Parametric 3D Modeling of a Customized Prosthetic Hand Finger for Additive Manufacturing

In this paper, a new method to design a custom finger for a hand prosthesis is proposed. The prosthetic finger is composed of a linkage mechanism and three shells that resemble the shape of human phalanges (acquired with a 3D scanner). The proposed method is based on a parametric Computer-Aided Design (CAD) that allows the 3D modeling of the finger according to the different anthropometric parameters derived from of the user. The 3D modeling process takes into account also manufacturing constraints related to the production technology. Additive manufacturing has been selected to reduce costs and allow the production of components with a complex geometry resembling the human finger. The method has been tested on an adult volunteer by developing a replica of the index. The compliance of the mechanism dimensions with the anthropometric measures has been verified and a FEM-based analysis has been performed to estimate mechanism robustness and deformations. A deviation analysis has been also carried out to evaluate the similarity in shape between the finger scan and 3D-modeled shells. Finally, the finger prototype has been manufactured using a Selective Laser Sintering printer and the trajectory of the fingertip has been compared with the human one.