Autolevel with NPN NO Inductive sensor problems
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G92 is not necessary when using G30. It will use the configuration provided in M558 and G31 to set the Z height.
The trigger height in G31 Z tells the firmware how far away from the bed the nozzle is when the probe triggers. So when it triggers during G30, it knows it's that high above the bed, and therefore, Z0 is established. The X and Y portion of G31 tells the firmware where the probe is in relation to the nozzle. G29 also uses the information from M558 and G31.
Makes sense?
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@phaedrux Yes certainly.
Let me try this. I think i understand the problem now. So my homing hits the endstop and gets a zero value from there. So the z trigger height is not used. That is why depending on the z end stop distance we see different heights in the above pictures. So the 0.7 (my z trigger) reflected on the distance from the z end stop 0..
One more thing. When typing the z trigger in G31 should it be negative?
eg G31 P1000 X-55 Y0 Z0.7
OR
G31 P1000 X-55 Y0 Z-0.7 -
It should be the value you get from doing the G30 S-1 procedure you linked above.
It will only be a negative value in cases where the nozzle ends up pressing down into the surface of the bed, like when using a nozzle contact probe like a piezoelectric.
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@phaedrux I mean it is not really negative but is it written like that? Writing it as a positive in the G31 gave the blue mesh result above which is below the xy plane.
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@gpetropoulos No you shouldn't flip the sign on it. The probe triggers before the nozzle touches the bed, correct? No after? That would be a positive value.
I'm hoping that after we change your homing file to use G30, and re run G29, we will get a better result.
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@phaedrux Certainly that solves the mesh problem at least. This looks much more consistent.
I used a negative value on G31. I am pretty sure that is it. I will run a test print and see for sure now.
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Using a negative value for G31 isn't consistent with how it should be working.
https://duet3d.dozuki.com/Wiki/GCode#Section_G31_Set_or_Report_Current_Probe_statusUse this to get the value.
https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height -
Updating my new Homeall using the z probe as z endstop.
; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool v2 on Thu Dec 13 2018 23:04:14 GMT+0200 (Eastern European Standard Time)
G91 ; relative positioning
G1 Z5 F6000 S2 ; lift Z relative to current position
G1 S1 X-235 Y-220 F6000 ; move quickly to X and Y axis endstops and stop there (first pass)
G1 X5 Y5 F6000 ; go back a few mm
G1 S1 X-235 Y-220 F360 ; move slowly to X and Y axis endstops once more (second pass)
G90 ; absolute positioning
G1 X160 Y100 F6000 ; move probe to bed center
G30 F1000 ; probe the bed
G1 X0 Y0 Z2 F6000 ; return to home position and 2mm higher than the surface; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 S2 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning -
@phaedrux Not clear to me yet. I will try with positive then first and report back.
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@gpetropoulos Yes that looks good, except that G30 won't take an F parameter. It will use the F value given in M558 in config.g. I suggested a value of 100 earlier.
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@phaedrux Yeah probably. I tried the 100 and was too slow.
I have F1000 in my M558 and probably that is being used. I started the test print and seems to be working like a charm. 
Thank you very much. I would not manage to get it done this fast without your help. Cheers!
Wish you the best and a Happy New Year mate.So for anyone confused set positive value for trigger height in G31 command!!
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Glad it's working properly now. I think the issue was a result of Z0 being set differently than what the G31 trigger height would have given, and the difference was resulting in the huge offset from the Z plane in the heightmap.
