After watching a video by shapeways about springs, I wondered if 3d printed springs would work for twisty puzzles.
Has anyone thought of this before? I would be a major convenience if the puzzle parts came with springs.

You don't even need a spring with 3D printing - a single flap of plastic, built into the design of a component, could bend and act just like a spring.

If you mean as a replacement for the metal spring in the screw/spring structure, I'd have to say no; nylon is a little too flexible and the springs would be very ineffective. I did use a printed spring in a trick lock design once and it worked very well, but they would have to be very thick to offer the same tensions as a metal spring.

I agree. Young's modulus for steel is about 200 GPa, whereas for nylon it is 2-4 GPa

Actually, you could use nylon as a direct replacement - BUT, you would have to:

1. Increase the thickness; and
2. Reduce the number of coils.