AutoHome vs ABL Z axis Height

[ex-egll]

Hi, Using the beckdac / Marlin code, if I do an AutoHome and then move the Z axis to zero the nozzle is 4.1mm above the glass. If I then do an ABL and move the Z axis to zero the nozzle is exactly where it should be.

I am assuming (probably a mistake) that the configuration.h value Z_PROBE_OFFSET_FROM_EXTRUDER is used for both ABL and AutoHome? Is there another value that would affect AutoHome but not ABL that could cause this discrepancy?

[kd7eir]

Hi, Using the beckdac / Marlin code, if I do an AutoHome and then move the Z axis to zero the nozzle is 4.1mm above the glass. If I then do an ABL and move the Z axis to zero the nozzle is exactly where it should be.

I am assuming (probably a mistake) that the configuration.h value Z_PROBE_OFFSET_FROM_EXTRUDER is used for both ABL and AutoHome? Is there another value that would affect AutoHome but not ABL that could cause this discrepancy?

Follow the section here about calibrating the Z offset - http://clough42.com/instructions/marlin-firmware-setup/

[ex-egll]

Thanks kd7eir, I used that reference to set up the ABL, and it works very well. Where my problem arose was when I selected AutoHome from the menu. This gave the 4.1mm discrepancy I was talking about.

[kd7eir]

If I auto home from the menu my hotend ends up in free space as well, but when I start a print the Z offset in Marlin lowers it to the correct clearance from the bed.

[ex-egll]

Thanks, it seems I either have an incorrect or no value in the Z offset. It appears that this Z offset only applies to Auto Home and has no effect on ABL?

Could you give me a clue as to where I can input an offset value?

Thanks