Thermal Runaway Error
Hey guys,
I need your help. I'm getting a "thermal runaway" error on my i3 mk3s printer. It appears that it's related to the hot end because you can see the temperature drop from 215c (using PLA) down under 100c. The bed temp is holding at 60c.
It just started shutting down last night. It occurs when the printer is laying down the 2nd layer on any file. I looked on youtube and found other guys with this same problem but they didn't offer any fixes. I'm sure if I put a VOM on the hot end that I would see a drop in voltage. At this point I guess I could check the resistance of the hot end and the thermistor. Also, I'll check my power supply voltages.
If those resistances and voltages checkout ok then I would guess that a chip on the main board is the problem.
Do any of you have any other ideas or solutions?
Thanks!
Gary
Best Answer by muddymaker:
Can you clarify by what you mean when you say that the hot end falls below 100c. Are you saying that it falls to a specific temperature then stays there? Does the temperature fluctuate?
When people experience a thermal runaway on either the heat bed or hot end it's usually attributed to a broken connection between the einsy board and the hot end/heat bed, very rarely is there a problem with einsy board itself.
How old is your MK3s? Is it an upgraded older MK3? Has it the braided wrap or the plastic spiral wrap? Was it a kit you put together yourself or did you purchase it assembled?
Prusa chat are very helpful and they can walk you through in diagnosing your problem very quickly and efficiently and they'll get you back up and printing in no time.
RE: Thermal Runaway Error
This sudden drop causes the cooling fan, it starts with 2nd layer. It tooks some time to the heater to compensate this shock. It can be easily solved with silicon sock. But you write, that the drop down is under 100c. That has to have another reason, most probably is the heater already wrong and would be good to replace it. You can measure the resistance, if somebody will post the normal value. I have MK2s, so will not help you.
Milos
RE: Thermal Runaway Error
Can you clarify by what you mean when you say that the hot end falls below 100c. Are you saying that it falls to a specific temperature then stays there? Does the temperature fluctuate?
When people experience a thermal runaway on either the heat bed or hot end it's usually attributed to a broken connection between the einsy board and the hot end/heat bed, very rarely is there a problem with einsy board itself.
How old is your MK3s? Is it an upgraded older MK3? Has it the braided wrap or the plastic spiral wrap? Was it a kit you put together yourself or did you purchase it assembled?
Prusa chat are very helpful and they can walk you through in diagnosing your problem very quickly and efficiently and they'll get you back up and printing in no time.
RE: Thermal Runaway Error
Hey there all!
Gary was this a recent occurrence of thermal runaway? I just went to print some items today and got a thermal runaway error as well. What appears to be happening is after the first layer my MK2.5's hot end will not go above 198-200. It gets up to temp when printing first layer all the way up to 215 and is printing fine otherwise.
I am not sure what it exactly it is, but I do need to update the firmware, as it just now reminded me to load the new version. Maybe it is something with the recent release?
-Trenton
RE: Thermal Runaway Error
Milo, thanks for your response and info. I haven't tested the resistances nor my power supply, yet. I'll do that tonight.
Gary
RE: Thermal Runaway Error
Hello Tony,
Thanks for your quick response and info.
My printer was an i3 mk3s kit that I purchased about 3 months ago. The Thermal Runaway error started last night. My printer has the braided wrap. That's good to know about the Einsy board rarely failing.
It heats up to 215c but then after starting the 2nd layer the temp begins to drop and continues to drop. I don't remember how low it goes but it drops to a critical level which causes the "Thermal Runaway" error to display. It very well could be a broken cable or maybe the thermistor is loose.
I'll go on the chat site and talk to Prusa after I check the resistances of the hot end and the thermistor. I'll also check the power supply voltages.
This is my first 3d printer and it has performed well so far. I'm impressed with the quality and performance. I'll eventually find a solution to the problem.
Thanks for your input!
Gary
RE: Thermal Runaway Error
Hello Trenton,
My Thermal Runaway error started last night. I'm beginning to believe that it's a loose thermistor or a broken cable I'm going to thoroughly check everything tonight and if I can't determine the problem then I'm going to do a Chat with Prusa techs.
