How I finally stopped blaming the printer for my own mistakes

The waiting-until-you're-calm part is the one I had to learn the hard way. I once messed with first layer height three evenings in a row on my MK3S because a PETG part kept lifting at the same corner. Turned out the model had a sharp thin point right there and nothing to do with the bed. A tiny chamfer on the bottom edge fixed it in five minutes after I'd alredy burnt through half a spool of filament chasing ghosts.

What finally helped me was keeping a notes file next to the printer. Date, what failed, what I changed. After a couple months I could actually see the pattern, that almost everything came back to geometry problems like sharp corners or unsupported bridges. Only a couple were machine stuff at all. The checking the underside of the model in the slicer is somethig I do now too. PrusaSlicer makes it easy to spin the part around and you'd be surprised how many models on Printables have hidden overhangs the designer clearly never printed themselves. I've started leaving comments on those files when I find one, mostly so the next person doesn't waste a weekend. Still worth walking past and glancing at the print mid-way though. My one repeat failure is big flat parts where I get lazy and skip the brim because I'm sure this time it'll be fine. It never is.

I found that when I'm using a diffrent kind of plastic it makes everything much messier. It doesn't matter if the printer is working right, the material itself can just get all gummy and start sticking to the nozzle or the bed in ways that are really frustrating to clean up. I had this one part where the plastic just built up everywhere and I couldn't even get the print to finish because the nozzle got totally gummed up with gunk. It felt like I was fighting the material more than the machine itself. Do you guys find one type of plastic is way more annoying to handle than the others?

Adding one to the checklist that bit me recently: make sure you're actually printing the file you think you are. I edited a part in the slicer, saved it, then grabbed the wrong file off the USB stick and printed the old version with the flaw still in it. Spent an hour second-guessing my settings before I noticed the finished part had the exact problem I'd already fixed. Now I delete old exports off the drive the same day I slice something new.

I can't fully sign off on the 'clean first layer means it's on the design from here on' logic. I babysit the first layer every time, and my machine still found ways to fail hours in. Had a spool tangle itself halfway through a long job and print fresh air for the last third. Also had a partial clog show up mid-print on a ten hour job when the first two hours were flawless. The first layer tells you the printer started honest, not that it stays that way. If I'm home anyway I'll still poke my head in every hour or so, cameras miss a lot of subtle stuff like stringing buildup.

Update: turned out I was the problem again, just in a new way. That reply about printing the wrong file off the stick hit close to home, because I'd saved my fixed version with a nearly identical name and kept slicing the old one. Renamed it clearly, watched the first layer like usual, and the print came out clean. No printer changes needed.