Strange move of 0 Point for Z axis when using mesh



  • Hi,

    I have a strange effect with bed compensation

    I am using the IR probe (V2). To get the correct trigger height I used the method describred https://www.duet3d.com/wiki/Using_mesh_bed_compensation with a manually calibrated bed and got 2.07mm for the trigger height.

    So I setup config.g:

    [[language]]
    ; ## ALLGEMEINES
    M550 PYellow Monster	; Name des Printers
    M552 S1                 ; Verbindung mit WiFi aufbauen
    
    ; ## BEWEGUNG
    ; M569 P0
    M569 P1 S0			; X: Drive 1 vorwärts
    M569 P2 S1			; Y: Drive 2 rückwärts
    ;M569 P3
    ;M569 P4
    M569 P5 S1			; Z: Drive 5 rückwärts
    M569 P6 S1			; Z: Drive 6 rückwärts
    M584 X1 Y2 Z5:6 E0:3:4		; Stepper zuordnen
    M350 X16 Y16 Z16:16 E16:16:16 I1 	; 16x Mikrostepping
    M574 
    M906 X1200			; X-Achse: 1200mA
    M906 Y2000			; Y-Achse: 2000mA in Reihe
    M906 Z1500:1500			; Z-Achse: 1500mA je Motor
    M906 E1800:1800:1800		; Extruder: 1700mA je Motor
    M203 X12000 Y12000		; Geschwindigkeit der Achsen in mm/min
    M566 X600 Y600 Z30 E20		; Maximae Gewschwindigkeitsänderung
    M208 X300 Y300 Z300		; Maximale Achsenlage
    M208 X-11 Y-9 S1		; Definition 0 Position
    M92 X100 Y100 Z800 E100.5:100.5:100.5		; Kalibrierung der Achsen
    M572 D0 S0.13			; Bowden Kompensation
    M572 D1 S0.13			; Bowden Kompensation
    M572 D2 S0.13			; Bowden Kompensation
    G21				; Angaben in Millimeter
    G90                             ; Verwendung absoluter Koordinaten
    M83 				; Für Extruder relative Koordinaten
    
    ; ## Z-PROBE / HOME
    M671 X-8.9:38.9 Y150:150	; Achsenposition für Ausgleich 
    M558 P1				; Z Probe Type
    G31 P500 Y-39 Z2.07		; Triggerpunkt definieren
    
    ; ## TEMPERATUR
    M305 P0 R4700 T100000 B3950	; Bett Temperatur Messung
    M305 P1 R4700 T100000 B3950	; Hotend Temperatur Messung
    
    ; ## TOOLS
    M563 P0 D0 H1			; Tool 0: Extruder 1
    G10 P0 R0 S0 X0 Y0		; Tool 0: Offset und Temperaturen 0
    M563 P1 D1 H1			; Tool 1: Extruder 2
    G10 P1 R0 S0 X0 Y0		; Tool 1: Offset und Temperaturen 0
    M563 P2 D2 H1			; Tool 2: Extruder 3
    G10 P2 R0 S0 X0 Y0		; Tool 2: Offset und Temperaturen 0
    M563 P3 D0:1:2 H1		; Tool 3: MIXER
    G10 P2 R0 S0 X0 Y0		; Tool 3: Offset und Temperaturen 0
    M567 P3 E0.34:0.33:0.33		; Tool 3: Standardmixer
    
    ; ## LOAD OVERRIDES
    M501
    
    

    and bed.g

    [[language]]
    ; ## MESH BED LEVELLING
    M208 Y340			; Temporäre Erhöhung maximale Achsenlage
    M557 X20:280 Y20:280 S260	; 4 Punkt Messung zum Auto Bed Levelling
    G29 S0				; Auto Bed Leveling durchführen und aktivieren
    M208 Y300			; Temporäre Erhöhung maximale Achsenlage
    
    

    After running G32 the trigger height changes automatically to 3.57 mm even (glass) bed is levelled quite good. What is me surprising to: When the Level map is displayed all 4 Z-points are around -0.7 instead of 0. So - you have an idea where I made the error?

    Best regards
    Holger


  • administrators

    Do you have a config-override.g file containing a G31 command that is overriding the trigger height you set in config.g?



  • No - content of config-override.g is below - but shouldn't in that case not also the trigger position after homing different? That changes after G32

    Best regards
    Holger



  • In the meantime I fear that is related to the fact, that the sensor do not give reproducable results for my glass bed :(.

    What I have done to come to this conclusion: With help of a piece of paper I measured manually 9 points in a 200 x 200 mm square. Afterwards I defined the same square and the 3x3 matrix with M557. The result was frightening: Even for the point where homing was made before a height of 0.3 mm is measured and the other results do not really fit to my manual measured results.

    So - do you think I would get better results wit the new BL touch? I read something about an ultrasonic sensor but didn't see any sensor like this. Any other suggestions?

    Best regards
    Holger


  • administrators

    Is your glass bed backed by a black surface as the fitting instructions require?



  • No because there is written:

    works as-is if placed directly on a PCB bed heater or other surface that does not reflect strongly.

    and it ist directly placed on a PCB bed heater…



  • and is that PCB Heater perfectly plain or does it have any printing on it?



  • No - there is a printing on it, but I checked already whether there is a difference or not - it does not matter. The lack of accuracy is all over the area


  • administrators

    What colour is the PCB heater?



  • Bet it's red with white printing on it and shiny to boot?



  • It is red to brown with black printing


  • administrators

    Try putting black paper between the bed heater and the glass.



  • Not sure if my issues are same - but def similar … Ive LOST Z0 and cannot seem to get back to it with a BL Touch ...


 

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