Fan override and multiplier

Marlin/Configuration_adv.h

@@ -3894,6 +3894,16 @@
 
 //#define REPORT_FAN_CHANGE   // Report the new fan speed when changed by M106 (and others)
 
+/**
+ * Adds UI and G-code (M106) options to control fan speed while printing.
+ *
+ * - Lock Fan Speed: To prevent G-code commands (i.e., M106) from altering the current fan speed.
+ * - Fan Speed Multiplier: Multiplies the fan speed set by G-code commands by a specified factor for fine-tuning.
+ *
+ * Note: Settings are not saved in EEPROM and will reset after a power cycle.
+ */
+//#define FAN_MULTIPLIER
+
 /**
  * Auto-report temperatures with M155 S<seconds>
  */

Marlin/src/gcode/temp/M106_M107.cpp

@@ -50,6 +50,9 @@
  *  I<index> Material Preset index (if material presets are defined)
  *  S<int>   Speed between 0-255
  *  P<index> Fan index, if more than one fan
+ *  L        Lock fan
+ *  U        Unlock fan
+ *  M<float> Fan speed multiplier between 0.1 and 10
  *
  * With EXTRA_FAN_SPEED enabled:
  *
@@ -59,6 +62,21 @@
  *           3-255 = Set the speed for use with T2
  */
 void GcodeSuite::M106() {
+  #if ENABLED(FAN_MULTIPLIER)
+    if (parser.seen('L')) {
+        thermalManager.lock_fan = true;
+      if (!parser.seenval('S')) return;
+    } if (parser.seen('U')) {
+      thermalManager.lock_fan = false;
+      return;
+    } else if (thermalManager.lock_fan) return;
+
+    if (parser.seenval('M')) {
+      thermalManager.set_fan_multiplier(parser.value_float());
+      if (!parser.seenval('S')) return;
+    }
+  #endif
+
   const uint8_t pfan = parser.byteval('P', _ALT_P);
   if (pfan >= _CNT_P) return;
   if (FAN_IS_REDUNDANT(pfan)) return;
@@ -98,6 +116,10 @@ void GcodeSuite::M106() {
  * M107: Fan Off
  */
 void GcodeSuite::M107() {
+  #if ENABLED(FAN_MULTIPLIER)
+    if (thermalManager.lock_fan) return;
+  #endif
+
   const uint8_t pfan = parser.byteval('P', _ALT_P);
   if (pfan >= _CNT_P) return;
   if (FAN_IS_REDUNDANT(pfan)) return;

Marlin/src/inc/Conditionals_post.h

@@ -2748,8 +2748,10 @@
   #ifndef FAN_MAX_PWM
     #define FAN_MAX_PWM 255
   #endif
-  #if FAN_MIN_PWM == 0 && FAN_MAX_PWM == 255
-    #define CALC_FAN_SPEED(f) (f ?: FAN_OFF_PWM)
+  #if FAN_MIN_PWM == 0 && FAN_MAX_PWM == 255 && !defined(FAN_MULTIPLIER)
+    #define CALC_FAN_SPEED(f) (f ? f : FAN_OFF_PWM)
+  #elif defined(FAN_MULTIPLIER)
+    #define CALC_FAN_SPEED(f) (f ? map(thermalManager.compute_multiplied_fan(f), 1, 255, FAN_MIN_PWM, FAN_MAX_PWM) : FAN_OFF_PWM) 
   #else
     #define CALC_FAN_SPEED(f) (f ? map(f, 1, 255, FAN_MIN_PWM, FAN_MAX_PWM) : FAN_OFF_PWM)
   #endif

Marlin/src/lcd/language/language_en.h

@@ -561,6 +561,9 @@ namespace LanguageNarrow_en {
   LSTR MSG_SINGLENOZZLE_UNRETRACT_SPEED   = _UxGT("Recover Speed");
   LSTR MSG_SINGLENOZZLE_FAN_SPEED         = _UxGT("Fan Speed");
   LSTR MSG_SINGLENOZZLE_FAN_TIME          = _UxGT("Fan Time");
+  LSTR MSG_LOCK_FAN                       = _UxGT("Lock Fan");
+  LSTR MSG_UNLOCK_FAN                     = _UxGT("Unlock Fan");
+  LSTR MSG_FAN_MULTIPLIER                 = _UxGT("Fan Multiplier");
   LSTR MSG_TOOL_MIGRATION_ON              = _UxGT("Auto ON");
   LSTR MSG_TOOL_MIGRATION_OFF             = _UxGT("Auto OFF");
   LSTR MSG_TOOL_MIGRATION                 = _UxGT("Tool Migration");

Marlin/src/lcd/menu/menu_temperature.cpp

@@ -219,6 +219,15 @@ void menu_temperature() {
 
     #if FAN_IS_M106ABLE(0)
       _FAN_EDIT_ITEMS(0, FIRST_FAN_SPEED);
+      #if ENABLED(FAN_MULTIPLIER)
+        if (thermalManager.lock_fan) {
+          ACTION_ITEM(MSG_UNLOCK_FAN, []{ thermalManager.lock_fan = false; ui.refresh(); });
+        } else {
+          ACTION_ITEM(MSG_LOCK_FAN, []{ thermalManager.lock_fan = true; ui.refresh(); });
+        }
+        editable.decimal = thermalManager.get_fan_multiplier();
+        EDIT_ITEM_FAST(float31, MSG_FAN_MULTIPLIER, &editable.decimal, 0.0f, 9.9f, []{ thermalManager.set_fan_multiplier(editable.decimal); }, true);
+      #endif
     #endif
     #if FAN_IS_M106ABLE(1)
       FAN_EDIT_ITEMS(1);

Marlin/src/module/temperature.cpp

@@ -284,6 +284,21 @@ PGMSTR(str_t_heating_failed, STR_T_HEATING_FAILED);
  * public:
  */
 
+#if ALL(HAS_FAN, FAN_MULTIPLIER)
+  void Temperature::set_fan_multiplier(float m){
+    fan_multiplier = m;
+    planner.sync_fan_speeds(fan_speed);
+  }
+
+  uint8_t Temperature::compute_multiplied_fan(uint8_t speed){
+    return constrain(speed * fan_multiplier, 1, 255);
+  }
+
+  float Temperature::get_fan_multiplier(){
+    return fan_multiplier;
+  }
+#endif
+
 #if ENABLED(TEMP_TUNING_MAINTAIN_FAN)
   bool Temperature::adaptive_fan_slowing = true;
 #endif

Marlin/src/module/temperature.h

@@ -597,6 +597,12 @@ typedef struct { raw_adc_t raw_min, raw_max; celsius_t mintemp, maxtemp; } temp_
 class Temperature {
 
   public:
+    #if ALL(HAS_FAN, FAN_MULTIPLIER)
+      bool lock_fan;
+      void set_fan_multiplier(float m);
+      uint8_t compute_multiplied_fan(uint8_t speed);
+      float get_fan_multiplier();
+    #endif
 
     #if HAS_HOTEND
       static hotend_info_t temp_hotend[HOTENDS];
@@ -1334,7 +1340,9 @@ class Temperature {
     #endif
 
   private:
-
+    #if ENABLED(FAN_MULTIPLIER)
+      float fan_multiplier = 1;
+    #endif
     // Reading raw temperatures and converting to Celsius when ready
     static volatile bool raw_temps_ready;
     static void update_raw_temperatures();