Integrated Flexible Finger

UPDATE 8.30.2016: Just uploaded V9 of this design, although I will leave the old version up as well. V9 removes some of the flex filament that made up the springs and only includes it in a strip along the back, which reduces the amount of force required to contract the finger. It will also probably extend the life of the part because there is much less TPU being moved.

I created this design because I was curious about the potential for combining flexible filament with stiff PLA. Thermoplastic polyurethane or TPU comes out of the extruder slightly tacky. Once cooled it doesn't stretch, but will flex and bend when force is applied returning to its original position afterwards. My idea was to incorporate a flexible joint with stiff structure to make it bend in predictable ways.

This my first design using TPU, so I decided to make something that I could test simply. After several versions figuring out print settings and rules of thumb for flexible filament I made a quick edit to t