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Replacing the Form 4L Backlight Unit

The Form 4L Backlight Unit contains an LED array and lenses to produce and focus the light that cures resin during the printing process. A damaged Backlight Unit may prevent the printer from printing properly.

Use this guide to remove and replace the Backlight Unit on a Form 4L generation printer.

Required Supplies:

Formlabs:

Backlight Unit
3 mm hex driver (included in the Form 4L tool caddy)

Third-party:

Nitrile gloves

Estimated time: 30 minutes

Preparing the workspace

Overview: Prepare the printer and a dust-free workspace for replacing the Backlight Unit.

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 cap 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.

NOTICE:

Wear gloves and hold the resin tank by the tank grips on either side to avoid contamination or damage to the underside of the tank.

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

WARNING:

Resin may cause skin irritation or an allergic skin reaction. Wear gloves when handling liquid resin or resin-coated surfaces. Wash skin with plenty of soap and water.

Open the printer cover and clean any resin pooled on and around the LPU with paper towels. Dampen the paper towels with isopropyl alcohol if necessary to fully remove the resin.

DANGER:

Fire hazard. IPA is flammable. Keep containers closed, and keep out of the reach of children.

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.

DANGER:

Performing maintenance on the printer while it is plugged in increases the risk of electric shock. Never remove the back panel of the printer while the printer is plugged in. Never reconnect the printer to power while the back panel is uninstalled.

Removing the Backlight Unit

Overview: Position the printer on its back to access and remove the Backlight Unit.

NOTICE:

Performing maintenance with the Backlight Unit removed increases the risk of contamination inside the optical cavity. Take care to prevent dust or debris from falling inside the printer.

Step 1: Remove the Wi-Fi antenna

Remove the Wi-Fi antenna from the back of the printer and set aside.

Step 2: Position the printer

Ensure that the build platform, resin cartridge, resin tank, and mixer have been removed from the printer to prevent damage. With the help of another person, grip the Form 4L by the bottom front and top rear corners. Carefully rotate the printer so that it is resting on the back surface with the bottom facing you. Leave at least 30 cm (12 in) of clear tabletop in front of the printer when it is lying down.

Step 3: Remove the Backlight Unit screws

Use a 3 mm hex driver to remove the 12 screws that secure the Backlight Unit to the bottom of the printer. Do not remove the Torx screws. Set the screws aside.

Step 4: Separate the Backlight Unit from the printer

Grip the two handles on the Backlight Unit. Carefully pull the Backlight Unit away from the printer and pivot it until it rests on the work surface.

NOTICE:

Take care not to touch the components inside the exposed optical cavity.

Step 5: Unplug the backlight cables

The backlight cables are located at the front of the Backlight Unit. Gently squeeze the plastic tabs to unplug the backlight cables from the Backlight Unit. Do not pull on the individual wires.

Step 6: Unhook the backlight cables

Open the cable management straps and remove the backlight cables.

Step 7: Disconnect the LED fan cables

The LED fan cables are located in the bottom-left of the optical cavity. Squeeze the plastic retaining clips and unplug the LED fan cables from the printer. Do not pull on the wires.

Step 8: Remove the Backlight Unit

Once all the cables are disconnected, remove the Backlight Unit from the printer. Set aside for disposal with electronic waste.

Installing the replacement Backlight Unit

Overview: Connect and install the replacement Backlight Unit.

Step 1: Position the replacement Backlight Unit in front of the printer

Place the replacement Backlight Unit on the workspace in front of the printer with the lens array facing up. Orient the Backlight Unit with the backlight cable connectors at the front.

NOTICE:

Do not touch the exposed lenses. Doing so may contaminate the lenses and lead to repeated print failures.

Step 2: Connect the LED fan cables

Connect the LED fan cable connectors to the LED fan cables at the back of the printer. The connectors make an audible and tactile click when secured.

Step 3: Connect the backlight cables

Connect the backlight cables to the Backlight Unit. The connectors make an audible and tactile click when secured.

Step 4: Route the cables

Route the backlight cables along the edge of the Backlight Unit and secure them with the cable management straps.

Step 5: Install the Backlight Unit

Lifting with the two handles, gently slide the Backlight Unit into the printer. Align the pins and screw holes to fully seat the Backlight Unit. Ensure the Backlight Unit is fully seated.

Notice:

Take care not to pinch the wire bundles at the back of the machine.
If the Backlight Unit is contaminated during the repair procedure, apply a small amount of clean IPA to a PEC*PAD and wipe the surface of the Backlight Unit to remove contamination or resin. Allow the Backlight Unit to air dry before installing it.

Step 6: Secure the Backlight Unit

Using a 3 mm hex driver, hand tighten the 12 screws on the bottom of the printer to secure the Backlight Unit.

Step 7: Position the printer

With the help of another person, grip the Form 4L by the bottom front and top rear corners. Carefully rotate the printer upright so it sits on its leveling feet.

Step 8: Install the Wi-Fi antenna

Reinstall the Wi-Fi antenna on the back of the printer.

Finalizing the repair

Overview: After installing the new Backlight Unit, 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.