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Klipper Nozzle Collision Homing

Info

This feature requires the BD sensor firmware version (you can obtain it by sending M102 S-1, not the hardware version on the sensor) to be V1.1b, greater than V1.2b, or a version purchased after March 2024. Otherwise, you need to use external hardware tools (such as STlink) to flash the firmware into the BD sensor.

When homing on soft PEI (like Whambam), do not heat the nozzle too high, as high temperatures may leave holes in the PEI.

How It Works

  • If the nozzle or bed stops due to collision, the distance data measured by the BD sensor will also stop changing. Then, the BD sensor will quickly output a stop signal.
  • The process of automatic z_offset calibration during G28 execution: It can be triggered after the nozzle touches the bed during homing—then slowly moves upward until the nozzle just leaves the bed—setting this position as the zero point for the Z-axis.

Benefits

  • Automatic Z-axis offset calibration.
  • You can still manually adjust the Z-axis offset for different filaments.
  • Overcome temperature drift.
  • Temperature drift changes the Z-axis offset but does not change the range of the bed mesh height map with the BD sensor. This means the bed mesh remains the same even at different temperatures.

How to Use

  • Add collision_homing and collision_calibrate to the [BDsensor] section.
[BDsensor]
collision_homing:0 # Set it to 1 to enable homing with nozzle collision sensing. Disable it by setting it to 0.
                   
collision_calibrate:0 # Set it to 1 to enable auto-calibration of the BD sensor with nozzle collision sensing. Disable it by setting it to 0.
# This means we do not need to manually move the nozzle on the bed and perform a paper test before sending the calibration command M102 S-6.
  • Sensitivity depends on speed. The slower the speed, the higher the sensitivity. Therefore, you need to adjust the Z-axis speed. The homing_speed and second_homing_speed should be in the range of 2 to 5.
Info

The nozzle should be cleaned or heated to soften filament residue. Do not set the speed too high or too low. If the speed is too high, it may damage your hotend or print bed; if the speed is too low, it may trigger in mid-air without the nozzle actually touching the print bed.

Reference Configuration

[stepper_z]
endstop_pin: probe:z_virtual_endstop
#position_endstop: 0.0
position_max: 250
homing_speed: 5
second_homing_speed: 3
homing_retract_dist: 5
homing_retract_speed: 2
Tip

z_hop (Z-axis hop height) and homing_retract_dist (homing retract distance) should be greater than or equal to 5.

Reference Configuration

[safe_z_home]
z_hop: 5

[stepper_z]
homing_retract_dist: 5
[BDsensor]
...
speed: 3 # This speed only works for the Z tilt and PROBE_ACCURACY command.
...
Tip

Reference configuration zero_reference_position

[bed_mesh]
horizontal_move_z: 1 # 0.7~1.0mm is recommended.
zero_reference_position: 150, 160 # Set this value to be the same as the home_xy_position in the safe_z_home section.
....

Test Homing

Please send the G28 Z command about 10 times, then check whether the output data on the console after each G28 Z command is stable.

G28 Z
Demo Video
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