An Integrated Approach to Product Family Redesign Using Commonality and Variety Metrics

Redesigning a product family entails carefully balancing the tradeoffs between commonality and differentiation that are governed by the underlying platform architecture. Numerous metrics for commonality and variety exist to support product family design; however, rarely are they used in concert to redesign platforms effectively. In this paper, we introduce an integrated approach using multiple product family metrics to establish an effective platform redesign strategy. Specifically, we present a detailed procedure to integrate the Generational Variety Index (GVI), Product Line Commonality Index (PCI), and Design Structure Matrix (DSM) to prioritize components for redesign based on variety and commonality needs. The integrated approach extends to the platform architecture and establishes a redesign strategy for interfaces between components in the platform architecture. To demonstrate the approach, case studies involving two generations of wireless computer mice and two families of dishwashers are presented. Ongoing and future work are also discussed.

Application of the Generational Variety Index: A Retrospective Study of iPhone Evolution

The generational variety index (GVI) helps identify the components of product variants that are most likely to require redesign in the future. These components can then be embedded with the flexibility required for them to be easily modifiable; the remaining components can be designed into a platform. This paper describes the application of the GVI technique in studying the evolution of the Apple iPhone, which was first released in 2007 and has since undergone multiple redesigns. The analysis includes the five generations of the iPhone (original, 3G, 3GS, 4, and 4S) and focuses primarily on mechanical sub-systems. The results of the analysis and subsequent design recommendations are compared with the actual design evolution of the iPhone product line. For certain subsystems, this comparison reveals a divergence in Apple’s design decision-making from the evolution recommended by the GVI technique. Limitations include its retrospective nature and the use of only publicly available data.

Validating the Generational Variety Index (GVI) Through Product Family Optimization: A Preliminary Study

Effective product platforms must strike an optimal balance between commonality and variety. Increasing commonality can reduce costs by improving economies of scale while increasing variety can improve market performance, or in our robot family example, satisfy various robot missions. Two metrics that have been developed to help resolve this tradeoff are the Generational Variety Index (GVI) and the Product Family Penalty Function (PFPF). GVI provides a metric to measure the amount of product redesign that is required for subsequent product offerings, whereas PFPF measures the dissimilarity or lack of commonality between design (input) parameters during product family optimization. GVI is examined because it is the most widely used metric applicable during conceptual development to determine platform components. PFPF is used to validate GVI because of its ease of implement for parametric variety, as used in this case. This paper describes a product family trade study that has been performed using GVI for a robot product family and compares the results to those obtained by optimizing the same family using PFPF. This work provides a first attempt to validate the output of GVI by using a complementary set of results obtained from optimization. The results of this study indicate that while there are sometimes similarities between the results of GVI and optimization using PFPF, there is not necessarily a direct correlation between these two metrics. Moreover, the platform recommended by GVI is not necessarily the most performance-optimized platform, but it can help improve commonality. In the same regard, PFPF may miss certain opportunities for commonality. The benefits of integrating the two approaches are also discussed.

Design for Variety: A Methodology for Developing Product Platform Architectures

Developing a robust, product platform architecture brings an important competitive advantage to a company. The major benefit is reduced design effort and time-to-market for future generations of the product. This paper describes a step-by-step method that aids companies in developing such a product platform architecture. Using the concept of specification “flows” within a product development project, the design for variety (DFV) method develops two indices to measure a product’s architecture. The first index is the Generational Variety Index (GVI), a measure for the amount of redesign effort required for future designs of the product. The second index is the Coupling Index (CI), a measure of the coupling among the product components. The design team uses these two indices to develop a decoupled architecture that requires less design effort for follow-on products.