I have my A1 plugged into a soecial surge protector that provides power to the rest of the outlets if the one trigger outlet draws enough power. So the printer is always on so that I can send stuff to it but doesn’t draw a lot of power. When it’s heating up and printing the power draw increases enough to trigger the rest of the outlets and a desk lamp turns on so I can see what’s being printed better. This is especially helpful at night when the desk lamp is the only light in the small office my printer is in. It’s been set up like this for 2 years and it’s been great.
This morning I was not actively printing anything and I went into the office and the desk lamp was on. I looked at the printer and it wanted to update the firmware, so I did so. Afterward the lamp stayed on. I rebooted the printer multiple times and while it’s rebooting obviously the lamp is off and when it boots back up the lamp stays on.
What is causing this increased power draw? Any ideas or insights?
For now I’m leaving it fully off but I’ll have to manually go in and turn it on before sending something to print which is less convenient.
AFAIK it’s a thermistor that is breaking causing thermal runaway. But this is can only happen during printing where heated/hotend is heating.
What you are thinking of is the NTC thermistor that was failing. That part was meant to limit the inrush current when the nozzle was rapidly heating. Its failure will just stop the nozzle from working at all. Which is precisely what should happen at failure. It is suspected they either got a bad batch of NTC thermistors or they were pushing the inrush current too close to the max rating. Bambu replaced a fair number of control boards and took the hit for not addressing these failures by not recalling the affected batch and replacing the offending board.
The plastic housing of the printer is a fire-retardant, high-temp polymer. And as far as I have read and know from my following of the issue, there have been no reported and verified fires caused by this particular problem. Just some scorched plastic and a bit of localized melting with the blown NTC.
But there does remain a non-zero chance of a real fire because of bad NTC. But it needs to be ignited by dust or little bits of filament that invades every nook and cranny on every printer in existence. If it bothers you and you are worried, clean your A1’s insides every year. Make it a routine maintenance thing.
Disclaimer: I do own an A1 mini (which is not affected by this issue). While my mini does exactly what I originally bought it for (before the ongoing attempt of Bambu to crash the plane), I’m under no illusion that Bambu is not a company I wish to support.
I though we fixed thermal runaway firmware issues like a decade ago for good…
Not when the sensor fails so the feedback to the firmware controlling it is incorrect and there is no thermal fuse.
Yes, even when the sensor fails.
If the feedback from the thermistor is either nonsense or doesn’t change as expected even when the heater is on/off for a certain time, that should trigger a thermal runaway error and halt the printer. That’s basic decade plus old Marlin code.
I’ve had two broken thermistors in my Ender 3. First one reported negative temperatures when it disconnected, so the printer immediately halted with a min temp error. The second reported something like 150C, which was in the acceptable range, except when it tried to heat it up and nothing changed for like 15 seconds, which triggered a halt.
Again, decade old marlin code. Not rocket surgery.
Thanks! I have a Mini so haven’t paid that much attention.
This issue does not affect the mini. That’s a different control board. I own a mini.