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.