The mixer drive assembly consists of a belt, encoder wheel, encoder board, mixer drive motor, mixer base, belt clamp, and idler pulley. All these components work together to operate the mixer as it travels across the resin tank to mix resin and detect debris. Any damage to the mixer drive assembly’s components may prevent the printer from functioning properly.
Use this guide to replace the mixer drive assembly.
Required Supplies:
Formlabs:
Third-party:
Estimated time: 1.5 hours
Preparing the workspace
Overview: Prepare the Form 4 and workspace for replacing the mixer drive assembly.
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 non-abrasive wipes. Dampen the wipes 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 touchscreen assembly
Overview: Remove the touchscreen assembly from the printer to access the motor drive assembly.
To remove the touchscreen assembly, follow the instructions in the repair guide Replacing the Form 4 touchscreen assembly. Complete the steps in the section "Removing the touchscreen assembly."
Removing the mixer encoder board
Overview: After removing the touchscreen assembly, remove the mixer encoder board.
Note:
If only the mixer encoder board needs to be replaced, complete the instructions in the following sections:
Step 1: Locate the mixer encoder board
The mixer encoder board is located on the left side of the linear bearing. It sits above the mixer idler pulley and is connected to the motherboard by the mixer encoder board cable.
Step 2: Unplug the mixer encoder board cable
Hold the connector by its plastic housing and gently squeeze the plastic tab to release the cable. Take care to not pull on the wires.
Step 3: Remove the mixer encoder board
Using a 2.5 mm hex driver, remove the two screws that secure the mixer encoder board to the printer. Set the screws aside. Remove the mixer encoder board from the printer and set it aside for disposal with electronic waste.
Installing the mixer encoder board
Overview: After removing the mixer encoder board, install the replacement mixer encoder board.
Step 1: Insert the new mixer encoder board
Insert the replacement mixer encoder board into the printer. When properly installed, the mixer encoder board sits vertically with its screw holes aligned with those in the printer frame. Ensure that the light source and photo sensor on the encoder board sits over the encoder wheel.
Thread the mixer encoder board retention screws into their screw holes. Using a 2.5 mm hex driver, tighten the screws to secure the mixer encoder board to the printer. Tighten until snug.
Step 3: Connect the mixer encoder board cable
Insert the mixer encoder board cable into its connector on the mixer encoder board. The connector makes an audible and tactile click when secured.
Note:
If the mixer encoder board is the only component that needs to be replaced, proceed to the section Reinstalling the touchscreen assembly.
Removing the mixer drive motor
Overview: After replacing the mixer encoder board, remove the mixer motor.
Step 1: Loosen the belt tensioning bolt
Using a 7 mm open-end wrench or needle nose pliers, loosen the belt tensioning bolt. Do not fully remove the bolt.
Step 2: Remove the mixer drive motor
Using a 2.5 mm hex driver, remove the four screws and washers that secure the mixer drive motor to the printer. Set the screws aside. Unloop the motor from the belt and slide it out of its bracket.
Step 3: Disconnect the mixer drive motor cable
Grip the mixer drive motor cable by its plastic housing. Gently pull the connector to remove it from the mixer drive motor. Take care to not pull on the wires. Set the mixer drive motor aside for disposal with electronic waste.
Replacing the mixer base and belt
Overview: After removing the mixer drive motor, remove and replace the mixer base and mixer drive belt.
Using a 2.5 mm hex driver, remove the four screws and washers that secure the mixer base to the linear bearing. Set the screws aside.
Gently lift the mixer base off the linear bearing. Take care not to tangle the mixer belt during removal.
The belt clamp is secured to the mixer base by four retention screws. Using a 2 mm hex driver, remove the screws. Set the screws aside. Set the belt clamp and the mixer base aside for disposal.
Slip the mixer drive belt off of the idler pulley on the left side of the printer. Set the belt aside for disposal.
Step 5: Mount the replacement mixer base
Mount the mixer base onto the linear bearing so that the screw holes on the mixer base and the printer align.
Thread the four mixer base retention screws and washers into their screw holes on the mounted mixer base. Using a 2 mm hex driver, tighten the retention screws. Do not overtighten the screws.
