Part Cooling Fan does not start at slow speeds

Prokktor

Hi,

I replaced my part cooling fan with a 12V model, but I had the same problem with the original JGAurora fan:

The fan can run at 1% or 2% power, but it needs around 20% power to start.
ATM I give it a slight push at the start of layer 2 but that cant be the solution...

Is there some way to tell cura to set the Fan speed to 30% for 0.1s at the start of layer 2 or at every fan speed change?

Regards,

Martin

Samuel Pinches

Hi Martin,

There's some options to do exactly this in the marlin firmware advanced configuration file (configuration_adv.h), around line 200.

Cheers,

Sam

/**
 * Controller Fan
 * To cool down the stepper drivers and MOSFETs.
 *
 * The fan will turn on automatically whenever any stepper is enabled
 * and turn off after a set period after all steppers are turned off.
 */
//#define USE_CONTROLLER_FAN
#if ENABLED(USE_CONTROLLER_FAN)
  //#define CONTROLLER_FAN_PIN -1        // Set a custom pin for the controller fan
  #define CONTROLLERFAN_SECS 60          // Duration in seconds for the fan to run after all motors are disabled
  #define CONTROLLERFAN_SPEED 255        // 255 == full speed
#endif

// When first starting the main fan, run it at full speed for the
// given number of milliseconds.  This gets the fan spinning reliably
// before setting a PWM value. (Does not work with software PWM for fan on Sanguinololu)
//#define FAN_KICKSTART_TIME 100

/**
 * PWM Fan Scaling
 *
 * Define the min/max speeds for PWM fans (as set with M106).
 *
 * With these options the M106 0-255 value range is scaled to a subset
 * to ensure that the fan has enough power to spin, or to run lower
 * current fans with higher current. (e.g., 5V/12V fans with 12V/24V)
 * Value 0 always turns off the fan.
 *
 * Define one or both of these to override the default 0-255 range.
 */
//#define FAN_MIN_PWM 50
//#define FAN_MAX_PWM 128

// @section extruder

AON

I am trying to understand this.
The A5 has three speeds (or so I thought)  OFF (0% = 0 RPM) ON SLOW (50% = 127.5RPM) and  ON FAST (100% = 255 RPM.
Are you saying it is completely variable speed and can be set to any% or RPM value from 0% to 100%?
I apologize if this is a dumb question but most of  what I am reading is presently over my head.
Thanks
Alan

Prokktor

Yes exactly that.
The fan gets a pwm signal from a mosfet on the mainboard. 
This resembles something like 0V to 24V for values from 0 to 255.
Those are not RPM, its simply a byte value, a tiny int or whatever you like to call it.
So 20% gets converted to 51 which then translates to around 4.8V for your 24V fan.
How many RPMs that is depends on your fan and the printer has no way of knowing that, it does not even know if the fan spinns at all.

Since the fan needs more volts to start spinning than it needs to keep spinning I opened this thread^^