An Introduction to Product Family Evaluation Graphs

With increasingly aggressive competition for market share, manufacturing companies are facing the challenge of providing nearly customized products at bulk prices. To achieve this, product families — a group of related products derived from a single product platform — have been used to provide strategic variety to satisfy customer requirements and simultaneously achieve economies of scale. Many methods for product family design have been developed. However, we still lack the ability to evaluate a product family based on quantitative tradeoffs between product family commonality and product family variety. In this paper, we introduce the Product Family Evaluation Graph (PFEG), which can assist product family designers choosing the “best” product family design among a set of product family design options. This method is complete in its formulation, but lacking in tools for implementation. It is our purpose to show the usefulness of such a method and discuss its foundation. We show how the tool can be used to compare candidate product family designs and used in the robust design of a single product family. In addition, we highlight the strategic factors and measures that are the basis for evaluating any product family. We offer ten example strategic factors — customization, market life, technological innovation, family size, complexity, development time, service and maintenance, environmental impacts, manufacturing cost, and production volume — that determine the ideal tradeoff strategy between commonality and variety. We also highlight the need for more research into the validity of these factors, the specific relationships between these factors, and a tradeoff strategy. The measures of commonality are shown to be well established. However, we show that there is still a glaring need for the quantitative evaluation of product family variety. In summary, this paper is intended as a starting place, an opening set of questions, and as a framework for the general solution to the problem of a quantitative evaluation of product family design.