Selecting alternatives in the conceptual design phase: application of Fuzzy-AHP and Pugh’s controlled convergence

Purpose: Conceptual design and, in particular, selection of conceptual design alternatives are proved to be crucial issues in product development. Selecting alternatives is a complex multicriteria decision making problem and represents a challenging task for engineering designers. Many different methods and techniques have been presented by literature in the last years but just a little use of them is often made by industry, due to several causes. One of them is that more efforts should be spent in presenting clear comparisons between the various approaches from an engineering design point of view. Such problem is tackled by the present paper which proposes the pairwise comparison of two of the most representative and widely used decision support methods. Method: The paper describes, implements and compares within a common framework the Fuzzy-Analytic Hierarchy Process (F-AHP) and the Pugh’s Controlled Convergence (PuCC) methods. A structured analysis of the results obtained by applying them to a common industrial case study is proposed. Four engineering criteria are adopted for their evaluation: complexity of computation, rating of alternatives, compatibility with group decisions making and approach suitability from an early design perspective. Result: The methods are evaluated with respect to a case study focused on the proposal of an innovative and low-cost solution for increasing the duration of heel tips in feminine shoes. The selection of the heel tip conceptual design alternatives presents complex design challenges because of the extremely hard geometric constraints and demanding design criteria. A decision making team is grouped by involving experts from the heels manufacturing industry, designers and manufacturers. Finally a sensitivity analysis is performed to investigate the dependence between the results and the preference weights. Discussion & Conclusion: Conceptual design is part of a heuristic process which requires an iterative approach for searching and manipulating solutions to find new hybrid technical alternatives, and for enhancing the communication within the design team. With respect to such scenario, PuCC seems, without doubts, to be more suitable than F-AHP for selection purposes. Nevertheless, especially for industrial purposes, the latter method has a more analytic form, that makes it proper for a software implementation and, consequently, more useful for engineering applications.