Design for additive manufacturing of customized cast with porous shell structures

Abstract

Additive manufacturing (AM) recently has been changing from conventional Rapid prototyping (RP) to direct fabrication of functional parts. As a direct fabrication method, a promising application of AM is to make personalized or customized parts; biomedical applications customized to human’s bodies can provide improved functionalities for an example. In this study, a customized plastic cast is developed to replace traditional plaster casts. For customization, its basic shape is defined out of three-dimensional (3d) scan data of a human arm. This cast is designed to have a number of holes for lighter weight and better ventilation, and to be printed using a Material extrusion (ME) type 3d printer that uses thermoplastic polymer filaments. Finite element (FE) analyses are then performed to evaluate the structural safety and stiffness of the printed cast with porosity. Considering that the structural safety and stiffness are degenerated due to the porous structure, design reinforcements are suggested to improve the bending stiffness of the porous cast. FE analyses are then performed with variations of design parameters of the reinforcement structures, from which we obtain the best design candidate that provides higher specific stiffness than the conventional solid structure. A porous-customized cast with lighter weight and better ventilation can thereby be developed successfully.