Solid freeform fabrication (SFF) methodologies allow arbitrarily complex shapes to be automatically built in a layered fashion directly from Computer Aided Design models. In the development of SFF techniques for tooling manufacture, the creation of parts with a high level of geometric accuracy is important. This research focuses on predicting, measuring, and minimizing tolerance loss in parts produced by thermal deposition based SFF processes. With thermal deposition, tolerance losses in SFF are caused by residual stress, taking the form of large-scale part warping or dimensional changes. The ability to predict and control tolerance loss is critical for manufacturing intricate assemblies with interconnecting parts such as injection mold tooling. Experiments and solid mechanics analyses are proposed to measure and predict tolerance loss in simple geometries and for fully complex three-dimensional parts. Results will be demonstrated by producing complex shaped, multi-material injection mold tooling. This research is central to the understanding of the fundamental issues which control part tolerance loss. It may lead to useful mathematical models for predicting part tolerance loss as a function of part geometry. The model-based test results could provide a good indication of the best means for maintaining part tolerance. The research is interdisciplinary in nature and it has a strong tie with industry.
