[BUG] (UBL 3-point mesh leveling 'broken')

[titanrw]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

G29 J seems to 'mess up' an already correct ubl grid.

This is on an ender 5 plus running mainboard 'BTT_SKR_MINI_E3_V2_0'

I was previously on 2.0.9.2, and everything worked correctly.

I upgraded to 2.1.1, and rebuilt the UBL grid, as I had to initialize eeprom. Saved grid to eeprom and verified it survives power cycles. This is the initial grid:

Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | -0.16  -0.05  +0.01 [-0.01] -0.09  -0.20  -0.25
Recv:    |
Recv:  5 | -0.27  -0.20  -0.17  -0.17  -0.19  -0.24  -0.22
Recv:    |
Recv:  4 | -0.26  -0.20  -0.22  -0.20  -0.20  -0.19  -0.13
Recv:    |
Recv:  3 | -0.27  -0.26  -0.22  -0.24  -0.17  -0.22  -0.01
Recv:    |
Recv:  2 | -0.26  -0.22  -0.30  -0.27  -0.21  -0.23  -0.03
Recv:    |
Recv:  1 | -0.26  -0.25  -0.30  -0.34  -0.29  -0.28  -0.06
Recv:    |
Recv:  0 | -0.27  -0.27  -0.30  -0.33  -0.30  -0.26  -0.07
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)

Max spread about 0.3mm. Decently good for a 350x350 bed I think?

My normal start g-code is:

G28 
G29 L1
G29 A
G29 J

I was doing the G29 J tilting correction, as the 5 plus has independent z-screws that are not 'belted' together. I try to align them as close as possible every time I power on the printer, but just in case they aren't exactly the same, I was using the mesh tilting to compensate.

However with 2.1.1 this is the mesh after the G29 J:

Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.85  +0.72  +0.55  +0.29  -0.02  -0.37  -0.65
Recv:    |
Recv:  5 | +0.63  +0.47  +0.26  +0.03  -0.23  -0.51  -0.73
Recv:    |
Recv:  4 | +0.54  +0.36  +0.11  -0.11  -0.34  -0.57  -0.74
Recv:    |
Recv:  3 | +0.42  +0.20  +0.00  -0.25  -0.42  -0.70  -0.73
Recv:    |
Recv:  2 | +0.33  +0.13 [-0.18] -0.39  -0.56  -0.82  -0.85
Recv:    |
Recv:  1 | +0.22  -0.00  -0.29  -0.56  -0.75  -0.97  -0.99
Recv:    |
Recv:  0 | +0.10  -0.13  -0.39  -0.66  -0.86  -1.06  -1.10
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)

This now has a spread of about 2mm. The z-screws are definitely not that far off. Not realizing this messed up the mesh, I damaged the build surface as the printer applied a -1mm offset when it was originally measured as almost 0.

As a work around for now, I've commented out the G29 J tilting, and it's printing ok with UBL on. When I get a chance, I'll try -bugfix. I also might just run 2.0-lts.

Bug Timeline

2.0.9.2 didn't exhibit the issue.

Expected behavior

UBL mesh correctly modified for slight z-screw tilt.

Actual behavior

UBL mesh multiplied almost 10-fold.

Steps to Reproduce

Run 'G29 J' after UBL mesh populated and active.

Version of Marlin Firmware

2.1.1

Printer model

Ender 5 plus

Electronics

Stock other than BTT SKR Mini E3 2.0

Add-ons

No response

Bed Leveling

UBL Bilinear mesh

Your Slicer

Cura

Host Software

OctoPrint

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

Configs, and bed visualizer images below:

2.1.1-configs.zip
Before G29 J:

After G29 J:

[Roxy-3D]

It would be helpful to know the values of the points it probed. It kind of looks like one of those points was way off and as a result it took a 'correct' mesh and tilted it funny to fit the points that were probed.

[titanrw]

Sorry for my ignorance, are these tilting point values returned during probing, or do you have to query for them with G-code?

I can check later today.

I did get 2.1-bugfix compiled, but haven't had a chance to flash and test. If it needs an eeprom init, rebuilding the grid takes a while. Is there no way to 'save' the grid and restore via the console?

[titanrw]

Did some more testing.

Figured out G29 J V4 to get the probed data.

