For this project I decided to create an articulating hand, I will continue to edit this design (mainly the palm) in order to equip it with servo motors so it can be remotely controlled.
Each finger has two hinge joints that provide a singular degree of freedom to replicate the true range of a human finger. The hinge joint’s design is two cones which protrude into impressions of themselves with small gap incorporated, this joint has to be printed in place in most cases. While the finger connects to the palm on a ball joint to provide it with two degrees of freedom. This joint can not be printed in place due to it relying on a friction fit, if printed in place the printer wouldn’t be able to recognize them as two distinct components and just print a continuous layer resulting in them fusing into one with no mobility.
Above is a proof of concept print for the ball joint. I was trying to determine the correct amount of overlap between the two concentric circles also the proper thickness/radius of fillet of the base to allow a tight hold of the ball between the two prongs. Ultimately a strong fit was achieved and was incorporated into the final design. The design hasn’t been printed yet but once it does an update to this post will be made. For now a link to the STL files on Thingverse will be provided below.
As promised an update on the print which can be seen below.
After printing multiple digits in varying sizes I found that the tightness of the hinge joints holding the linkages together needs to revised. They do not provide the resistance that is required to feel robust, this can be resolved by tightening tolerances or changing the joint type.