AutoHome vs ABL Z axis Height

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?

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Originally Posted by 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?

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

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.

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.

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