Deriving Design Robustness Index: a Model-Based Method for Evaluating the Robustness of Product Concepts

Robustness against geometric deviations is a crucial success factor in product development. While early-stage Robust Design (RD) methods aim to improve robustness to reduce later costly iterations, they often fail to quantify the impact of concept-specific geometric deviations on the functional fulfillment of product concepts. This paper presents an Embodiment Function Relation and Tolerance (EFRT)-based method for quantitatively evaluating the robustness of product concepts against geometric deviations. Using the EFRT-based method, the Design Robustness Index is derived through a six-step process as a quantitative measure to evaluate and compare the robustness of different concepts. A case study of a coining machine demonstrates the practical application of the method. The indices generated by the method are initially validated through a comparison with empirical testing consisting of rapid prototyping and simulation with surrogate models. The results show a strong alignment between theoretical evaluation and empirical testing for the 16 different concepts. The proposed method can support design engineers in quantitatively evaluating how product concepts respond to geometric deviations in the early development stages, giving them a stronger foundation to make informed design decisions. It has the potential to reduce the risk of costly iterations caused by geometric deviations and ensure more reliable products.