When I started my first 3D printing blog it was all about the printer, the fiddling I needed to do to get it working and the repairs I needed to do to keep it working. As things have progressed I've reported less on the tinkering on the machine and more on the projects that come from the machine, but I'm still frequently tinkering.
This weekend I had a significant repair. My printer has been suffering a slow degradation in quality that I couldn't track down. I tried changing nozzles, PTFE tubes, all the simple fixes, and nothing was getting my quality back to what it once was until I took the entire extrusion mechanism apart and discovered that the plastic parts that hold the plastic in place as it fed in had melted and warped.
It's hard to tell in the picture because they're black, but these parts massively warped in parts. They're made from molded ABS, not 3D printed, but still suffered from eventual melt down. Fortunately when I bought the upgraded extruders they sent me extras of this part that I was able to just swap right in, and once I did my quality immediately returned. But this does raise an interesting point about plastic parts on a machine designed to melt plastic.
As cool as the idea about the RepRap project is, I think there's a fundamental flaw in the methodology that isn't often discussed. Yes you can use a 3D printer to print the parts for a 3D printer, but if those parts are made of the same material you're planning on using the 3D printer to melt you're likely going to have problems or a never ending cycle of "print the replacement parts now before you need them... oops, I need them now." In my opinion fancy high temp plastics can be used if you want your home made printer to print ABS, ABS parts should be used for a PLA-only 3D printer, and PLA should never be used for a 3D printer. But this goes against the "a printer that can print itself" tagline of the RepRap project, so I recognize that some people night not be cool with that, and that's okay. This is just, like, my opinion.