Here's the console output:

Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | -0.16  -0.05  +0.01  -0.01  -0.09  -0.20  -0.25
Recv:    |
Recv:  5 | -0.27  -0.20  -0.17  -0.17  -0.19  -0.24  -0.22
Recv:    |
Recv:  4 | -0.26  -0.20  -0.22  -0.20  -0.20  -0.19  -0.13
Recv:    |
Recv:  3 | -0.27  -0.26  -0.22 [-0.24] -0.17  -0.22  -0.01
Recv:    |
Recv:  2 | -0.26  -0.22  -0.30  -0.27  -0.21  -0.23  -0.03
Recv:    |
Recv:  1 | -0.26  -0.25  -0.30  -0.34  -0.29  -0.28  -0.06
Recv:    |
Recv:  0 | -0.27  -0.27  -0.30  -0.33  -0.30  -0.26  -0.07
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3

Send: G29 J V4
Recv: Tilting mesh (1/3)
Recv: Bed X: 50.00 Y: 50.00 Z: 0.01
Recv:                 Corrected_Z=0.26
Recv: Tilting mesh (2/3)
Recv: Bed X: 310.00 Y: 50.00 Z: 0.01
Recv:                 Corrected_Z=-0.64
Recv: Tilting mesh (3/3)
Recv: Bed X: 180.00 Y: 310.00 Z: 0.10
Recv:                 Corrected_Z=0.24
Recv: bed plane normal = [0.0034720,-0.0016478,0.9999926]
Recv: X:225.00 Y:317.00 Z:11.97 E:0.00 Count X:18000 Y:25360 Z:9576
Recv: ok P15 B3

Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.79  +0.69  +0.55  +0.31  +0.03  -0.30  -0.56
Recv:    |
Recv:  5 | +0.58  +0.44  +0.26 [+0.05] -0.18  -0.44  -0.63
Recv:    |
Recv:  4 | +0.49  +0.34  +0.11  -0.08  -0.29  -0.49  -0.64
Recv:    |
Recv:  3 | +0.38  +0.18  +0.01  -0.22  -0.36  -0.62  -0.63
Recv:    |
Recv:  2 | +0.29  +0.12  -0.17  -0.35  -0.50  -0.73  -0.74
Recv:    |
Recv:  1 | +0.19  -0.01  -0.27  -0.52  -0.68  -0.88  -0.88
Recv:    |
Recv:  0 | +0.08  -0.13  -0.37  -0.61  -0.79  -0.96  -0.98
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3

It's detecting +0.26 compared to -0.64.

I tried running G29 J again immediately after this:

Send: G29 J V4
Recv: Tilting mesh (1/3)
Recv: Bed X: 50.00 Y: 50.00 Z: 0.01
Recv:                 Corrected_Z=0.01
Recv: Tilting mesh (2/3)
Recv: Bed X: 310.00 Y: 50.00 Z: 0.01
Recv:                 Corrected_Z=0.89
Recv: Tilting mesh (3/3)
Recv: Bed X: 180.00 Y: 310.00 Z: 0.11
Recv:                 Corrected_Z=0.01
Recv: bed plane normal = [-0.0033987,0.0016721,0.9999928]
Recv: X:225.00 Y:317.00 Z:11.97 E:0.00 Count X:18000 Y:25360 Z:9576
Recv: ok P15 B3
Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.11  +0.21  +0.27  +0.24  +0.16  +0.05  -0.01
Recv:    |
Recv:  5 | -0.00  +0.06  +0.08 [+0.09] +0.06  +0.01  +0.02
Recv:    |
Recv:  4 | +0.01  +0.07  +0.04  +0.06  +0.05  +0.05  +0.11
Recv:    |
Recv:  3 | +0.00  +0.01  +0.04  +0.02  +0.08  +0.03  +0.23
Recv:    |
Recv:  2 | +0.01  +0.05  -0.04  -0.01  +0.05  +0.02  +0.22
Recv:    |
Recv:  1 | +0.01  +0.02  -0.03  -0.08  -0.03  -0.02  +0.18
Recv:    |
Recv:  0 | +0.01  +0.00  -0.03  -0.07  -0.04  -0.01  +0.18
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3

+0.01 to +0.89. Almost exactly the same absolute difference as the first time.

However the mesh is 'normal'. It's the same reletive 'shape', just offset up a little.

At this point I downloaded, configured, and compiled 2.0.9.5. Exactly the same thing as above.

