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Pulling at the Digital Thread: Exploring the Tolerance Stack Up Between Automatic Procedures and Expert Strategies in Scan To Print Processes

T. Mahan, N. Meisel, C. McComb, and J. Menold
2019, Journal of Mechanical Design

While the combination of 3D scanning and printing processes holds much promise for the field of new product development, problems with repeatability and accuracy have limited the wider spread adoption of 3D scan to print processes. Some studies have explored the errors inherent in higher fidelity scan to print (S2P) processes, yet few have explored the errors in S2P processes that leverage affordable rapid non-contact digitizers. No studies have explored the strategies experts in digital fabrication employ to mitigate geometric and dimensional errors throughout the S2P process. To address these gaps, a controlled study was conducted using data from 27 scans collected with a common off-the-shelf non-contact optical digitizer and a relatively simple workpiece. Additionally, a behavioral study was conducted with 13 experts in digital fabrication; actions were recorded and later analyzed using hidden Markov modeling. The geometric and dimensional integrity of the digital models was found to be significantly out of tolerance at various phases of the S2P process, as compared to the truth model. Larger errors were found more consistently in the beginning of the S2P process, but these errors were not sufficiently filtered out during the remainder of the process. Experts strategies were not beneficial and digital models produced by experts were found to be significantly smaller than truth models, indicating a trend to “over-clean” digital models. Our findings imply that designers leveraging off-the-shelf RE tools may encounter significant barriers when attempting to integrate digitization tools into the design process.