Klipper: Internal error on command:"PID_CALIBRATE"

[Michael-Bell]

pi@octopi:~/klipper $ git rev-parse HEAD
62fc5dc2884c41eb45880b0e9c988cabb025d1c1

Running on a Pi3 with a genuine E3D V6 heater and thermister. I run PID_CALIBRATE HEATER=extruder TARGET=220, then the temperature graph will look like

I've attached my log.

I think this is the relevant error message:

Internal error on command:"PID_CALIBRATE"
Traceback (most recent call last):
  File "/home/pi/klipper/klippy/gcode.py", line 188, in process_commands
    handler(params)
  File "/home/pi/klipper/klippy/gcode.py", line 69, in <lambda>
    func = lambda params: origfunc(self.get_extended_params(params))
  File "/home/pi/klipper/klippy/extras/pid_calibrate.py", line 39, in cmd_PID_CALIBRATE
    Kp, Ki, Kd = calibrate.calc_final_pid()
  File "/home/pi/klipper/klippy/extras/pid_calibrate.py", line 132, in calc_final_pid
    midpoint_pos = sorted(cycle_times)[len(cycle_times)/2][1]
IndexError: list index out of range

[muenznej]

Hi, i had such an issue with my volcano and a new thermistor. The error occurs as far as i understand because the heater verifier code throws an error if heating up takes too long.

First: check if your thermistor settings are correct ( i used a thermocouple and calibrated it ref. #1022 )
Second: The problem for me was/is:
The heater is maybe only 30 Watts and you probably have strong part cooling fans running which cause a cooling of the nozzle (especially if you are close to the print bed) and your heater just cannot handle fast enough. I increased the tolerances for heater errors and did the PID for lower target temperature (with blowers and heat bed close). When i print i ramp the cooling over 5 layers from 0 to 100% which helps the PID to tolerate the temperature drops.

hope it makes any sense and helps :-)

[Michael-Bell]

I'm away from the printer for a few days, so I cannot test anything now, but to clarify it can heat up and maintain temps pretty well with Marlin. It would also heat quckly and run calibration at a lower temp without issue. Only when running a high temp PID test it has a curve to heating and never gets to the proper temp, only 200C usually when throwing the error. Did not seem to matter if I had it at 200 and run command or it was at ambient and running the command.

[muenznej]

Hi,

[...] Only when running a high temp PID test it has a curve to heating and never gets to the proper temp, only 200C usually when throwing the error. Did not seem to matter if I had it at 200 and run command or it was at ambient and running the command.

that was the same for me and its also running properly at 250°( when it has reached that point) but the rate of change kills the PID tolerance that is set up in this code:

# Heater and temperature sensor verification. Heater verification is
# automatically enabled for each heater that is configured on the
# printer. Use verify_heater sections to change the default settings.
#[verify_heater heater_config_name]
#heating_gain: 2
#   The minimum temperature (in Celsius) that the heater must increase
#   by when approaching a new target temperature. The default is 2.
#check_gain_time:
#   The amount of time (in seconds) that the heating_gain must be met
#   in before an error is raised. The default is 20 seconds for
#   extruders and 60 seconds for heater_bed.
#hysteresis: 5
#   The difference between the target temperature and the current
#   temperature for the heater to be considered within range of the
#   target temperature. The default is 5.
#max_error: 120
#   The maximum temperature difference a heater that falls outside the
#   target temperature range may accumulate before an error is
#   raised. For example, if the target temperature is 200, the
#   hysteresis is 5, the max_error is 120, and the temperature is
#   reported at 185 degrees for 12 seconds then an error would be
#   raised (or 24 seconds at 190, or 120 seconds at 194, etc.). The
#   default is 120.

The tolerance time and temperature error is defined in that sections and their defaults are listed. You could circumvent the error completely by setting check_gain_time (i think) to a very high value i.e.: check_gain_time: 999999.
I think its just a low power heater issue and marlin has a larger acceptance for that.

[KevinOConnor]

As mentioned above, the root cause of the above error is a "veryify_heater" check. It looks like you will need to tune the default verify_heater settings for your extruder.

-Kevin

[KevinOConnor]

I'm going to close this as I think the original question was answered.

-Kevin