SFF processes have demonstrated the ability to produce parts with locally controlled composition. In the limit, processes such as 3D Printing can create parts with composition control on the length scale of 100 microns. To exploit this potential, new methods to model, exchange, and process parts with local composition need to be developed. An approach to modeling a part’s geometry, topology, and composition will be presented. This approach is based on subdividing the solid model into sub-regions and associating analytic composition blending functions with each region. These blending functions define the composition throughout the model as mixtures of the primary materials available to the SFF machine. Various design tools will also be presented, for example, specification of composition as a function of the distance from the surface of a part. Finally, the role of design rules specifying maximum concentrations and concentration gradients will be discussed. Introduction This research into modeling and designing components with locally controlled composition is part of a larger project funded by the National Science Foundation titled "The Distributed Design and Fabrication of Metal Parts and Tools by 3D Printing." The overall goal of this project is to identify the barriers preventing designers from accessing the unique and useful capabilities of SFF processes such as 3DP and provide solutions. One of the identified barriers is the inability for designers and manufacturers to work with models of graded compositions. To address this issue, we are researching methods to represent, design, exchange, and process these models with the intention of promoting the use and research of Local Composition Control through 3DP by a wider audience. Background: Local Composition Control (LCC) through 3D-Printing (3DP) Solid Freeform Fabrication (SFF) refers to a class of manufacturing processes that build objects in an additive fashion directly from a computer model. Although most build from a single material and in layers, a few SFF processes possess the capability to fabricate objects from multiple materials in a near point-wise fashion. The combination of these two features allows for the possibility of Local Composition Control (LCC) through which graded compositions can be manufactured from the base materials available to the SFF machine ,. One such SFF process capable of LCC is 3D Printing . Conventional 3DP manufactures a part by selectively binding powder together according to a computer model. The build cycle begins by spreading a layer of powder over the print bed. A print head then traverses the bed, selectively depositing binder over the regions corresponding to the interior of a slice of the Spread powder Apply binder Lower print bed Finished part @@@@@@ @@@@@@ @@@@@@ @@@@@@
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