Replacing the Form 4 Light Processing Unit fan

The LPU fan cools the Form 4 optical system. Damage to the LPU fan may cause the optical system to overheat and prevent the printer from functioning properly.

Use this guide to replace the Form 4 LPU fan.

Estimated time: 45 minutes

Overview: Prepare the Form 4 and workspace for replacing the LPU 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 cartridge

Remove the resin cartridge and close the vent cap to prevent resin from dripping off of the bite valve 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 fan from the printer.

Step 1: Remove the left panel retention screws

Use a 2.5 mm hex driver to remove the four screws securing the left panel to the printer. Set the left panel and the screws aside.

Step 2: Rotate the printer

Rotate the printer onto its right side so the LPU fan is facing up.

Step 3: Disconnect the cable

Release the cable that connects to the LPU fan by pressing on the plastic tab on the connectors. Take care when unplugging the cable to avoid damage. Once the plastic tab is pressed, the cable easily slides from the connector. Do not pull on the wires.

Step 4: Remove the tape

The LPU fan is secured by tape. Carefully remove the tape from the LPU fan. Set the tape aside for reuse during installation.

Step 5: Remove the LPU fan

The LPU fan is secured to the printer frame with three rubber pins. Grip the LPU fan and lift it out of the printer. If the LPU fan is difficult to remove or the rubber mounting pins become damaged during removal, proceed to the next section Optional: Replacing the fan mounting hardware.

Overview: Replace the fan mounting hardware to remove the LPU fan from the printer.

Step 1: Remove the Backlight Unit

To access the fan mounting hardware, the printer's backlight unit must be removed. To remove the backlight unit, follow the instructions in the repair guide Replacing the Form 4 Backlight Unit. Complete the steps in the section Removing the Backlight Unit.

Step 2: Locate the fan mounting hardware

The fan mounting hardware consists of three rubber pins that mount the LPU fan in the printer.

Step 3: Remove the fan mounting hardware

Use flush cutters or scissors to cut the three rubber mounting pins.

Step 4: Remove the fan mounting hardware and the LPU fan

Grip the LPU fan and remove it from the printer. Remove the cut pieces of the mounting pins from the printer. Set the cut pieces aside for disposal and the LPU fan aside for disposal with electronic waste.

Step 5: Install the lower fan mounting hardware

The lower fan mounting hardware consists of two rubber pins. Insert the replacement rubber mounting pins into the two lower holes in the sheet metal.

Step 6: Grip the upper mounting pin

The upper fan mounting hardware is a single rubber pin. Grip the rubber pin with a pair of needle nose pliers, leaving 5–10 mm of the pin visible above the pliers.

Step 7: Insert the mounting pin

Use the pliers to insert the rubber pin into the bottom of the printer between the black plastic optics shroud and the sheet metal until the rubber pin pops through the upper fan mounting hole. Take care not to touch or damage any optical components in the printer.

Step 8: Position the mounting pin

Using fingers or a second pair of pliers, pull the rubber pin fully into position.

Overview: Install the replacement LPU fan.

Step 1: Install the LPU fan

Place the LPU fan in the printer. Align the three rubber pins with the holes in the fan.

If the rubber mounting pins do not thread into the holes, use a pair of needle nose pliers to pull the pins into position. Push down on the fan until the fan is properly seated and the pins are fully seated in their holes.

Step 2: Reconnect the 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: Attach the tape

Reattach the tape to the LPU fan to secure it to the printer. Press firmly on the tape to adhere it to the fan and printer frame.

Step 4: Reinstall the Backlight Unit (Optional)

If you previously uninstalled the Backlight Unit to access the fan's rubber mounting pins, reinstall the Backlight Unit. Follow the instructions in the repair guide Replacing the Form 4 Backlight Unit. Complete the steps in the section Installing the replacement Backlight Unit.

Step 5: Mount the left panel

Place the left panel on the printer. Ensure that the screw holes in the panel align with those in the printer frame and that it sits flush with the touchscreen assembly and the back of the machine.

Step 6: Install the left panel screws

Use a 2.5 mm hex driver to install the four screws that secure the left panel to the printer. Tighten the screws until snug.

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

Step 1: Power on the printer

Connect the power cable to the printer and the power supply. The printer initializes.

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.