The Light Processing Unit (LPU) contains the printer’s laser diode, galvanometer, and other mirrors and lenses that aim the laser along its path for each layer of a print. The LPU sits within the LPU housing, which travels left and right underneath the resin tank. A malfunctioning LPU will prevent the printer from printing properly.

Use this guide to replace the Form 3 Light Processing Unit.

所要時間（目安）： 20～30分

Overview: Prepare the Form 3 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 LPU or into the printer cavity.

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

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.

ステップ4：作業スペースを準備する

プリンターの周囲に作業スペースを確保します。作業スペースはよく換気された埃のない場所に確保してください。

ステップ5：プリンターのキャビティをクリーニングする

プリンターのカバーを開きます。プリンター庫内の底面や壁面等にレジンが付着している場合、ペーパータオルですべて拭き取ってください。レジンがこびり付いている場合は、必要に応じてイソプロピルアルコール（IPA）で湿らせたペーパータオルでこびり付いたレジンを溶かしながら拭き取ってください。

ステップ7：プリンターの電源を切る

タッチスクリーンに表示されたら、メンテナンスを続行する前に電源ケーブルを抜きます。プリンターの電源ケーブルを電源に接続したままで作業を実施しないでください。プリンタの電源ケーブルをコンセントに差し込んだまま、LPUを交換すると、プリンタが故障し、修理不能になります。

ステップ8：LPUハウジングをクリーニングする

LPUハウジングの周辺やプリンターに付着しているレジンをペーパータオルで拭き取ります。レジンがこびり付いている場合は、必要に応じてイソプロピルアルコール（IPA）で湿らせたペーパータオルでこびり付いたレジンを溶かしながら拭き取ってください。

Overview: After moving the LPU housing into its maintenance position, remove and unplug the LPU.

Step 1: Cover the laser window

The roller holder, located on top of the LPU housing, has a clear window in the middle through which the laser passes. Cover the window with a lint-free cover, such as a PEC*PAD, to protect it during maintenance.

Step 2: Loosen the LPU housing screws

Use the provided 3 mm hex driver to fully loosen the three hex screws in the LPU housing. The screws are located towards the rear of the left side of the LPU housing. Loosen the screws until they disengage from the LPU.

Step 3: Remove the LPU from the LPU housing

Unseat the LPU from the LPU housing by pressing on the thumb screw while pulling on the plastic cover on the right side of the LPU. Do not pull on the LPU’s circuit board.

Once the LPU begins to move, loosen and remove the thumb screw. Continue to pull on the plastic guard until the LPU is fully free and rests to the right of the LPU housing.

Step 4: Disconnect the ribbon cable

Tilt the LPU forwards, towards the front of the printer. A black ribbon cable will be visible, attached to the rear of the LPU.

There is a small tab at the base of the ribbon cable plug. Press it toward the left side of the printer (i.e., toward the cable), and gently pull on the plug to disconnect the ribbon cable from the LPU. You may find it easier to use a small plastic tool, such as a pair of tweezers, to press on the tab.

Step 5: Disconnect the front cables

Tilt the LPU backwards, towards the rear of the printer. Three cables will be visible, connected to the front of the LPU. Disconnect each of the three cables by gripping its plug and gently pulling it away from the LPU.

Step 6: Remove the LPU

Remove the LPU from the printer and place it aside. If the LPU has resin on it or in it, place the LPU on a paper towel away from the printer to avoid contaminating other surfaces.

Overview: If the LPU ribbon cable has been damaged before or while replacing the LPU, remove and replace the ribbon cable.

Step 1: Disconnect the ribbon cable from the printer

Using the provided 2 mm hex driver, unscrew and remove the two 2 mm screws holding the LPU ribbon cable retention clip to the printer frame.

There is a small tab at the base of the ribbon cable plug. Press it toward the left side of the printer (i.e., toward the cable), and gently pull on the plug to disconnect the ribbon cable from the printer. You may find it easier to use a small plastic tool, such as a pair of tweezers, to press on the tab.

Remove the retention clip from the ribbon cable and set it aside.

Step 4: Thread the ribbon cable through the LPU housing

Thread the free end of the ribbon cable to the left, behind the LPU housing. Then, thread it back into the LPU housing through the small rectangular hole in the left side of the LPU housing.

Step 5: Secure the ribbon cable

Insert the two 2 mm hex screws into the ribbon cable retention clip and thread them into the printer frame. Using the provided 2 mm hex driver, tighten both screws until snug.

Overview: After removing the old LPU, connect and install the replacement LPU.

Step 1: Clean the LPU housing

If there was resin on the old LPU, clean the inside of the LPU housing with paper towels before continuing. Dampen the paper towels with isopropyl alcohol if necessary to fully remove the resin.

Step 2: Prepare the LPU

Carefully remove the new LPU from its packaging. Do not remove the cover from the module at this time. Insert the LPU into the printer in the same orientation as the old module.

Step 3: Reconnect the front cables

Tilt the LPU backwards, towards the rear of the printer. Reconnect the three cables to the front of the LPU, ensuring that each is fully seated. Each plug is sized so that it will only fit into the appropriate connector.

Hand tighten the three hex screws to ensure that they thread into the LPU properly. Finish tightening the hex screws using the provided hex driver until they are finger tight. Do not overtighten the screws.

Once you have tightened the hex screws, check and re-tighten the thumb screw if necessary.

Overview: After installing the new 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. The printer will initialize. The LPU will move back to its home position and perform a calibration.

Step 2: 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.