Strange behavior extruder temperature

[lukics]

Yesterday I finished (whatever finished means) my first Voron up to the state I can print the extra parts I need.
It is a Formbot kit. Overall I am impressed.

During the prints, I got a few aborts of printing with extruder heater issues. I had to set verify_heater - max_error to 400.
What I see is that for no reason the temperature dropped and looking at the power of the heater the power is not holding against this drop as expected, bust is below 100%.

In the example below a print was aborted (1) by an error of the heater, and the repetition of the print shows exactly the same pattern (2) the exemption for succeeding is the increased max_error value:



I cannot explain this perfect match.

During the print I also see sporadic oscillation of the temperature, and the steady stable periodes. I did a PID calibration.



Any Idea what to look at?
I will at next try the smoothing option of the thermistor, and do PID calibration again.

 

[NoGuru]

The thermistor or heater is bad, or you have a bad wire or terminal connection. I am going to guess that you print in the center of the bed?
If this happens only in a certain spot on the bed, its a broken wire or bad connection on the toolhead, if its random the thermistor or heater is bad.

 

[lukics]

The thermistor or heater is bad, or you have a bad wire or terminal connection

That was my first guess, as I was making my first experience crimping the wires for the toolhead PCB connector. Though this does not explain the carbon copy curve on my first picture after retrying the same print.

 

[lukics]

The problem was solved by adding
[extruder] smooth_time: 1
I am sure that this is just covering symptoms of something deeper. I anyhow plan to do a can-bus conversion and hope to fight different problems.