Thanks for your inquiry. I'll add info to this Post once I find a solution and that should help you troubleshoot your printer.
Thanks!
Gary
RE: Thermal Runaway Error
any conclusions so far?
RE: Thermal Runaway Error
Hi Gary,
to rule out the part cooling fan, try slicing a model with the normal settings, but set the cooling fan to come on after 2 layers instead of 1 layer, see if the issue changes to the third layer!
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Thermal Runaway Error
i am having this exact issue right now! i've been trying to figure this out for the last 3 weeks.
i have to manually turn down the fan speed to 100-130 to prevent the thermal runaway error.
i even printed a new fan shroud (in PETG) because i notice that the one installed was slightly melted.
has anyone resolved this issue? i have had no issues with my Prusa until recently
thanks
-Leonard
RE: Thermal Runaway Error
On my MK3S I do not have a problem, but on my MK2.5S I get thermal runaway all the time with the standard Prusa setting. Attached is the setting I use for my eSun PLA and PETG, it works all the time with excellent results.
the first clip is for PLA the second is PETG
RE: Thermal Runaway Error
thank you very much... i will try this!!!
although... i am very curious as to why i am getting this error now. i got my Prusa I3 MK3S this past April, and it has been awesome until recently.
i have made to modifications (aside from printing a new fan shroud) and i use the default settings in the PrusaSlicer. when i look at the fan speed during the 2nd layer print, the fan is at 255.
-Leonard
RE: Thermal Runaway Error
Hi Leonard,
may I ask where you found the alternate fanshroud> I haven't seen on for the Mk3S yet!
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Thermal Runaway Error
i'm sorry if you misunderstood. i downloaded the fan shroud model from Prusa and printed it. my original one was slightly melted.
-Leonard
RE: Thermal Runaway Error
no problems Leonard...
I don't print ABS so I have resin printed part cooling fan shrouds which seem to work Ok
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Thermal Runaway Error
no problems Leonard...
I don't print ABS so I have resin printed part cooling fan shrouds which seem to work Ok
Joan
How long is the queue for having you print resin fan shrouds?
RE: Thermal Runaway Error
I am also seeing this issue after upgrading my MK2.5 to the MK2.5S. Up until the upgrade it has been working great.
I have watched as it prints and it happens after the first lay when the fan turns on. I watched the temperature of the extruder as reported on the LCD and after the fan turns on the temperature starts to drop. It continues to drop until it is about 15 degrees below what it was programmed for then the Thermal Runaway error occurs. On the surface that seems to be what it should do under the conditions that I am seeing. So, that would lead me to believe that my extruder can't get hot enough. However, if the fan is disabled in Slicer it will print fine. When it fails I never see the fan speed decrease. Why not? The firmware can read the thermistor and can control the fan speed so when it sees that the temperature is dropping why doesn't it decrease the fan speed to allow the heater to bring the temperature back up? I have read a lot of different solutions for this Thermal Runaway issue but it seems to me that it should be solved in the firmware - not with bandaids.
I do have a silicone sock on my extruder and have looked at all of the suggestions that have been put out here in the Forum. The only thing I haven't tried was to change to the 40W heater as was suggested in one post. That might work but doesn't seem like it shouldn't be needed. I have been printing on my printer for a couple of years without issues. Since I did just do an upgrade I looked very critically at everything to make sure it wasn't caused by something I did. When I adjusted the fan speed in Slicer and that fixed the issue it seems clear that the heater is not at fault. I am guessing that new fan shroud is just more efficient and the heater can't keep up with the cooling.
On a related note I have noticed that when it goes into thermal runaway that the extruder isn't lifted from the print. So when it cools down the extruder is stuck to the printed filament. That means that the the safest way to get it loose is to heat everything back up and then move the Z axis up. I think the firmware should do that automatically.
RE: Thermal Runaway Error
I saw this when the unit was pre-heated to PLA... then I selected hotend PID tuning.