This is an example of a 3D printed living hinge that also doubles as a spring made with PLA. The material isn't usually the best choice for flexible applications - especially when the living hinge ...

This is the worst possible setup to print living hinges: PLA isn’t terribly flexible, and here the flexible bits have to be printed vertically, which really isn’t ideal to withstand cracking.

Yet when the application isn’t heavy-duty like in this clamp-on connector, even PLA printed “against the grain” works well too: this connector can spread its hooks linearly 3 mm apart and the living hinges don’t crack or weaken even after many cycles.