Thought some folks might find these tips helpful from Proto Labs in Make Magazine
From the article:
Polypropylene is useful for designs that incorporate living hinges.
Seen plenty of wood ones. Polypropylene also appears to be laser safe. This seems like something to remember for later!
Proto Labs has a whole series of tips for injection molders and 3D printers:
Yes it is laser safe and can also be 3D printed. Living hinges in PP are simply a thin piece that bends, a Tic-Tac lid is an example.
I use PP strips with ribbon cable to make flexible connections as a simple light weight alternative to drag chains on my 3D printers.