MakerGear Forum

So maybe a week ago I installed a new thermistor in my hot end, and I've had to increasingly run it at higher and higher temperatures to get the PLA to flow normally. I tried multiple, reliable filaments, and they all had flow issues at the normal temperatures.

After needing to turn it up to "260 C", I assumed all these needed temperature increases were due to a faulty thermistor. I swapped it out for my old one. There wasn't anything wrong with the old one, I just preferred to use a fresher component.

I started heating the hot end to 230, and readings were fluctuating a little, but increasing towards the goal temperature. I stop paying close attention, and about 30 seconds later the whole hot end just exploded out of the groovemount. Molten plastic spattered everywhere, and smoke was pouring out of the groovemount. MAXTEMP was tripped, and pronterface was displaying readings of over 300 degrees C.

So... what the hell. Was this a computer error? Why did it take so long for the printer to realize it was over-heating? My best guess is the thermistor wiring, but I want to figure out exactly what's wrong before burning another ~$50 in replacement parts. I should also point out that I never messed with the firmware, or did anything to bypass the built-in safety measures.

http://i.imgur.com/mVxnJF1.jpg
http://i.imgur.com/TQYujfb.jpg
http://i.imgur.com/3vrCrng.jpg

Edit: on a side note, can I pry the metal housing off my backup bed probe to make a hotend replacement probe? They look the same.

ouch...the pic of the glass bed is like an m2 massacre lol. hmm not sure what happened there. if you had a little glitch in the thermistor you wont have the issue anymore. your just going to get a whole new hot end from makergear so all that will be included.

Update:

I tested the thermistor that led to the explosion, and it has a bad connection that gives fluctuating readings. So if I were to guess, the bad wiring somehow gave false low temp readings, leading to overheating. The overheated hot end then melted the groovemount's threads and turned the filament into hot gas, causing internal pressure.

On a side note, I needed the increased nozzle temperatures because there was a deposit of carbonized PLA in the tip. I confirmed the thermistor was working normally by checking the temperature of oven-heated oil and boiling water. Fortunately the M2 is a tank and I didn't damage it by running it at 260.

Best of all, Makergear is sending me fresh components to replace the ones ruined. I really appreciate that