Volumetric multi-texturing for functionally gradient material representation

Solid Freeform Fabrication (SFF) methods have demonstrated the potential to manufacture parts from Functionally Gradient Materials (FGM). One of the keys to success is an accurate and systematic represention of varying material distributions in the geometry. This paper introduces a method called Volumetric Multi-Texturing (VMT) to represent a three dimensional density gradient. The scheme originates from volumetric rendering by texturing, which is used in computer graphics to create fuzzy objects such as clouds and smoke. By analogy, FGM design is envisaged as creating material clouds in a confined geometric space in a structured and controllable manner. Another motivation for pursuing this approach is that, based on our research into expected applications, material gradients will be emphasized near the surface of a part. Our method exploits procedural and implicit schemes to design and acquire density information. The implicit procedural approach, as opposed to an input database, allows a user to interactively create and modify the design patterns without explicitly changing the individual values in the database. Further, it promises convenience in process planning, and efficiency in data storage and computation time. The material gradient modeler is applied to a boundary representation (B-rep) model of the part. Therefore, this scheme can be easily integrated most commercial solid modelers. The theoretical approach, design procedure, and tool path generation for fabricating example parts are presented in the paper.