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Jan 21 16 4:59 PM

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The Ada hand struggles to grip objects. 

To find a way to make the fingers great at gripping objects, while maintaining an integrated and aesthetically pleasing design. 

1. The solution must enable the Ada hand to grip objects without them dropping or slipping.
  • See problem section
2. It must be lightweight and affordable.
  • The Ada hand is a lightweight and affordable robotic hand, these are key characteristics that a solution musn't impact
3. It must be as simple as possible.
  • To enable quick and easy manufacture and easy editing.
4. It must be durable and/or replaceable if it wears out. 
  • Fingertips get the most wear and should therefore be replacable without replacing the whole hand.
5. The solution must be licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
  • Since the original Ada hand is released under the this license, any derivatives must be distributed under the same license.

Design a set of mouldable Silicone fingertips. There are fingertip grips available which give the hand an excellent grip, however these are ugly to look at and come off the fingers easily. Due to their super soft gel-like surface they collect dirt easily. Mouldable fingertips could be custom designed to fit onto the end of the fingers and to be the right shore hardness and shape to grip effectively. All of the fingertips could be exactly the same, making it easy to order them in large bulk for manufacture and making them easily replaceable if they wear out. Users could use the colour of the silicone fingertips as a further design choice. 
1. The fingertips should be a standard shape and size for all fingers.
2. They should connect easily to the fingers with no nuts, bolts or adhesives.
3. They should not slip off easily.
4. They should be very grippy and spongy, capable of gripping a vast variety of objects.
5. They should be easy to clean. 

1. Use a home silicone moulding kit to prototype solutions.
2. Use a 3D printer to make the moulds.
​3. Rapidly prototype moulds with sugru.

Last Edited By: JoelGibbard Jan 21 16 5:32 PM. Edited 3 times

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#1 [url]

Jan 27 16 6:54 PM

Hello JoelGibbard

What`s the possibility of the use of CyberSkin instead of silicone ? I had previous experiences in the erotic industry with this material. Maybe can solve the grip problem.

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#2 [url]

Jan 27 16 11:58 PM

Hello everyone. I solved this problem on my prosthetic hand designs. I used a moulding silicone with 25 Shore-A hardness. I 3D printed the moulds and then poured the silicone in. It takes several hours for the silicone to harden. The finger and the fingertip are shaped like a puzzle, a simple snap-fit connection. The grip is pretty good!

Here are some renders and photos that I have right now:




This is another hand model:


Last Edited By: ivomaric Jan 30 16 8:01 PM. Edited 1 time.

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#3 [url]

Jan 28 16 9:08 AM

This is great work Ivo, thanks for sharing. Would you be open to sharing your design files with an open source license? (You keep full credit of course)

Did you hit any issues with the silicone? Do you have a link for the supplier you used? We tried something similar with some silicone we bought on Amazon and had mixed results. Sometimes the fingertips would come out with bubbles in them, and while grippy, we had trouble getting then to stay in a Ninjaflex finger, but it looks like the fingers in your design are SLS nylon?

Either way that's pretty much what we had in mind, we just need to find a way to make that work in the Ada hand. ;)

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#4 [url]

Jan 28 16 10:05 AM

Thanks Joel :). I bought it in a local store that sells art supplies. I think it's a RTV-2 type silicone (it is sold under some brand name here). No problems, it's easy to remove from the mould, has no smell and is not sticky. I haven't tried Ninjaflex yet so I don't know how it behaves. Yes, my hands are SLS printed on Shapeways. Actually, I'm just redesigning the hand from the bottom picture so it can be printed on FDM printers and when I'm done I can share it with you :). Right now the joints are interlocked and can only be made with SLS.

There is also another way to do it- make the entire bottom side of the finger out of a single silicone piece with 2 or 3 thinner creases that will act as joints (like ADA fingers). The upper side can be hard plastic split into 2 or 3 pieces that will give it rigidity and have connections and holes for the tendon. I hope that made sense :). I'll try to make some good sketches to show you.

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#5 [url]

Jan 28 16 10:14 AM


Thanks Ivo, those fingertips look really nice. Another challenge we want to post on here is fingernails, which enable you to tighten the strings, so with those in place there could be a hard attachment point for the silicone.

I'm not quite sure I understand what you described (why does it need joints?) sketches would be great ;)

You may have trouble getting the joints working nicely for FDM printers, if it turns out to be a non-starter, stick with sls! It's come down loads in price lately and would probably end up preventing a lot of design and prototyping headaches!

My colleague mentioned you were looking for our design files by the way, which we've now hosted here.

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#6 [url]

Jan 30 16 5:15 PM

This is the other version that I was talking about. The core of the finger is made of silicone. Two 3D printed shells on top give rigidity.


The advantage is that it can be easily assembled and disassembled and the whole bottom surface of the finger is grippy :).


... And this one below fits better with Ada's design.


I haven't printed this yet but I think it could work.

Last Edited By: ivomaric Jan 30 16 8:10 PM. Edited 1 time.

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#7 [url]

Feb 11 16 5:43 PM

That's nice Ivo,

One suggestion would be for the plastic part to also encapsulate the tendon channels to reduce friction (tendons sliding through silicone may cause issues). The other possible issue might be breakage of the joints, ninjaflex is a lot stronger than silicone (well, the silicone we've tested anyway).

Looks really nice.


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#9 [url]

Feb 14 16 4:36 PM

Hi Drew. I designed my hands to be printed on SLS printers because I wanted low mass and high strength. I also use moulded silicone fingertips. I print it on Shapeways and it costs around 100 euros, a lot more than Enable hands. I could make it open source but I don't know if it is too expensive for Enable volunteers? However, I am working on a simpler variant that can be printed on FDM printers. It's not finished yet but I can email you the design files if you want? Do you use Fusion 360?

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#10 [url]

Mar 5 16 1:41 PM

I just tested the finger design I mentioned above. It is easy to make and it works. The entire bottom surface is very grippy. But it's not worth it. It flexes too much when picking up heavier objects.



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#12 [url]

Sep 19 16 3:02 PM

I think you should take a look at the Xbox one elite controller grip on the back, it's very smooth and pleasant to touch !
I really think it'll do the job.

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#13 [url]

Nov 8 16 7:12 PM


I really like both of your designs! I wish my multi-material printer was here already! I've been wanting to print these hands with filaflex in the fingers for grips. Having the hard shell for the structure and the tips in the filaflex like the first design you posted.

I'm hoping to print both materials in the same print, then change out the tips as they wear. I won't have my new printer for a couple of months, but I really like where you are headed with this.

Would you mind sharing your files to your designs? I'd definitely like to try out the first one and make some molds myself. I think you asked someone above if they had Fusion360, which is what I use.

Let me know!


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