A Metric for Evaluating Design Commonality in Product Families

TLDR

Product families grow by adding variations to meet market needs, but unchecked component variation increases complexity, threatening productivity and quality, so effective variation management is essential. The study aims to reduce non‑value‑added variations across product family models while preserving customer choice. We introduce the Product Line Commonality Index, an objective measure of component commonality, and demonstrate its use through a Walkman case study benchmarking product families. The index reveals a product family’s modularity and its capacity to lower part counts by promoting multi‑functionality. Reference code: S1050-0472(00)02704-5.

Abstract

Many companies develop a market strategy built around a family of products. These companies regularly add new product variations to the family in order to meet changing market needs or to attract a broader customer base. Although the core functionality remains essentially unchanged across the products within a family, new functions, feature combinations and technologies are incorporated into each new product. If allowed to grow unchecked, these component variations, commonly referred to as “complexity”, can result in a loss of productivity or quality. The challenge lies in an effective management of product variations in the design studio and on the manufacturing floor. The key is to minimize non-value added variations across models within a product family without limiting customer choices. In this paper we discuss the factors that contribute to product complexity in general, and present an objective measure, called the Product Line Commonality Index, to capture the level of component commonality in a product family. Through our Walkman case study, we present a simple yet powerful method of benchmarking product families1. This method gauges the family’s ability to share parts effectively (modularity) and to reduce the total number of parts (multi-functionality). [S1050-0472(00)02704-5]