You can bend [reasonably thin] PLA with boiling water if you need to curve it slightly.
This means you can print your piece flat (and save on effort/support material) and then bend it as needed later.
It works great for stuff like the ear pieces on glasses and it’s stupidly easy.
I printed the ear pieces flat, threw it into a pot and poured enough boiling water on it to cover it. After about 3 seconds, I pulled the piece out with tongs and bend it over a glass.
The best thing about this is that the PLA doesn’t seem get hot to the touch (It might if the piece was really thick or if it was submerged in the water for a long time) so it’s easy to work with and it can be re-boiled if you get the shape wrong, which I clearly didn’t nail the first time.
You can see in the first picture, the 3D printed ear piece has a totally different bend than the original, so I just held it over the pot and poured boiling water from the kettle onto the problem areas briefly and reshaped until it matched the original frame almost exactly.
Then I just super-glued the new ear piece (and almost my fingers) onto the frame and the glasses were done!
As far as I can tell, this doesn’t degrade the plastic much if at all, but it seems like the kind of thing you should try to do as infrequently as possible.
In the future, I might try bending stuff at more extreme angles – things like rings, bracelets, head pieces/crowns… Who knows, but it’s definitely an interesting thing to fiddle with. It definitely seems like it might have some applications in cosplay…