Under the umbrella of the Sports Innovation Challenge at Imperial College London, a team of Year 2 Bioengineering students assessed and further developed the design of the 3D-printed, ADA V1.1 hand made available by Open Bionics. The project deliverables were aimed towards their Engineering Design Project module, which offers Year 2 Bioengineering students the opportunity to tackle a real design problem by applying the principles learned in other modules (physiological, electrical, mechanical, materials) and learning to work as a team.

 

Thank you to Franz Tapia Chaca, the project team leader, who has kindly shared the details of this Engineering Design Project with the CREATE Education Project.

Team at Demo Day. From left to right: Leina, Aishwarya, Franz, Inês,Daniele, Diana, Hannah, Ilaria and Enrico

Project Aim

To build, assess and develop the open source, 3D-printed ADA V1.1 hand made available by Open Bionics.

Project Stages

  • Problem definition

We began printing the components of the ADA V1.1 hand in PLA-filament to get a feel of how everything fit together. At the time, we were faced with a challenge when printing the Palm part, as it took about 1 day to print entirely. Due to this long duration, we could not look after the print overnight, during which it would fail. This occurred 3 times, and we realised that this was due to clogging of the nozzle or knotting of the filament. However, as a team, we believed that breaking down the hand into smaller parts i.e. fingers separated from the palm, would reduce the chance of print failures and allow for an ease in replacing parts. This was the largest change we would bring about to the hand.

Moreover, we also carried out background research to understand the user needs and concluded what technicalities would be required to meet them. To achieve this, we also had the opportunity of meeting bionic arm user Nigel Ackland to discuss more about his experience in using a bionic arm.

User Requirements

  1. Continue offering 5 degrees of freedom, 1 for each finger, and the ability for the fingers to flex and extend fully.
  2. Remain 3D-printable, with a simple design to print with ease.
  3. Be compatible with a 3D-printed socket
  4. Be easy to assemble and disassemble
  5. Be lightweight and comfortable to use
  6. Be durable and tough
  7. Be battery-powered

 

  • Concept generation

After deciding that we would break down the palm into separate components, my team and I began to brainstorm about concepts that would allow for this to work. We worked on different concepts of joints, as these allow for each phalanx of the fingers to connect and move relative to each other, including the palm. Therefore, we produced different sketches and evaluated each of them based on how they would allow for fingers and palm to be reconnected after being printed separately, and continue to allow for flexion and extension of the fingers.

The concept that we chose was inspired by the flexible joints of the Flexi-Hand 2, developed by Gyrobot from Thingiverse. We are thankful that projects like these are shared under open-source licenses, allowing for sharing and adaptation of concepts.

 

  • Technical development

After choosing the concept of a flexible joint, we designed a part that would fit into the ADA V1.1 hand on 3D CAD software SolidWorks. To achieve this, we took measurements from the palm. The part was then imported onto Blender, another 3D-design software that OB used to develop their hand, that we also learned to use to modify its parts. We mainly used this software to further develop the hand in other aspects.

From the design of the joint and how it would be placed within the fingers, we realised that though the joints would be flexible, the degree of bending would be affected by certain parameters. These parameters include the thickness, length and location of the joint, relative to a pivoting point.

When trying to model the joint as a beam to carry out mechanical bending analysis, we soon learned that for a part made by an additive process such as 3D-printing, such analysis or even through finite-element modelling may not be possible. With that in mind, we are still interested in learning how we can quantify the stresses that the flexible joint experiences during flexion and extension of the fingers.

 

  • Detail Design

At this point, we were suggested by our supervisors to carry out trial and error tests. We carried forward to our next deliverable by producing technical drawings and schematics for each aspect of further development, which included the flexible joints and the cut extrusions into the fingers where they would fit.

Afterwards, my team and I prepared a presentation to the rest of our year group and project supervisors about the work that we had done so far, including the product requirements, benefits of 3D-printing, concepts generated and chosen for further development, and finally a timeline for manufacture, with the deadline as the Demonstration Day on March 22nd, 2017.

 

  • Manufacture realisation

Towards this next deliverable, my team and I acted upon our manufacturing timeline by 3D-printing more parts with the support of our Department of Bioengineering and the Imperial College Advanced Hackspace. We printed our entire prototype with a grey PLA-filament that we received as support from the CREATE Education Project, which allowed us to obtain a smooth finish for the hand at the end.

Another aspect that we worked on is the increase the grip of the fingers when these and the palm are printed in PLA, a rigid material. We accomplished this by applying Sugru, which Jude Pullen, past head of R&D and technology at Sugru, helped us obtain and suggest us on such implementation.

Finally, to assess whether our further developments met the initial user requirements from the Product Specification, we carried out several tests in our Departmental lab prior to demonstration.

Aishwarya proudly presenting the Imperial Hand

Benefits of incorporating 3D printing

The largest benefit of incorporating 3D-printing into the development of prosthetic limbs is low-cost production. When speaking with Nigel Ackland, he stated that his bionic arm costed more than 25,000 pounds entirely. However, using 3D-printing technology allows that cost to be reduced to just a few thousand. My team and I learned this as we worked on this project, and that this is also the overall aim of UK start-up Open Bionics – to develop more affordable bionic prostheses.

To conclude

Through this blog, the aspects of the final design of the Imperial Hand is outlined, based on the different requirements that were initially set in the Product Specification document. In addition, my team and I aim to share our project and what we have learned with the 3D-printing community, with hopes to inspire others, especially students, to take part in 3D-printing, prototyping projects such as this one.

Welcome, visitor. Files are available to download with this content. Please sign up to Download. Sign up or Login