Heatbed Thermal Runaway
Midway through a print my Prusa I3 MK2 MM produces a message:
Error: HEATBED THERMAL RUNAWAY
Printing then stops. This has happened three times, both via Octoprint and printing directly from the SD card.
The last few entries of the Octoprint terminal log look like this:
Send: M105
Recv: ok T:241.5 /240.0 B:77.5 /90.0 T0:241.5 /240.0 @:28 B@:127
Send: M105
Recv: ok T:241.3 /240.0 B:77.5 /90.0 T0:241.3 /240.0 @:38 B@:127
Send: M105
Recv: ok T:240.0 /240.0 B:77.5 /90.0 T0:240.0 /240.0 @:77 B@:127
Recv: Error: HEATBED THERMAL RUNAWAY
The B (bed temp, I think) value (77.5) has drifted down from its initial setting of 90. (I am assuming that's what's happening -- I can't find a decoder ring for the terminal shorthand.)
Any troubleshooting suggestions?
Re: Heatbed Thermal Runaway
http://shop.prusa3d.com/forum/search.php?keywords=thermal+runaway
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Heatbed Thermal Runaway
Thanks, Peter.
Re: Heatbed Thermal Runaway
Peter's suggested search enabled me to solve the problem.
No loose wires, no broken wires, no bad solder joints, no flaky connections, no issues with electronics...
The "thermal runaway" in this case was caused by my attempting to print a small part in PET in the center of the print bed -- right above the bed's heat sensor. Heat from the PET part (240°C) was confusing the bed's heat sensor, which was trying to maintain 90°C.
The solution, which I found in the search results, was to move the part away from the center of the bed.
Re: Heatbed Thermal Runaway
Thanks for this. I had the exact same thing happen while printing PETG and was immediately worried that I had a defective printer. Did a quick search and this post came up. I was able to re-arrange objects on the print bed and the problem was solved. 