Z_offset not applied after home

General Discussion
1

I have a custom-made printer, but I’ve designed the gantry to match the dimensions and belt layout of the Voron 2.0. This allows me to install a Voron Tap and Stealthburner. In my setup, the bed moves in the Z direction, not the nozzle.

Setting z_offset in the [probe] section seems to have no effect after homing. Regardless of the z_offset value, the bed is pushed up into the nozzle until the Tap optical sensor is triggered.

At that point, I manually move the bed down and run PROBE_CALIBRATE. I calibrate and get a value of -1.903, which I then save to the config.

However, if I home again, the bed is once again pushed into the nozzle until the Tap is triggered. In the Fluidd interface, I see Z reported as -1.903. If I then manually set Z to 0, the nozzle appears to be at the correct height.

Is this how it’s supposed to work? Does Z only move to 0.0 at the start of a print?

[stepper_z]
step_pin: P0.22
dir_pin: P2.11
enable_pin: !P0.21
microsteps: 16
#rotation_distance: 2.811    # 1.33 for 8 micro steps
rotation_distance: 2.515 ; 2.6  ; 3.16    # 1.33 for 8 micro steps
#endstop_pin: !P1.25
endstop_pin: probe:z_virtual_endstop  # Using virtual endstop based on the probe
#position_endstop: 0.0
position_min: -2
position_max: 220

# [static_digital_input z_endstop]
# pin: P1.25

[probe]
pin: ^!P2.0   # Inductive sensor pin (replace with your actual pin)
x_offset: 0   # Adjust based on your probe's position relative to the nozzle
y_offset: 0   # Adjust as necessary
#z_offset: 0.0 # This will need to be calibrated
speed: 5.0    # Speed at which probing is done

[homing_override]
axes: xyz
set_position_x: 0
set_position_y: 0
gcode:
    G91                    ; Relative positioning
    G0 X20 Y20             ; Move XY forward by 20mm before homing
    G90                    ; Switch back to absolute positioning
    G28 Y0
    G28 X0
    G0 X100 Y100
    G28 Z0



#*# <---------------------- SAVE_CONFIG ---------------------->
#*# DO NOT EDIT THIS BLOCK OR BELOW. The contents are auto-generated.
#*#

#*# [probe]
#*# z_offset = -1.903
~
2

Please attach, as it was requested, the klippy.log to your next post.

How did you obtain the actual value?

3

To get the value. I first lowered the bed enough so probe_calibrate worked . Then I adjust using its UI until the nozzle rubbed against a piece of paper. I then as instructed from the terminal did a SAVE_CONFIG

4

If I’m understanding your post correctly, your Z end stop triggers above your nozzle. So yes, when you home, the bed is going to press into your nozzle because that’s what homing is: Keep moving until the end stop is triggered, and then that’s the new z = 0 that the offset modifies. You need to physically move the endstop so it triggers before you hit the nozzle.

5

Ok. I guess I just thought it would move to z=0 after homing. In the past I haven’t used probes much so probably haven’t noticed.

6

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