1 Advances in Multiple Material Solid Freeform Fabrication Richard H. Crawford, Joseph J. Beaman, David L. Bourell, and Kristin L. Wood Laboratory for Freeform Fabrication The University of Texas at Austin Abstract Due to their layer-based nature, Solid Freeform Fabrication (SFF) techniques offer the possibility of fabricating parts in which the material properties vary in three dimensions. Such a capability promises to allow engineers components and parts that are truly optimized with respect to material properties. This presentation discusses research at The University of Texas at Austin to develop a multiple materials capability for one SFF technique, selective laser sintering. Efforts to develop a representation for heterogeneous solid parts are described, and predicted methodologies for heterogeneous part design will be discussed. The status of efforts to realize a multiple material SLS workstation will then be reviewed. 1 Introduction We believe that layer-based fabrication techniques, which have been termed Solid Freeform Fabrication (SFF), offer the possibility of exciting new manufacturing techniques for applications that can benefit from multiple material componentry. Imagine what would be possible if we could control the material composition of a part at any point in three dimensions. Over the past four years, we have challenged many designers in a variety of industries with this prospect. The answers we received have convinced us of the value of develop multiple material SFF. In particular, we have identified two types of applications. In the first, the part consists of two (or more) materials that do not mix (e.g., conductors and insulators). We have termed this type of application “discrete multiple material” SFF. In the second class of parts, the materials are mixed in a variety of continuous concentrations. These materials systems have been termed “functional gradient materials” (FGM) in the literature. FGMs will be manufactured by continuous SFF. The material gradient may be one-, two-, or three-dimensional. Research in the Laboratory for Freeform Fabrication at The University of Texas at Austin focuses on development of the Selective Laser Sintering (SLS) process. SLS uses a laser to selectively melt a powder layer to create the cross-section of a part (see Figure 1). Once the layer is completed, a new layer of powder is deposited by a counter-rotating roller and scanned such that not only is the next cross-section created, it is also fused to the previous layer. As successive layers are scanned this way, a three-dimensional part is fabricated. The SLS process is licensed to DTM Corp., Austin, TX. Multiple material SLS will require development in three areas. The first is a modified material delivery system. The current roller-based system is designed for handling a single type of powder. The second development necessary for multiple material SLS, as well as other multiple processes, is a representation of the material distribution in the part. The third area of development focuses on identification of compatible material systems that can be processed by SLS and that meet customer requirements. In this paper, we report on our progress in these three areas.