Thermal Runaway at various times throughout 3 hour print
I'm trying to print a PLA part on a 2.5S Printer. In the slicer, I've set my fan min to 20% and max to 30%. The first print was about 20 minutes in and I got a Thermal Runaway. I wasn't watching. Reset, cleared bed, restarted. I watched for a while and checked regularly. Missed it again at about 1 hour into the print. Thermal Runaway! UGH! Reset, restarted, watched, checked, this time I caught it about 1.5 hours in and the nozzle temp was dropping. Setpoint was 210 and it was at 190 and going down fast. I covered the nozzle fan and the temp stabilized then began to climb. I waited and it eventually climbed back up to 210. I removed the fan cover (small piece of paper with hole so some air could pass through) and continued to watch. It ran stable until about 2:45 into the print and Thermal Runaway again. Missed it! ARGHHH! If the temp is dropping, why is the fan running? I seriously think there's a bug somewhere! Why does it work to cover the fan when the temp reads low and then it stabilizes and climbs back to set point? I can't get anything done because I have to stay close and babysit this *&^%^ printer! Anyone have any ideas or suggestions what's going on and how to fix this? I have an 8 hour print I need to do soon. There's no way I'm going to be able to get through this without sitting right in front of this thing for 8 hours!!!
RE: Thermal Runaway at various times throughout 3 hour print
I've been experiencing a similar issue. However, the difference is that I've been printing in PLA for over 8 years on my 2.5S with no problems. (Details here: https://forum.prusa3d.com/forum/original-prusa-i3-mk2-5s-mk2-5-general-discussion-announcements-and-releases/thermal-runaway-25/#post-731280)
I have a motion capture camera with 24/7 hour monitoring in front of my printer so I can catch problems. (Details: https://www.amazon.com/Kasa-Smart-Home-Security-Camera/dp/B08GHX9G5L) It has been invaluable in catching symptoms. I watch for first layer problems and lifting corners. Recently I moved the camera to view both the print and the LCD readout.
I've been considering the Prusa Knowledge Base on the topic ( https://help.prusa3d.com/article/thermal-runaway-i3-series_2131) and hypothesizing that my problem is related to a loose sensor. There appears to be a threshold for me. 220º seems to run fine, but not feed my FLEX filament reliably. 225º produces the THERMAL RUNAWAY error. This could indicate a temperature differential tolerance between the ambient room temp and the target nozzle temp. My next experimentation will focus on the fan.
Ref: "Thermal Runaway is configured to shut down the printer when the temperature drops by more than 15 °C for more than 45 seconds. If the temperature reading doesn't recover in the set time period, the printer will shut down and display the Thermal Runaway error."
RE:
I found this...
"Thermal Runaway is a typically thermistor problem. Disconnect the plug from the printer board and measure the internal resistance of the thermistor, it should be 100k ohms at 25 degrees c. "
...the thread is lengthy and detailed. I'm going to work my way through the info to see what I can find in my setup.
RE: Thermal Runaway at various times throughout 3 hour print
I was able to resolve, partially, my issue. First, I reflashed my firmware to an older version. Maybe four or five versions older. Second, prior to slicing, I turned off auto temperature control? Sorry, I'm not at my computer right now so I don't remember. But basically, I went through all the advanced settings and disabled anything related to auto temperature adjustment. I was able to print multiple prints now just fine.
RE: Thermal Runaway at various times throughout 3 hour print
Confirmd. After having replaced the hotend thermistor and even the board due to continued thermal runaway error without any success, downgrading the frimware of my MK3S to version 3.11.0 (!!!) has resolved the issue.