Merge pull request #7379 from thinkyhead/bf_manual_bed_level_floor

Manual Bed Leveling: Goto previous Z height at each probe point

Marlin/Marlin_main.cpp

 
   inline void _manual_goto_xy(const float &x, const float &y) {
     const float old_feedrate_mm_s = feedrate_mm_s;
-
     #if MANUAL_PROBE_HEIGHT > 0
+      const float prev_z = current_position[Z_AXIS];
       feedrate_mm_s = homing_feedrate(Z_AXIS);
-      current_position[Z_AXIS] = LOGICAL_Z_POSITION(Z_MIN_POS) + MANUAL_PROBE_HEIGHT;
+      current_position[Z_AXIS] = LOGICAL_Z_POSITION(MANUAL_PROBE_HEIGHT);
       line_to_current_position();
     #endif
 
 
     #if MANUAL_PROBE_HEIGHT > 0
       feedrate_mm_s = homing_feedrate(Z_AXIS);
-      current_position[Z_AXIS] = LOGICAL_Z_POSITION(Z_MIN_POS); // just slightly over the bed
+      current_position[Z_AXIS] = prev_z; // move back to the previous Z.
       line_to_current_position();
     #endif
 

Marlin/ultralcd.cpp

       // Utility to go to the next mesh point
       inline void _manual_probe_goto_xy(float x, float y) {
         #if MANUAL_PROBE_HEIGHT > 0
+          const float prev_z = current_position[Z_AXIS];
           line_to_z(LOGICAL_Z_POSITION(Z_MIN_POS) + MANUAL_PROBE_HEIGHT);
         #endif
         current_position[X_AXIS] = LOGICAL_X_POSITION(x);
         current_position[Y_AXIS] = LOGICAL_Y_POSITION(y);
         planner.buffer_line_kinematic(current_position, MMM_TO_MMS(XY_PROBE_SPEED), active_extruder);
         #if MANUAL_PROBE_HEIGHT > 0
-          line_to_z(LOGICAL_Z_POSITION(Z_MIN_POS));
+          line_to_z(prev_z);
         #endif
         lcd_synchronize();
       }