Thermal Runaway  

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Durahl
(@durahl)
Eminent Member

Greetings!

I'm currently facing a problem with my MMU2S equipped i3 MK3S that is Thermal Runaway ( not Bed Thermal Runaway! ) related...

Since building the Kit, I've run through two Spools of Prusament PLA without issues though none of the parts printed so far have had a surface size like the Electronics Mounting Plate I'm building for a Tamiya 1:16 Gepard 1A2 Display Stand Model I'm converting into a Full-Option RC one:

With the Prusa provided Settings, the problem with these large parts usually manifests itself the second ( literally! ) the Part Cooling Fan kicks in while the second Bottom Layer is being laid out - Doing another part, I just witnessed the Hotend Temp rapidly falling from it's set 215°C and by the time I managed to change the Fan from 255 to 220/200 and reducing the Speed from 100% to 90% using the Printers Interface the temp had already dropped to 204°C thus barely above the threshold for another Thermal Runaway abortion ( AFAIK a 15°C difference ).

What problem am I looking at? Bad default Settings? Broken Hardware?
Where in PrusaSlicer can I find the Fan and Speed settings I keep dialing at the Printer itself? I'd like to make a specific profile to deal with such large parts.
Are there any other options on how I can deal with this issue?

Thanks in advance! =)

Posted : 04/10/2019 3:25 pm
nikolai.r
(@nikolai-r)
Noble Member

Here is what's happening:
Default PLA settings are pretty aggressive. First layer is being printed slow/no fan, but second layer is full speed. Means the heater block is being cooled by a fast filament extrusion and in addition part cooling fan starts to blow max power. In combination with with first layer set to 215C and second 205C, the heater turns off once second layer begins to print. So you have a steep fall in temp. Regular PID calibration is not sufficient for this case. PID control kicks too late in and not aggressive enough. The result is usually either -10C hopping or temp runaway error.

Solution:
Just put a silicone sock on the heat block: https://www.amazon.com/Genuine-E3D-Silicone-Sock-Original/dp/B077TKBKR3/

Other options are:

  • PID recalibration for more aggressive control
  • Reduce the speed
  • Reduce fan speed for second/third layer so PID control has more time to adjust
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Posted : 04/10/2019 6:33 pm
bobstro liked
sam.d10
(@sam-d10)
Eminent Member

Just check that your heater cartridge is 40W if it is it should have a red cable if it is blue then it is a 30W which shouldn't come with the printer. Although this isn’t most likely the case you might as well just check to be sure.

Posted : 04/10/2019 7:31 pm
Karl Herbert
(@karl-herbert)
Noble Member

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 05/10/2019 2:57 am
Karl Herbert
(@karl-herbert)
Noble Member

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/thermal-runaway-low-temp-extruder/#post-154674

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 05/10/2019 3:05 am
allen.m2
(@allen-m2)
Estimable Member
Posted by: @nikolai-r

Here is what's happening:
Default PLA settings are pretty aggressive. First layer is being printed slow/no fan, but second layer is full speed. Means the heater block is being cooled by a fast filament extrusion and in addition part cooling fan starts to blow max power. In combination with with first layer set to 215C and second 205C, the heater turns off once second layer begins to print. So you have a steep fall in temp. Regular PID calibration is not sufficient for this case. PID control kicks too late in and not aggressive enough. The result is usually either -10C hopping or temp runaway error.

Solution:
Just put a silicone sock on the heat block: https://www.amazon.com/Genuine-E3D-Silicone-Sock-Original/dp/B077TKBKR3/

Other options are:

  • PID recalibration for more aggressive control
  • Reduce the speed
  • Reduce fan speed for second/third layer so PID control has more time to adjust

Best explanation I have seen so far for what is happening.  In my case I just made the layer temps the same to stop it from shutting off the extruder heater.  It compensates for the added heat dissipation just fine this way for me.

Posted : 09/10/2019 5:09 pm
elizabethbrown2240
(@elizabethbrown2240)
New Member

hello,

which mechanism works here?

Have you ever try DIY it?

Posted : 12/10/2019 7:54 am
Durahl
(@durahl)
Eminent Member

I thought I'd report back on my findings regarding my Thermal Runaway issue...

I've tested both the Prusa Support suggested PID Tuning, which may have helped with but certainly hasn't eliminated problem, and an E3D Silicone Sock, I already had on order when I opened the thread, and the latter one seems to be doing a really good job in preventing the problem from manifesting as I'm currently reprinting the very same parts I've done the last time and the temperature barely managed to drop 5°C when when the 2nd Layer, with both increased Extrusion speeds and Partcooling Fan, starts kicking in.

Soo... Yea... My money's ( literally ) on the E3D Silicone Sock.

Posted : 19/10/2019 4:22 pm
Karl Herbert
(@karl-herbert)
Noble Member

Thank you for the feedback. I think it was a good working combination from pidtuning and silicone sock.

Wish you many successfull prints!

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 19/10/2019 9:07 pm
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