Merge pull request #10032 from thinkyhead/bf2_unknown_z_no_raise

[2.0.x] Add UNKNOWN_Z_NO_RAISE to prevent Z grinding

Marlin/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/default/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/AlephObjects/TAZ4/Configuration.h

@@ -824,6 +824,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/AliExpress/CL-260/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Anet/A6/Configuration.h

@@ -879,6 +879,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Anet/A8/Configuration.h

@@ -811,6 +811,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Azteeg/X5GT/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/BIBO/TouchX/cyclops/Configuration.h

@@ -804,6 +804,8 @@ const bool Z_MIN_PROBE_ENDSTOP_INVERTING = true; // set to true to invert the lo
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 10  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/BIBO/TouchX/default/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 10  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/BQ/Hephestos/Configuration.h

@@ -792,6 +792,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/BQ/Hephestos_2/Configuration.h

@@ -805,6 +805,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 5    // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/BQ/WITBOX/Configuration.h

@@ -792,6 +792,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Cartesio/Configuration.h

@@ -803,6 +803,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Creality/CR-10/Configuration.h

@@ -814,6 +814,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 5  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Creality/CR-10S/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 4    // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Creality/CR-10mini/Configuration.h

@@ -823,6 +823,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 5  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Creality/Ender-2/Configuration.h

@@ -808,6 +808,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Creality/Ender-4/Configuration.h

@@ -814,6 +814,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Felix/Configuration.h

@@ -786,6 +786,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Felix/DUAL/Configuration.h

@@ -786,6 +786,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/FolgerTech/i3-2020/Configuration.h

@@ -811,6 +811,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 2    // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Geeetech/GT2560/Configuration.h

@@ -819,6 +819,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Geeetech/I3_Pro_X-GT2560/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 8  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Geeetech/Prusa i3 Pro B/bltouch/Configuration.h

@@ -820,6 +820,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Geeetech/Prusa i3 Pro B/noprobe/Configuration.h

@@ -819,6 +819,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Infitary/i3-M508/Configuration.h

@@ -808,6 +808,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/JGAurora/A5/Configuration.h

@@ -816,6 +816,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/MakerParts/Configuration.h

@@ -824,6 +824,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Malyan/M150/Configuration.h

@@ -828,6 +828,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Malyan/M200/Configuration.h

@@ -803,6 +803,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Micromake/C1/basic/Configuration.h

@@ -808,6 +808,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Micromake/C1/enhanced/Configuration.h

@@ -808,6 +808,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Mks/Sbase/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/RepRapWorld/Megatronics/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/RigidBot/Configuration.h

@@ -802,6 +802,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/SCARA/Configuration.h

@@ -815,6 +815,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/STM32F10/Configuration.h

@@ -807,6 +807,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Sanguinololu/Configuration.h

@@ -835,6 +835,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 4    // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/TheBorg/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/TinyBoy2/Configuration.h

@@ -855,6 +855,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Tronxy/X1/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Tronxy/X5S/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 10 // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Tronxy/XY100/Configuration.h

@@ -815,6 +815,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                            // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/UltiMachine/Archim2/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Velleman/K8200/Configuration.h

@@ -833,6 +833,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 // K8200: it is usual to have clamps for the glass plate on the heatbed
 #define Z_HOMING_HEIGHT 4   // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                             // Be sure you have this distance over your Z_MAX_POS in case.

Marlin/src/config/examples/Velleman/K8400/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Velleman/K8400/Dual-head/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/Wanhao/Duplicator 6/Configuration.h

@@ -814,6 +814,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/adafruit/ST7565/Configuration.h

@@ -804,6 +804,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/FLSUN/auto_calibrate/Configuration.h

@@ -934,6 +934,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 15   // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/FLSUN/kossel/Configuration.h

@@ -934,6 +934,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 15   // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/FLSUN/kossel_mini/Configuration.h

@@ -934,6 +934,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 15   // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/Hatchbox_Alpha/Configuration.h

@@ -936,6 +936,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/generic/Configuration.h

@@ -921,6 +921,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/kossel_mini/Configuration.h

@@ -924,6 +924,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 15 // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/kossel_pro/Configuration.h

@@ -924,6 +924,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/delta/kossel_xl/Configuration.h

@@ -933,6 +933,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/gCreate/gMax1.5+/Configuration.h

@@ -817,6 +817,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 #define Z_HOMING_HEIGHT 10   // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/makibox/Configuration.h

@@ -807,6 +807,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/stm32f103ret6/Configuration.h

@@ -805,6 +805,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/tvrrug/Round2/Configuration.h

@@ -799,6 +799,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/config/examples/wt150/Configuration.h

@@ -809,6 +809,8 @@
 
 //#define NO_MOTION_BEFORE_HOMING  // Inhibit movement until all axes have been homed
 
+//#define UNKNOWN_Z_NO_RAISE // Don't raise Z (lower the bed) if Z is "unknown." For beds that fall when Z is powered off.
+
 //#define Z_HOMING_HEIGHT 4  // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                              // Be sure you have this distance over your Z_MAX_POS in case.
 

