BLTouch calibrated, nozzle still dives into the bed I am having a few problems with my BLTouch. I have calibrated it several times using different methods and get the nozzle being 1.3&nbsp;mm lower than the BLTouch pin so a Z offset of -1.3&nbsp;mm. This works fine for auto homing, bed levelling and using code G1 Z0 to lower to where needed. However when using Cura to print the nozzle homes exactly as it should then drives the nozzle in to the bed as it starts or tries to start to print and not just a little bit either. Anyone have any ideas?

Start G-code is:


G28 ;Home
G29 ;Probe
G1 Z15.0 F6000 ;Move Platform down 15 mm
G92 E0
G1 F200 E3
G92 E0
This answer is intended to be a generic answer for Z-offset determination. The question is not clear on how the Z-offset has been determined. It appears as if this distance is measured, while in reality this cannot be measured.

A touch (or a inductive or capacitive) probe uses a trigger point to determine the distance of the probe trigger point to the bed print surface. Correct installation is trivial, as is the determination of the nozzle to trigger point definition. For a touch sensor, the probing element is either stowed, fully deployed, or pushed in during leveling up to the point that the trigger point is reached and the probe stowes the rest of the pin, see figure:



The M851 Zxx.xx offset is determined by lowering the nozzle beyond the  trigger point until the nozzle hits a paper sheet. If the stowed position to nozzle distance is used, the distance is too large and the nozzle will dive into the bed on printing.