New printer assembly (MK3s) - thermal runaway
Hi
I just finished assembling my new MK3s this weekend and dialed in the first layer. A few of the prints I've tried have ended with a hot end thermal runaway error. I'm printing with PETG.
Target temp is 240C and drops to 221C after about 35 min.
When I had this problem in my MK2s I solved the problem by turning up the current supplied by the power supply. Can that be done on the Mk3s? I have the new black power supply.
RE: New printer assembly (MK3s) - thermal runaway
I just performed a PID calibration following this post: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-general-discussion-announcements-and-releases/howto-pid-calibration-your-way/#post-87597 . Extruder fan was set to 100%.
It didn't help. Now I'm having temperature oscillations. PID gains were turned up for P, I, and D by the calibration and I still have a hot end thermal runaway.
It's happening at the exact same spot every time it seems, on the 6th layer. Fans are set to turn on after the 3rd layer and are set to max 40%.
I'm trying to print this Raspberry Pi case: https://www.thingiverse.com/thing:2334119
RE: New printer assembly (MK3s) - thermal runaway
Oscillations are to be expected if you PID tune with the fan on and then try to heat with it off. It's the nature of how PID works.
It's not uncommon to have your hot end cool too much if you have a part that tends to reflect air back up to cool the heat block.
Install a silicone sock on your hot end. (and re-tune the PID).
RE: New printer assembly (MK3s) - thermal runaway
I just tried printing with the fan completely OFF. I again had a hot end thermal runaway error in the EXACT SAME PLACE on the 6th layer.
Each time I have this failure it always happens in the same place.
RE: New printer assembly (MK3s) - thermal runaway
Sounds like you have either a broken thermistor cable or a broken heater cartridge cable that is intermittent. Hard to say which without additional diagnostics like measuring the resistance of each while flexing various parts of the cable.
Time to dig up some spares (or find and repair the break if you have the skills...)