Thermal runaway
I completed the Mk4/Mk4S upgrade on Monday. All tests passed except the nozzle heating. After reading here, I removed the silicone sock and the test passed. I tried a simple print and after a couple of minutes received a thermal runaway error. I contacted Prusa support and did some testing including swapping out the HF nozzle with my old one. Support got back to me with the usual beginner questions. In the meantime, my testing revealed that the error occurred only after the print cooling fan came on. Support asked for some pictures of the print head and suggested it might be a cooling fan issue. After the print completes the first layer and the fan turns on, the temperature drops (230C -> 220C for example), but doesn't stop. The error occurs when it gets below 200C.
I reinstalled the silcone sock thinking it might provide some insulation. It did and the printer works extremely well now. In the meantime, support has not replied to my repeated emails (last one was early Wednesday). I know I can print with a silicone sock, but I think the printer is supposed to work without it. I'm at a loss as to what the problem might be. Bad heater block, insufficient power (wiring issue)... Any ideas on where I might look or what replacement part I should order?
Or should I try recontacting support with a new ticket? Thanks for any tips or hints you can supply.
RE:
I have had this issue while printing petg. I read somewhere, based Prusa advice the solution was to print another object away from the print. So I too would like to get to the bottom of this issue.
Note: I have an mk3S+
i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]
RE: Thermal runaway
You know that on the MK4 there is an option for the silicone sock in the display menu somewhere under hardware setup, right? You must set this option correctly according to the fact if you have the sock installed or not. Setting this option the wrong way could cause problems with the heating control.
RE: Thermal runaway
Yes, I’ve been aware of that setting since I upgraded from my Mk3S to a Mk4 last November. It was set correctly for all my testing.