This paper attempts to provide an understanding of some of the issues involved in creating a physical scale model of an assembly using (primarily) rapid prototyping (RP) technology and to develop a semi-formal methodology of interest to scale model builders that guides the process. The methodology starts with either the full scale assembly or the CAD files and all assembly liaison diagrams which are then transformed into the scaled versions assuming use of a nominal scale factor. In the process a “scaling structure table” is created that documents the transformation and it only needs to focus on scaling issues, vs. angular dimensions and other geometric constraints which are invariant with respect to scale. The case study assembly used in this effort is a previously designed hand-powered breadfruit shredder of modest complexity. For various reasons, the process was not as simple as applying the nominal scale factor to all relevant dimensions. The transformation process included strategically adding special scaling features such as ribs, wall thickening, and fillets to ensure adequate strength, and merging of a subassembly into a single part. The final step was to create the physical scale model using mostly plastic-based RP.

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