Decouple filament minimum print speed from overhang slowdown (#3859)

src/libslic3r/GCode.cpp

@@ -4978,7 +4978,6 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
 
     double e_per_mm = m_writer.extruder()->e_per_mm3() * _mm3_per_mm;
 
-    double min_speed = double(m_config.slow_down_min_speed.get_at(m_writer.extruder()->id()));
     // set speed
     if (speed == -1) {
         int overhang_degree = path.get_overhang_degree();
@@ -5364,7 +5363,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             }
         }
     } else {
-        double last_set_speed = std::max((float)EXTRUDER_CONFIG(slow_down_min_speed), new_points[0].speed) * 60.0;
+        double last_set_speed = new_points[0].speed * 60.0;
 
         gcode += m_writer.set_speed(last_set_speed, "", comment);
         Vec2d prev = this->point_to_gcode_quantized(new_points[0].p);
@@ -5408,7 +5407,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             }
 
             const double line_length = (p - prev).norm();
-            double new_speed = std::max((float)EXTRUDER_CONFIG(slow_down_min_speed), pre_processed_point.speed) * 60.0;
+            double new_speed = pre_processed_point.speed * 60.0;
             if (last_set_speed != new_speed) {
                 gcode += m_writer.set_speed(new_speed, "", comment);
                 last_set_speed = new_speed;

src/libslic3r/PrintConfig.cpp

@@ -2941,7 +2941,8 @@ def = this->add("filament_loading_speed", coFloats);
 
     def = this->add("slow_down_min_speed", coFloats);
     def->label = L("Min print speed");
-    def->tooltip = L("The minimum printing speed for the filament when slow down for better layer cooling is enabled, when printing overhangs and when feature speeds are not specified explicitly.");
+    def->tooltip = L("The minimum printing speed that the printer will slow down to to attempt to maintain the minimum layer time "
+                     "above, when slow down for better layer cooling is enabled.");
     def->sidetext = L("mm/s");
     def->min = 0;
     def->mode = comAdvanced;