We have been diligently working to refine our finger design before printing our another prototype to test. As is shown in the blog post picture, there have been some significant changes from our prior prototypes, specifically in the way we plan to attach the flexor tendon into the finger, and the design of the lateral joint.
Before this design, we had planned to run the flexor tendon through the finger in a single run, and tie it off externally at the tip of the finger. With this revised design, we plan on running the flexor tendon in a double pass, and have it loop in the tip of the finger. This way, the flexor tendon will still perform its function as necessary, but it will not be exposed on the end. We think that this will continue to further our goal of a sleek and clean design, while not inhibiting any functionality. The double pass will be twisted together at the lateral joint of the finger, and run in a single pass to the linear actuator, where it will be attached.
We’re still working on a lateral joint design, but as shown in the picture, we’re coming closer to a final design to prototype. As we have stated before, we want our finger design to be easily replaced for the amputee. So, if in an unfortunate situation where a finger would break, it would be effortless for the amputee to replace said finger. We’re leaning toward some form of snap on/snap off design for the finger, but will update more on this in a later blog post.
Further on the lateral design, we’re working on a pull-pull, rudder-like system for lateral movement. Essentially, we will have the linear actuator that pulls the finger closed, but we will also have a servo motor with two strings attached to opposite sides of the motor, which will be attached to opposite sides of the lateral joint. When the servo pulls in one rotational direction, it will pull the finger to one side, and vice versa. We think this is the most viable design for our approach to be cost effective thus far.
A few other changes with this design that differ from our original finger design is overall structure. We have rid our design of a great deal of “negative” space, so there isn’t a great deal of open space in each finger. We think that this will provide a more structurally sound finger design.
On that note, we will be testing some of our initial finger design prototypes that we have printed already, for their durability. With the help of Steve Weinstock, the Lab Manager of the Engineering Tower building on campus, we will be using the Instron machine to do both a pull test, from fingertip to the lateral joint, as well as a three-point bending test on the side of the finger structure. We hope to have these tests done this coming week, and post the results in our next blog post.
-Krobohand Group