Loadcell Not Calibrated #31523 (CORE One) #26523 (MK4S) #13523 (MK4) #27523 (MK3.9S) #21523 (MK3.9)

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What happened?

The Prusa CORE One, and the Original Prusa MK4/S, MK3.9/S are equipped with a loadcell, which detects whether the nozzle is close enough to the steel sheet for printing and prevents damage from the nozzle digging into the steel sheet. 

During a selftest, the loadcell is tested. The loadcell can also be tested at any time through the printer menu. If the loadcell calibration is not done, or the printer does not recognize that it has been done, it will show the message: "Loadcell calibration is not finished. Finish the calibration first."

Error name: Loadcell Not Calibrated

Error code: #31523 (CORE One) #26523 (MK4S) #13523 (MK4) #27523 (MK3.9S) #21523 (MK3.9)

How to fix it? 

A visual inspection

Access the right side of the LoveBoard, where the loadcell cable is connected. To remove the side LoveBoard cover, on CORE One loosen two M3x6 bolts, on MK4/S and MK3.9/S loosen one M3x10 bolt. 

Once accessed, locate the loadcell connector and cable, and check for any loose cable, disconnected cable, or visible damage. 

Re-test the loadcell

Navigate to LCD Menu -> Control -> Calibrations & Tests -> Loadcell Test to initiate a loadcell test. 

During the test, you will be asked to tap the nozzle at a specific time, and a progress bar shown on the screen is filled, depending on the pressure applied to the loadcell. If the bar is not filled or is filled irregularly, please contact our customer support. 

Tapping of the nozzle can be done with a finger, as well as with a hard object. 

Loadcell white pad - visual check 

Ensure to have the PG-assembly-adapter before continuing with the following procedure. If you do not have it, you can print it using the below files, depending on the printer you will use: 
PG-assembly-adapter printed with MK4/S
PG-assembly-adapter printed with MK3/S/+

1. If any filament is loaded, unload the filament, then wait for the printer to fully cool down. After that, turn the printer off.
2. Remove the PG-case, together with the PG-ring, gearbox, and main plate. Remove all of these parts in one piece. 

3. The top part of the loadcell is now visible and has a white pad attached to it. Without touching the white pad, check it for damage. 

4. Reassemble the block of PG-case, PG-ring, gearbox, and main plate. In case the parts are not in one block, follow the dedicated steps from the Nextruder assembly manual, depending on your printer version. 
5. Perform the gearbox alignment.