AUTOTEMP default proportions (#17560)

Marlin/Configuration_adv.h

@@ -206,7 +206,7 @@
   // A well-chosen Kc value should add just enough power to melt the increased material volume.
   //#define PID_EXTRUSION_SCALING
   #if ENABLED(PID_EXTRUSION_SCALING)
-    #define DEFAULT_Kc (100) //heating power=Kc*(e_speed)
+    #define DEFAULT_Kc (100) // heating power = Kc * e_speed
     #define LPQ_MAX_LEN 50
   #endif
 
@@ -262,18 +262,28 @@
 #endif
 
 /**
- * Automatic Temperature:
- * The hotend target temperature is calculated by all the buffered lines of gcode.
- * The maximum buffered steps/sec of the extruder motor is called "se".
- * Start autotemp mode with M109 S<mintemp> B<maxtemp> F<factor>
- * The target temperature is set to mintemp+factor*se[steps/sec] and is limited by
- * mintemp and maxtemp. Turn this off by executing M109 without F*
- * Also, if the temperature is set to a value below mintemp, it will not be changed by autotemp.
- * On an Ultimaker, some initial testing worked with M109 S215 B260 F1 in the start.gcode
+ * Automatic Temperature Mode
+ *
+ * Dynamically adjust the hotend target temperature based on planned E moves.
+ *
+ * (Contrast with PID_EXTRUSION_SCALING, which tracks E movement and adjusts PID
+ *  behavior using an additional kC value.)
+ *
+ * Autotemp is calculated by (mintemp + factor * mm_per_sec), capped to maxtemp.
+ *
+ * Enable Autotemp Mode with M104/M109 F<factor> S<mintemp> B<maxtemp>.
+ * Disable by sending M104/M109 with no F parameter (or F0 with AUTOTEMP_PROPORTIONAL).
  */
 #define AUTOTEMP
 #if ENABLED(AUTOTEMP)
-  #define AUTOTEMP_OLDWEIGHT 0.98
+  #define AUTOTEMP_OLDWEIGHT    0.98
+  // Turn on AUTOTEMP on M104/M109 by default using proportions set here
+  //#define AUTOTEMP_PROPORTIONAL
+  #if ENABLED(AUTOTEMP_PROPORTIONAL)
+    #define AUTOTEMP_MIN_P      0 // (°C) Added to the target temperature
+    #define AUTOTEMP_MAX_P      5 // (°C) Added to the target temperature
+    #define AUTOTEMP_FACTOR_P   1 // Apply this F parameter by default (overridden by M104/M109 F)
+  #endif
 #endif
 
 // Extra options for the M114 "Current Position" report

Marlin/src/module/planner.cpp

@@ -2973,9 +2973,18 @@ void Planner::set_max_jerk(const AxisEnum axis, float targetValue) {
 #if ENABLED(AUTOTEMP)
 
   void Planner::autotemp_M104_M109() {
-    if ((autotemp_enabled = parser.seen('F'))) autotemp_factor = parser.value_float();
-    if (parser.seen('S')) autotemp_min = parser.value_celsius();
-    if (parser.seen('B')) autotemp_max = parser.value_celsius();
+
+    #if ENABLED(AUTOTEMP_PROPORTIONAL)
+      const int16_t target = thermalManager.degTargetHotend(active_extruder);
+      autotemp_min = target + AUTOTEMP_MIN_P;
+      autotemp_max = target + AUTOTEMP_MAX_P;
+      autotemp_factor = AUTOTEMP_FACTOR_P;
+    #endif
+
+    if (parser.seenval('S')) autotemp_min = parser.value_celsius();
+    if (parser.seenval('B')) autotemp_max = parser.value_celsius();
+    if (parser.seenval('F')) autotemp_factor = parser.value_float();
+    if (!autotemp_factor) autotemp_enabled = false; // F0 will disable autotemp
   }
 
 #endif