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3D Printed Prosthetics - The Raptor Hand

  • 4 April 2015
  • Author: Dan Santee
  • Number of views: 3135
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3D Printed Prosthetics - The Raptor Hand

Prosthetic hands can be incredibly expensive - the latest models costing upwards of $10,000. It's even more expensive for children, as they need to be constantly adjusted and updated with the child's growing body. Fortunately for parents, the 3D printing world is changing that for the better.

I'd been reading about 3D printed prosthetics and their very low cost, and thinking about a friend's daughter who had been born without her left hand. I asked them if I could try to print a prosthetic hand for her, which they agreed to. There are several 3D hand models available, but since I've never tried anything like this, I wanted to start simple. The e-NABLE Raptor Hand is about as simple as you can get while still looking pretty hand-like, so that's the one I used. You can take a few simple measurements of the remaining hand and enter them on their web site, and it will produce a set of .STL files (3D printer files) which can be used to print the hand.

It took several runs to get all the frames, joints, fingers and connecting parts printed, at which point I vapor-smoothed the visible parts to make them look better, but also to remove any rough surfaces or edges. My friends purchased the parts kit from the e-NABLE web site which contains things like screws, elastic, Velcro, padding, etc. (about $50), and I assembled everything.

The kit contained much more than was needed, and the next time I do something like this, I think I can get just the necessary pieces for a little less money. For example, the kit comes with screws for the joints, but the hand model I used included printed pins which would have worked, as well. In the end, the padding, Velcro, a few screws and the fingertips (for grip) were all that was required to build the model.

The first time she tried it on, she couldn't move it much at all. I realized that the kit came with both adult and child versions of the elastic, and I had used the much tighter adult version. After I changed out the elastic to the more child-appropriate strength, she could open and close the hand using just her wrist. After she began using the hand, we found a weakness where one of the control threads connects to the finger, so I reinforced it with a small piece of metal (okay, a staple). My friend also modified the way the Velcro keeps the hand part connected to her wrist - which is one of the things I really like about this model. We can modify it to fit her needs, it can grow with her, and it costs almost nothing. She's only been using it a couple of weeks so far, but she loves showing it off in school, and is always figuring out new things she can do with it!

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