A sensor unit is a device that can sense force signals and convert the force signals into usable output electrical signals according to certain rules. In order to detect the condition of the surface pressure of the heat bed, 3 ceramic force sensors are installed on the bottom of the heat bed.
There are 2 small circuit boards called the heatbed piezo interface boards that are installed inside the heatbed, heatbed sensor 1 and heatbed sensor 2 are connected to them.
When the following 3 conditions are met at the same time, or obvious physical damage on the sensor can be seen, you need a sensor replacement.
1. You got an error message “The sensitivity of heat bed force sensor 1/2/3 is too low. The electronic connection to the sensor may be broken.”
2. Also a check was done by following the HMS guide, but did not solve the issue.
3. The service team approved the replacement.
Please follow this guide steps carefully in order to perform the replacement. Make sure the machine is powered OFF before commencing any disassembly and assembly.
We choose the sensor 1 and the heatbed piezo interface board as an example to guide in this replacement, but the replacement for the other 2 sensors and the other heatbed piezo interface board are similar.
Power ON the printer, navigate to the movement menu on the LCD screen, and adjust the Z position of the heat bed to the middle. Once done, power OFF the printer and remove the top glass cover plate, and then move the toolhead to the excess chute.
The protective cover is fixed by 4 buckles. You can remove it by unlocking one side first and then the other.
Unscrew the 3 pretension nuts to unlock the heat bed from the metal bracket. Note that there is also a rubber ring on top of each nut.
Open the heat bed carefully, because of the cable inside, and remove the loose pretension springs. In order to continue the procedure, the heat bed needs to be temporarily supported. You can use a block to support the upper part of the heat bed (see picture below).
Now you can disconnect the 2 connecting cables from the heatbed piezo interface board, remove the 2 screws and remove the board.
Unscrew the 2 screws on the bottom, and remove the sensor with the holder.
Prepare the new sensor to be installed. Note that there are 2 limit posts to help ease the installation (see picture below). Lock in the 2 screws to secure the sensor.
Install the heatbed piezo interface board on the bracket, lock in the 2 screws, and connect the 2 cables.
Hold the upper part of the heat bed and remove the support block you just used. Install the pretension springs to the heat bed screws one after another. In general, you only need to install the front two springs, because the rear one will not fall off.
Now you can close the heat bed and mount them together. Gently press from the top of the heat bed, and confirm that all three stubs can pass through the holes on the sensor holder.
Place the rubber ring on the 3 pretension nuts and then screw them in evenly, a little at a time. DO NOT lock them yet. Continue to screw in the nuts evenly, until the studs are flush with the bottom of the nuts (see picture below).
Now you need to install the protective cover. Same as when removing it, install one side first, then the other side.
Connect the power cord and turn on the power.
Make sure the chamber is clear of any prints or extrusions on the bed. Then go to the settings menu on the LCD screen, select the Calibration tab, and press “Start Calibration”
If everything went according to plan, and no errors or warnings occur during the calibration, the replacement was successfully completed. Otherwise, check the connections and retry again. If any issues persist, please contact the service team for further assistance.