Add Z_AFTER_DEACTIVATE to account for gravity (MarlinFirmware#18906)

Marlin/Configuration.h

@@ -1076,18 +1076,18 @@
 #define Z_ENABLE_ON 0
 #define E_ENABLE_ON 0 // For all extruders
 
-// Disables axis stepper immediately when it's not being used.
+// Disable axis steppers immediately when they're not being stepped.
 // WARNING: When motors turn off there is a chance of losing position accuracy!
 #define DISABLE_X false
 #define DISABLE_Y false
 #define DISABLE_Z false
 
-// Warn on display about possibly reduced accuracy
+// Turn off the display blinking that warns about possible accuracy reduction
 //#define DISABLE_REDUCED_ACCURACY_WARNING
 
 // @section extruder
 
-#define DISABLE_E false             // For all extruders
+#define DISABLE_E false             // Disable the extruder when not stepping
 #define DISABLE_INACTIVE_EXTRUDER   // Keep only the active extruder enabled
 
 // @section machine

Marlin/Configuration_adv.h

@@ -809,24 +809,30 @@
 #define INVERT_Z_STEP_PIN false
 #define INVERT_E_STEP_PIN false
 
-// Default stepper release if idle. Set to 0 to deactivate.
-// Steppers will shut down DEFAULT_STEPPER_DEACTIVE_TIME seconds after the last move when DISABLE_INACTIVE_? is true.
-// Time can be set by M18 and M84.
+/**
+ * Idle Stepper Shutdown
+ * Set DISABLE_INACTIVE_? 'true' to shut down axis steppers after an idle period.
+ * The Deactive Time can be overridden with M18 and M84. Set to 0 for No Timeout.
+ */
 #define DEFAULT_STEPPER_DEACTIVE_TIME 120
 #define DISABLE_INACTIVE_X true
 #define DISABLE_INACTIVE_Y true
-#define DISABLE_INACTIVE_Z true  // Set to false if the nozzle will fall down on your printed part when print has finished.
+#define DISABLE_INACTIVE_Z true  // Set 'false' if the nozzle could fall onto your printed part!
 #define DISABLE_INACTIVE_E true
 
-#define DEFAULT_MINIMUMFEEDRATE       0.0     // minimum feedrate
-#define DEFAULT_MINTRAVELFEEDRATE     0.0
+// If the Nozzle or Bed falls when the Z stepper is disabled, set its resting position here.
+//#define Z_AFTER_DEACTIVATE Z_HOME_POS
 
 //#define HOME_AFTER_DEACTIVATE  // Require rehoming after steppers are deactivated
 
-// Minimum time that a segment needs to take if the buffer is emptied
-#define DEFAULT_MINSEGMENTTIME        20000   // (µs)
+// Minimum time that a segment needs to take as the buffer gets emptied
+#define DEFAULT_MINSEGMENTTIME        20000   // (µs) Set with M205 B.
+
+// Default Minimum Feedrates for printing and travel moves
+#define DEFAULT_MINIMUMFEEDRATE       0.0     // (mm/s) Minimum feedrate. Set with M205 S.
+#define DEFAULT_MINTRAVELFEEDRATE     0.0     // (mm/s) Minimum travel feedrate. Set with M205 T.
 
-// Slow down the machine if the look ahead buffer is (by default) half full.
+// Slow down the machine if the lookahead buffer is (by default) half full.
 // Increase the slowdown divisor for larger buffer sizes.
 #define SLOWDOWN
 #if ENABLED(SLOWDOWN)

Marlin/src/lcd/dogm/status_screen_lite_ST7920.cpp

@@ -819,16 +819,9 @@ void ST7920_Lite_Status_Screen::update_status_or_position(bool forceUpdate) {
     }
 
     if (countdown == 0 && (forceUpdate || position_changed()
-      #if DISABLED(DISABLE_REDUCED_ACCURACY_WARNING)
-        || blink_changed()
-      #endif
-    )) {
-      draw_position(current_position, true
-        #if DISABLED(DISABLE_REDUCED_ACCURACY_WARNING)
-          && all_axes_known()
-        #endif
-      );
-    }
+      || TERN(DISABLE_REDUCED_ACCURACY_WARNING, 0, blink_changed())
+    ))
+      draw_position(current_position, TERN(DISABLE_REDUCED_ACCURACY_WARNING, 0, all_axes_known()));
   #endif
 }
 

Marlin/src/module/planner.cpp

@@ -1281,7 +1281,7 @@ void Planner::recalculate() {
 void Planner::check_axes_activity() {
 
   #if ANY(DISABLE_X, DISABLE_Y, DISABLE_Z, DISABLE_E)
-    xyze_bool_t axis_active = { false };
+    xyze_bool_t axis_active = { true, true, true, true };
   #endif
 
   #if HAS_FAN
@@ -1316,7 +1316,10 @@ void Planner::check_axes_activity() {
     #if ANY(DISABLE_X, DISABLE_Y, DISABLE_Z, DISABLE_E)
       for (uint8_t b = block_buffer_tail; b != block_buffer_head; b = next_block_index(b)) {
         block_t *block = &block_buffer[b];
-        LOOP_XYZE(i) if (block->steps[i]) axis_active[i] = true;
+        if (ENABLED(DISABLE_X) && block->steps[X_AXIS]) axis_active[X_AXIS] = true;
+        if (ENABLED(DISABLE_Y) && block->steps[Y_AXIS]) axis_active[Y_AXIS] = true;
+        if (ENABLED(DISABLE_Z) && block->steps[Z_AXIS]) axis_active[Z_AXIS] = true;
+        if (ENABLED(DISABLE_E) && block->steps[E_AXIS]) axis_active[E_AXIS] = true;
       }
     #endif
   }

Marlin/src/module/stepper/indirection.h

@@ -848,7 +848,13 @@ void reset_stepper_drivers();    // Called by settings.load / settings.reset
 #define DISABLE_AXIS_Y() do{ DISABLE_STEPPER_Y(); DISABLE_STEPPER_Y2(); CBI(axis_known_position, Y_AXIS); }while(0)
 
 #define  ENABLE_AXIS_Z() do{ ENABLE_STEPPER_Z();  ENABLE_STEPPER_Z2();  ENABLE_STEPPER_Z3();  ENABLE_STEPPER_Z4(); }while(0)
-#define DISABLE_AXIS_Z() do{ DISABLE_STEPPER_Z(); DISABLE_STEPPER_Z2(); DISABLE_STEPPER_Z3(); DISABLE_STEPPER_Z4(); CBI(axis_known_position, Z_AXIS); }while(0)
+
+#ifdef Z_AFTER_DEACTIVATE
+  #define Z_RESET() do{ current_position.z = Z_AFTER_DEACTIVATE; planner.sync_plan_position(); }while(0)
+#else
+  #define Z_RESET()
+#endif
+#define DISABLE_AXIS_Z() do{ DISABLE_STEPPER_Z(); DISABLE_STEPPER_Z2(); DISABLE_STEPPER_Z3(); DISABLE_STEPPER_Z4(); CBI(axis_known_position, Z_AXIS); Z_RESET(); }while(0)
 
 //
 // Extruder steppers enable / disable macros