Auto bed leveling, rectangle bug?

In Marlin 1.0.2 I have:

#define LEFT_PROBE_BED_POSITION 0

Actual position when it performs this probe:

SENDING:M114
X:23.01 Y:128.04 Z:20.88 E:0.00 Count X: 22.99 Y:128.00 Z:21.17

Then if I do (which is probably dangerous):

#define LEFT_PROBE_BED_POSITION -20

X:3.01 Y:128.04 Z:20.88 E:0.00 Count X: 2.99 Y:128.00 Z:21.17

Note that when X is 0, it is touching the X minimum endstop.

Why does this happen?

I am doing a home command before I attempt this.

G28, then G29.

G29 moves around and does the probing successfully, but it doesn't seem to respect the coordinates specified in the file.

My travel limits section:

// Travel limits after homing
#define X_MAX_POS 148
#define X_MIN_POS 0
#define Y_MAX_POS 150
#define Y_MIN_POS 0
#define Z_MAX_POS 86
#define Z_MIN_POS 0

#define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
#define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)
#define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)

My auto bed leveling section:

//============================= Bed Auto Leveling ===========================

#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)
#define Z_PROBE_REPEATABILITY_TEST  // If not commented out, Z-Probe Repeatability test will be included if Auto Bed Leveling is Enabled.

#ifdef ENABLE_AUTO_BED_LEVELING

// There are 2 different ways to pick the X and Y locations to probe:

//  - "grid" mode
//    Probe every point in a rectangular grid
//    You must specify the rectangle, and the density of sample points
//    This mode is preferred because there are more measurements.
//    It used to be called ACCURATE_BED_LEVELING but "grid" is more descriptive

//  - "3-point" mode
//    Probe 3 arbitrary points on the bed (that aren't colinear)
//    You must specify the X & Y coordinates of all 3 points

  #define AUTO_BED_LEVELING_GRID
  // with AUTO_BED_LEVELING_GRID, the bed is sampled in a
  // AUTO_BED_LEVELING_GRID_POINTSxAUTO_BED_LEVELING_GRID_POINTS grid
  // and least squares solution is calculated
  // Note: this feature occupies 10'206 byte
  #ifdef AUTO_BED_LEVELING_GRID

    // set the rectangle in which to probe
    #define LEFT_PROBE_BED_POSITION -20
    #define RIGHT_PROBE_BED_POSITION 125
    #define BACK_PROBE_BED_POSITION 125
    #define FRONT_PROBE_BED_POSITION -10

     // set the number of grid points per dimension
     // I wouldn't see a reason to go above 3 (=9 probing points on the bed)
    #define AUTO_BED_LEVELING_GRID_POINTS 2


  #else  // not AUTO_BED_LEVELING_GRID
    // with no grid, just probe 3 arbitrary points.  A simple cross-product
    // is used to esimate the plane of the print bed

      #define ABL_PROBE_PT_1_X 15
      #define ABL_PROBE_PT_1_Y 120
      #define ABL_PROBE_PT_2_X 15
      #define ABL_PROBE_PT_2_Y 15
      #define ABL_PROBE_PT_3_X 120
      #define ABL_PROBE_PT_3_Y 120

  #endif // AUTO_BED_LEVELING_GRID


  // these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
  // X and Y offsets must be integers
  #define X_PROBE_OFFSET_FROM_EXTRUDER -23
  #define Y_PROBE_OFFSET_FROM_EXTRUDER -3
  #define Z_PROBE_OFFSET_FROM_EXTRUDER -20.9

  #define Z_RAISE_BEFORE_HOMING 5       // (in mm) Raise Z before homing (G28) for Probe Clearance.
                                        // Be sure you have this distance over your Z_MAX_POS in case

  #define XY_TRAVEL_SPEED 4000         // X and Y axis travel speed between probes, in mm/min

  #define Z_RAISE_BEFORE_PROBING 25    //How much the extruder will be raised before traveling to the first probing point.
  #define Z_RAISE_BETWEEN_PROBINGS 10  //How much the extruder will be raised when traveling from between next probing points

  //#define Z_PROBE_SLED // turn on if you have a z-probe mounted on a sled like those designed by Charles Bell
  //#define SLED_DOCKING_OFFSET 5 // the extra distance the X axis must travel to pickup the sled. 0 should be fine but you can push it further if you'd like.

