Comparing functional analysis methods for product dissection tasks

Booth, Joran W.; Reid, Tahira; Eckert, Claudia and Ramani, Karthik (2015). Comparing functional analysis methods for product dissection tasks. Journal of Mechanical Design, 137(8), article no. 081101.



The purpose of this study is to begin to explore which function identification methods work best for specific design tasks. We use a 3-level within-subject study (n=78) to compare three strategies for identifying functions: energy-flow, top-down, and enumeration. These are tested in a product dissection task with student engineers who have minimal prior experience. Participants were asked to dissect a hair dryer, power drill, and toy dart gun and generate function trees to describe how these work. The function trees were evaluated with several metrics including the total number of functions generated, the number of syntactical errors, and the number of unique (relevant and non-redundant) functions. We found no statistical, practical, or qualitative difference between the trees produced for each method. We also found some generalized findings through surveys that the most difficult aspects of using functional decomposition include identifying functions, choosing function verbs, and drawing the diagram. Together, this may also mean that for novice engineers, simpler methods, such as enumeration, should be taught prior to more complicated methods so students can grasp core concepts such as identifying functions and structuring function diagrams.

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