Developing and Assessing Commonality Metrics for Product Families: A Process-Based Cost-Modeling Approach

To be competitive in today´s global economy, firms must deliver more products that are viable in the marketplace for shorter times. The use of product families allows firms to meet these needs in a cost-competitive manner. The determination of which components to share and which should be unique is very important to the development of product families. Commonality metrics are presented with the goal of assessing (at the early stages of development) the ability of the product family to reduce costs. The methodology of process-based cost modeling is used to project product development, fabrication, and assembly costs in both the standalone and shared situations. A case study of two automotive instrument panel beams is analyzed. Linear-regression analysis shows that when compared to total cost savings, a simple piece commonality metric and a fabrication-investment-weighted metric have higher R² than a mass- or piece-cost-weighted metric. When correlated to fixed cost savings, the fabrication-investment-weighted metric has the highest R² (0.62) and is significant at the 0.025 level. Fixed cost savings are proposed as the desired quantity when assessing product family efficiency.