Thermistor died, over heated hotend
Posted: Fri May 02, 2014 12:08 am
After putting in my 2nd thermistor I got some great test prints for various filaments, ABS, PLA, WOOD, Bridge... The first thermistor died after a couple of hours of printing. The second one gave me 20+ hours of printing before it slowly started to give false values.
It started when a nozzle jammed from too much heat raising up in the hotend, and the filament got wedged in the PETF tube. I cleared that and let the printer cool down. Or so I thought. I step away for just a few minutes, came back, and the temp read 27C. It previously read in the 200C-220C range. It didn't click that it cooled off way to fast. But I don't have a great sense of time to begin with. So needless to say I have 2 small burns on 2 fingers. As the printer continued to cool off it dropped down to -19C. Which was pretty impressive, and a clear sign of a problem.
I noticed extra blackness around the nozzle, so I took the hotend (now cold) out of the printer and realized the power resistors are now very loose. I went further and took them out, and cleaned up the RTV. Both resistors have melted spots, and crackes in the cases. And the hotend feed tube insulator bent a a little!
I think the thermistor went bad which caused the board to keep applying power to the resistors, which over heated the hotend, which melted the feed tube insulator a little...
I might be down a bit, but the bird feeder was coming out great!
-Max
It started when a nozzle jammed from too much heat raising up in the hotend, and the filament got wedged in the PETF tube. I cleared that and let the printer cool down. Or so I thought. I step away for just a few minutes, came back, and the temp read 27C. It previously read in the 200C-220C range. It didn't click that it cooled off way to fast. But I don't have a great sense of time to begin with. So needless to say I have 2 small burns on 2 fingers. As the printer continued to cool off it dropped down to -19C. Which was pretty impressive, and a clear sign of a problem.
I noticed extra blackness around the nozzle, so I took the hotend (now cold) out of the printer and realized the power resistors are now very loose. I went further and took them out, and cleaned up the RTV. Both resistors have melted spots, and crackes in the cases. And the hotend feed tube insulator bent a a little!
I think the thermistor went bad which caused the board to keep applying power to the resistors, which over heated the hotend, which melted the feed tube insulator a little...
I might be down a bit, but the bird feeder was coming out great!
-Max