Commonality Indices for Assessing Product Families

Manufacturing companies need to satisfy a wide range of customer needs while maintaining manufacturing costs as low as possible, and many are faced with the challenge of providing as much variety as possible for the marketplace with as little variety as possible between products as discussed in Chapter 1. The challenge, then, when designing a family of products is in resolving the tradeoff between

product commonality

and

distinctiveness

: if commonality is too high, products lack distinctiveness, and their individual performance is not optimized; on the other hand, if commonality is too low, manufacturing costs can increase substantially (Simpson, et al., 2001). Commonality has many advantages beyond improving economies of scale: decreased lead-time and risk during product development (Collier, 1980); decreased inventory, handling costs and processing time; reduced product line complexity, set-up and retooling time, and increased productivity (Collier, 1979; Collier, 1981). However, too much commonality within a product family can hinder innovation and creativity and even compromise product performance (Krishnan and Gupta, 2001). Commonality is best obtained by minimizing the non-value added variations across the products within a family without limiting the choices of the customers in each market segment, i.e., make each product within a family distinct in ways customers notice and identical in ways that customers cannot see.