In the Form 3L/Form 3BL, the optical components—the laser diodes and mirrors—are contained in two modules called the Light Processing Units (LPUs). The LPUs, sitting inside the LPU housing, move left and right in the printer during each layer of a print. The laser light exits the LPUs through an anti-reflective coated glass optical window mounted on top of the LPU housing. The glass optical window preserves print quality and reliability by protecting the components inside the LPUs from dust, oil, and resin contamination. Keep the glass optical window clean to ensure successful prints.

The LPU housing, with the LPUs, roller holder, and glass optical window, sits in the LPU garage on the right side of the printer when a print is not running. The LPU garage protects the glass optical window from most forms of contamination, but dust can still accumulate on the glass surface over time. As the laser light passes through the glass optical window, any such contamination can cause the laser light to diffuse or weaken, resulting in print defects.

To maintain the glass optical window, inspect the glass surface for dust, oil, or contamination using a flashlight, LED, or cell phone light. If dust, oil, or contamination is noted, clean the glass optical window following Formlabs instructions. As with most optical surfaces, minimal cleaning is the best cleaning.

Estimated time: 10 minutes

Always remove the build platform, resin cartridges, and resin tank before performing maintenance on the printer to avoid dripping resin into the printer cavity.

1. Lift the platform lock and remove the build platform.
2. Close all resin cartridge vent caps and remove the resin cartridges.
3. Remove the resin tank from the printer. Place the resin tank in its case.
4. Set the tank case aside with the build platform and resin cartridges on a clean, flat surface.

Inspect the optical window for dust, oil streaks, fingerprints, or cured resin.

To access the maintenance option through the printer’s touchscreen:

1. Put on a new, clean pair of nitrile gloves.
2. With the printer plugged in and powered on, tap the wrench icon to access the Settings screen, then tap Maintenance > Motor Moves. The Motor Moves screen appears. Tap and hold Left (<) to move the LPU housing to the middle of the printer cavity. Other controls on this screen fully sweep the LPU housing across the printer cavity and control the build platform carriage.
3. When prompted by the touchscreen, disconnect the power cable before continuing with maintenance.

4. Shine a secondary light source (for example, a flashlight, LED or cell phone light) onto the optical window to reveal any hidden contamination on the glass surface.
   • Hold the light source at the shallowest angle possible. From the edges of all three accessible sides (that is, left, front, and right), scan the light back and forth across the optical window.

Remove dust and other loose contaminants, which can interfere with the laser.

To remove dust:

1. Put on a new, clean pair of nitrile gloves.
2. Use a rubber bulb air blower to gently remove any visible dust from the optical window.
   • Make sure to remove any large particles that may scratch the glass surface.
3. Use a new PEC*PAD to remove any remaining dust from the optical window with a dry wipe.
   • Wipe slowly, pulling the PEC*PAD toward you, repeating until you have cleaned the entire glass surface.
   
4. Proceed with a wet wipe only if the dry wipe does not clean the glass completely.

Wet wipe the glass optical window only if oil, smudges, fingerprints, or resin contamination is visible. Only use PEC*PADs and non-recycled isopropyl alcohol with a concentration of 90% or higher to clean the glass surface as any other cleaning agent or material may degrade the anti-reflective coating.

To clean with a wet wipe:

1. Put on a new, clean pair of nitrile gloves.
2. Apply a small amount of IPA to a new PEC*PAD.
3. Wipe the optical window slowly with the PEC*PAD, pulling the PEC*PAD toward you. Repeat this step until you have cleaned the entire glass surface.
4. Use your secondary light source to inspect the optical window. Repeat the wipe if any streaks are visible.
   • Multiple passes may be necessary to achieve a streak-free surface. Each PEC*PAD can be used multiple times by refolding the material to expose a fresh surface for each pass on the glass panel.
5. Dry wipe the glass surface again with a new PEC*PAD to remove any remaining streaks.

Further troubleshooting

If streaks are difficult to remove, contact Formlabs Support or your authorized reseller. When requesting help, please provide photos of the optical window illuminated by a secondary light source and a list of attempted cleaning steps.

After cleaning the glass optical window, power on the printer to complete the maintenance process. Close the cover and connect the power cable to the printer and the power supply. The printer initializes and the LPU housing moves back to its home position to perform a calibration.