Anyone who works with 3D printers knows that they fail quite often and sometimes quite spectacularly. This bubble of melted plastic from the wrong end of the hotend was caused by a tiny wisp of plastic from the print skirt detaching from the bed and jamming the hotend fan, which caused the cold side of the hotend to heat up. This not only destroyed the printed parts around the hotend, but also accumulated the fed plastic as a blob on the wrong end. All things considered, this is quite mild compared to the single worst failure of a 3d printer that I have ever owned. 18 hours into a 30 hour print, I came down to see this:

I was attempting to print something from a batch of ancient filament I bought in a lot off Facebook Marketplace. Filament that had been left open and exposed for probably a year or so. I got (what I thought was) a fantastic deal on it! 6kg across 9 colors for $50, and most of it printed fine after being dried out in an oven. I didn’t realize that the rolls would be hiding a ticking time-bomb.

When I removed the print head, I saw the full extent of the damage: a blob of plastic too large to be easily removed. Most extruder blobs can be pulled off with pliers while the hotend is heated, but this was so large that the 40W heater couldn’t melt enough to free itself. I had to use a saw and an angle grinder with a cutting wheel to remove large chunks of plastic from the blob to make the resutant mess manageable. Once I had removed enough of the remaining plastic that subsequent cuts may have damaged the hotend, I suspended the entire assembly in an oven and allowed the plastic to soften and slough off.

Ultimately, some part of the original clog or my subsequent attempt to resolve it damaged the nozzle and hotend throat, and that cheap filament suddenly cost me an additional $100, wiping out any savings. Good filament is worth the money, especially at the $20/kg price point.