today I started a print as usual, went to the room next door, and suddenly my whole apartment started smelling awful. I ran to the printer and saw heavy smoke coming from the hotend area — the fan shroud had already started to melt. I immediately unplugged the printer and got the extinguisher ready (just in case). The printer head was parked in its preheat position, but the hotend was clearly way hotter than that. I looked at the logs (I’m not an expert, just curious) and noticed that right before it happened, the extruder was heating normally at 220 °C with full PWM power. Then the log shows some retransmit errors, then some kind of restart happened (seems like during the restart the heater stayed at full power?). After restarting, it immediately showed the nozzle temperature around 263 °C, but with target = 0 — meaning the heater should have been off, but clearly wasn’t?
Is this behavior normal? Maybe it’s my fault and I’m overlooking something? How to prevent this?
I’m sure one more minute and things would have gone south really quickly.
I once had a mofset on a mainboard short closed… Looking at your log your thermistor seems okay but also shows no abnormal high temperatures. Sounds like your heater kept running AFTER MCU shutdown.
In other words, this is likely a fire hazard and you should disconnect your extruder heater from the mainboard until we can diagnose the possible thermistor issues.
As far as I understand the logs, there was some kind of shutdown? The log just stopped logging with target set to 220 degrees. I can’t tell if the extruder was already overheating at that moment. Well, if it did, for sure something that should measure the temps is broken.
Tanks! Will definitely update as soon as I know what went wrong
I startet the printer (with my extinguisher close :D) and checked. After setting the Nozzle to 240, everything was fine. It was keeping the Temperature +/- 5 degrees. In addition I took of the print head and checked the the thing with the white a red cable (heater and temp sensor?) - everything clean and cables looking nice.
I bought the Printer used and can’t tell for sure if the software is original. But I do know, for multiple printing hours nothing came close to smelling burnt.
If the ECU shut down and the heater indeed stayed on full power, this would be some scary stuff tbh lol. For sure I won’t use that thing till I know why that happened. Also I might should contact elegoo and ask them?
Maybe the +/- 5 were a bit to pessimistic… I did a check as followed:
1: Startet the printer, immediately “MCU Shutdown ADC out of range”
2: Restarted the firmware. Everything seemed okay. I set the target to 240. Everything seemed fine (to me), first few seconds temps changed +/- 2 degrees, but afterwards everything was as stable - +/- 0.2.
3: I started to wiggle the Printhead (still not mounted) and nothing changed, then I started to poke the red cable, afterwards the whit cable. By poking the white cabe right at the connection to the red board, the (displayed) temps varied drastically. Then same error as in Step 1. Not the temps at - 47 lol.
Unfortunately I couldn’t screenshot the last drastic changes. They were about +/- 50 or something. Some screens attached and also the log.
So, i guess ether the male or female part of the connector from the thermistor is broken? But isn’t the MCU supposed to even shutdown if the values don’t increase as expected? Or they did slowly close to the edge go shutdown, but not close enough? But due to the transmission errors I guess the shutdown was something else? Or maybe that was the point where I cut the power supply. But also that doesn’t make sense because heater was at full power although temp target was reached……
Maybe I should mention, I replaced the Thermistor. But; since everything was working (or at least printing) fine. There were no signs at all of overheating or significant wrong temperature. At least the prints looked fine.
Edit: Connector on the board and on the cable looks good. The cable musst be broken on the inside
Edit2: I checked the resistance of the thermistor. There must be a broken cable. Same behavior as on the printer, the values changing as soon as I touch the cable near the connector.
I downloaded the first log from the web interface of the printer about right after stuff started smoking.
That’s the point. It didn’t state anything relating to a malfunction. Idk if the transmission error are related to me shutting off the printer (after seeing it smoking), or related to some internal errors and afterwards the printhead startet smoking.
Yes, the cable of the thermistor is broken for sure. But how can it get that far, that parts of the printhead start melting? The fan of the heating element (not the other part fans) wasn’t spinning.
After the MCU Shutdown yesterday, the fan clearly started spinning immediately just after the error message appeared.
When you have an intermittent connection which sounds like it ranges from a dead short to normal operation to completely open then all bets are off when you run things repeatedly. The monitoring software tries to handle things but gets different conditions and goes tilt.
Think of it in human terms; you are given the task of reaching and maintaining a set temperature with nobody supporting you and limited options. The temperature indicator ranges from reasonable, to impossibly cold to close to what you expect and then to impossibly hot and then back again how would you respond?
The only comment I would is how I respond when I get strange temperature readings: I immediately investigate the thermistor, the cable and connectors. I try to move the toolhead/thermistor to different positions while monitoring the temperature. I restart the machine (power cycle). If there is any concern or uneasy feeling, I replace the thermistor and cable.
