Heightmap issue.

Joel

After sorting some things out ( thanks for the help ) after reconfiguring my Voron 2.4, I am having height map issues. First problem was very big deviations which I knew were not real, slowed down the Z probe and that was solved. Now the deviation looks good ( not much ), but the map gets pushed down below the table.

What I usually do,

Turn on machine and home all axis.
bed level till below .01mm
rehome Z
check/set Z offset
mesh level

This is what I get. what could be causing this offset?
Thanks

Simone

@Joel hi i had the same problem some time ago you need to have a 'reference' offset from the tool to the bed

Simone

@Joel https://docs.duet3d.com/User_manual/Reference/Gcodes#g31-set-or-report-current-probe-status you need to use this command

Simone

@Simone
this is an example

M558 P5 C"^probe" H8 F1000 T2000 A2 S0.03 ; Z probe connected to Duet 2 E0 endstop input
M557 X30:180 Y30:180 S30 ; define mesh grid 215
G31 Z2.5 X-8 Y22 ; Z parameter trigger height

Joel

Hi,

So I do have this,

M558 P5 C"!^io4.in" H5 F120 T12000
G31 P500 X0 Y0 Z-.45
M557 X20:330 Y20:330 S77.5

The tool offset is actually very accurate. changes ever so slightly when I change nozzles. For now I'm not using mesh and just do a new Z offset if I change nozzles.

Phaedrux

We'd need to see your config.g and homing files to get an idea of where your offset is coming from.

How are you homing Z? How did you get G31 Z-0.45? That would mean the nozzle tip is half a mm below the bed surface when the probe triggers. Does that sound right?

Review this and see if you're setting Z0 correctly or not.

https://docs.duet3d.com/en/User_manual/Connecting_hardware/Z_probe_testing

oliof

@Phaedrux negative offset might be correct for TAP probe, but that's for @Joel to confirm.

Joel

Yes, it is a tap probe, I lower the nozzle until it just touches the bed, then lower until it triggers.

What's the tag that inserts a code block so it easier to read? I post some of the shorter ones now.

If something changes I run my Z offset macro which adds or subtracts a bit an gets placed in config-override.g

; Probed tool offsets
G10 P0 Z0.04

my z home macro is,

G91 ; relative positioning
G1 H2 Z10 F4000 ; lift Z relative to current position
G90 ; absolute positioning
G1 X175 Y175 F10000 ; go to first probe point
;G90 ; absolute positioning
;G1 X175 Y175 F4000 ; go to first bed probe point and home Z
G91 ; set relative move
G1 Z-999 H1 F500 ; quickly home Z
G1 z5 ; Lift z for final probe
G30 ; home Z by probing the bed
G90
G1 X5 Y5 F10000
G1 Z10 F2000

M501

my z offset macro is,

T0
M291 P"Press ""OK"" if you would you like to calibrate the Z-offset for this Tool Cartridge." R"Calibrate Z-Offset" S3
M291 P"Homing, please wait..." R"Calibrate Z-Offset" S1
M208 Z-2 S1 ; allow movement below Z0
G1 X175 Y175 Z8 F4000 ; move to center of bed
M558 P0
G30 S-2
M208 Z-.5 S1 ; allow slight - Z so zoffset can work
G1 Z10 ; drop build plate
G1 X10 Y10 F4000
M558 P1 C"!^io4.in" H5 F500 T10000 ; restore probe type
G31 P500 X0 Y0
M291 P"Z-offset calibration complete! " R"Calibrate Z-Offset" S1 T3
M500 ; save results
M501 ; load new data

Joel

@Phaedrux

I was cleaning up my config.g file and going through it. It brought a question to mind that when I changed something, the height map started working, but I'm not sure why.

In my config file, there is a line G31 P500 X0 Y0 Z-.45 . This setup the offsets for the probe

At the end of my config file there is a G10 X0 Y0 Z0 which I thought was another tool offset, how does it relate to G31? When I do my Z-offset macro, it adds a line to config-override that is a G10 P0 Z xxxx. I thought this was an adjustment to the offset in the G31 Z-.45 offset.

When I commented out the G10 X0 Y0 Z0 in my config.g the height map was still broken. When I changed it G10 X0 Y0 Z-.45 ( to match the G31 setting ), the heightmap started working.

What should I be doing here?

I still don't know how to do the insert gcode thing, so I will attach my config.g as a file

Config.g.txt

Thanks
Joel

Joel

I think I found my issue,

In my Z-offset routine, when I was restoring the probe type, I did not restore the Z trigger height.

Once I fixed the G31 command, the height map works as expected.