Hollies Hand

Various holidays and work commitments finally resolved themselves and Hollie was able to come and try on the coloured hand. She was very happy with the results and it taking it home to try out more.

IMG_2920_2She also told me that she had been getting a lot from the earlier prototype I gave her. The stronger her arm became the more she could use the hand. So I’ve decided to slightly detour my plans and combine that prototype with this design and create the functional hand, hopefully within the next month.

If you know anyone else who is interested in this type of prosthetic then get in contact with me using the contact us form.

I designed a cosmetic hand for Hollie whilst my work on the Anthromod V2.0 hand continues. I based it on the 3D scan I already had and some photographs provided by her father. As time goes on I plan to refine the process and create the model from an actual hand rather than a casting. This would allow me to add the flesh textures instantly and avoid painting the textures in Blender.

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Hollie will be trying out the hand on Friday, so I will post an update then. I am also looking for anyone else interested in this type of cosmetic prosthesis. If you are, or know someone who is you can contact me via the contact us form. The ideal candidates will be those with a Transradial amputation just below the wrist, who have a complete other hand. Alternatively if they have a shortened forearm and small palm (like Hollie) I’ll take a look at it. If you don’t have a complete hand I may also be able to create a hand based on another’s hand, with the scale and skin tone matched.

Eventually I aim to offer this as a paid service, and I will begin a pre-order system soon. Either here or via a crowdfunding platform like Indiegogo. Of course the great advantage of 3D printing is that once the modelling service is paid for the costs of a second hand are much lower. This compares very favourably with labour intensive methods such as silicone cosmetic prosthetics where the second hand costs the same as the first.

Here is a photo of the hand and socket post assembly and plus silicone processing. Loom bands optional.

Hollies hand

Hey everyone. I have some big news about my current prosthetics project. I have gone and ordered the prosthetic hand from shapeways and it should be arriving in a weeks time. This has effectively been paid for by those who have bought from my shapeways shop, so thank you to all of you.

 

render4 render3 render1 front

As you may be able to tell from the above renders I have finally learned how to use Blenders Cycles render engine!

 

Whilst the elastic elements don't yet neatly fit within the fingers this is due to the hand being quite small. As Hollie grows bigger they should disappear in later designs. 

 

You may notice that the tendon torsioners are similar to James Holmes Siedle's design. This is because I re-engineered the idea for use in SLS nylon. I adjusted each block so they sat parallel with the back of the arm to maintain a sleek look. I also made two version of the rotary part of the tensioner.

 

I'll update the blog once I receive the hand. Hopefully it'll be ready for Hollie to start using.

Some of you may now about Bioloids.

These are cute little humanoid robots designed for research and playing football, although there may be some other uses. Anyway I noticed that they lacked one thing… well ok two things…. in the form of hands. Yes you can put together some parts to make a gripper, but it’s a bit large and not as anthropomorphic as the rest of the bot. I decided to remedy this, and thanks to Trossen robotics putting the CAD parts online I got to playing around with it. It turned out to be surprisingly easy to design parts that would fit. Since I don’t have a Bioloid, or a spare servo I can’t really test this, but I might end up putting it on shapeways.

Design1-R2 Design1-R3 Design1-R4 Design1-R5 Design1-R6 Design1-R1

 

In other news I am still working on the full size prosthesis for Hollie, as well as the conventional robot hand. I’m just working on the kinks regarding the nylon printed springs. It’s proving to be very much a goldilocks thing, where no designs yet are just right.

One big issue is the hysteresis of the spring. It starts at position A, moved to position C, but doesn’t move back to A, but partway between them to B. Luckily movement between B and C is reliable and predictable. The problem is that if I print in position A I need to know that position B will be ok.

The following is an overview of how I went about about creating Hollies unique Robohand.

The first step involved Hollies father creating a series of alginate molds of both her left and right hands. Instructables gives a large number of tutorials on this process, with a number of them being focused on hands.

He then used these alginate molds to make plaster models of Hollies hands.

Design Plaster cast

I then took these plaster models and used a technique called Photogammetry to turn these models into Computer models. The particular tools I used were 123d catch and Autodesk recap 360. These are both free Autodesk products that let you turn a number of photos into a 3D model.

Design Photogammetry fullNow the hand looks a little different from the white plaster cast.

I used a grey paint to bring out the contrast in the hand.

I also added coloured dots to the hand which gives myself and the software reference points to find in 3D space.

The final addition I made used a giant coloured QR code, which the model rests on. The QR code serves the purpose of helping the software know the surface is flat, as well as giving reference points to pick. The colour is also there to help me identify which precise square I’m using as an alignment mark. Trying to identify a black square out of many black squares is needlessly difficult.

The resulting model looks something like this:

Design 3D scan model

Not very useful, so I used another free bit of software called Blender, to edit out the parts of the mesh I don’t need.

Blender gave me some useable models, but photogammetry isn’t perfect and so I used a somewhat less free piece of software called Zbrush to tidy things up further, as well as to re-position the fingers.

Design Blender Scan cleaned up right Design Blender Scan lower res

Quickly back to Blender to create a printable model,to scale things correctly and to mirror Hollies full hand. Then I printed out the first models on my Lulzbot printer. This gave me a direct comparison to the plaster cast hand to check.

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I will describe how I combined the two models to  create the fitting hand in Part 2