Mk2.5 Hot End overheat but nozzle temp on screen shows correct?
Today I was preheating and loading some filament, and got a max tep error as soon as the filament started feeding in. I thought that it was odd because the screen said 230, but within a split second it went to 500+
So to test it I started printing some PETG at 230c and everything was normal. I then started hearing popping noises like you would if the filament was wet. I thought it was odd, but its been humid here so I let it run because again the screen said 230c. I stepped away for about a minute. I returned, to notice a heavy plastic smell. The display screen still read 230c. ❗ I knew something was wrong so I shut it down by pushing the reset button. Immediately I got a maxtemp error, the display read 500C+ ❗
The first layer of PETG that was printing is PERMANENTLY fused to my PEI sheet. And my extruder parts are melted.
Is this a thermistor issue?
Or did my Rambo board go wonky?
Thermistor is relatively new, as I replaced it about 4 months ago when one of the wires stripped on the original after my 2.5 upgrade. Its been running fine since then.
I'm not plugging this thing back in until I have a few things to check out. Anyone have thoughts, or tests I can do?
Re: Mk2.5 Hot End overheat but nozzle temp on screen shows correct?
Have you checked for a frayed cable to the heater cartridge? If the two wires touch, that could probably sink enough current to make something in the Rambo overheat and give you that strong plastic smell. If the 12V got to the block and thermistor cartridge, I wouldn't be surprised if that read as some maximum temperature. If it was arcing, too, that could be the popping sound, though (very) damp filament is also possible.
The melted parts and plastic fused to the PEI, though, do indicate that the temperature was way too high, and that doesn't quite fit my thoughts.
The combination of things does seem to indicate a major failure of some sort. At least you'd stepped away for only a minute...