Impact of Light-Weight Design on Manufacturing Cost - A Review of BMW i3 and Toyota Corolla Body Components

OEMs are investigating opportunities to reduce vehicle mass, driven by a need to meet upcoming CAFE targets, increase the range and reduce battery size of EVs. A number of lightweight materials including high strength steels, aluminum alloys, plastics and composites are now in production. To facilitate development of corporate R&D and commercialization plans for new materials, it is beneficial to understand the current manufacturing costs for production components, and their impact on piece price at different volumes. This paper investigates design and cost impact of light-weighting with respect to front door and floor assembly of Toyota Corolla and BMW i3. Toyota Corolla has a traditional steel body and is sold in high volumes while BMW i3 has relatively low annual sales and is primarily made of composite, aluminum and plastic parts. This study identifies good practices by BMW for both light-weighting and low / medium volume production where reduction in tooling costs become significant. Differences in design, manufacturing processes, production costs as well as cost of light-weighting ($/lb saved) between the Corolla and i3 subassemblies are discussed. The analysis was performed under ARPA-E funding and is based on review of component teardown data, identification of manufacturing and assembly processes. Ricardo developed a database and detailed analysis model to calculate cost to manufacture at various production volumes.