Cooling: add per-printer non-zero fan PWM floor and fix N=0 fan ramp override (#13715)

* Cooling: add per-printer non-zero fan PWM floor and fix N=0 ramp override
* updated parameter naming

src/libslic3r/GCode/CoolingBuffer.cpp

@@ -719,6 +719,9 @@ std::string CoolingBuffer::apply_layer_cooldown(
     // Second generate the adjusted G-code.
     std::string new_gcode;
     new_gcode.reserve(gcode.size() * 2);
+    // ORCA: per-printer minimum non-zero fan PWM. Applied at every part-cooling fan emission below so any
+    // non-zero command is raised to at least this percent (0 disables the clamp).
+    const unsigned int part_cooling_fan_min_pwm = static_cast<unsigned int>(std::max(0, m_config.part_cooling_fan_min_pwm.value));
     bool overhang_fan_control= false;
     int  overhang_fan_speed   = 0;
     bool internal_bridge_fan_control= false; // ORCA: Add support for separate internal bridge fan speed control
@@ -727,7 +730,7 @@ std::string CoolingBuffer::apply_layer_cooldown(
     int  supp_interface_fan_speed = 0;
     bool ironing_fan_control= false; // ORCA: Add support for ironing fan speed control
     int  ironing_fan_speed   = 0; // ORCA: Add support for ironing fan speed control
-    auto change_extruder_set_fan = [ this, layer_id, layer_time, &new_gcode,
+    auto change_extruder_set_fan = [ this, layer_id, layer_time, &new_gcode, part_cooling_fan_min_pwm,
         &overhang_fan_control, &overhang_fan_speed,
         &internal_bridge_fan_control, &internal_bridge_fan_speed,
         &supp_interface_fan_control, &supp_interface_fan_speed,
@@ -743,11 +746,11 @@ std::string CoolingBuffer::apply_layer_cooldown(
         int full_fan_speed_layer = EXTRUDER_CONFIG(full_fan_speed_layer);
         supp_interface_fan_speed = EXTRUDER_CONFIG(support_material_interface_fan_speed);
 
-        if (close_fan_the_first_x_layers <= 0 && full_fan_speed_layer > 0) {
+        // ORCA: previously a silent override forced `close_fan_the_first_x_layers` from 0 up to 1 whenever a ramp
-            // When ramping up fan speed from close_fan_the_first_x_layers to full_fan_speed_layer, force close_fan_the_first_x_layers above zero,
+        // was configured (`full_fan_speed_layer > 0`), so the first printed layer always had the fan disabled.
-            // so there will be a zero fan speed at least at the 1st layer.
+        // That hid the user's literal "no cooling for the first 0 layers" setting and produced a non-zero starting
-            close_fan_the_first_x_layers = 1;
+        // factor on the ramp denominator. The override has been removed: with N=0 and M>0 the ramp now genuinely
-        }
+        // starts on layer 0 at a factor of 1/M and reaches 100% at layer M-1, matching the intent of the option.
         if (int(layer_id) >= close_fan_the_first_x_layers) {
             float   fan_max_speed             = EXTRUDER_CONFIG(fan_max_speed);
             float slow_down_layer_time = float(EXTRUDER_CONFIG(slow_down_layer_time));
@@ -806,7 +809,7 @@ std::string CoolingBuffer::apply_layer_cooldown(
             m_fan_speed = fan_speed_new;
             m_current_fan_speed = fan_speed_new;
             if (immediately_apply)
-                new_gcode  += GCodeWriter::set_fan(m_config.gcode_flavor, m_fan_speed);
+                new_gcode  += GCodeWriter::set_fan(m_config.gcode_flavor, m_fan_speed, part_cooling_fan_min_pwm);
         }
         //BBS
         if (additional_fan_speed_new != m_additional_fan_speed) {
@@ -980,26 +983,26 @@ std::string CoolingBuffer::apply_layer_cooldown(
 