With the teeth on the belt facing inward, align the belt between the belt clamp screw holes in the mixer base.
Place the new belt clamp over the belt teeth, aligning its screw holes with those in the mixer base. Ensure that the teeth on the belt protrude through the slots in the clamp. Thread one belt clamp retention screw into each of the four screw holes, then use a 2 mm hex driver to tighten until snug.
Replacing the mixer idler pulley and encoder wheel assembly
Overview: After removing the mixer drive motor, replace the mixer idler pulley and encoder wheel assembly.
The mixer idler and encoder wheel assembly are located on the left side of the printer above the plastic power supply shroud.
Step 2: Remove the mixer idler pulley and encoder wheel assembly
Using a 3 mm hex driver, remove the shoulder bolt that secures the mixer idler pulley and encoder wheel assembly to the printer. Set the mixer idler pulley and encoder wheel assembly aside for disposal.
Step 3: Mount the mixer idler pulley and encoder wheel assembly
Loop the mixer belt onto the mixer idler pulley and encoder wheel assembly. Mount the assembly and the belt on to the printer so that the screw hole on the printer and on the assembly align. Ensure that the light source and photo sensor on the encoder board sits over the encoder wheel.
Step 4: Secure the mixer idler pulley
Thread the shoulder bolt into its screw hole. Using a 3 mm hex driver, secure the shoulder bolt to the mixer idler pulley and encoder wheel assembly and printer. Tighten until snug.
Installing the mixer drive motor
Overview: After replacing the mixer idler pulley and mixer encoder wheel assembly, replace the mixer drive motor.
Insert the mixer drive motor cable into its connector on the replacement mixer drive motor. The connector makes an audible and tactile click when secured.
Raise the mixer drive motor into its mount so that the screw holes on the motor line up with the screw holes on the printer.
Thread the washers and the mixer drive motor retention screws into the screw holes. Using a 2.5 mm hex driver, loosely install the screws. Hold the motor in place during installation until secure.
Tensioning the mixer belt
Overview: After installing the mixer drive motor, tension the mixer belt.
Step 1: Position the belt
Move the mixer base to the left side of the printer. Slide the motor to the left and loop the belt around the motor pulley.
Step 2: Download an audio tuner app
Install an audio tuner smartphone app on a smartphone. Formlabs has tested and recommends:
Step 3: Measure the belt tension
Notice:
This step should be performed in a location free of HVAC fans, machines, and other background noise. This is important to ensure that the belt tension is set accurately. If the tuner does not settle on a frequency or the reported frequency does not change after modifying the belt tension, relocate to a quieter space.
Open the tuner app on the smartphone. Hold the bottom of the smartphone near the middle of the mixer belt without touching the belt. Pluck the belt with a finger and note the frequency measured by the tuner app. Repeat until you are able to measure consistent readings. Make a note of the readings for later use. If the tuner does not settle on a frequency, relocate to a quieter space.
A properly-tensioned mixer belt should produce a sound between 86–96 Hz when plucked.
Note:
Make sure that the belt does not come into contact with the smartphone during frequency measurement.
Use a 7 mm open-end wrench to turn the belt tensioning bolt. A clockwise rotation increases tension and a counterclockwise rotation decreases tension.
Repeat steps 3 and 4 until the tuner app reports a frequency of 86–96 Hertz. If the measured tension was higher than this range, loosen the bolt. If the measured tension was lower than this range, tighten the bolt.
Once the belt is properly tensioned, use a 2.5 mm hex driver to tighten the four mixer drive motor screws. Tighten until snug.
Reinstalling the touchscreen assembly
Overview: After replacing the mixer drive assembly, reinstall the touchscreen assembly onto the printer.
To reinstall the touchscreen assembly, follow the instructions in the repair guide Replacing the Form 4 touchscreen assembly. Complete the steps in the section "Installing the replacement touchscreen assembly."
Finalizing the repair
Overview: After installing the new mixer drive assembly, 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 will turn on and initialize.
Step 2: Test the repair
Insert a resin cartridge, resin tank, build platform, and mixer, then start a print. Check that the mixer moves properly and remains attached to the mixer base. Contact Formlabs Support or your authorized reseller to share the results of the procedure.
