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Collision Sensing of Marlin

info

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

How It Works

  • Automatically performs z-axis offset calibration when executing G28: It can be triggered after homing (when the nozzle touches the platform) - then it moves slowly upward until the nozzle just leaves the platform - and this position is set as the 0 point of the z-axis.

Benefits

  • Automatic z-axis offset calibration.
  • At the same time, you can still manually adjust the z-axis offset for different filaments.
  • Overcomes temperature drift.
  • Temperature drift will change the z-axis offset, but it will not change the range of the bed mesh height map with the BD sensor. This means that even if the temperature is different, the bed mesh is the same.
Tip

The code for this feature is in the pull request list of the official Marlin GitHub: https://github.com/MarlinFirmware/Marlin/pull/27243 So please use the following Marlin code: https://github.com/markniu/MarlinPULL/tree/bugfix - 2.1.x

How to Use

Enable BD_SENSOR, and add #define BD_SENSOR_CONTACT_PROBE in configuration.h It should look like this:

#define BD_SENSOR
#if ENABLED(BD_SENSOR)
  #define BD_SENSOR_PROBE_NO_STOP // Probe bed without stopping at each probe point`
  #define BD_SENSOR_CONTACT_PROBE // it uses nozzle collision sensing to probe while homing`
#endif

  • Increase the speed of the probe in configuration.h.

  • The sensitivity depends on the speed, so you need to adjust the speed of the Z-axis.

  • The homing_speed (homing speed) and second_homing_speed (secondary homing speed) should be in the range of 3 to 10, here is the Z-axis probe feed rate.

  • For example:

 #define Z_PROBE_FEEDRATE_FAST  (5*60)
 #define Z_PROBE_FEEDRATE_SLOW  (5*60)
  • In Configuration_adv.h, increase the homing lift of the Z-axis to more than 4 mm.
#define HOMING_BUMP_MM      { 5, 5, 5 }

Test Homing

  • Please send the G28 Z command about 10 times, or use the M48 command to see if it is stable.
Demo Video