This time we set up to deal with a huge task. Create a robot hand for our friend.
The requirements were harder to meet this time and the final product was good enough to have our friend happy and most important, could use his new robot hand for performing tasks that previously he could not.
The arm itself can be improved, it is not intended to be a medical device or close to one, it is a tool for sporadic use that can bring some joy to our friend and its a work in progress.
Everything started from the measurements of his right arm to be able to size the device correctly and create a socket for his left arm that could fit. One of the requirements was to avoid having a complicated harness or structure that would not allow him to wear or fit himself the device alone. Therefore a simple socket with the form of his right arm was printed and tested for fit. It was lined up with thick felt and cotton textile to avoid direct contact of his arm to the printed plastic just to be on the safer side.
First models were intended to be held by Velcro and the adapter for the functional end of the device was supposed to be a snap fit. That proved to be quiet difficult to achieve, have it to lock itself easy enough that can be installed with one hand and tight enough so that wont disconnect itself by some small effort.
The device continued to evolve, so the first idea was to deliver a simple end device that could perform some task, like a cup holder. This was good idea and it worked. Unfortunately this device proved to be too long and not so useful at the end. So the next iteration came up.
More tests and more ideas came up, so new designs were tested. Here another approach for the socket and elbow, this time taking advantage of a previous design made available in Thingiverse by C3D_Miguel called Ugunugu Elbow that allows for several degrees of rotation while having a simple lock mechanism (Thing:3001427).
This design was adapted to the socket and slightly resized. Also finally an end device with a different approach, this time, a prehensor type end device was designed. First iterations were tested.
