Add option to wait for cooling temperature when changing filament.

src/libslic3r/GCode/WipeTower.cpp

@@ -350,11 +350,11 @@ class WipeTowerWriter
 		return *this;
 	}
 
-	// Set extruder temperature, don't wait by default.
-	WipeTowerWriter& set_extruder_temp(int temperature, bool wait = false)
+	// Set extruder temperature, optionally wait.
+	WipeTowerWriter& set_extruder_temp(int temperature, bool wait)
 	{
         m_gcode += "G4 S0\n"; // to flush planner queue
-        m_gcode += "M" + std::to_string(wait ? 109 : 104) + " S" + std::to_string(temperature) + "\n";
+        m_gcode += "M" + std::string(wait ? "109 R" : "104 S") + std::to_string(temperature) + "\n";
         return *this;
     }
 
@@ -639,6 +639,7 @@ void WipeTower::set_extruder(size_t idx, const PrintConfig& config)
         m_filpar[idx].cooling_moves           = config.filament_cooling_moves.get_at(idx);
         m_filpar[idx].cooling_initial_speed   = float(config.filament_cooling_initial_speed.get_at(idx));
         m_filpar[idx].cooling_final_speed     = float(config.filament_cooling_final_speed.get_at(idx));
+        m_filpar[idx].cooling_wait_for_temp   = float(config.filament_cooling_wait_for_temp.get_at(idx));
         m_filpar[idx].filament_stamping_loading_speed     = float(config.filament_stamping_loading_speed.get_at(idx));
         m_filpar[idx].filament_stamping_distance          = float(config.filament_stamping_distance.get_at(idx));
     }
@@ -898,13 +899,14 @@ void WipeTower::toolchange_Unload(
 
     const bool do_ramming = m_semm || m_filpar[m_current_tool].multitool_ramming;
     const bool cold_ramming = m_is_mk4mmu3;
+    const int cold_ramming_temperature = old_temperature - 20;
 
     if (do_ramming) {
         writer.travel(ramming_start_pos); // move to starting position
         if (! m_is_mk4mmu3)
             writer.disable_linear_advance();
         if (cold_ramming)
-            writer.set_extruder_temp(old_temperature - 20);
+            writer.set_extruder_temp(cold_ramming_temperature, false);
     }
     else
         writer.set_position(ramming_start_pos);
@@ -1042,9 +1044,13 @@ void WipeTower::toolchange_Unload(
                 writer.retract(stamping_dist_e, m_filpar[m_current_tool].unloading_speed * 60.f);
             }
 
+            if (m_filpar[m_current_tool].cooling_wait_for_temp && i == number_of_cooling_moves - 2 && cold_ramming) {
+                // Do at least one full cycle at the cooling temperature before warming up again.
+                writer.set_extruder_temp(cold_ramming_temperature, true);
+            }
             if (i == number_of_cooling_moves - 1 && change_temp_later) {
                 // If cold_ramming, the temperature change should be done before the last cooling move.
-                    writer.set_extruder_temp(new_temperature, false);
+                writer.set_extruder_temp(new_temperature, false);
             }
 
             float speed = initial_speed + speed_inc * 2*i;

src/libslic3r/GCode/WipeTower.hpp

@@ -250,6 +250,7 @@ class WipeTower
         int                 cooling_moves = 0;
         float               cooling_initial_speed = 0.f;
         float               cooling_final_speed = 0.f;
+        bool                cooling_wait_for_temp = false;
         float               ramming_line_width_multiplicator = 1.f;
         float               ramming_step_multiplicator = 1.f;
         float               max_e_speed = std::numeric_limits<float>::max();