  //If defined, the Probe servo will be turned on only during movement and then turned off to avoid jerk
  //The value is the delay to turn the servo off after powered on - depends on the servo speed; 300ms is good value, but you can try lower it.
  // You MUST HAVE the SERVO_ENDSTOPS defined to use here a value higher than zero otherwise your code will not compile.

  #define PROBE_SERVO_DEACTIVATION_DELAY 300


//If you have enabled the Bed Auto Leveling and are using the same Z Probe for Z Homing,
//it is highly recommended you let this Z_SAFE_HOMING enabled!!!

  #define Z_SAFE_HOMING   // This feature is meant to avoid Z homing with probe outside the bed area.
                          // When defined, it will:
                          // - Allow Z homing only after X and Y homing AND stepper drivers still enabled
                          // - If stepper drivers timeout, it will need X and Y homing again before Z homing
                          // - Position the probe in a defined XY point before Z Homing when homing all axis (G28)
                          // - Block Z homing only when the probe is outside bed area.

  #ifdef Z_SAFE_HOMING

    #define Z_SAFE_HOMING_X_POINT (X_MAX_LENGTH/2)    // X point for Z homing when homing all axis (G28)
    #define Z_SAFE_HOMING_Y_POINT (Y_MAX_LENGTH/2)    // Y point for Z homing when homing all axis (G28)

  #endif

  #ifdef AUTO_BED_LEVELING_GRID	// Check if Probe_Offset * Grid Points is greater than Probing Range
    #if X_PROBE_OFFSET_FROM_EXTRUDER < 0
      #if (-(X_PROBE_OFFSET_FROM_EXTRUDER * AUTO_BED_LEVELING_GRID_POINTS) >= (RIGHT_PROBE_BED_POSITION - LEFT_PROBE_BED_POSITION))
	     #error "The X axis probing range is not enough to fit all the points defined in AUTO_BED_LEVELING_GRID_POINTS"
	  #endif
	#else
      #if ((X_PROBE_OFFSET_FROM_EXTRUDER * AUTO_BED_LEVELING_GRID_POINTS) >= (RIGHT_PROBE_BED_POSITION - LEFT_PROBE_BED_POSITION))
	     #error "The X axis probing range is not enough to fit all the points defined in AUTO_BED_LEVELING_GRID_POINTS"
	  #endif
	#endif
    #if Y_PROBE_OFFSET_FROM_EXTRUDER < 0
      #if (-(Y_PROBE_OFFSET_FROM_EXTRUDER * AUTO_BED_LEVELING_GRID_POINTS) >= (BACK_PROBE_BED_POSITION - FRONT_PROBE_BED_POSITION))
	     #error "The Y axis probing range is not enough to fit all the points defined in AUTO_BED_LEVELING_GRID_POINTS"
	  #endif
	#else
      #if ((Y_PROBE_OFFSET_FROM_EXTRUDER * AUTO_BED_LEVELING_GRID_POINTS) >= (BACK_PROBE_BED_POSITION - FRONT_PROBE_BED_POSITION))
	     #error "The Y axis probing range is not enough to fit all the points defined in AUTO_BED_LEVELING_GRID_POINTS"
	  #endif
	#endif

	
  #endif
  
#endif // ENABLE_AUTO_BED_LEVELING

Hi
it is the offset from the extruder. Marlin substract the half from offset. #define X_PROBE_OFFSET_FROM_EXTRUDER -23 + an - before the value 23 is the direction where the z probe Endstop is right or left from nozzle.
My english´s not so good, hope it help´s

Thomas

Hi it is the offset from the extruder. Marlin substract the half from offset. #define X_PROBE_OFFSET_FROM_EXTRUDER -23 + an - before the value 23 is the direction where the z probe Endstop is right or left from nozzle. My English´s not so good, hope it help´s
conveyor components
adolf