The LPU (Light Processing Unit) fan filter prevents dust and debris from contaminating the Form 4L optical system. A dirty filter can cause issues with print quality; clean or replace it to keep printing and to prevent damage to your printer.

Use this guide to clean or replace the LPU fan filter on the Form 4L.

Estimated time: 10 minutes

Overview: Prepare the Form 4L and a dust-free workspace for replacing the LPU fan filter

Step 1: Remove the build platform

Remove the build platform first to avoid dripping resin onto the Light Processing Unit (LPU).

Step 2: Remove the resin cartridges

Remove the resin cartridges and close the vent caps to prevent resin from dripping off of the bite valves and into the printer.

Step 3: Remove and store the resin tank and mixer

Unlatch the mixer and resin tank. Remove the resin tank and cover it with its lid. Set the tank aside on a clean, flat surface.

Step 4: Prepare the workspace

Clear a workspace around your printer. Ensure that the workspace is well-ventilated and free of dust.

Step 5: Clean the printer

Open the printer cover and clean any resin pooled on and around the LPU with non-abrasive wipes. Dampen the wipes with isopropyl alcohol if necessary to fully remove the resin.

Step 6: Unplug the printer

Disconnect the power cable before continuing with maintenance. Do not perform maintenance on the printer while it is connected to power. Wait five minutes after disconnecting the printer from power before proceeding.

Overview: Access and remove the LPU fan filter.

Step 1: Remove the mesh filter

Remove the mesh filter from the right side of the printer. Set the filter aside.

Step 2: Remove the lower right panel

Use a 2.5 mm hex driver to remove the four screws securing the lower right panel to the printer. Remove the screws and the panel and set them aside.

Step 3: Remove the LPU fan filter

Disengage the fan retainer by pulling downwards and swinging the wire arm towards you. Remove the LPU fan filter by pulling straight down on the filter’s body. Set the filter aside.

Step 4: Vacuum the fan filter (optional)

If you are cleaning the fan filter rather than replacing it, vacuum both sides of the filter until it is clean and free from dust or debris. After cleaning the filter, reinstall it following the steps below.

If you cannot fully clean the contamination or you continue to experience issues related to the filter after cleaning, replace the filter.

Overview: Mount and secure the replacement LPU fan filter.

Step 1: Install the replacement filter

Slide the fan filter under the wire filter retainer and push upwards until fully seated. Pull downwards on the filter retainer and swing it beneath the filter to secure the filter in place.

Step 2: Mount and secure the lower right panel

Align the screw holes in the lower right panel with those in the printer frame. Thread one mounting screw into each of the four screw holes. Use a 2.5 mm hex driver to tighten until snug.

Step 3: Reinstall the mesh filter

Place the mesh filter over the grate on the right side of the printer.

Overview: After installing the new LPU fan filter, power on the printer and perform final checks.

Step 1: Power on the printer

Close the printer door and connect the power cable to the printer and the power supply. Turn on the switch at the back of the printer. The printer will turn on and initialize.

Step 2: Run a test print

Insert any missing consumables and upload and start a print. Perform a small test print to ensure that the printer works normally. Contact Formlabs Support or your authorized reseller to share the results of the procedure.