I guess I should start by saying that I broke my 3D printer.
I was running an overnight print and sometime during the night the heatsink fan stopped working. Unfortunately the Prusa i3 MK2 can’t sense that and continued trying to print. When I checked it in the morning It was still moving but the print head was about 2 inches above where the part stopped. I assumed it was just a clog and went through the steps I usually go through to fix that. It was at this time that I realized something else was wrong.
Like I said the heatsink fan stopped spinning. This by itself is a bummer but after my $10 replacement came in and I installed it the printer still wouldn’t extrude. As it turns out, or at least what it seemed like to me, the PTFE tube that runs through the heatsink got too warm and the filament got soft too early. This is because the heatsink wasn’t being cooled and was allowed to heat up with the hot end.
I initially thought that the tube got soft and fused shut but I don’t think that actually happened. PTFE is generally safe up to 600 C which is well above the operating temperature of any filament I’ve ever seen. What I do think happened is that the fan stopped, the heatsink warmed up and the usually cool filament that runs through it became too soft too early. At that point the extruder motor/gear wasn’t able to build up pressure behind the filament to push it out the nozzle and it clogged.
What I Tried First
Unfortunately looking back I probably could have fairly easily fixed it right then. It’s likely I could have let the heatsink warm back up and let the filament get soft so that I could have pushed or pulled it out. Instead I let everything cool, took it all apart and tried to pull the PTFE out. This didn’t work. I wasn’t able to pull the PTFE out and instead ripped off the part that stuck out of the heatsink. I think there was a chunk of solid plastic in the tube that prevented it from being removed. At this point I got very frustrated and didn’t touch it for a day or two…
The Actual Solution
After much Googling I realized that the easiest solution would be to just replace the heatsink, heatbrake and PTFE tube. Thankfully this wasn’t terribly expensive, even with genuine E3D parts it came out to about $50 with 2-day Amazon Prime shipping. Not bad.
The parts came in and everything went together great. I followed the online guide from E3D and had no issues. The hardest part was putting the extruder assembly back together because I’m stubborn and refused to re-read the Prusa Assembly Guide. But I got there eventually, tested it and it worked great!
I’m very glad that I got the MK2 as a kit. Having built it I had a much better idea of how things worked and what could have gone wrong. That said, now that I have a pretty good idea of how they work I’ll probably get a pre-built or mostly pre-built printer next time.
I actually still have some work to do to get back to printing but it’s just calibration. Unfortunately since I had to rebuild the entire extruder all my calibration had to be reset. That sucks but it’ll just take some more time. I also have the MK2.5 upgrade kit coming in June so I may not spend too much time getting everything perfect since I’ll be doing another rebuild then. One great thing about the MK2.5 upgrade is a filament sensor that’s able to tell if filament is there and if it’s moving so hopefully this won’t happen again!