Z Probe Offset and Mesh Leveling Confusion

Trixxter

Hi dc42,

im homing with IR Probe.

Exactly, I use thermopaper to drop the nozzle and set G92 Z0.
After that i repeat
G1 Z5
G30 S-1
at least five times - the average value i use to offset z. in G31.

This works fine ( on that local spot) until i use mesh leveling.

dc42

OK, so what happens when you try to use mesh bed compensation by sending G29 S0?

Trixxter

Then it runs the mesh probes - and shows and me my hightmap.
When i Home Z again and check the nozzle hight, it would dig into the bed by about 0.5mm@ Z0 after that.

Phaedrux

Try this before running the G29

; Clear current mesh compensation map and disable compensation.
;
M561			; Disable any current bed compensation
G29 S2			; Clear mesh bed compensation parameters
G28			; Home all
G29 S2			; Clear mesh bed compensation parameters
G29      ; run mesh compensation probe routine

dc42

@trixxter said in Z Probe Offset and Mesh Leveling Confusion:

Then it runs the mesh probes - and shows and me my hightmap.
When i Home Z again and check the nozzle hight, it would dig into the bed by about 0.5mm@ Z0 after that.

How does the height map look?

Trixxter

Ok i try to describe what i have just done with results. Thank you for helping me even with my bad english

Heated up everything
Homed all axis
G32 to see if my bed is still where it belogs

G32
Manual corrections required: 0.00 turn up (0.00mm) 0.01 turn down (0.00mm) 0.03 turn down (0.01mm) 0.01 turn down (0.00mm)

Put the nozzel down, probed with thermopaper
Ran my IR Makro:

Stopped at height 2.350 mm 21:52:11
Stopped at height 2.350 mm21:52:08
Stopped at height 2.345 mm21:52:05
Stopped at height 2.348 mm21:52:02
M98 P"0:/macros/Z -IR kalibrieren"
Stopped at height 2.345 mm

Put 2.348 as Z Offset ( G31 P500 X 28 Y 10 Z 2.348) in config.g

Restarted Checked the Z Offset again, fine.
M561 ; Disable any current bed compensation
G29 S2 ; Clear mesh bed compensation parameters
G28 ; Home all
G29 S2 ; Clear mesh bed compensation parameters
G29

as discribed above by Phaedrux Result:

36 points probed, mean error -0.024, deviation 0.014
Height map saved to file heightmap.csv

Homed Z again an try to test the offset. - nozzle would have digged (this time slighly) into the bed.
IR Makro:
Stopped at height 2.388 mm
Stopped at height 2.385 mm
Stopped at height 2.382 mm
Stopped at height 2.382 mm
M98 P"0:/macros/Z -IR kalibrieren"
Stopped at height 2.382 mm
M561
G29 S2
IR Makro:
Stopped at height 2.345 mm
Stopped at height 2.340 mm
Stopped at height 2.345 mm
Stopped at height 2.350 mm
M98 P"0:/macros/Z -IR kalibrieren"
Stopped at height 2.348 mm

After disabling the MBL Offset Offset it what it supposed to be again...
Is this the way it works?
What is a good reproducable way to level the bed for a good first layer hight?

Phaedrux

@trixxter I think your map looks pretty good. It's far flatter than mine!

Is there a specific problem that is happening?

Is the compensation being applied when you move the head around the bed? Do you see movement of the Z axis?

If you tell the printer to go to Z0 slowly does it end with the nozzle touching the bed? Or is it going too far? It looks like you are calibrating the trigger height correctly.

If you do a test print, does the first layer go as expected?

I use this set of macros to go through a bed leveling routine so that each time it's exactly the same. https://www.dropbox.com/sh/f0zp6hxrnt6yr1p/AAAuEKOsHR03w4ITug_ksFVCa?dl=0

First getting the probe trigger height and measuring it's offset. Then mechanically moving the nozzle to the 3 leveling screws and adjusting those with paper. And then running a mesh grid compensation.

Trixxter

With activated MBL the nose would dig into the bed.
As you can see in Pos. 8 there is about 0.05 added to the Z Value.

The first layer gets too thin and print fails.

After I deactivate MBL the Z values are lower again.

Trixxter

Still cant get it to work fne. I guess im completely missunderstanding this concept.
After MBL, where (X/Y) does the duet expect to be Z 0?

Phaedrux

Z0 should be the nozzle just touching the bed.

Did you get a chance to look at the macros I linked above? There must be something missing or just a little off somewhere.

Are you probing with a heater bed or cold? Are you measuring nozzle height hot or cold?