The Light Processing Unit (LPU) fans cool the Form 4L optical system. Damage to the LPU fans may cause the optical system to overheat and prevent the printer from functioning properly.

Use this guide to replace one or both of the LPU fans.

Estimated time: 20–30 minutes

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

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: Remove the LPU cooling fan that is being replaced.

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: Remove the filter mount

Use a 3 mm hex driver to remove the three screws securing the filter mount to the printer. Remove the filter mount and screws and set them aside.

Step 5: Remove yellow tape

Peel off the tape that goes around the fan duct and temporarily stick it on a clean surface.

Step 6: Unhook the cable harness

A cable harness is held in place with bendable cable ties. Bend the cable ties to unhook the harness.

Step 7: Remove the LPU fan

Use a 2.5 mm hex driver to remove the three screws securing the LPU fan that you are replacing. The bendable cable tie is secured to the fan by one of the three screws—remove the cable tie and set it aside with the fan screws.

Step 9: Remove the other LPU fan (optional)

If you are replacing both fans, repeat steps 7–8 for the other fan.

Overview: Mount and secure the replacement LPU cooling fan.

Step 1: Orient the replacement fan

Orient the replacement fan to fit in its mounting location within the printer. The front and back cooling fans are the same part in two different orientations.

Step 2: Connect the LPU fan cable

Reconnect the cable that connects the LPU fan to the printer. The plastic tabs should click into place to secure the connection. Take care not to pull on the wires.

Step 3: Install the LPU fan

Place the fan into the printer, aligning the screw holes in the fan with the corresponding screw holes in the printer frame. Install the black cable tie onto the replacement fan at the same screw hole as on the old fan. Thread one screw into each of the three screw holes, then use a 2.5 mm hex driver to tighten until snug. Take care not to pinch or crush the wiring behind the fan.

Step 4: Install the other replacement LPU fan (optional)

If you are replacing both fans, repeat steps 1–3 for the other fan.

Step 5: Hook the cable harness

Secure the cable harness away from the fan blades by bending the black cable ties around the wires.

Step 6: Replace the yellow tape

Replace the yellow tape around the fan duct.

Step 7: Install the filter mount

Place the filter mount over the LPU fans, aligning the screw holes in the mount with the corresponding screw holes in the printer frame. Thread one screw into each of the three screw holes, then use a 3 mm hex driver to tighten until snug.

Step 8: Install the LPU fan 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 9: 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 10: Reinstall the mesh filter

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

Overview: After installing the new LPU cooling fan, 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.