Random Temperature Spikes
Has anyone seen random spikes in their hot end temperature before?
I've had my printer working beautifully for just over a year and this has started to happen in the past few days. I notice that it only happens after the hot end has been at temperature for a while. If I run a print, it will be fine for the first ~15 minutes before the spikes appear.
I think something is going on with the thermistor since the spikes are way too fast to be the real temperature. In addition, I have a thermocouple hooked up to my hot end and it doesn't see them.
The problem with the spikes is that it really messes with the PID loop for the hot end and occasionally it can make the temperature go so low that filament stops extruding.
Does anyone have suggestions for fixing this?
Re: Random Temperature Spikes
You may have recently melted your fan shroud, or moved the hot end a bit so more air is flowing around it, or past the heater or thermistor wires, etc. As a test, turn off the print fan and watch temps. If they are stable without the fan then you know it's air flow variation.
Re: Random Temperature Spikes
I tried running a print without the fan, but there was no change in the temperature spikes. It also looks like they are more frequent when the extruder is at one end of the it's travel than the other. I'm printing a part that is basically a hollow square and the temperature spikes are now very periodic.
Re: Random Temperature Spikes
I tried running a print without the fan, but there was no change in the temperature spikes. It also looks like they are more frequent when the extruder is at one end of the it's travel than the other. I'm printing a part that is basically a hollow square and the temperature spikes are now very periodic.
unnamed.png
Sounds like strong evidence of a broken wire or loose connection.
Re: Random Temperature Spikes
Yeah - sounds broken for sure.
Do a preheat only - no printing - and monitor the temps; if in preheat you see any major change you know you have a control issue; if it is stable, then a wire is most likely the cause.
And as a last thought, when was the last time you did a PID calibration?
Re: Random Temperature Spikes
Thanks! It is in fact a broken cable. I narrowed down the issue to the location where the cable bundle enters the extruder. It looks like the thermistor and heater cartridge wires have been rubbing badly against the plastic there. The insulation isn't broken, but I'm guessing that moving back and forth stressed the wire enough to snap it inside and now it intermittently comes detached when the extruder is in the right spot. I can make the thermistor disconnect when I pull on the wire there.
I'll replace it soon, but for now I've decided to give it a makeshift splint so I can keep printing 🙂
I've never done a PID calibration before. Is that a useful thing?