The rear heater assembly is one of two heaters in the Form 3L that bring the resin in the resin tank up to its optimal temperature before printing. If the rear heater is malfunctioning or broken, the preprint process may take longer than usual to complete. Prints started before the resin comes up to temperature may fail.

Use this guide to remove and replace the Form 3L rear heater assembly.

Estimated time: 30 minutes (additional time may be required to allow the heater to cool if the printer was recently in use)

Overview: Prepare the Form 3L and a dust-free workspace for replacing the rear heater assembly.

Step 1: Remove the build platform

Remove the build platform first to avoid dripping resin onto the LPU or into the printer cavity.

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

Remove the resin tank, place it in the resin tank case, and cover it with its lid. Set the case and 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. Prepare additional space for storing the rear panel of the printer during maintenance.

Step 5: Clean the printer cavity

Open the printer cover. Clean any resin pooled on the printer floor, inside the printer cavity, with paper towels. Dampen the paper towels with isopropyl alcohol if necessary to fully remove the resin.

Step 6: Unplug the networking cables and wi-fi antenna

Disconnect the Ethernet and USB cables from the printer, if they are connected. Unscrew and remove the Wi-Fi antenna.

Step 7: 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. If the printer was recently in use, the rear heater assembly will be warm. wait at least two hours for the heater to cool.

Overview: Remove the rear shell of the printer.

Step 1: Remove the Wi-Fi antenna nut

Unscrew and remove the nut from the base of the Wi-Fi connector. The Wi-Fi connector is attached to the printer’s motherboard and remains in place when the rear shell is removed.

Overview: Unscrew, unplug, and uninstall the rear heater assembly.

Step 1: Locate the rear heater assembly

Locate the rear heater assembly, positioned on the left side of the printer when looking at the machine from the back. The heater can be identified by its fan and shroud.

Step 2: Disconnect the thermistor and fan cables

Unlatch the cable management clip located to the left of the heater assembly by pressing down on the tab while pulling the ring in the opposite direction. Remove the wires from the clip.

Unplug the 2-pin cable for the thermistor (blue) and the 3-pin cable for the rear heater assembly fan (red, white, and black). When disconnecting the cables, grip the connectors and separate them from one another. Do not pull on the wires themselves.

Overview: Mount and secure the new rear heater assembly.

Step 1: Reconnect the rear heater assembly wires

Attach the crimped connectors to the posts of the replacement rear heater assembly. Ensure that the red wire is attached to the middle post of the replacement rear heater assembly.

Step 2: Mount and secure the replacement heater assembly

Tuck the blue thermistor wires into the groove of the rear heater assembly shroud to avoid pinching them against the printer frame. Position the replacement rear heater assembly on its mounting surface, aligning the four screw holes in the shroud with the four screw holes in the printer frame. Thread each of the four screws into the screw holes. Tighten the screws using the included 2 mm hex driver until finger tight. When installed correctly, the rear heater assembly shroud sits flush against and slopes down away from the printer frame.

Step 3: Reconnect the thermistor and fan cables

Reconnect the thermistor cable and fan cable. The connectors will only plug into each other properly in the correct orientation. Be careful not to bend the pins in the connectors. Insert the wires back into the cable management clip, and push down on the loop to engage the latch.

Overview: After performing any other maintenance procedures, reinstall and secure the rear shell.

Overview: After reinstalling the rear shell, 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. The printer will initialize.

Step 2: Test the repair

Start a print to test the replacement rear heater assembly. Monitor the printer to ensure it preheats the resin properly. Contact Formlabs Support or your authorized reseller to share the results of the procedure.