PETG, TPU, and the Fancy Stuff You Don't Need Yet
Last lesson: PLA first, always. This one covers everything after PLA, and mostly why "after" sits a lot further out than people think.
Every couple classes somebody shows up with a spec sheet memorized. They want PETG, or they saw a flexible phone case online and want TPU, or a cousin told them carbon-fiber-filled filament is the real stuff. Fancy filament feels like leveling up. But you haven't cleared level one. Level one is PLA.
My rule, unsoftened: get 100 good prints in PLA before you touch anything else. Then bring up PETG. 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, skips the hot enclosure, doesn't warp the second a draft hits, and 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 stack a second layer of problems on top of the printer problems you haven't solved yet. Bad trade this early. You won't know if the failed print is your settings or the material, and you'll guess wrong more often than not.
Case in point. My first print ever was that little test boat everybody runs on a new machine. Mine came out like melted candle wax. Amber still calls it "the shipwreck." It's on my shelf, on purpose. That was PLA, on a bed that wasn't level, and it still took me a minute to pin the bed as the problem, not the filament, not the settings, not the model. Run PETG that day and I'd have had three 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. Stronger than PLA, handles heat better — think a water bottle left in a hot car; PETG won't warp where PLA might soften — and 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 oozes a thin thread between moves if your retraction settings aren't dialed in, and dialing in retraction is its own small project. It also grips the bed almost too well sometimes, to the point people crack their glass plate prying a print off. It's not hard. It's a new set of things to learn, and you want 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. Genuinely fun once you can print it. 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 your PLA prints come out clean. I'll help you figure out whether 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 wears out a brass nozzle faster than plain PLA. Serious use needs a hardened nozzle. 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. 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 whether PLA truly 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.