Heater extruder temperature decoupling

recoush

Heater cartridge 65w 24V power
ramps 1.4 Arduino 2560
maybe it's is the 1.0 firmware? As i don't remember it doing with 0.94

24v 65w heater, at 1st power on set point is 230 C Max is set @330
Problem,
it overruns the 230@C preset by at least 35 Degrees, decoupling By oi at 265-280
seems to always overrun at the 1st power on to 230C

at which point it decuples at 265C Clear the warning, it comes down the set temperature of 230C after the overrun as long as i clear the error no power reset required.

I tried changing PID but does not seem to have any effect just continues to over run the preset of 230C
Open to suggestions
Recoush

recoush

adding initial or 1st power on is always an overrun and requires an acknowledgement.
subsequent new prints after the initial power on overrun are
ie 2nd 3rd usually over runs, but at 266 starts then starts to drop back down to the 230 setpoint

RAyWB

/** PID control only works target temperature +/- PID_CONTROL_RANGE. If you get much overshoot at the first temperature set, because the heater is going full power too long, you need to increase this value. For one 6.8 Ohm heater 10 is ok. With two 6.8 Ohm heater use 15. */

#define PID_CONTROL_RANGE 20

above text is copied from github configuration.h

as i guess 20 is your selected value i suggest to increase to 40 or just play around a bit

recoush

Excellent Will give that a check and set (Tests) sound like the place to start :>)
found it was set @20 changed, Now set @40
Thank you much appreciated

recoush

played with this value up to 80, still same result. Changed it back to 40
Looked into the config tool version 1.xx and found this item
DECOUPLING_TEST_MAX_HOLD_VARIANCE=20 C

said, mine being over by at least 35 Degree C
changed this to 35 Degree C

also changed extruder decouple time period from 12 to 30
if it over runs it cools down to the preset rather then alarm decouple
will continue to try variations to minimize over run
not the best fix but working
thanks

Repetier

Set heat manager to bang-bang and see how much it swings just by enabling power and disabling. Especially on first heat up you see when it crosses target temp it disables heater. Then you see how much it overshoots without any extra heat. I think that is the minimum variance. Actually pid will not start with no power so has more overshoot. You can also drop it if you reduce max. pid value so it does not use 65W for heating, which is why the swings are so big - just pure overpowered.

recoush

agree,
set at 250 C (PetG) the overshoot was 30C 281C then dropped back down.
The 35C is just high enough for the overshoot
going to re configure with the tool when i Have some more time to test :>)

recoush

Switched to bang-bang also set max pid to 225 from 255 left decoupling max hold at 35 and pid control range at 40
very little change still overshoots as long as the alarm is not re-occurring.

going to keep testing to see what if anything drops the overrun temperature.
thanks

Repetier

I assume you already did a pid calibration with M303 to check different combos of PID values? I think to reduce first overshoot you need to have a big damping. Also check in a temperature graph the output power over temperature. It shows max pid until target-control range and then it gets interesting how fast it reduces output and when it reactivates it to prevent going down too far.

recoush

actually doing that now :>)

Of course this after the fact.
My most recent prints have been failing, seems to overshoot then undershoot then decouple after having started printing.

So i am being super hopeful that the auto tune, helps fix this issues
Happy New Year!
Recoush

recoush

autotuned came up with this
M303 E0 S250 C10
results
KP2.42
Ki 0.02
KD20.83

2nd pass
just m303
KP2.54
KI0.08
KD20.31

Looks real close

recoush

Ran this routine after reading anther autotune Pid
M303 P0 S250 X0 R10 C1
results
KP1.72
KI0.06
KD 30.31

If i read this program sequence correctly it seems to have autosave to Eeprom
recoush

Repetier

- M303 P<extruder/bed> S<printTemerature> X0 R<Repetitions> C<method>- Auto

detect pid values. Use P<NUM_EXTRUDER> for heated bed. X0 saves result in

EEPROM. R is number of cycles. method 0 = classic, 1 = some overshoot, 2 = no

overshoot, 3 = pessen, 4 = Tyreus-Lyben

So yes X0 would save result to eeprom. You should see it then in eeprom editor of your host.

recoush

Yes, That worked my prints and Extruder temperature are back to Normal.
Makes sense since i changed to higher wattage heater :>)
thank You
Recoush