BL Touch taking wrong measurements (Ender 3 V2)

[silverhammer]

Hi FolksI just installed my BL Touch in my Ender 3 V2 and just can’t figure out how to get it to work properly. The installation went fine. I connected the BL Touch to my V.4.2.7 board and made sure the wires are shielded and disconnected the Z-Stop-switch which is not needed anymore. I homed the printer on the Z Axis and set the Z Offset to -2.10 using a sheet of paper and feeling the resistance. I then disabled the stepper and moved the head to the 4 corners and manually adjusted them using the wheels under the print bead to achieve a similar amount of resistance. Then homed the Z-Axis again and set the new Z Offset to -2.25 to adjust for the corrections made. Back in the menu, I now create a new Mesh. The printer and BL Touch proceed just as I would expect. Get the home position, take 2 measurements at each point (3x3) and prompt me to save the mesh. Up to here everything seems normal. If I now make sure the box “levelling active” is checked and try to start a test print, the print doesn’t really work. The print head is too low. So low that it leaves marks on the print bead and the the molden PLA cannot leave the nozzle. I did a lot of troubleshooting and did write down my results – but I have no clue how to solve the problem. I hope you can help. I created 6 meshes back-to-back to verify that the BL Touch measures “correctly”. Please note, that all measurements have been performed with a cold nozzle and print bed (22° and 27°).The attached file shows where the measurepoints are on the printbed. Since I somehow cannot add a table in this thread, I attached a screenshot of the measurements below. Here are my findings: 1. The fact, that the 6 measurements where somewhat similar to each other (max difference =0.15 mm), tells me, that BL Touch is measuring reliably. 2. The fact that the corners and the home point (points nr. 1, 3, 5, 7, 9) all have a similar negative value, tells me, that the manually performed bed levelling was done quite well ????3. The fact that the value of the points 2 and 7, which are the points closest to the metal clamp holding the print bed in place are also closest to zero, tells me, that the print bed might be a bit warped. 4. The fact that the tesprint only prints properly where the measurements 2 and 7 have been taken (which are closest to zero), shows, that the measurements in the other spots somehow is not working properly.5. The fact, that point number 5, which is the home point which is used to adjust the Z Offsets is not the closest to zero, makes me think, something is wrong. 6. The fact that adjusting the Point Z Offset manually with a piece of paper takes me back to values around 0 and +0.25 shows, that something is going on here. Does anyone have an idea, why my BL Touch is taking measurements way lower than it should?I’m glad for any help!Kind regardsSilverhammer