Mechanical Engineering Department
BS in Mechanical Engineering
Quality of Life Plus has been improving the lives of many wounded servicemen and first responders around the country. Its mission is to foster and generate innovations to aid and improve the quality of life for those injured in the line of duty. This project is the fifth iteration of designing a prosthetic hand for an active duty Navy SEAL. The first iterations have been myoelectric systems where sensors are attached to the user’s muscles to actuate the prosthetic. However, the most recent has been a purely mechanical system, and was shoulder actuated. The design was more robust, it was lightweight compared to the first iterations, and it is also waterproof. This project is made out of Titanium 6AL-4V, which offers a great strength-to-weight ratio, is robust, reliable and easy to assemble.
This project took a different avenue of approach when manufacturing the prosthetic hand. The vast majority of the hand was 3D-printed using the latest technology of direct metal laser sintering. The material chosen for this device is Ti 6-4, where it was printed and donated by Lawrence Livermore National Laboratory located in Livermore, CA. Most of the hardware was made out of stainless steel and was purchased from McMaster Carr, and the Sure-Lok was obtained from a previous iteration. The prosthetic hand will include shock cord, non-flexible cable to withstand up to 200 lbs. per finger and a break cable that will interlock the fingers, palm and gantlet sub systems of the prosthetic. The device will also include a silicon sleeve with an embedded plate that will attach to the palm. The sleeve will attach via suction to the users residual and has been proven to work as he currently uses a similar device with a purely aesthetic hand.
This prosthetic was designed by analyzing the Raptor Hand created by e-Nable, an organization that helps small children by creating prosthetic hands that can be easily printed and assembled. In order to actuate our prosthetic, the user will need sufficient wrist movement and strength for proper function. Since our client has full mobility of his wrist, this will be the best method. The prosthetic uses a Sure-Lok to allow the user to maintain a grip without applying any excess force. The non-flexible cable will maintain a tension that will allow the user to grip and hold heavy items over a long period of time.
Once the Sure-Lok is not active, the flexible cord will spring the fingers back into the initial position. The thumb is not connected to any cables and is spring loaded to allow the user to manually place the thumb in three different positions.
During the initial inspection of the titanium parts received, the team noticed that the support material was still intact and needed to be removed. This will delay the assembly and testing of the titanium prototype. The support material will be removed via Electric Discharge Machining (EDM), which is a controlled process that is used to remove metal by electric spark erosion. The electric spark is used as the cutting tool to erode the work piece to the desired surface finish. Once completed, the hand will be assembled and tested and will be sent to the client’s prosthetist to implement the silicon sleeve.
Furthermore, our donor has agreed to reprint the prosthetic to allow any improvements of the design. This will be done towards the end of the summer. Several of our team members will remain in contact with the sponsor and LLNL to oversee the completion of this design.
Available for download on Wednesday, June 10, 2020