Kickstarter Hand finger
by Anthromod, published
The little finger from the http://www.kickstarter.com/projects/anthromod/3d-printed-robotic-hand/
We originally said we'd share the finger joints, but thought hey why not just share a complete finger instead. This is effectively the finger that went out for the Â£10 and Â£15 reward tiers.
20+cm of flexible wire. I used AFW 7x7 Surflon Micro Supreme 40lb.
Rubber bands. Should be small enough to stretch 10-20mm whilst supplying force. I used dreadlock hair bands!
2x 3x16mm screws. I used socket head screws.
1x 3x20mm screw.
3x M3 nuts. I used nyloc, to get a better grip.
1 crimp. AFW size #3
Ok the files are as I developed for the purpose of printing. So they're split in half because it means no overhang when printing. They also have a continuous base because some small parts would otherwise pull away. I printed at a 0.25mm layer height, which matches the base layer thickness.
Once the parts have printed, it's best to remove the plastic where the screw holes are. This can be done carefully with an exacto knife. Cut off any other extra material.
I printed in ABS so I glued the halves together with acetone. Pure acetone works well and avoids edge splurge you get from abs+acetone glue.
Depending on your desired finish level, it's best to sand or acetone now. Pay special attention to the hinge sides. Drill out the screw holes and tendon holes in the distal phalange. 3.2mm and 1.5mm drill bits respectively.
Place the 16mm long screws through the finger joints, and the 20mm screw though the knuckle joint. Make sure the hinges can turn without resistance. Once turning freely apply the nuts to the screws. Tighten but not so far that they clamp the joints shut.
Thread the tendon through the distal phalange. Thread on the crimp and form a tight loop. Shortest length nearest the finger and the longer outside. Squeeze until secure. Cut off extra tendon wire carefully as it may spring away with some speed. Thread remaining tendon through other finger sections.
Now place the elastic bands on the back of the fingers joints. They should be under tension and so unable to come loose. Apply more bands until return force is what you want.
Voila you should now have the beginnings of a working robot!