PETG, TPU, and the Fancy Stuff You Don't Need Yet
Last lesson was PLA first, always. This one's about everything after PLA, and mostly why "after" should be a lot further away than people think.
Every couple classes somebody shows up with a spec sheet already memorized. They want to know about PETG, or they saw a flexible phone case online and want TPU, or somebody's cousin told them carbon-fiber-filled filament is the real stuff. I get it. Fancy filament feels like leveling up. But you haven't finished level one yet, and level one is PLA.
Here's my actual opinion, not softened: get 100 good prints in PLA before you touch anything else. Then come talk to me about PETG. I mean that as close to literal as advice gets. Not 100 prints total, counting the shipwreck ones. A hundred good ones, where the bed's level, the first layer's clean, and the thing came off the plate looking like what you designed.
Why PLA first isn't just me being stubborn
PLA is forgiving. It sticks to the bed easily, it doesn't need a hot enclosure, it doesn't warp on you the second a draft hits it, and it prints at a lower temperature that's easier on your hotend. Every problem you'll learn to diagnose — bed leveling, first-layer adhesion, stringing, warping — you can learn on PLA without the material fighting you at the same time.
PETG and TPU add a second layer of problems on top of the printer problems you haven't solved yet. That's a bad trade this early. You end up not knowing if the failed print is your settings or the material, and you'll guess wrong more often than not.
Case in point. My very first print ever was that little test boat everybody prints when they first get a machine going. Mine came out looking like melted candle wax. Amber still calls it "the shipwreck," it's on my shelf, I keep it there on purpose. That was PLA, on a bed that wasn't level, and it still took me a minute to figure out the bed was the actual problem and not the filament, not the settings, not the model. If I'd been running PETG that day I'd have had three different things to blame and no idea which one was guilty. PLA narrows down what can be wrong. That's worth something when you're new.
What PETG actually is, briefly
PETG is the next reasonable step up. It's stronger than PLA, handles heat better — think a water bottle left in a hot car, PETG won't warp where PLA might soften — and it's a decent choice for things that live outside or take some abuse. Garage brackets, outdoor plant hooks, that kind of thing.
But it's stringier than PLA by nature. It likes to ooze a thin thread between moves if your retraction settings aren't dialed in, and dialing in retraction settings is its own small project. It also sticks to the bed almost too well sometimes, to the point people crack their glass plate prying a print off. It's not hard. It's just a new set of things to learn, and you want to be learning one new thing at a time, not five.
TPU, briefly
TPU is flexible filament, the stuff phone cases and gaskets and flexible hinges are made from. It's genuinely fun once you can print it. It is also a pain for a beginner printer to feed reliably, because it's soft and your extruder can buckle it instead of pushing it through. Direct-drive printers handle it fine. A lot of beginner machines are bowden-style, where the filament travels through a tube before it gets to the hotend, and TPU through a long bowden tube is an exercise in frustration. Ask me about it after you've got your PLA prints coming out clean. I'll help you figure out if your specific printer can even handle it well.
Carbon fiber, wood-fill, glow-in-the-dark, all that
Fun. Also abrasive on your nozzle, sometimes literally — carbon fiber filament will wear out a brass nozzle faster than plain PLA will. You'd need a hardened nozzle for serious use. That's a $15-20 part and a swap you don't need to think about yet. File it under "later."
The actual plan
Print in PLA. Fail in PLA. Level your bed, slow your first layer down, get your dimensions right — all the stuff we've covered — until it's boring. Boring is the goal. Boring means you've got the machine figured out. Then, when you have a real reason — you need something waterproof, or heat-resistant, or flexible — go get a small spool of PETG and expect the first two or three prints to string a little while you tune retraction. That's normal. It's not a sign you bought the wrong filament.
Before next time
Don't buy anything new. Look at whatever you're printing this week and ask yourself honestly whether PLA can't do it, or whether you just want to try the fancy stuff. Most of the time it's the second one. Mine usually is too.