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Kickstarter Hand finger

by Anthromod, published

Kickstarter Hand finger by Anthromod Jul 20, 2013

Description

The little finger from the 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 £10 and £15 reward tiers.

Recent Comments

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Really really nice design. Kudos
It would be really nice to have a double jointed finger on the Robohand. Would you mind if I tried to remix the 2?
If it's not an issue could you share the cad files?

Would it be to much if we humbly begged for a thumb??? Nice work by the way! I love your design.

Hi Anthromod,

Cool finger, nice work! What size servos are you using to move the finger?

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Instructions

Other ingredients:
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!

Comments

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1Robomaker on Oct 23, 2013 said:

Would it be to much if we humbly begged for a thumb??? Nice work by the way! I love your design.

jaredwilliams on Aug 7, 2013 said:

Hi Anthromod,

Cool finger, nice work! What size servos are you using to move the finger?

GentlemanFaun on Jul 30, 2013 said:

Would it be possible to make this work for the RoboHand prosthetic? I love the number of joints and flexibility of these fingers, and it looks like it uses a similar cable mechanism for movement.

My dad and I have been working on improving and modifying the Robohand all summer, and this is almost exactly what we were looking for for my new left fingers.

Anthromod on Jul 31, 2013 said:

Hi GentlemanFaun. That's something I'm interested in doing. Right now though I'm busy fulfilling some Kickstarter reward commitments as well as some commissioned work. It shouldn't be too hard to create a hybrid of the two.

wmhilton on Jul 21, 2013 said:

Awesome! It's great to see the fingers coming to reality!

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