u/flugv1

Hi,

I’m trying to troubleshoot a first layer / bed mesh issue on an Alfawise U20 converted to Klipper.

Setup:

• Printer: Alfawise U20
• Board: BTT Manta E3EZ + CB1
• Firmware: Klipper + Moonraker
• Probe: BLTouch
• Build surface: removable PEI sheet
• Bed mounts: recently changed from springs to silicone spacers
• Current nozzle: 0.4 mm
• Current material: PETG, for a functional enclosure

Relevant config:

[bltouch]
sensor_pin: ^PA6
control_pin: PA7
x_offset: -40
y_offset: -10
# active z_offset before the latest tuning was around 0.750

[stepper_z]
endstop_pin: probe:z_virtual_endstop
position_min: -5

[bed_mesh]
speed: 120
horizontal_move_z: 5
mesh_min: 35, 6
mesh_max: 250, 198
probe_count: 7, 7
algorithm: bicubic

What I already checked / changed:

• removed, cleaned and reseated the PEI sheet
• checked there was no dust/debris under the sheet
• replaced the bed springs with silicone spacers
• redid SCREWS_TILT_CALCULATE
• checked the BLTouch mount and toolhead by hand
• checked the X carriage for obvious play
• checked the Z coupler / lead screw
• cleaned the nozzle

Bed mesh:

The mesh appears to be active during the print. Example live state:

bed_mesh profile: default
gcode Z: 0.30
homing_origin Z: -0.3
save_config_pending: true

The current start G-code runs:

BED_MESH_CALIBRATE ADAPTIVE=1 ADAPTIVE_MARGIN=5

I previously had a typo (ADAPTATIVE_MARGIN), which is now fixed. I also realized I need [exclude_object] and object definitions in the G-code for adaptive mesh to actually limit the probed area.

Example mesh I got:

-0.258 -0.290 -0.237 -0.250 -0.185 -0.212 -0.138
-0.255 -0.297 -0.265 -0.302 -0.250 -0.292 -0.233
-0.295 -0.330 -0.273 -0.300 -0.220 -0.263 -0.220
-0.193 -0.150 -0.145 -0.105 -0.168 -0.295 -0.247
-0.240 -0.287 -0.030 -0.043 -0.125 -0.290 -0.217
-0.247 -0.307 +0.025 -0.225 -0.282 -0.343 -0.273
-0.263 -0.328 -0.255 -0.318 -0.245 -0.290 -0.200

Range is about:

0.3675 mm

Problem:

Even though the mesh appears active, the first layer does not visually look properly compensated. I had to do a lot of live Z adjustment during the print using:

SET_GCODE_OFFSET Z_ADJUST=... MOVE=1

I also used several times:

Z_OFFSET_APPLY_PROBE

Klipper reported successive pending BLTouch z_offset values like:

1.850
1.025
1.175

Looking at the full adjustment history, the value that seems most consistent might be closer to around 1.05, but the amount of live adjustment needed feels excessive.

Questions:

1. Would you suspect:
   • inconsistent BLTouch readings?
   • probe location bias depending on XY position?
   • a slightly twisted X axis?
   • probe/toolhead mount flex?
   • or simply an invalidated z_offset after changing from springs to silicone spacers?
2. Is a mesh range of about 0.37 mm already too much to expect clean compensation?
3. Would the correct diagnostic order be:
4. near the center, then at several XY positions, followed by two consecutive BED_MESH_CALIBRATE runs to compare the matrices?
5. If the probe is repeatable at the same point but varies depending on XY position, would [axis_twist_compensation] be relevant?
6. Would you recommend adding BLTouch sampling settings such as:

Planned next steps:

1. heat the bed to printing temperature and wait a few minutes
2. run PROBE_ACCURACY SAMPLES=10 near the center
3. run PROBE_ACCURACY at several XY positions
4. run two full bed meshes in a row without touching anything
5. compare the matrices
6. only then redo a clean PROBE_CALIBRATE and save config

Does that diagnostic order sound right?

Thanks!