strange behavior from the thermistor

[jens55]

@siam this kind of behaviour is a common failure mode for thermistors. Not necessarily the exact failure you are seeing but the rapidly changing temperature swings that are much faster than what the heated mass could reasonably swing if the supply current was stopped and restarted. I am specifically talking about the quick sharp excursion in temperature and not the slower overall temperature change.
You would likely see a slow deterioration/worsening with time.
Get yourself a new thermistor.

[SIam]

in this case i will try a new one thanks for your assistance

[SIam]

That was not the solution i have changed the Hotend and Thermistor after this i was able to print. Now i wanted to Start a new Print and i get always the error :

8.4.2021, 20:50:50	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.1°C/sec
8.4.2021, 20:50:16	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.3°C/sec
8.4.2021, 20:49:39	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.4°C/sec
8.4.2021, 20:47:28	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.4°C/sec
8.4.2021, 20:45:07	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.2°C/sec
8.4.2021, 20:44:19	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.3°C/sec
8.4.2021, 20:43:30	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.3°C/sec
8.4.2021, 20:42:49	Error: Heater 1 fault: temperature rising much more slowly than the expected 1.4°C/sec

What surprises me is that the expected temperature is constantly different ? The next thing is that this errors occur the most times at the same Temperature, although the temperature continues to rise as you can see here in this Video.
show video

[jens55]

@siam, did you run heater tuning after you changed the thermistor?
Did you use the correct data points for your new thermistor (in case it was different from the previous version)

[SIam]

@jens55 said in strange behavior from the thermistor:

@siam, did you run heater tuning after you changed the thermistor?

yes i have done

Did you use the correct data points for your new thermistor (in case it was different from the previous version)

The new thermistor is The same type as the old one

[jens55]

@jens55, ugh, that is one ugly temperature graph! The good thing is that you don't have the sharp spikes and drops you had before.
Go ahead and see what re-tuning the hot end will do for you.

[jens55]

Hmmmm .... how did the tuning process go? Anything unusual? If you just turn on the hot end and let it sit without printing, what does the temperature do ?

[SIam]

@jens55 said in strange behavior from the thermistor:

@jens55, ugh, that is one ugly temperature graph! The good thing is that you don't have the sharp spikes and drops you had before.
Go ahead and see what re-tuning the hot end will do for you.

Retuning is running now and the hotend has reached 220 C° ....

Here the log info

8.4.2021, 21:48:51	Auto tuning heater 1 completed after 3 idle and 10 tuning cycles in 510 seconds. This heater needs the following M307 command:
 M307 H1 R1.294 C288.4:230.7 D4.05 S1.00 V24.3
Send M500 to save this command in config-override.g
8.4.2021, 21:45:56	Auto tune starting phase 3, fan on
8.4.2021, 21:43:45	Auto tune starting phase 3, fan off
8.4.2021, 21:41:52	Auto tune starting phase 2, heater settling
8.4.2021, 21:40:25	Auto tune starting phase 1, heater on
8.4.2021, 21:40:20	M303 T0 S220
Auto tuning heater 1 using target temperature 220.0°C and PWM 1.00 - do not leave printer unattended

and here a picture of the process

and now it seems my printer will be kidding me i have save the settings and loaded with m501 and now i get this message:

8.4.2021, 21:50:23	M501
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 205C

[jens55]

@siam, I believe the thermistor is working well but that something is messed up in the setup parameters. Unfortunately I do not know config files well enough to help but I am sure that before long somebody else will pop up with the answer.
The warning that you are getting is for the bed heater and not the nozzle heater. Maybe verify that the correct parameters ended up in the right file as it is odd to get a bed heat warning when you were messing with the nozzle temperature.

[SIam]

@jens55 said in strange behavior from the thermistor:

Hmmmm .... how did the tuning process go? Anything unusual? If you just turn on the hot end and let it sit without printing, what does the temperature do ?

after the pid tuning i can reach 220 c° without error and the temperature is stable range 219.8 - 220.1 C°

[jens55]

@siam, so everything is working now?

[SIam]

@jens55 said in strange behavior from the thermistor:

@siam, I believe the thermistor is working well but that something is messed up in the setup parameters. Unfortunately I do not know config files well enough to help but I am sure that before long somebody else will pop up with the answer.
The warning that you are getting is for the bed heater and not the nozzle heater. Maybe verify that the correct parameters ended up in the right file as it is odd to get a bed heat warning when you were messing with the nozzle temperature.

Ok your right is heater 0 not 1

[SIam]

@jens55 said in strange behavior from the thermistor:

@siam, so everything is working now?

happy too early ....

The temperature goes now slowly down and is no longer highly regulated

and now heater error ....

8.4.2021, 22:15:17	Error: Heater 1 fault: temperature excursion exceeded 15.0°C (target 220.0°C, actual 203.9°C)

[jens55]

@siam, dang, I thought we had it sorted Is it dropping while you are printing or just when it is sitting there? If it happens while you are printing then try without printing. Do you have the part cooling fan on maybe? try without the part cooling fan.
I am really grasping at straws here and am quickly running out of things to try ......

[SIam]

@jens55 said in strange behavior from the thermistor:

dang, I thought we had it sorted Is it dropping while you are printing or just when it is sitting there? If it happens while you are printing then try without printing.

Until this evening i was able to print without problems but since a couple of hours is printing impossible. Because the printer reaches not the print temperature anymore

Do you have the part cooling fan on maybe? try without the part cooling fan.

part cooling is off

I am really grasping at straws here and am quickly running out of things to try ......

that's my problem too !!

[jens55]

@siam, the only thing that is left is the possibility of an intermittent power connection to the heater. Either from flexing due to the printhead moving about or, if the power cables are interrupted anywhere for a connector, from a bad connector.
Try disconnecting and re-installing all connectors (including the one on the Duet board). Bad connections can develop over time and produce a bit of resistance that in turn will reduce power delivered to the heating element.

[SIam]

@jens55 it seems that i have found my work over the weekend .... in the hope of finding the fault