3D Printed Prosthetic Finger

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The aim of this project is to develop our own 3D printed prosthetic hand, to gather information and experience about the project and the field of prosthetics.

First Iteration Prototype: Getting the Idea Started

Started by developing a single finger. In this iteration the components of the finger were made of foam wrapped in cylinders, and the structure of the finger was given 2 springs in between the different parts. The parts were held together with tape and elastic bands. Attached to each part a small tube made of paper: we connected a wire going through these tubes to a mini servo, at the base of the finger,used to power its movement.

This prototype didn't function as we wanted, but gave us useful feedback to proceed: the spring was too strong for the mini servo to pull the finger down completely. Moreover, it allowed for weird movements along all axis, whereas we wanted a straight, regular movement of the finger opening and closing.

Second Stage: Sketching for 3D printed mechanics parts

We then started thinking about creating the real parts of the finger through 3D printing. Below we show the first "final" idea of how the fingers were going to function.

Second Iteration Prototype: The Mechanics
The first 3D printed finger was a success in terms of mechanical functioning: the snap fit mechanisms proved to work well in terms of friction and usability, and we were glad to be able to avoid screws etc. in the process. However, a mistake in 3D modeling caused the finger to be a lot bigger than a real-size finger, so we had to go back to Solidworks.

Third Iteration Prototype: Reducing the Size

The attempt to reduce the size of the prototype was partly a success. We had the finger in a realistic size (although not exactly looking realistic).

However, the tubes we added onto the components to get the wires through were not function properly. Because we did not include inside the finger, but on top/bottom, the force required by the servo to move the finger was still too high to bear.

The mechanics were working, but not functional enough for the electronics to do their part (at least, with our student-budget servos).

Fourth Stage: Rethinking the Model
We decided to take a step back, go through every single part of the finger and make it better. Think of every possible problem and try our best to solve it beforehand.

The results after these night sessions of work were extremely positive.

Fourth Iteration Prototype:

This new prototype was thought through a lot more than the previous ones.

We implemented a slicker design to hide the rotating mechanisms, as well as creating blocks for the finger to have a range of movement closer to the real one. We made the fingers so that the wires could go through them on the inside, and created a block of the tip of the finger to secure the wires to be fixed at that point.

After a little bit of sanding on the internal mechanisms, the mechanics of the finger were working wonderfully.

And we were glad to see that the electronics also functioned very well with this new prototype.

The Future: a full hand, and innovative technology.

Of course, this is a small percentage of what a prosthetic hand really is. Not only do we need to finish the robotics part of the full hand, but we actually need to dive into the technology of sensing muscle movement and translating that into movement of the prosthetics.

The vision for the future is to finish the robotics of the hand, and dive into a wide range of technologies for picking up muscle movement and decoding it properly. During the past we months we already had the chance to try out a few things, such as the Myo ArmBand for gesture control.

For now, this is a small step in the right direction.