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Feb 8 16 7:05 AM

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I have been asked by a local family to help by printing and building a hand for their son Kayden who is 12 and I wondered if there is suggested way to size the hand so that it is a more natural size for a child?  I wanted to print and build the hand first and when we are happy I will purchase all the parts and fit them.


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#2 [url]

Feb 8 16 11:37 AM

HI Cliff,

Thanks for your message. The Ada hand is not a medical device and its therefore not recommended that it be used as a prosthetic. Open Bionics are working on prosthetic devices which will be available in the future and these will be available for children aged 10 upwards.

If you wanted to make a smaller version of the Ada hand I would recommend using just 3 motors and wiring the index and middle fingers together and the ring and little fingers together.

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#3 [url]

Feb 8 16 12:02 PM

Hi All,

we are well aware that it is not a medical device but given that all the NHS will provide is a claw that is very poor and heavy so he tends not to use it we thought why not try openSource devices and see what can be done. Joel you actually met Kayden and his family at an event late last year and it's from that day I was asked by his mum Sharon to help with building a hand to give him some function back and to be honest just looking at the video's it's far far suprior to anything he has ever had and I guess will ever get.

All I need to do is work out if making the hand smaller is a good idea due the fit of the motors etc or just make a full size hand and see how he gets on, but I will need a forearm for it to attach to as well kif you have any suggestions.


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#4 [url]

Feb 8 16 1:05 PM

Hi Cliff, I would probably start by printing out (on paper) the outline of the top view of the hand at 1:1 scale. Draw on the paper the dimensions you think you want to achieve and calculate the reduction ratio (the length you want divided by the original length). Then you could scale the palm/fingers/top cover by this ratio in blender but leave the motors/pcb/pcb holder at the original scale - they will probably pop through the sides of the model. Print out the scaled model on paper and verify that it looks right. Then see if the pcb assembly can fit at all (there is some plastic that can be trimmed off one side of the pcb holder, but maybe not enough), if it doesn't you will need to take the pcb external and use a daughter board to connect the motors to the board via ribbon cable or similar- make sure the cable you use can support the max current the motors will draw and also that the cable length does not impede the signalling. You will need to find space in the hand for this daughter board. Also check that the thumb motor will fit, if it doesn't you may need to find an alternative motor. Then you can start removing finger motors and rearranging them. I would start by trying to align the actuator arm to point down the centre line between the fingers it is intended to actuate, though there may be a good reason to align one of the motors directly on the index finger, you may need to experiment here. You would then need to make sure the cable channeling lines up, print, test and iterate. Good luck jd.

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#5 [url]

Feb 8 16 2:45 PM

Thanks Cliff,

Was that at the Reach event?

Yes Jaundice suggests a very good approach. There are models of all of the physical components in the blender files so you can design something that works with the existing PCB and actuators. It's not particularly complicated to scale the palm down and get a working "puppet". The hard part will be fitting all of the actuators and electronics inside it. The daughter board Jaundice describes doesn't need to have any active components on it, just motor connectors and cables to extend the motor cables to reach the PCB if you house it outside of the hand. Another option is to keep the PCB inside the hand and it might just look a little large. The PCB is going to take up a lot of space if it's housed on the socket anyway so aesthetically I'm not sure it makes that much difference.

To design the socket, you can use the "Structure" sensor from Occipital or photogrametry to generate an arm scan and then use the "Shrinkwrap" modifier in Blender to build a mesh that would fit around the arm. Then you just need to connect the arm to the socket.

I'll let you know if we have any opportunities for Kayden to test our prosthetic prototypes in the future.

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#6 [url]

Feb 8 16 3:47 PM


Yes it was at the reach event I believe and I am planning to build him a hand so hopefully the kind trial offer can be given to another child but I will let him make that decision.


Thanks for the workflow that sounds about where I was thinking but I hadn't thought to print on paper first so you just saved me a bunch of plastic as I was going to print and iterate in PLA as I have lots hanging around but your idea is much better. I may look to see if I can house the PCB in the forearm but again it comes back to size and after all he is 12 so adult to real life size may not be that much but will have a play and let you know.

As for the PCB I've not looked yet but is there opportunity or making it smaller for use in child hands in the future? and has it thought about moving the motors into the forearm in these cases for smaller children? Just ideas is all.

Will let you know how I get on.


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#7 [url]

Jun 15 16 7:51 PM

Hi, everyone.

I'm starting to learn about this project.

And after reading this post i didnt understand when you say "Not a medical device".

Saying that "Not a medical device" i understand that this project are not supposed to be used for real people who lost their hand? I'm right understood that?

If my understood are correct, what is the propose of this project?

I'm pritty sure i'm wrong of my undestanding, just need to be sure.


Last Edited By: angelocarlotto Jun 15 16 8:18 PM. Edited 1 time.

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#8 [url]

Jun 16 16 8:27 AM

Hi angelocarlotto,

The Ada hand has been designed to be used by researchers, hobbyists and developers. 

We have provided a fully functional Open Source robotic hand (Ada) that anyone can download and print themselves, as we feel the developer community can play a huge roll in furthering the development of advanced, low-cost robotic and bionic hands. Also, everyone wants a cool robotic hand to play with and to their various hobbyist and research projects.

At Open Bionics we are also currently working to certify our range of custom bionic hands as medical devices, which we aim to release early 2017.

I hope that clears up any misunderstanding.

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#9 [url]

Jun 19 16 9:32 PM


Thanks a lot by the clarification about this subject.

I opened another topic to discus what is needed to turn this project into a medical device.

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