Lulzbot Taz Pro - Thermal Runaway Malfunction

This is the first time this has happened to my Lulzbot Taz Pro.

The first occurrence was 300mm into a print, 75% of the skirt, then bam. Thermal runaway detected on hot end 1, please reset printer immediately.

The second occurrence happened on the subsequent print attempt, at the beginning of the purge process.

I thought this was some weird problem with my gcode file generated from lulzbot cura, but… I went to “Change Filament”, then set to 200C, and the temperature spiked to 250C. Thermal runaway. Molten blobs of filament running down from hot end 1.

Does anyone else have experience with this issue? I fear some part of the printer is broken, and it hasn’t even been a year since I got it.

There are a few things that can trigger this … it can be a failed thermistor, but it can also be a loose thermistor or poor connection. Contact LulzBot support (see: )

I have seen this error when I chang d the printer enclosure; it was an airflow and ventilation issue.
Hope this helps!

I’ve had this and learned that it is more ‘thermal out of bounds’ rather than ‘runaway’. Meaning that it can be that the temperature got too low, and that is what happened with one design where the infill started to blow the fan air too much back to the nozzle, and cool it down too much. In that case I could re-orient the design on the bed so that the short side was crossing the x-path, rather than the long side.