I then went back to 2.0.9.2 (that was previously ok) and got this:

Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | -0.160  -0.050  +0.015  -0.015  -0.085  -0.200  -0.250
Recv:    |
Recv:  5 | -0.270  -0.200  -0.175  -0.170  -0.190  -0.240  -0.220
Recv:    |
Recv:  4 | -0.260  -0.200  -0.220  -0.200  -0.200  -0.195  -0.130
Recv:    |
Recv:  3 | -0.270  -0.260  -0.220 [-0.240] -0.170  -0.220  -0.015
Recv:    |
Recv:  2 | -0.260  -0.220  -0.300  -0.270  -0.210  -0.230  -0.030
Recv:    |
Recv:  1 | -0.260  -0.250  -0.300  -0.340  -0.290  -0.275  -0.065
Recv:    |
Recv:  0 | -0.270  -0.270  -0.300  -0.330  -0.300  -0.260  -0.070
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Send: G29 J V4
Recv: Tilting mesh (1/3)
Recv: Bed X: 50.00 Y: 50.00 Z: -0.05
Recv:                 Corrected_Z=0.20
Recv: Tilting mesh (2/3)
Recv: Bed X: 310.00 Y: 50.00 Z: -0.17
Recv:                 Corrected_Z=0.07
Recv: Tilting mesh (3/3)
Recv: Bed X: 180.00 Y: 310.00 Z: 0.09
Recv:                 Corrected_Z=0.23
Recv: bed plane normal = [0.0005274,-0.0003733,0.9999998]
Recv: X:225.00 Y:317.00 Z:12.10 E:0.00 Count X:18000 Y:25360 Z:9680
Recv: ok P15 B3
Send: M113 S2
Recv: ok P15 B3
Send: M155 S30
Recv: ok P15 B3
Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.184  +0.262  +0.296  +0.234  +0.133  -0.014  -0.095
Recv:    |
Recv:  5 | +0.051  +0.090  +0.084 [+0.057] +0.006  -0.076  -0.087
Recv:    |
Recv:  4 | +0.039  +0.068  +0.016  +0.005  -0.027  -0.053  -0.020
Recv:    |
Recv:  3 | +0.007  -0.015  -0.006  -0.057  -0.019  -0.100  +0.073
Recv:    |
Recv:  2 | -0.005  +0.003  -0.108  -0.110  -0.081  -0.133  +0.036
Recv:    |
Recv:  1 | -0.028  -0.049  -0.131  -0.202  -0.184  -0.200  -0.021
Recv:    |
Recv:  0 | -0.060  -0.091  -0.153  -0.214  -0.216  -0.207  -0.049
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)

This time, Z was detected as +0.20 to + 0.07. A 0.13mm difference is more what I would have expected.

The resulting mesh is the 'same', just offset up a bit.

I'm just going to stick with 2.0.9.2 for now.

[aero4]

I also have problems with UBL coming from 2.0.9.2 to 2.1.1. And I think it's the same issue. I probed the bed muliple times and saved it to EEPROM. But when validating it with G26 (of course G29 J before) the mesh seems totally tilted! This happened on two different printers and that's why I looked into here.
I have to revert to 2.0.9.2 to use the printer...
So I am already looking forward to fix this issue.

[aero4]

Are there any updates concerning this bug? Is it already fixed in the bugfix branch?

[github-actions]

This issue has had no activity in the last 60 days. Please add a reply if you want to keep this issue active, otherwise it will be automatically closed within 10 days.

[aero4]

I tested version 2.1.2 and the issue didn't occur so far. So it seems to be fixed with Marlin 2.1.2 and respectively with the issue #24622.
So this issue can be closed from my point of view...

[titanrw]

I just tried 2.1.2, and it's having the same issue.

2.1.2 console output:

Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.08  +0.16  +0.20  +0.14  +0.05  -0.10  -0.17
Recv:    |
Recv:  5 | -0.04  +0.01  +0.00  -0.02  -0.07  -0.14  -0.15
Recv:    |
Recv:  4 | -0.03  +0.00  -0.05  -0.05  -0.08  -0.10  -0.07
Recv:    |
Recv:  3 | -0.05  -0.07  -0.05 [-0.10] -0.06  -0.14  +0.04
Recv:    |
Recv:  2 | -0.05  -0.03  -0.14  -0.14  -0.11  -0.15  +0.02
Recv:    |
Recv:  1 | -0.05  -0.07  -0.15  -0.22  -0.19  -0.21  -0.02
Recv:    |
Recv:  0 | -0.07  -0.10  -0.16  -0.21  -0.21  -0.20  -0.04
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3
Send: G29 J V4
Recv: Tilting mesh (1/3)
Recv: Bed X: 50.00 Y: 50.00 Z: -0.01
Recv:                 Corrected_Z=0.06
Recv: Tilting mesh (2/3)
Recv: Bed X: 310.00 Y: 50.00 Z: -0.11
Recv:                 Corrected_Z=-0.70
Recv: Tilting mesh (3/3)
Recv: Bed X: 180.00 Y: 310.00 Z: 0.06
Recv:                 Corrected_Z=0.04
Recv: bed plane normal = [0.0029235,-0.0013995,0.9999948]
Recv: X:225.00 Y:317.00 Z:12.10 E:0.00 Count X:18000 Y:25360 Z:9680
Recv: ok P15 B3
Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.72  +0.63  +0.49  +0.26  -0.02  -0.33  -0.58
Recv:    |
Recv:  5 | +0.52  +0.39  +0.21 [+0.01] -0.21  -0.46  -0.64
Recv:    |
Recv:  4 | +0.44  +0.29  +0.07  -0.11  -0.31  -0.51  -0.64
Recv:    |
Recv:  3 | +0.34  +0.14  -0.02  -0.24  -0.37  -0.62  -0.62
Recv:    |
Recv:  2 | +0.26  +0.09  -0.19  -0.36  -0.50  -0.72  -0.73
Recv:    |
Recv:  1 | +0.17  -0.03  -0.28  -0.52  -0.67  -0.86  -0.85
Recv:    |
Recv:  0 | +0.06  -0.14  -0.37  -0.60  -0.77  -0.93  -0.95
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3

Reflashed 2.0.9.2 without changing anything hardware wise on the printer.

2.0.9.2 output:

(Didn't get the pre-tilt mesh, but it was basically the same. Corrected Z values are way less with simply a firmware flash.)

Send: G29 J V4
Recv: Tilting mesh (1/3)
Recv: Bed X: 50.00 Y: 50.00 Z: 0.01
Recv:                 Corrected_Z=0.08
Recv: Tilting mesh (2/3)
Recv: Bed X: 310.00 Y: 50.00 Z: -0.08
Recv:                 Corrected_Z=0.09
Recv: Tilting mesh (3/3)
Recv: Bed X: 180.00 Y: 310.00 Z: 0.03
Recv:                 Corrected_Z=0.02
Recv: bed plane normal = [-0.0000519,0.0002481,1.0000000]
Recv: X:225.00 Y:317.00 Z:11.93 E:0.00 Count X:18000 Y:25360 Z:9544
Recv: ok P15 B3
Send: G29 T
Recv: 
Recv: Bed Topography Report:
Recv: 
Recv:     (  1,359)                                      (359,359)
Recv:         0       1       2       3       4       5       6
Recv:  6 | +0.080  +0.166  +0.207  +0.152  +0.058  -0.082  -0.156
Recv:    |
Recv:  5 | -0.022  +0.024  +0.024 [+0.005] -0.039  -0.114  -0.118
Recv:    |
Recv:  4 | -0.004  +0.032  -0.013  -0.017  -0.042  -0.061  -0.020
Recv:    |
Recv:  3 | -0.006  -0.021  -0.005  -0.049  -0.004  -0.078  +0.102
Recv:    |
Recv:  2 | +0.012  +0.027  -0.077  -0.072  -0.036  -0.080  +0.095
Recv:    |
Recv:  1 | +0.019  +0.005  -0.069  -0.134  -0.108  -0.118  +0.068
Recv:    |
Recv:  0 | +0.017  -0.007  -0.062  -0.116  -0.110  -0.095  +0.071
Recv:         0       1       2       3       4       5       6
Recv:     (  1,  1)                                      (359,  1)
Recv: 
Recv: ok P15 B3

Since it's only me having the problem now, it must be something in my configs.

Aero4, which printer do you have 2.1.2 running on? Can you post your config?

[aero4]

To be honest I didn't probe the bed twice and compared the values, I just probed once and there were no issues while printing... If you want I can run the same code as you did for testing.

I am running Marlin 2.1.2 on a custom printer based on the Velleman K8200 with a "3DTouch" probe. I always track the differences I modify in the config files which are the following:

[titanrw]

Hello.

Thanks for the config difference from default.

