Critical to the selection requirements for additive manufacturing (AM) is the need for appropriate materials. Materials requirements for AM include the ability to produce the feedstock in a form amenable to the specific AM process, suitable processing of the material by AM, capability to be acceptably post-processed to enhance geometry and properties, and manifestation of necessary performance characteristics in service. As AM has matured, specific classes of material have become associated with specific AM processes and applications. This paper gathers this information for each of the seven categories of ISO/ASTM AM categories. Polymers, metals, ceramics and composites are considered. Microstructural features affecting AM part properties are listed. Service properties of AM parts are described, including physical, mechanical, optical and electrical properties. An additive manufacturability index is proposed.

Commercial laser sintering (LS) machines have been used for years in a variety of rapid prototyping applications. Emphasis in the LS research community has moved towards rapid manufacturing: the creation of engineered structural components. However, the mechanical properties of LS parts are often inconsistent compared to their molded counterparts. This is due to a variety of factors including feedstock uniformity, microstructure evolution due to LS processing, and the overall ability of commercial LS machines to reliably form structural parts without thermal degradation of the feedstock powder. This paper will review the current state of the art of commercial LS machines, and discuss the resulting implications for rapid manufacturing. Particular focus will be paid to the role of part bed temperature variations due to non-uniform heating, unsteady cooling due to natural convection currents in the part chamber, and how these and other phenomena may impact the design of laser control systems.

Sustainability is a consideration of resource utilization without depletion or adverse environmental impact. In manufacturing, important sustainability issues include energy consumption, waste generation, water usage and the environmental impact of the manufactured part in service. This paper deals with three aspects of sustainability as it applies to additive manufacturing. First is a review of the research needs for energy and sustainability as applied to additive manufacturing based on the 2009 Roadmap for Additive Manufacturing Workshop. The second part is an energy assessment for selective laser sintering (SLS) of polymers. Using polyamide powder in a 3D Systems Vanguard HiQ Sinterstation, energy loss during a build was measured due to the chamber heaters, the roller mechanism, the piston elevators and the laser. This accounted for 95% of the total energy consumption. An overall energy assessment was accomplished using eco-indicators. The last topic is electrochemical deposition of porous SLS non-polymeric preforms. The goal is to reduce energy consumption in SLS of non-polymeric materials. The approach was to mix a transient binder with the material, to create an SLS green part, to convert the binder, and then to remove the open, connected porosity and to densify the part by chemical deposition at room temperature within the pore network. The model system was silicon carbide powder mixed with a phenolic transient binder coupled with electrolytic deposition of nickel. Deposition was facilitated by inserting a conductive graphite cathode in the part center to draw the positive nickel ions through the interconnected porous network and to deposit them on the pore walls. The Roadmap for Additive Manufacturing Workshop was sponsored by the National Science Foundation under Grant CMMI-0906212 and by the Office of Naval Research under Grant N00014-09-1-0558. The electrolytic deposition research was sponsored by the National Science Foundation, Grant CMMI-0926316.