         if (need_set_fan) {
             if (fan_speed_change_requests[CoolingLine::TYPE_OVERHANG_FAN_START]){
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, overhang_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, overhang_fan_speed, part_cooling_fan_min_pwm);
                 m_current_fan_speed = overhang_fan_speed;
             } else if (fan_speed_change_requests[CoolingLine::TYPE_INTERNAL_BRIDGE_FAN_START]){ // ORCA: Add support for separate internal bridge fan speed control
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, internal_bridge_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, internal_bridge_fan_speed, part_cooling_fan_min_pwm);
                 m_current_fan_speed = internal_bridge_fan_speed;
             }
             else if (fan_speed_change_requests[CoolingLine::TYPE_SUPPORT_INTERFACE_FAN_START]){
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, supp_interface_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, supp_interface_fan_speed, part_cooling_fan_min_pwm);
                 m_current_fan_speed = supp_interface_fan_speed;
             }
             else if (fan_speed_change_requests[CoolingLine::TYPE_IRONING_FAN_START]){
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, ironing_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, ironing_fan_speed, part_cooling_fan_min_pwm);
                 m_current_fan_speed = ironing_fan_speed;
             }
             else if(fan_speed_change_requests[CoolingLine::TYPE_FORCE_RESUME_FAN] && m_current_fan_speed != -1){
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_current_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_current_fan_speed, part_cooling_fan_min_pwm);
                 fan_speed_change_requests[CoolingLine::TYPE_FORCE_RESUME_FAN] = false;
             }
             else
-                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_fan_speed);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_fan_speed, part_cooling_fan_min_pwm);
             need_set_fan = false;
         }
         pos = line_end;

src/libslic3r/GCode/FanMover.cpp

@@ -230,7 +230,10 @@ void FanMover::_remove_slow_fan(int16_t min_speed, float past_sec) {
 
 std::string FanMover::_set_fan(int16_t speed) {
     //const Tool* tool = m_writer.get_tool(m_currrent_extruder < 20 ? m_currrent_extruder : 0);
-    return GCodeWriter::set_fan(m_writer.config.gcode_flavor.value, speed);
+    // ORCA: apply the per-printer non-zero fan PWM floor so reposted fan commands respect the clamp too.
+    const int floor_pct = m_writer.config.part_cooling_fan_min_pwm.value;
+    const unsigned int part_cooling_fan_min_pwm = floor_pct > 0 ? static_cast<unsigned int>(floor_pct) : 0u;
+    return GCodeWriter::set_fan(m_writer.config.gcode_flavor.value, speed, part_cooling_fan_min_pwm);
 }
 
 

src/libslic3r/GCodeWriter.cpp

@@ -1092,9 +1092,13 @@ std::string GCodeWriter::unlift()
     return gcode;
 }
 
-std::string GCodeWriter::set_fan(const GCodeFlavor gcode_flavor, unsigned int speed)
+std::string GCodeWriter::set_fan(const GCodeFlavor gcode_flavor, unsigned int speed, unsigned int part_cooling_fan_min_pwm)
 {
     std::ostringstream gcode;
+    // ORCA: clamp non-zero fan commands up to the configured PWM floor so fans that can't spool at low duty
+    // cycles still start reliably. Zero (fan off) is preserved exactly so disable-fan commands are never altered.
+    if (speed > 0 && part_cooling_fan_min_pwm > 0 && speed < part_cooling_fan_min_pwm)
+        speed = part_cooling_fan_min_pwm;
     if (speed == 0) {
         switch (gcode_flavor) {
         case gcfTeacup:
@@ -1129,7 +1133,9 @@ std::string GCodeWriter::set_fan(const GCodeFlavor gcode_flavor, unsigned int sp
 std::string GCodeWriter::set_fan(unsigned int speed) const
 {
     //BBS
-    return GCodeWriter::set_fan(this->config.gcode_flavor, speed);
+    // ORCA: pick up the per-printer PWM floor from the active config.
+    return GCodeWriter::set_fan(this->config.gcode_flavor, speed,
+                                static_cast<unsigned int>(std::max(0, this->config.part_cooling_fan_min_pwm.value)));
 }
 
 //BBS: set additional fan speed for BBS machine only

src/libslic3r/GCodeWriter.hpp

@@ -98,7 +98,9 @@ public:
     void set_xy_offset(double x, double y) { m_x_offset = x; m_y_offset = y; }
     Vec2f get_xy_offset() { return Vec2f{m_x_offset, m_y_offset}; };
     // To be called by the CoolingBuffer from another thread.
-    static std::string set_fan(const GCodeFlavor gcode_flavor, unsigned int speed);
+    // ORCA: `part_cooling_fan_min_pwm` (0-100, default 0) is a floor applied only when `speed` is non-zero, used to overcome
+    // PWM start-up thresholds on fans that won't spool below a certain duty cycle. A `speed` of 0 is always honoured.
+    static std::string set_fan(const GCodeFlavor gcode_flavor, unsigned int speed, unsigned int part_cooling_fan_min_pwm = 0);
     // To be called by the main thread. It always emits the G-code, it does not remember the previous state.
     // Keeping the state is left to the CoolingBuffer, which runs asynchronously on another thread.
     std::string set_fan(unsigned int speed) const;

