Synchronizing offsets for Z probe, homing, mesh compensation

gnydick

Not sure how to most concisely ask this...

My homing and 4 lead-screw auto-leveling works great. My current bed has a dip in the middle because I just replaced glass with a layer of PEI, so I lost the rigidity of the glass. So now, I have to run mesh compensation in order to make up for the dip.

The mesh compensation seems to be following the surface of the bed just fine, but it's way too close to the bed, it's grinding into it.

My question is, if the Z-home works perfectly, why does the mesh comp at the same position drive the nozzle through the bed?

dc42

How are you homing Z: using an endstop switch, or using a Z probe? Please post your homez.g and homeall.g files.

Please post a screen shot of your height map.

Which firmware version are you using?

gnydick

@dc42

Using a Z probe.

0_1558546940733_eea9126b-0b98-47e8-89d1-4824d85ad161-image.png

homez.g

G1 X139 Y177.5
G91                ; relative positioning
G1 S1 Z-350 F1500  ; move quickly to Z axis endstop and stop there (first pass)
G1 Z2 F1500        ; go back a few mm
G1 S1 Z-3 F360      ; move slowly to Z axis endstop once more (second pass)
G1 Z2
G1 S1 Z-3 F60
G1 Z1
G1 S1 Z-2 F30
G1 Z.5
G1 S1 Z-1 F10
G1 Z10 F1500
G90
G92 Z12.07

homeall.g

M98 Phomex.g
M98 Phomey.g
M98 Phomez.g

0_1558546894499_88ac89c1-311d-49d1-b623-09b6a5e85409-image.png

dc42

Your homez.g file is nowhere near correct for homing using a Z probe. Please read https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z_using_a_Z_probe.

gnydick

@dc42 While unconventional, it works as it has the right offset added in, it functionally does the same thing. Does doing it this way actually cause things not to work properly?

dc42

@gnydick said in Synchronizing offsets for Z probe, homing, mesh compensation:

@dc42 While unconventional, it works as it has the right offset added in, it functionally does the same thing. Does doing it this way actually cause things not to work properly?

The problem is that you need to keep the G92 offset in our homez.g/homeall.g files and the Z probe trigger height in your G31 command in sync. Also you need to keep your Z homing speed and Z probing zspeed in sync to ensure consistent trigger height. So I advise against it.

gnydick

@dc42 ok. that's what I've been doing. But, I switched over to your suggestion.