Marlin/src/gcode/calibrate/G28.cpp

@@ -221,9 +221,15 @@ void GcodeSuite::G28(const bool always_home_all) {
 
     #endif
 
-    if (home_all || homeX || homeY) {
+    #if ENABLED(UNKNOWN_Z_NO_RAISE)
+      const float z_homing_height = axis_known_position[Z_AXIS] ? Z_HOMING_HEIGHT : 0;
+    #else
+      constexpr float z_homing_height = Z_HOMING_HEIGHT;
+    #endif
+
+    if (z_homing_height && (home_all || homeX || homeY)) {
       // Raise Z before homing any other axes and z is not already high enough (never lower z)
-      destination[Z_AXIS] = Z_HOMING_HEIGHT;
+      destination[Z_AXIS] = z_homing_height;
       if (destination[Z_AXIS] > current_position[Z_AXIS]) {
 
         #if ENABLED(DEBUG_LEVELING_FEATURE)

Marlin/src/module/probe.cpp

@@ -57,25 +57,6 @@ float zprobe_zoffset; // Initialized by settings.load()
   const int z_servo_angle[2] = Z_SERVO_ANGLES;
 #endif
 
-/**
- * Raise Z to a minimum height to make room for a probe to move
- */
-inline void do_probe_raise(const float z_raise) {
-  #if ENABLED(DEBUG_LEVELING_FEATURE)
-    if (DEBUGGING(LEVELING)) {
-      SERIAL_ECHOPAIR("do_probe_raise(", z_raise);
-      SERIAL_CHAR(')');
-      SERIAL_EOL();
-    }
-  #endif
-
-  float z_dest = z_raise;
-  if (zprobe_zoffset < 0) z_dest -= zprobe_zoffset;
-
-  if (z_dest > current_position[Z_AXIS])
-    do_blocking_move_to_z(z_dest);
-}
-
 #if ENABLED(Z_PROBE_SLED)
 
   #ifndef SLED_DOCKING_OFFSET
@@ -353,6 +334,27 @@ inline void do_probe_raise(const float z_raise) {
 
 #endif // BLTOUCH
 
+/**
+ * Raise Z to a minimum height to make room for a probe to move
+ */
+inline void do_probe_raise(const float z_raise) {
+  #if ENABLED(DEBUG_LEVELING_FEATURE)
+    if (DEBUGGING(LEVELING)) {
+      SERIAL_ECHOPAIR("do_probe_raise(", z_raise);
+      SERIAL_CHAR(')');
+      SERIAL_EOL();
+    }
+  #endif
+
+  float z_dest = z_raise;
+  if (zprobe_zoffset < 0) z_dest -= zprobe_zoffset;
+
+  NOMORE(z_dest, Z_MAX_POS);
+
+  if (z_dest > current_position[Z_AXIS])
+    do_blocking_move_to_z(z_dest);
+}
+
 // returns false for ok and true for failure
 bool set_probe_deployed(const bool deploy) {
 
@@ -376,13 +378,21 @@ bool set_probe_deployed(const bool deploy) {
 
   // Make room for probe to deploy (or stow)
   // Fix-mounted probe should only raise for deploy
-  if (
   #if ENABLED(FIX_MOUNTED_PROBE)
-      deploy
+    const bool deploy_stow_condition = deploy;
   #else
-      true
+    constexpr bool deploy_stow_condition = true;
   #endif
-  ) do_probe_raise(max(Z_CLEARANCE_BETWEEN_PROBES, Z_CLEARANCE_DEPLOY_PROBE));
+
+  // For beds that fall when Z is powered off only raise for trusted Z
+  #if ENABLED(UNKNOWN_Z_NO_RAISE)
+    const bool unknown_condition = axis_known_position[Z_AXIS];
+  #else
+    constexpr float unknown_condition = true;
+  #endif
+
+  if (deploy_stow_condition && unknown_condition)
+    do_probe_raise(max(Z_CLEARANCE_BETWEEN_PROBES, Z_CLEARANCE_DEPLOY_PROBE));
 
   #if ENABLED(Z_PROBE_SLED) || ENABLED(Z_PROBE_ALLEN_KEY)
     #if ENABLED(Z_PROBE_SLED)