Re: Bedlevelling (all types) is always slightly off.

Hi Roxy,

Ok so following that guide :

1) The printer should be able to successfully print a small object at the center of the bed with no bed leveling system active.



Interesting to note, from the skirt you can see the bed tilts upwards towards the right.

2) Bed levelling, did the following, manually entered one by one :

M502          ; Reset settings to configuration defaults...
M500          ; ...and Save to EEPROM. Use this on a new install.
M501          ; Read back in the saved EEPROM.  

M190 S60      ; Not required, but having the printer at temperature helps accuracy
M104 S150     ; Not required, but having the printer at temperature helps accuracy

G28           ; Home XYZ.
G29 P1        ; Do automated probing of the bed.

G29 T         ; View the Z compensation values.
G29 S1        ; Save UBL mesh points to EEPROM.
G29 A         ; Activate the UBL System.
M500          ; Save current setup. WARNING: UBL will be active at power up, before any `G28`.

G26 B60 C H200 T3.0

This is the G26 print :



Here the tilt seems to go the other way, so that the "virtual" bed is effectively higher on the left (well front left).

It almost feels like the levelling code is over-compensating?

This is the output from the `G29 T` stage :

Recv: Bed Topography Report:
Recv: 
Recv: (0,9)                                                                   (9,9)
Recv: (10,185)                                                                (180,185)
Recv:      .          .          .          .          .          .          .          .          .          .
Recv: 
Recv:      .          .          .          .          .          .          .          .          .          .
Recv: 
Recv:  -1.190   -0.938   -0.675   -0.445  [-0.215]   0.057    0.242    0.432    0.607    0.802
Recv: 
Recv:  -1.160   -0.903   -0.648   -0.435   -0.185    0.070    0.307    0.465    0.687    0.822
Recv: 
Recv:  -1.098   -0.865   -0.628   -0.355   -0.098    0.115    0.307    0.487    0.667    0.865
Recv: 
Recv:  -1.050   -0.807   -0.563   -0.335   -0.098    0.122    0.332    0.538    0.717    0.903
Recv: 
Recv:  -1.025   -0.743   -0.533   -0.302   -0.098    0.142    0.367    0.558    0.742    0.945
Recv: 
Recv:  -0.995   -0.730   -0.508   -0.263   -0.033    0.190    0.380    0.592    0.760    0.952
Recv: 
Recv:  -0.970   -0.720   -0.498   -0.260   -0.070    0.153    0.397    0.570    0.770    0.992
Recv: 
Recv:  -0.893   -0.705   -0.480   -0.265   -0.033    0.190    0.395    0.595    0.820    0.957
Recv: (10,10)                                                                    (180,10)
Recv: (0,0)                                                                     (9,0)

Actually, just a thought, is it possible the levelling code is making assumptions about INVERT_X_DIR & INVERT_Y_DIR?

Mine is :

INVERT_X_DIR: false
INVERT_Y_DIR: false
INVERT_Z_DIR: true

I believe the "defaults" are :

INVERT_X_DIR: false
INVERT_Y_DIR: true
INVERT_Z_DIR: false