Heater Decoupled by Fan

Tooluser

Arduino Mega Ramps 1.4

I am trying to connect the cooling fan on pin 9,  I am getting 6.5 volts at the terminals, the fan turns on when the print starts but then the heater decouples after a few layers. So I am thinking that I have the settings right but something is conflicting?

This is the set up I have in Config.h.

#define FAN_BOARD_PIN -9  // was -1 (pins.h says Fan is on pin 9)

This line is from the "Start Configuration String" under Config.h

"fanBoardPin": -9,   // was -1

This line from "Pins.h" 

 #define ORIG_FAN_PIN      9

//#define HEATER_2_PIN       9  // This line I disabled

any good Advice??

Thanks

Repetier

Check your temperature graph if the temperature goes down when enabling the fan and then comes up. This would mean you are cooling the extruder and not the filament below extruder like it should be. The temperature controller then needs some time to get it back to temperature and the drop is bigger then the allowed variance. Then you would need to increase

#define DECOUPLING_TEST_MAX_HOLD_VARIANCE 20

Tooluser

Thanks for that, I found that the fan is working correctly from the settings, when it operates the bed temperature drops slowly to 105 C and then shuts down the print, I would not have thought that a small fan (40x40mm) could have such a large impact on the heated bed! However there seems to be no effect on the temperature of the extruder so I will try some changes on the  command line you cite above.

Tooluser

Ok, problem solved, had to increase #define DECOUPLING_TEST_MAX_HOLD_VARIANCE 20  to 40 to maintain heat balance on heated bed, also made deflector for end of fan cowling to deflect airstream away from hot end. Seems to be working fine, Thanks .

Tooluser

No!  spoke too soon.  Problem reappears, heated bed keeps dropping out during heating, have changed DECOUPLING_TEST_MAX_HOLD_VARIANCE 20 as far as 120 and makes no difference, am now getting  " Error Temp:  raised too slow. Rise = 0.38 after 31049ms"  so what does this mean and what needs changing to solve problem?

Repetier

DECOUPLING_TEST_MAX_HOLD_VARIANCE is a region to be hold when end temperature is reached. This message . raised too slow - comes during inital heatup and means in

// Time to see a temp. change when fully heating. Consider that beds at higher temp. need longer to rise and cold

// beds need some time to get the temp. to the sensor. Time is in milliseconds! Set 0 to disable

#define HEATED_BED_DECOUPLE_TEST_PERIOD 300000

the bed must gain 1°C whcih was defined here

// Minimum temp. rise we expect after the set duration of full heating is over.

// Always keep a good safety margin to get no false positives. If your period is e.g. 10 seconds

// because at startup you already need 7 seconds until heater starts to rise temp. for sensor

// then you have 3 seconds of increased heating to reach 1°C.

#define DECOUPLING_TEST_MIN_TEMP_RISE 1

So with default values this mean your bed heted up 0.38°C in 5 minutes.

Tooluser

Fixed all my problems, I used a thin metal plate with tape over it on the hot bed, bad idea! the metal dissipates the heat quicker than the heating element can supply enough heat and firmware trips out the bed.  Second issue was I moved the power supply unit above and to one side of the heated bed for better access, did not realise that the cooling fan inside the power unit was blowing cold air across heated bed, enough to cause the firmware to trip out every 30 minutes or so. It created a feedback loop of the fan cooling heated bed and firmware telling power unit to put out more power! Get's to a point it can't supply anymore power and system shuts off.  Just thought someone else might benefit from my stupid mistakes.

Regards

Tooluser

FireflyNJ

I had this issue, dryrun was on and would not stay off.

But because of my inexperience (my first time building a 3d printer) did not know better not to check on 'have heatbed' and not have it connected.