It’s not super obvious from this picture, but my hotend’s thermistor shorted, and it heated up until it melted the PEEK barrier and the barrel fell out! This is what’s left of the barrier. Fortunately I have a spare - still working on getting it all together with the extruder block.
The groovemount is just a couple millimeters too short in the extruder block.
What firmware are you running that doesn’t have protections against shorted thermistors?
Marlin will stop heating when thermistor shorted.
Well - I am running Marlin, so maybe it wasn’t that. That’s the only thing I can think of though. My thermistor has some precariously close uninsulated leads. I can’t think of any other way the temp could have gone uncontrolled like that.
If I remember correctly, a thermistor’s resistance decreases with an increase in temperature. If your thermistor shorted, your system should think its very very hot and shut off the heat. However, if your thermistor circuit had an open circut, that might look like it wasn’t warm enough.
// The minimal temperature defines the temperature below which the heater will not be enabled It is used
// to check that the wiring to the thermistor is not broken.
// Otherwise this would lead to the heater being powered on all the time.
#define HEATER_0_MINTEMP 5
#define HEATER_1_MINTEMP 5
#define HEATER_2_MINTEMP 5
#define BED_MINTEMP 5
// When temperature exceeds max temp, your heater will be switched off.
// This feature exists to protect your hotend from overheating accidentally, but NOT from thermistor short/failure!
// You should use MINTEMP for thermistor short/failure protection.
#define HEATER_0_MAXTEMP 275
#define HEATER_1_MAXTEMP 275
#define HEATER_2_MAXTEMP 275
#define BED_MAXTEMP 150
You must have something wrong on these setting.