Thermal Runaway Error During Filament Load

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mitchfx
Posts: 63
Joined: Thu Mar 24, 2016 12:46 am

Thermal Runaway Error During Filament Load

Postby mitchfx » Sat Jul 07, 2018 10:11 pm

I just got a Thermal Runaway error and restart while loading filament via the utility (215c) on my 2.5 year old N2 Plus. I've never had this before and have not installed the thermal protector upgrade. After reading several threads on the forums I have some ideas about what might be going on, but would appreciate any advice for recommended "next steps" to make sure there's nothing seriously wrong with my printer.

Thanks,
M

Jetguy
Posts: 2513
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: Thermal Runaway Error During Filament Load

Postby Jetguy » Sat Jul 07, 2018 10:48 pm

You cannot know until you properly install the thermal protector.
That's the entire point, without it, you cannot detect certain error and thus troubleshoot blind.
If you install it, and it then throws a maxtemp error- that then guarantees you have a cable fault- something that cannot be detected stock.

Jetguy
Posts: 2513
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: Thermal Runaway Error During Filament Load

Postby Jetguy » Sat Jul 07, 2018 11:07 pm

Again, just the facts:
You have a 2.5 year old machine. All that time, all those prints, millions of times of flexing the ribbon cable.
You got the error when using load filament, which also commands a preheat to a set temp (default 215C) and wait for that temp to be reached.
That would indicate one of 2 things, either the temp was not being reported because of a break in the ribbon cable, and since you did not have the thermal protector installed, that means that error goes undetected. So then the heater is heating up totally uncontrolled because there is no real temp reporting back of the actual temp. Then say you bumped the head just right, that then makes contact in the broken wire and reports back the real and now very much too hot extruder throwing the thermal runaway code. OR, because again, you commanded a preheat from cold, and the thermal runaway protection in firmware is watching for a temp rise in a certain time period, and so because again, the real temp is not reported back, and this error goes undetected without the thermal protector installed, only after the timeout where the temp did not rise then the firmware throws a fault. I think that is 40 seconds hard coded in the firmware (1.1.16 looking at the source code). Again, 40 seconds is long enough under certain conditions the extruder can overheat when temps are not being reported back.


All the thermal protector does is plug in at the mainboard between the ribbon cable and mainboard. It's job is detect to cable failure break even if it only happens intermittently. How it does this is it's depending on the real temp report signal (analog voltage) back from the extruder head breakout. That voltage corresponds to 10mv per degree C. So 250C is 2.5V with 0V being 0C and 5V being 500C. As you can see, the voltage under most conditions should be say 2.15V or less. The thermal protector is just a high value resistor (1 meg) attached to the 5V. When that cable breaks connection, then the voltage the mainboard reads is raised to 5V instantly shutting off the heater and throwing the firmware into safety. It's a simple thing, but running without it is simply something I consider a bad move by users. There is literally no good reason to not install it and using a printer without it is asking for a thermal runaway event.


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