Hi,

Enough needs-finding. Enough research. Enough preparation. This week, our team jumped head-first into prototyping.

Our strategy involved focusing on the design for each joint. Our work followed a general methodology: low-fidelity prototype for proof-of-concept, CAD on Fusion360, and 3D print. I feel like this description forfeits much nuisance, so for the sake of illustration, here was what prototyping the knee joint involved.

We started low-fidelity prototyping with straws, string, pipe cleaners, and clothes pins, and during this process, we realized we needed to decide between two main ideas. One idea was incorporating protrusion at the knee that would prevent the joint from being extended and could be swappable to demonstrate various ranges of motion. The other was a string connected both sides of the joint that would have a similar function as a tendon but whose lengths can be controlled by a spool to allow for adjustable flexibility. After creating a chart of the pros and cons, presenting our ideas to our design mentors, and later speaking with our client, we determined that the string idea would be more streamlined. Afterward, I designed the joint on Fusion360 and printed the part. Of course, that was not the end of it. I ran into several issues, including piecing the upper and lower leg components being impossible, the range of motion being too great, and the string being hard to thread through the “leg”. Nearly a dozen versions later, our team was finally somewhat satisfied with the knee joint.

Besides the knee, we prototyped the shoulder, hip, and elbow. We presented our progress at the end of the week to our client, Prince, who liked the mechanisms except for the one for the elbow, which we had planned to design using swappable torsion springs. His concern was the springs becoming lost, so he preferred if we could develop a mechanism with fewer parts, a goal on which we are continuing to work.

Prototyping is also the stage where our team began specializing in roles and responsibilities. Running parallel to my CADing of the joints, my other team members began working on casting and molding. After researching, observing, and attempting the process, our team managed to create a cast for our baby doll’s lower leg so far. However, silicon is quite expensive!

 

That concludes my recount of this week.

Bye,

Andrew Sun