.

docs/Config_Reference.md

@@ -2906,6 +2906,12 @@ a shutdown_speed equal to max_power.
 #   The fan speed (expressed as a value from 0.0 to 1.0) that the fan
 #   will be set to when its associated heater is enabled. The default
 #   is 1.0
+#min_rpm: 0
+#   The minimum expected fan speed in RPM. Klipper shuts down if the
+#   fan is enabled but fan RPM reading from the tachometer is below
+#   this value. This parameter is optional but tachometer_pin must
+#   be specified for this parameter to be valid.
+```
 ```
 
 ### [controller_fan]

klippy/extras/heater_fan.py

@@ -3,9 +3,11 @@
 # Copyright (C) 2016-2020  Kevin O'Connor <[email protected]>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
+import logging
 from . import fan
 
 PIN_MIN_TIME = 0.100
+SAFETY_CHECK_INIT_TIME = 3.
 
 class PrinterHeaterFan:
     def __init__(self, config):
@@ -22,6 +24,13 @@ def __init__(self, config):
         self.fan_speed = config.getfloat("fan_speed", 1., minval=0., maxval=1.)
         self.last_speed = 0.
         self.enabled = 1
+        self.name = config.get_name().split()[-1]
+        self.num_err = 0
+        self.max_err = 3
+        self.min_rpm = config.getint("min_rpm", 0, minval=0)
+        if self.min_rpm > 0 and self.fan.tachometer._freq_counter is None:
+            raise config.error(
+                "'tachometer_pin' must be specified before enabling `min_rpm`")
         gcode = self.printer.lookup_object('gcode')
         gcode.register_mux_command(
             "SET_HEATER_FAN", "HEATER_FAN", self.name,
@@ -32,6 +41,9 @@ def handle_ready(self):
         self.heaters = [pheaters.lookup_heater(n) for n in self.heater_names]
         reactor = self.printer.get_reactor()
         reactor.register_timer(self.callback, reactor.monotonic()+PIN_MIN_TIME)
+        if self.min_rpm > 0:
+            reactor.register_timer(
+                self.fan_check, reactor.monotonic()+SAFETY_CHECK_INIT_TIME)
     def get_status(self, eventtime):
         return self.fan.get_status(eventtime)
     def callback(self, eventtime):
@@ -58,6 +70,25 @@ def cmd_SET_HEATER_FAN(self, gcmd):
             curtime = self.printer.get_reactor().monotonic()
             print_time = self.fan.get_mcu().estimated_print_time(curtime)
             self.fan.set_speed(print_time + PIN_MIN_TIME, 0.0)
+    def fan_check(self, eventtime):
+        rpm = self.fan.tachometer.get_status(eventtime)['rpm']
+        has_err = False
+        if rpm is not None:
+            for heater in self.heaters:
+                current_temp, target_temp = heater.get_temp(eventtime)
+                if current_temp > self.heater_temp and rpm < self.min_rpm:
+                    has_err = True
+        if has_err:
+            self.num_err += 1
+            if self.num_err > self.max_err:
+                msg = "'%s' spinning below minimum safe speed of %d rev/min" % (
+                    self.name, self.min_rpm)
+                logging.error(msg)
+                self.printer.invoke_shutdown(msg)
+                return self.printer.get_reactor().NEVER
+        else:
+            self.num_err = 0
+        return eventtime + 1.5
 
 def load_config_prefix(config):
     return PrinterHeaterFan(config)