Thermal Runaway only when printing

General Discussion
1

I use Klipper on my Ender 3 Pro.
This setup worked for months without problems.

Suddenly whenever i print something after reaching about 2mm Z-Height (no matter what i print),
Klipper shuts down with a thermal runaway error.

When i heat the nozzle without printing i can keep the temperature for hours (when making sure its not reset to 0 after the timeout)
without getting any errors, also it hold the temperature just fine.

I already did a PID Tune but that did not help.

What can i do to figure out what the problem is, i dont want to randomly buy a new heater/thermistor without knowing that those are actuably broken…

2

Hello @JappyJan !

Have you checked if the cables to the hotend are in proper shape, no lose connection, no broken cable.

Also, you may share the klippy log.

3

Hey just checked again, and yes all cables seem to be good, no loose contacts etc.

And here is my klippy.log

klippy.log (16.6 KB)

4

On what system is your Klipper running?

5

its a raspberry pi4 running raspbian (32 bit)
klipper was installed through KIAUH.sh

6

Does this support runtime logs like octoprint.log?

7

i dont know what you mean by that :confused:

i am not running octoprint, and i did not start with an octopi installation but with a clean raspbian installation.

8

The log you posted doesn’t contain an error. We need a log with the error to diagnose. In my experience these errors are always hardware like a loose pin or partially broken wire, or the hotend or bed can’t maintain temperature when the cooling fan turns on. A log with the error would make it possible to determine the likely cause.

9

Like Jake said, I’ve had the same error if the thermistor wire comes loose.

10

Sorry for the late reply, been busy a lot…

Here is a link that would most definitely contain logs from a failed print
klippy.log (5.8 MB)

11

Looking at your log it seems:

  • You are requesting a bed temperature of 45°C
  • Then you increase bed temperature to 110°C
  • Your bed heater struggles with reaching the target but does not manage to do so until Klipper errors out

Following questions:

  • You wrote that you get the error at Z=2mm: Do you start printing before the bed has reached its temperature?
  • Are you sure that a Ender 3 Pro bed even is able to reach and sustain 110°C (which is quite high for the standard Chinese beds)