Klipper aborted the print with:
Heater extruder not heating at expected rate Transition to shutdown state: Heater extruder not heating at expected rate See the ‘verify_heater’ section in docs/Config_Reference.md
Before any of this started,I goobered my original Rapido, so I replaced it with a Rapido 2. It’s been in the printer since April, but I haven’t done a ton of printing with it. After the replacement, all was well for a while. At some point, Klipper started randomly tripping thermal runaway protection. The spikes were instantaneous, so I suspected a wire break. It wouldn’t be my first and they’re usually easy to find. I moved the tool head around trying to find it with no success. I pulled apart both cable chains (yay Voron) to look for the wire break and didn’t find one. I flipped the printer updside down and connections at the MCU - everything was fine. I went through the hot end and inadvertently pulled the thermistor out of the m3 slug. Here’s a stock photo:
Suspecting a potential wire break at the thermistor, I manipulated the wiring to no real effect. Inside the M3 bung was some dried white stuff, which I think was probably Boron Nitride Paste. I bought some more from Slice Engineering and reinstalled the thermistor.
Two things changed after this. First, the terminator seems to be reading lower than it did before. I say this because I have a ton more stringing than I did previously. Second, the temperature is no longer spiking but it is doing this high frequency oscillation thing now.
The oscillation only happens once the printer is moving quickly. If it’s still, or moving slowly, things are fine.
Thoughts? I’m suspecting the thermistor, but would like to troubleshoot if possible vs just throwing parts at the printer.
Not sure what steps you can take to confirm the issue outside of replacing parts; but you could try swapping the thermistor with a new one and seeing if that fixes the issue, and if not keeping the spare on hand for future replacement. Your issue looks like it doesn’t appear until the hotend has been heated for a bit so it could be some internal connection coming loose from the thermal expansion and not something more obvious like a broken wire. It’s gotta be that or the heater itself.
Also you might PID tune the heater after the thermal paste replacement if you suspect it’s not reading correctly.
I suspect it’s motion/jiggling around related. I guess I could whip up some g-code to see what happens when the printer is still vs when it’s moving rapidly.
Thanks for the nudge, will follow up.
Isn’t it because of an extruding speed change ?
I wouldn’t think so, the printer never did this previously. I need to put together some g-code to make the print head move around at a pretty high rate, but without actually extruding anything.
Plotting the percentage of power that klipper use would help.
Did yo utried to make the head move cold, without extruding, to see if it have weird behavior ?The PWM signal once it starts getting jittery is basically only 0 or 100% and corresponds pretty well to the swings in temperature.
I’ve moved the head hot and cold by hand and haven’t gotten any weird behavior. Normally when I have a wire break there’s a very specific location that will reliably fail. That’s not the case this time.