Thermal Runaway
So I've just encountered my first ever issue with a prebuilt MK3s+ that I've had a few months now. Up until now been a beast and was easy to add "upgrades" (light bar, octopi, etc.)
The error I got was thermal run away and a M112 called (Emergency Stop). This was while printing via Octopi through USB connection. I power cycled the machines and removed the failed print (not adept enough to manually resume print yet). After which I had the home command sent via Octopi which I've done in the past. This time after doing the mesh probing the hot end stopped at the home position and then just started smoking! I just turned it off from there.
Since this is my first Prusa and I got it assembled I haven't even swapped nozzles yet. The heater block was a little messy before, and now it looks just fried, likely just burnt filament (on my cheap Anycubic I use a heat gun and wire brush to clean after removing it).
So my question is this, do I just need to disassemble the hot end and clean the nozzle and heat block, and then attempt to reprint? Do I need to replace thermal resistor? Where do I even start?
Checked the Prusa academy hoping for some basic maintenance guides but didn't find any.
Thanks in advance for helping out a newbie!
Best Answer by Diem:
That hotend doesn't look too bad.
Rebuild then go through the whole maintenance process including the electronics checks
https://help.prusa3d.com/article/i3-printer-regular-maintenance_2072
Make sure the nozzle is inserted correctly.
Pay particular attention to the diagrams at the bottom of this page:
https://help.prusa3d.com/en/article/changing-or-replacing-the-nozzle-mk2-5s-mk3s-mk3s_2069
then try printing.
If the thermal runaway recurs then unplug the thermistor at the Einsy end and measure the resistance on the wires, it should show a lowish value that will change according to temperature, not a dead short or open circuit.
Use the layout chart here: https://help.prusa3d.com/article/einsy-rambo-electronics-wiring-mk3-mk3s-mk3s_2107
Let us know how you get on.
Cheerio,
RE: Thermal Runaway
So I found the maintenance guides under "help", who know! Well I went ahead and was able to remove the hot end. I see now that it appears I had filament leaking from the heat break above the block. Guessing this leaking on to thermal cables could cause the over heat? As a side note, since I purchased this fully assembled, would this be a warranty fix or considered "wear and tear". I wouldn't think a properly assembled heat break should leak above the heater block.
RE: Thermal Runaway
That hotend doesn't look too bad.
Rebuild then go through the whole maintenance process including the electronics checks
https://help.prusa3d.com/article/i3-printer-regular-maintenance_2072
Make sure the nozzle is inserted correctly.
Pay particular attention to the diagrams at the bottom of this page:
https://help.prusa3d.com/en/article/changing-or-replacing-the-nozzle-mk2-5s-mk3s-mk3s_2069
then try printing.
If the thermal runaway recurs then unplug the thermistor at the Einsy end and measure the resistance on the wires, it should show a lowish value that will change according to temperature, not a dead short or open circuit.
Use the layout chart here: https://help.prusa3d.com/article/einsy-rambo-electronics-wiring-mk3-mk3s-mk3s_2107
Let us know how you get on.
Cheerio,
RE: Thermal Runaway
Thanks Diem!
I had stripped down to just metal bits of the hot end with filament on them. Soaked them over night in some Goof Off (solvent cleaner), scrubbed it all clean to almost like new, followed the rest of the guides you provided and I appear to working fine now.
I've completed the self test and live z adjustment. Just going to print another temp tower just for sanity check, but I think I'm good now, though I did order an ED3 Revo incase it didn't work and wouldn't you know it they got it to my house in like a day, so now I need to decide if I should go ahead and switch or keep it stock till it burns out.
Thanks again!
RE: Thermal Runaway
with firmware 3.12 now released, I would suggest keeping your revo in it's box, until prusa sort out the issues between the thermal model and revo hotends.
regards joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE:
I was just reading about that too. I had also updated the firmware while I was cleaning up the parts.
Figured like any good first step debug, make sure all drivers and software are up to date. In this case it seems to break 3.12, though if I'm reading right, we can disable the broken part and essentially have the same thermal protection as in 3.11.
Though I to get the biggest bang for my buck, I'll probably keep it stock till it and the nozzles I have burn out, hopefully by then the Revo issue will be resolved.