src/libslic3r/Preset.cpp

@@ -1326,7 +1326,7 @@ static std::vector<std::string> s_Preset_machine_limits_options {
 static std::vector<std::string> s_Preset_printer_options {
     "printer_technology",
     "printable_area", "extruder_printable_area", "bed_exclude_area","bed_custom_texture", "bed_custom_model", "gcode_flavor",
-    "fan_kickstart", "fan_speedup_time", "fan_speedup_overhangs",
+    "fan_kickstart", "part_cooling_fan_min_pwm", "fan_speedup_time", "fan_speedup_overhangs",
     "single_extruder_multi_material", "manual_filament_change", "file_start_gcode", "machine_start_gcode", "machine_end_gcode", "before_layer_change_gcode", "printing_by_object_gcode", "layer_change_gcode", "time_lapse_gcode", "wrapping_detection_gcode", "change_filament_gcode", "change_extrusion_role_gcode",
     "printer_model", "printer_variant", "printer_extruder_id", "printer_extruder_variant", "extruder_variant_list", "default_nozzle_volume_type",
     "printable_height", "extruder_printable_height", "extruder_clearance_radius", "extruder_clearance_height_to_lid", "extruder_clearance_height_to_rod",

src/libslic3r/Print.cpp

@@ -133,6 +133,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
         "fan_cooling_layer_time",
         "full_fan_speed_layer",
         "fan_kickstart",
+        "part_cooling_fan_min_pwm",
         "fan_speedup_overhangs",
         "fan_speedup_time",
         "filament_colour",

src/libslic3r/PrintConfig.cpp

@@ -3724,6 +3724,28 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(0));
 
+    // ORCA: minimum non-zero part cooling fan speed.
+    def = this->add("part_cooling_fan_min_pwm", coInt);
+    def->label = L("Minimum non-zero part cooling fan speed");
+    def->tooltip = L("Some part-cooling fans cannot start spinning when commanded below a certain PWM duty cycle. "
+                     "When set above 0, any non-zero part-cooling fan command will be raised to at least this percentage "
+                     "so the fan reliably starts. A fan command of 0 (fan off) is always honoured exactly. "
+                     "This clamp is applied after every other fan calculation (first-layer ramp, layer-time interpolation, "
+                     "overhang/bridge/support-interface/ironing overrides), so scaling still operates within the range "
+                     "[this value, 100%]."
+                     "\nIf your firmware already disables the fan below a threshold (for example Klipper's "
+                     "[fan] off_below: 0.10 shuts the fan off whenever the commanded duty cycle is below 10%), "
+                     "this option and the firmware threshold should ideally be set to the same value. Matching them "
+                     "(e.g. off_below: 0.10 in Klipper and 10% here) guarantees the slicer never emits a non-zero "
+                     "value that the firmware would silently drop, and the fan never receives a value below the one "
+                     "you know it can actually spool at."
+                     "\nSet to 0 to deactivate.");
+    def->sidetext = L("%");
+    def->min = 0;
+    def->max = 100;
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionInt(0));
+
 
     def = this->add("time_cost", coFloat);
     def->label = L("Time cost");

src/libslic3r/PrintConfig.hpp

@@ -1309,6 +1309,10 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionFloat,               fan_kickstart))
     ((ConfigOptionBool,                fan_speedup_overhangs))
     ((ConfigOptionFloat,               fan_speedup_time))
+    // ORCA: minimum PWM (as a percent 0-100) emitted when the part-cooling fan is asked for a non-zero speed.
+    // Used to overcome the PWM start-up threshold on fans that cannot spool below a certain duty cycle.
+    // A value of 0 (the default) leaves behaviour unchanged. A fan command of 0 (off) is always honoured.
+    ((ConfigOptionInt,                 part_cooling_fan_min_pwm))
     ((ConfigOptionFloats,              filament_diameter))
     ((ConfigOptionBoolsNullable,       filament_adaptive_volumetric_speed))
     ((ConfigOptionStrings,             volumetric_speed_coefficients))

src/slic3r/GUI/Tab.cpp

@@ -4500,6 +4500,8 @@ void TabPrinter::build_fff()
         line.append_option(optgroup->get_option("fan_speedup_overhangs"));
         optgroup->append_line(line);
         optgroup->append_single_option_line("fan_kickstart", "printer_basic_information_cooling_fan#fan-kick-start-time");
+        // ORCA: PWM floor for fans that won't spool at low duty cycles.
+        optgroup->append_single_option_line("part_cooling_fan_min_pwm", "printer_basic_information_cooling_fan#minimum-non-zero-part-cooling-fan-speed");
 
         optgroup = page->new_optgroup(L("Extruder Clearance"), "param_extruder_clearance");
         optgroup->append_single_option_line("extruder_clearance_radius", "printer_basic_information_extruder_clearance#radius");