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ABL and G30

Posted by roko 
ABL and G30
May 21, 2019 08:35AM
I have a question about G30 and ABL.
I have a TEVO Tornado MKS Gen-L board Marlin 1.1.9, BL Touch clone.
When I autohome the probe seems to be moved to the center of the bed and the X-Y coordinates reflect the actual nozzle location. I understand that.
But when it does the homing for Z, It probes at the current location of the probe, and does not move to the displayed X-Y coordinates, In my case X190 Y170.
That seems wrong to me,
When I do a G29 the coordinates shown on the display are for the nozzle not the probe's actual location at the time.
Could someone point me to a line in my configuration I might have missed? Thanks.
Re: ABL and G30
May 28, 2019 09:53PM
To add to my question, If the probe offsets are X-20 Y-20 does a G29 record the value that is shown on the LCD with coordinate offsets factored in? For example if the displayed coordinates show X170 Y190 during the G29, the probe will be at X150 Y170, so will the Z value, lets say it is -0.05, be stored in EEPROM as X170 Y190 Z offset is #, or does it get stored as a corrected location with Z offset #?
Re: ABL and G30
May 29, 2019 12:08AM
G29 will use the position of the probe to store the correction value. So it will, for example, put the probe at 10,10 and use the value it measures there when the nozzle is at 10,10 when printing.
Having the probe in the center of the bed when homing Z is also the correct behavior.
The LCD will never show the probe location when probing - just the nozzle position. But it will take the probe offset into account when using the probed values to correct the Z axis.
Re: ABL and G30
May 29, 2019 06:40AM
Thank you, thats what I thought, for some reason I was thinking the probe shoud be moving to the nozzle position and then reading when a G30 is done. All is good.
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