Required Supplies:
Formlabs:
- Light Processing Unit 4 (LPU 4)
- 2.5 mm hex driver (included in the Form 4 tool caddy)
Third-party:
- Nitrile gloves
WHITE PAPER
Replacing the Form 4 Light Processing Unit
Replacing the Form 4 Light Processing Unit
In Form 4 generation printers, the printer's backlight shines through a component called the Light Processing Unit 4 (LPU 4) to print. The LPU 4 contains an LCD panel, heaters, and sensors that form an important part of the Form 4 optical system. The LPU mounts to the Form 4 and sits under the resin tank. A malfunctioning LPU can prevent the printer from printing properly.
Use this guide to replace the Light Processing Unit 4 (LPU 4).
Estimated time: 15–30 minutes
Preparing the workspace
Overview: Prepare the printer and a dust-free workspace for replacing the LPU.
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.
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.
Removing the LPU
Overview: Loosen the housing screws and remove the LPU.
Notice:
This step involves removing the LPU, which exposes the Form 4 optical system. While the LPU is removed from the printer, ensure that no dust or debris falls into the optical cavity.
Step 1: Loosen the LPU housing screws
Open the printer cover. Use a 2.5 mm hex driver to loosen the eight captive hex screws in the LPU housing.
Step 2: Unplug the HDMI cable
Carefully lift the LPU and tilt it so that the bottom faces you. Locate the LPU's HDMI cable. Squeeze the plastic retaining clip and unplug the HDMI cable from the LPU.
Step 3: Disconnect the tank heater cable
Release the tank heater cable by squeezing the tab on the connector and pulling directly away from the LPU. Do not pull on the cable itself.
Step 4: Remove the LPU
Remove the LPU from the printer and set it aside for disposal with electronic waste.
Installing the replacement LPU
Overview: After removing the old LPU, connect and install the replacement.
Step 1: Connect the tank heater cable
Position the LPU so the connector ports are oriented towards the back of the printer. Plug the tank heater cable into the connector on the LPU. The plastic tab should click into place to secure the cable.
Step 2: Connect the HDMI cable
Plug the HDMI cable into the port on the LPU. Ensure that the two prongs on the plastic retaining clip snap into place.
Step 3: Mount the LPU
Ensure that the optical cavity and LPU are free from dust and debris. Place the LPU onto the optical cavity and align the screw holes.
Step 4: Thread the housing screws
Use a 2.5 mm hex driver to loosely thread the eight captive hex screws in the LPU housing.
Step 5: Secure the LPU
Once all screws are loosely threaded, tighten the screws in a diagonal pattern as shown above. The screws should be secure but not overtightened. To avoid overtightening, grip the short end of the hex driver.
Finalizing the repair
Overview: After installing the replacement LPU, power on the printer and perform final checks.
Step 1: Power on the printer
Close the printer cover and connect the power cable to the printer and the power supply. Turn on the switch at the back of the printer. The printer initializes.
Step 2: Align the build platform
On the touchscreen, tap Settings > Tools > Align build platform. Follow the on-screen instructions.
Step 3: Run a test print
Insert any missing consumables and upload and start a print. Check that the print starts normally and the parts print successfully. Contact Formlabs Support or your authorized reseller to share the results of the procedure.