It could be a few things. Check all the things.
this post was submitted on 14 Sep 2023
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This is a good start, but if you check all the things and the issue persists, check other things.
Very true! It's those other things that can sometimes bite you.
Thermistor is the only thing that I can think of... Hopefully tightening it works. It doesn't happen unless the print head is in motion, which makes me think that's the problem. Otherwise, the temperature is stable and completes PID tuning without issue.
It could be a loose wire, or a one that is about to snap off. If the cable is bad or on the way out, it could easily be screwing with the resistance measurement. I wouldn't think that just a loose thermistor could cause that mess of a graph, but who knows.
It's the motion bit that you mentioned that gave us just a little more data.
If you can isolate the wire for the thermistor, jiggle it around at different points to see if you can replicate the rapid temperature changes.
Hmm, I might have to order a new replacement and see if that helps then. I had replaced the hot end assembly with the spare that came with the printer a couple weeks ago. I was very careful with the change, but I suppose it's possible I damaged a wire in the process. It's been running smoothly since then though, until today when the temperature started swinging wildly.
Yeah, something got loose or broken. Try your best to isolate the fault while you wait for a replacement though. It's always good to know absolutely sure what happened to hopefully prevent the issue again in the future.
No, thats a graph.
Have you tried leveling your bed?
On a serious note, do you have thermal grease on the thermistor?
I assume so? The original hot end came with it pre-applied, so I think the spare the printer came with should too, but I haven't checked this one.
Dont assume, it makes an ASS out of U and ME. Check it
That looks like what I've had with bad thermistors or wiring on the edge of totally breaking, surprised it didn't trip any thermal protection, when that happened on my prusa it estopped and my Voron did as well. I def recommend keeping a pile of thermistors with microfit connectors, they're pretty cheap and they can go bad, it's an easy debug step to swap a thermistor out to rule out wiring issues.
It did actually, this screen shot was taken immediately before it shut down. I'll pick up a few replacements and try swapping it out.
No, that's interference from a higher current source.
Most likely your stepper motor wires run in series with the thermistor.
Looking at how the wires are plugged in, you might be on to something here. The extruder stepper seems to be wired into the same port as the breakout board that the thermistor is connected to. If that is the problem though, any ideas how can I fix it and why it's only showing up now? I've had this printer for maybe 2 years now and I installed klipper on it last month, but this issue only began a few days ago.
Any changes to wiring? connectors?
I replaced the hot end assembly a couple weeks ago, but I didn't make any changes to the way things were wired. I plugged it in to the same connectors as before.
replaced it why?
With the exact same hotend?
Yeah the exact same, it was the spare that came with the printer. I had messed up the original a little while ago when I changed out the nozzle from a V6 to a MK8 before I knew they were meant for different hot ends. The threading was the same and I thought that meant they were compatible... It had plastic leaking from around the heater block after that and after not using the printer for a bit, I did some research into where I went wrong and how to swap the parts out for the clean spare.
Sorry, I'm a little confused.
So you attempted to replace the nozzle or the hotend at first?
and when you had a problem you replaced the hotend?
Yeah that's right, I bought the wrong nozzle and using it messed up my hotend. Replacing the whole hotend at that point was easier than trying to clean the plastic out from all the places it had leaked into.
Alright, well then I wouldn't rule out a very loose connection at the thermistor then.
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I'd probably test the thermistor's reading with no steppers active. (unplug them if you have to)
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If signal is still noisy, pull the thermistor out and test. (possibly replace thermisitor)
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If it's not noisy, move the hotend around with the steppers off and see if it gets noisy with motion. go back to 2
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If it's still not noisy, it's definitely EMF from the steppers, and you'll need to replace the wire to the sensor. ideally with shielded wire and try not to run it along the same path as the stepper wires.