# Marlin 1.1.9 mesh editing causes the nozzle to hit the bed and UBL is not correcting the leveling issues

ISSUE 1

The printer is having a physical bed size of 315 x 315 mm and there are 2 stepper motors that drive the extruder up and down. The 2 Z-steppers are synced and I already have a process to make sure they are re-synced every while and when requried.

I have Marlin 1.1.9 and I have an inductive sensor, and I managed to get to this result with G29 P1:

Recv:         0       1       2       3       4       5       6       7       8       9
Recv:  9 | +2.287  +2.817  +2.732  +2.668  +2.622  +2.417  +2.455  +2.257  +2.250  +2.195
Recv:    |
Recv:  8 | +2.242  +2.762  +2.695  +2.630  +2.575  +2.417  +2.455  +2.257  +2.250  +2.195
Recv:    |
Recv:  7 | +2.197  +2.707  +2.657  +2.592  +2.528  +2.425  +2.528  +2.305  +2.387  +2.267
Recv:    |
Recv:  6 | +2.120  +2.670  +2.592  +2.572  +2.512  +2.443  +2.492  +2.330  +2.342  +2.315
Recv:    |
Recv:  5 | +2.105  +2.660  +2.505  +2.562  +2.475  +2.405  +2.457  +2.298  +2.305  +2.260
Recv:    |
Recv:  4 | +2.210  +2.702  +2.542  +2.622  +2.517  +2.410  +2.540  +2.305  +2.298  +2.225
Recv:    |
Recv:  3 | +2.310  +2.673  +2.657  +2.640  +2.550  +2.510  +2.582  +2.347  +2.335  +2.260
Recv:    |
Recv:  2 | +2.265  +2.673  +2.665  +2.640  +2.585  +2.463  +2.552  +2.370  +2.250  +2.207
Recv:    |
Recv:  1 | +2.372  +2.747  +2.707  +2.677  +2.665  +2.492  +2.585  +2.423  +2.298  +2.255
Recv:    |
Recv:  0 |[+2.253] +2.685  +2.653  +2.710  +2.582  +2.467  +2.590  +2.523  +2.312  +2.253
Recv:         0       1       2       3       4       5       6       7       8       9


Based on the documentation and guides available for UBL, I have followed the following sequence:

1. Enabling UBL in the firmware

2. Run G29 P1

3. Then run G29 P3 to fill the blank spots

4. Once I'm done with a good result, I did G29 F10, G29 S1, G29 L1, G29 A

5. Then M500, M501, G28

6. I wanted to show 0 for the Z-axis while homed, so I typed G29 P6 Cxx whatever shown on the LCD, then M500, M501, G28 - so that I got 0 for Z-axis value

7. I then did the printing height by:

a. Moving the print head to the middle of the bed

b. Slowly lowering the nozzle until I got it at 0.1 mm above the bed

c. Then again did G29 P6 Cxx whatever number that was showing on the LCD now

d. M500, M501, then G28

e. Then tested a few times to make sure it is good

8. In my slicer, I added G29 L1 and G29 A after the G28 command so that the UBL system gets activated.

After all the above, I don't seem to get a good first layer because as you see there is a warp in the bed and I was expecting that the levelling that I've done would correct this however where the warp is, I see the layer line squished and on the opposite side I see it actually thin and not really pushed to the bed. I tried to observe the Z-axis motors to see if any corrections are happening, but they just did not move for the whole first layer..

ISSUE 2

I have configured the inductive probe to trigger approximately when the nozzle is 4 mm above the glass, so I configured the Z-offset for the probe to -4 mm.

When I build the mesh and save it, I home the printer, and at home, the nozzle is 3 to 4 mm below the bed, then when I want to manually adjust the bad points in the mesh, I go to the menu, and find the mesh edit commands in the UBL menu and select it. The nozzle will immediately move to the first point without even lifting Z up so it hits the bed and the whole x-carriage will be just forced to lift up in its place and be tensioned while what should happen is that the nozzle should be moved up first then it should go to the first point to edit it.

So is there anything of what I've done above not right? Or it is actually working but my bed is so badly bent that I need to replace it and is my Z-home position too low so I need to raise it up?

I have the Configuration.h file attached for reference.

• Not a solution, but my inductive Z home is a little buggy and crashes into the plate every couple months, luckily the machine has “jaw couplers” installed on the two Z axis, so the printer isn’t damaged. Like these: britech3d.com/product/… May 16 at 21:04