src/libslic3r/Preset.cpp

@@ -519,7 +519,7 @@ static std::vector<std::string> s_Preset_filament_options {
     "filament_colour", "filament_diameter", "filament_type", "filament_soluble", "filament_abrasive", "filament_notes", "filament_max_volumetric_speed", "filament_infill_max_speed", "filament_infill_max_crossing_speed",
     "extrusion_multiplier", "filament_density", "filament_cost", "filament_spool_weight", "filament_loading_speed", "filament_loading_speed_start", "filament_load_time",
     "filament_unloading_speed", "filament_unloading_speed_start", "filament_unload_time", "filament_toolchange_delay", "filament_cooling_moves", "filament_stamping_loading_speed", "filament_stamping_distance",
-    "filament_cooling_initial_speed", "filament_purge_multiplier", "filament_cooling_final_speed", "filament_ramming_parameters", "filament_minimal_purge_on_wipe_tower",
+    "filament_cooling_initial_speed", "filament_purge_multiplier", "filament_cooling_final_speed", "filament_cooling_wait_for_temp", "filament_ramming_parameters", "filament_minimal_purge_on_wipe_tower",
     "filament_multitool_ramming", "filament_multitool_ramming_volume", "filament_multitool_ramming_flow", 
     "temperature", "idle_temperature", "first_layer_temperature", "bed_temperature", "first_layer_bed_temperature", "fan_always_on", "cooling", "cooling_slowdown_logic",
     "cooling_perimeter_transition_distance", "min_fan_speed",

src/libslic3r/Print.cpp

@@ -238,6 +238,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             || opt_key == "filament_minimal_purge_on_wipe_tower"
             || opt_key == "filament_cooling_initial_speed"
             || opt_key == "filament_cooling_final_speed"
+            || opt_key == "filament_cooling_wait_for_temp"
             || opt_key == "filament_purge_multiplier"
             || opt_key == "filament_ramming_parameters"
             || opt_key == "filament_multitool_ramming"

src/libslic3r/PrintConfig.cpp

@@ -1379,6 +1379,16 @@ void PrintConfigDef::init_fff_params()
     def->mode = comExpert;
     def->set_default_value(new ConfigOptionFloats { 3.4 });
 
+    def = this->add("filament_cooling_wait_for_temp", coBools);
+    def->label = L("Wait for the nozzle to cool before the last cooling move");
+    def->tooltip = L("During the cooling moves, the nozzle gradually approaches the optimal temperature for forming "
+                     "a good filament tip prior to unloading. If the ambient temperature is too high, the nozzle may not "
+                     "reach the desired temperature, resulting in stringing which can cause blobs or misloads later. "
+                     "When checked, the printer will wait for the optimal temperature before finishing the last cooling "
+                     "move to increase the chances of a good tip. This option requires at least 2 cooling moves to work.");
+    def->mode = comExpert;
+    def->set_default_value(new ConfigOptionBools { false });
+
     def = this->add("filament_purge_multiplier", coPercents);
     def->label = L("Purge volume multiplier");
     def->tooltip = L("Purging volume on the wipe tower is determined by 'multimaterial_purging' in Printer Settings. "

src/libslic3r/PrintConfig.hpp

@@ -843,6 +843,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionFloats,              filament_cooling_initial_speed))
     ((ConfigOptionFloats,              filament_minimal_purge_on_wipe_tower))
     ((ConfigOptionFloats,              filament_cooling_final_speed))
+    ((ConfigOptionBools,               filament_cooling_wait_for_temp))
     ((ConfigOptionPercents,            filament_purge_multiplier))
     ((ConfigOptionStrings,             filament_ramming_parameters))
     ((ConfigOptionBools,               filament_multitool_ramming))

src/slic3r/GUI/Tab.cpp

@@ -2323,6 +2323,7 @@ void TabFilament::build()
         optgroup->append_single_option_line("filament_cooling_moves");
         optgroup->append_single_option_line("filament_cooling_initial_speed");
         optgroup->append_single_option_line("filament_cooling_final_speed");
+        optgroup->append_single_option_line("filament_cooling_wait_for_temp");
         optgroup->append_single_option_line("filament_stamping_loading_speed");
         optgroup->append_single_option_line("filament_stamping_distance");
         optgroup->append_single_option_line("filament_purge_multiplier");