect to clean it every 5 to 10 prints. Wipe it with ethanol and a microfiber cloth in a crosshatch pattern. For the upper window, remove the cassette and use the telescoping mirror to guide an ethanol-wetted polyester swab. Wipe in one direction only, then wait five minutes for the ethanol to evaporate.
What should a bureau do?
Treat optics as part of quality control, not just a maintenance chore. Log every cleaning against print hours. When surface quality or tolerances drift, check the windows before changing settings. On the Fuse 1+ 30W, Formlabs’ optics check print shows an optical cleanliness scan and a calculated laser power. If laser power stays under 80% after cleaning, Formlabs says to contact support.
Related on the Solvi blog: SLS Orange Peel: Why It Happens and How to Fix It; SLS Powder Cleanup: How to Keep Dust Under Control; SLS Cooldown: How Hot Can You Unpack a Build?.
Sources: Formlabs forum “Fuse 1+ Upper Laser Window Cleaning?” thread; Formlabs: Cleaning the upper laser window; Formlabs: Cleaning the optical cassette; Formlabs: Evaluating diagnostic print results.