What do you mean when you say you don't probe the bed twice? I do use "#define MULTIPLE_PROBING 2" and it looks like you don't.

The other main difference I see is that I use "#define ENABLE_LEVELING_AFTER_G28" whereas you use "#define RESTORE_LEVELING_AFTER_G28". I don't fully understand one vs the other. I've got a 7x7 grid and you use 6x6, but my bed is 350mm compared to 200.

What does your start gcode look like?

[aero4]

Sorry for the late reply,

you're welcome.

I only probed the bed once and used these values for the bed grid and didn't repeat that.
No I don't use the MULTIPLE_PROBING setting ...

To be honest I also don't fully understand every single setting I used. I took most of the probing settings from tutorials and they were proved to be working so far.

This is my starting GCode:

M117 Preparing...

M107 ; switch part fan off

M42 P6 S255 ; switch fans on
M777 P8 S1 ; switch light on

G91 ; set relative coordinates
G0 E-10 F900 ; retract 10mm with 900mm/min
G90 ; set absolute coordinates

M117 Homing...
G29 L1 ; load bed mesh from slot 1
G28 ; home all axes
M117 Auto leveling...
G29 J ; measure postion with 3 points

M117 Preparing...

G0 X0 Y0 F4800 ; go to home position with 4800mm/min speed
G0 Z0 F1500; go to z home position

T0 ; select tool 0
G91 ; set relative coordinates
G0 E22 ; extrude 22mm with 900mm/min speed
G90 ; set absolute coordinates

M117 Printing...

[titanrw]

Can you run the following G code right after the printers been powered up and post the console output after it's ran?

It won't print anything, but does need to move the head around.

G28 ;home

G29 L1 ;load mesh

G29 A  ;activate mesh

G29 T  ;show mesh pre tilt

G29 J V4 ;tilt mesh showing probed Z values

G29 T  ;show mesh post tilt.

[aero4]

Sure, this is my console output when sending the commands you stated:

SENT: G28
READ: Active Extruder: 0
READ: Active Extruder: 0
READ: X:49.10 Y:95.00 Z:12.40 E:0.00 Count X:1577 Y:6104 Z:26453
SENT: G29 L1
READ: Mesh loaded from slot 1
READ: Done.
SENT: G29 A
READ: Unified Bed Leveling System v1.01 active
SENT: G29 T
READ: 
READ: Bed Topography Report:
READ: 
READ:     ( 10,185)                              (190,185)
READ:         0       1       2       3       4       5      
READ:  5 | -0.18  -0.16  -0.14  -0.09  -0.19  -0.41 
READ:    |
READ:  4 | +0.03  -0.01  -0.05  -0.09  -0.14  -0.37 
READ:    |
READ:  3 | +0.00  -0.02  -0.04  -0.06  -0.14  -0.34 
READ:    |
READ:  2 | -0.02  -0.04  -0.06 [-0.08] -0.17  -0.41 
READ:    |
READ:  1 | +0.16  +0.07  -0.02  -0.12  -0.27  -0.42 
READ:    |
READ:  0 | +0.11  +0.02  -0.07  -0.16  -0.30  -0.51 
READ:         0       1       2       3       4       5      
READ:     ( 10, 10)                              (190, 10)
READ: 
SENT: G29 J
READ: Tilting mesh (1/3)
READ: Tilting mesh (2/3)
READ: Tilting mesh (3/3)
READ: X:69.55 Y:183.00 Z:12.40 E:0.00 Count X:2234 Y:11758 Z:26453
SENT: G29 T
READ: 
READ: Bed Topography Report:
READ: 
READ:     ( 10,185)                              (190,185)
READ:         0       1       2       3       4       5      
READ:  5 | -0.22  -0.19  -0.15 [-0.09] -0.17  -0.38 
READ:    |
READ:  4 | -0.03  -0.05  -0.08  -0.10  -0.13  -0.34 
READ:    |
READ:  3 | -0.06  -0.06  -0.07  -0.07  -0.14  -0.32 
READ:    |
READ:  2 | -0.09  -0.09  -0.09  -0.09  -0.17  -0.39 
READ:    |
READ:  1 | +0.09  +0.02  -0.06  -0.14  -0.28  -0.41 
READ:    |
READ:  0 | +0.04  -0.04  -0.11  -0.18  -0.31  -0.50 
READ:         0       1       2       3       4       5      
READ:     ( 10, 10)                              (190, 10)

It looks quite right I guess?