I’ll start off with a recent one. I forgot to connect the hotend cooling fan when remounting the hotend. After a while the printer jammed and the whole toolhead got so hot that it started to melt. The brass inserts were coming out of their sockets and the hotend stood at an angle instead of straight down.

I also noticed that the “teflon” tube connecting the extruder to the hotend was not in fact teflon. The slowly melting ABS was blowing a bubble in that tube and it was clearly starting to melt.

It was quite a pain in the ass to fix as I did not have a second toolhead nor a second 3D printer to print a new one so I had to fix the extruder/hotend in place using 2-part glue hoping that the printer lasts long enough to print a new toolhead.

I should probably have either a thermal fuse or a smart filament sensor that notices jams as well. When your hotend cooling fan fails, or the operator forgets to connect it, the filament will jam in the heatbreak and if it goes long enough the whole hotend will be plastic-meltingly hot. A jam sensor should see it before the toolhead starts to melt.

  • ahmedezat_katteb@lemmy.worldEnglish
    1·
    4 days ago

    The tube that turned out not to be PTFE is a nasty surprise. On the fan side, if you run Klipper: heater_fan only switches the fan on above a temperature, it can’t tell that the fan is unplugged. A fan with a tachometer wire and tachometer_pin set at least shows you the RPM, and you could add a macro that pauses the print if it reads zero while the hotend is hot.

    The low-tech version is to look at the heatsink fan spinning after any toolhead work, before the first heat-up. Cheap habit compared to rebuilding a melted toolhead.

    • Rolivers@discuss.tchncs.deOPEnglish
      1·
      4 days ago

      I… may have short circuited the hotend fan mosfet and broke it. I just let them run at full speed since then.