Add option to fix E/D ratio

Work around for slicers producing buggy gcode.

Marlin/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/Marlin_main.cpp

    */
   inline void gcode_M905() {
     stepper.synchronize();
-    planner.advance_M905(code_seen('K') ? code_value_float() : -1.0);
+    
+    float newD = -1;
+    float newW = -1;
+    float newH = -1;
+    
+    if (code_seen('K')) {
+      float newK = code_value_float();
+      if (newK >= 0.0)
+        planner.set_extruder_advance_k(newK);
+    }
+
+    SERIAL_ECHO_START;
+    SERIAL_ECHOPAIR("Advance factor: ", planner.get_extruder_advance_k());
+    SERIAL_EOL;
+    
+    if (code_seen('D'))
+      newD = code_value_float();
+    if (code_seen('W'))
+      newW = code_value_float();
+    if (code_seen('H'))
+      newH = code_value_float();
+
+    if (newD > 0 && newW > 0 && newH > 0) {
+      float E_D_ratio = newW * newH / (sq(newD / 2) * M_PI);
+      planner.set_E_D_ratio(E_D_ratio);
+      SERIAL_ECHO_START;
+      SERIAL_ECHOPAIR("E/D ratio: ", E_D_ratio);
+      SERIAL_EOL;
+    }
+    else if (newD != -1 || newW != -1 || newH != -1) {
+      planner.set_E_D_ratio(0);
+      SERIAL_ECHO_START;
+      SERIAL_ECHOPGM("E/D ratio: Automatic");
+      SERIAL_EOL;
+    }
   }
 #endif
 

Marlin/example_configurations/Cartesio/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/Felix/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/Hephestos/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/Hephestos_2/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/K8200/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 140 // start value for PLA on K8200
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/K8400/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/RigidBot/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/SCARA/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/TAZ4/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/WITBOX/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/delta/generic/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/delta/kossel_mini/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/delta/kossel_pro/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/delta/kossel_xl/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/makibox/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/example_configurations/tvrrug/Round2/Configuration_adv.h

 
 #if ENABLED(LIN_ADVANCE)
   #define LIN_ADVANCE_K 75
+
+  /**
+   * Some Slicers produce Gcode with randomly jumping extrusion widths occasionally.
+   * For example within a 0.4mm perimeter it may produce a single segment of 0.05mm width.
+   * While this is harmless for normal printing (the fluid nature of the filament will
+   * close this very, very tiny gap), it throws off the LIN_ADVANCE pressure adaption.
+   *
+   * For this case LIN_ADVANCE_E_D_RATIO can be used to set the extrusion:distance ratio
+   * to a fixed value. Note that using a fixed ratio will lead to wrong nozzle pressures
+   * if the slicer is using variable widths or layer heights within one print!
+   *
+   * This option sets the default E:D ratio at startup. Use `M905` to override this value.
+   *
+   * Example: `M905 W0.4 H0.2 D1.75`, where:
+   *   - W is the extrusion width in mm
+   *   - H is the layer height in mm
+   *   - D is the filament diameter in mm
+   *
+   * Set to 0 to auto-detect the ratio based on given Gcode G1 print moves.
+   *
+   * Slic3r (including Prusa Slic3r) produces Gcode compatible with the automatic mode.
+   * Cura (as of this writing) may produce Gcode incompatible with the automatic mode.
+   */
+  #define LIN_ADVANCE_E_D_RATIO 0 // The calculated ratio (or 0) according to the formula W * H / ((D / 2) ^ 2 * PI)
+                                  // Example: 0.4 * 0.2 / ((1.75 / 2) ^ 2 * PI) = 0.033260135
 #endif
 
 // @section leveling

Marlin/planner.cpp

 
 #if ENABLED(LIN_ADVANCE)
   float Planner::extruder_advance_k = LIN_ADVANCE_K,
+        Planner::E_D_ratio = LIN_ADVANCE_E_D_RATIO,
         Planner::position_float[NUM_AXIS] = { 0 };
 #endif
 
                             && extruder_advance_k
                             && (uint32_t)esteps != block->step_event_count
                             && de_float > 0.0;
-    if (block->use_advance_lead)
-      block->abs_adv_steps_multiplier8 = lround(extruder_advance_k * (de_float / mm_D_float) * block->nominal_speed / (float)block->nominal_rate * axis_steps_per_mm[E_AXIS_N] * 256.0);
+    if (block->use_advance_lead) {
+      // Check if we should use the fixed E_D_ratio
+      if (UNEAR_ZERO(E_D_ratio)) {
+        block->abs_adv_steps_multiplier8 = lround(extruder_advance_k * (de_float / mm_D_float) * block->nominal_speed / (float)block->nominal_rate * axis_steps_per_mm[E_AXIS_N] * 256.0);
+      }
+      else {
+        block->abs_adv_steps_multiplier8 = lround(extruder_advance_k * E_D_ratio * block->nominal_speed / (float)block->nominal_rate * axis_steps_per_mm[E_AXIS_N] * 256.0);
+      }
+    }
 
   #elif ENABLED(ADVANCE)
 
   }
 
 #endif
-
-#if ENABLED(LIN_ADVANCE)
-
-  void Planner::advance_M905(const float &k) {
-    if (k >= 0.0) extruder_advance_k = k;
-    SERIAL_ECHO_START;
-    SERIAL_ECHOPAIR("Advance factor: ", extruder_advance_k);
-    SERIAL_EOL;
-  }
-
-#endif

Marlin/planner.h

     #if ENABLED(LIN_ADVANCE)
       static float position_float[NUM_AXIS];
       static float extruder_advance_k;
+      static float E_D_ratio;
     #endif
 
     #if ENABLED(ULTRA_LCD)
     #endif
 
     #if ENABLED(LIN_ADVANCE)
-      void advance_M905(const float &k);
+      static void set_extruder_advance_k(const float &k) { extruder_advance_k = k; };
+      static float get_extruder_advance_k() { return extruder_advance_k; };
+      static void set_E_D_ratio(const float &ratio) { E_D_ratio = ratio; };
     #endif
 
     /**