Discovering relationships between modularity and cost

While much has changed in product modularity research in the 18 years since the independence axiom, some basic questions remain unanswered. Perhaps the most fundamental of those questions is whether increasing modularity actually saves money. The goal of the research behind this paper was to clearly define the fundamental relationship between product modularity and product cost. Our previous work in modular product design provided a complete package of a product modularity measure and amodular design method. The “best” measure was created and verified after correcting common performance problems among the seven measures, finally subtracting the averaged relationships external to modules from the averaged relationship within modules. After comparing and finding better design elements among four representative modular design methods, the “best” method was developed that includes product decomposition, multicomponent reconfiguration and elimination, and an extended limiting factor identification. The “best” method/measure package quickly yields redesign products with higher modularity. To seek out relationships between product life-cyclemodularity and product life-cycle cost, modular product design experiments were implemented for four off-the-shelf products using the new measure/method package applied to increase both functional and retirement modularity. The modularity data recorded for each redesign included retirement modularity, manufacturing modularity and assembly modularity. Each redesign’s life-cycle cost was also obtained based on several classical costmodels. The cost data recorded for each redesign included retirement cost, manufacturing cost, and assembly cost. The best relationships came from the retirement viewpoint. However, there is not a significant relationship between any life-cycle modularity and any life-cycle cost unless there are significantly large modularity changes. Life-cycle modularitycost relationships are more likely to exist in data pools generated from that life-cycle redesign viewpoint. The beginning of modular redesign, where greater modularity improvements are seen, is more effective at reducing costs. Cost savings depend the appropriateness of the modularity matrix’s product architecture representation from a cost savings viewpoint.