Coping with product variety in automobile assembly: A study of the manufacturing chain and final assembly line operations at two North American manufacturers

This dissertation explores the impact on manufacturing operations of increased product variety due to “Mass Customization” (Pine, 1993), using automobile final assembly at two major manufacturers as representative cases.; In automobile manufacturing variant vehicles are usually produced in sequence on a single assembly line fed by supply and subassembly lines. We identified Sequencing Points (SP's) on the latter, where the variant components required at a given workstation (WS) are sequenced to match the vehicle variants, SP locations being decided by trading off sequence flexibility against size of required inventories.; The impacts of variety on formal strategy and on informal line operator tactics were then studied by direct observation, informal interviewing and time recording. Element times were analyzed statistically in relation to component variety at six WS's on a truck assembly line. At this firm high cycle-time variants were accommodated within an overall lower average cycle-time by sequence rearrangement using a formal algorithm.; Quantitative studies being hampered by lack of a variety metric, we adapted the (information theoretic) entropy metric, renaming it “Variety”, and recognizing three types viz. Manifest, Parts Selection, and Assembly Methods Variety. Using variant incidence rates and sequences up to length three, their values were estimated at several typical WS's and Variety was found to diminish with length of sequence considered. The variant sequencing algorithm mentioned above was found to reduce Parts Selection Variety, while modularized component interfacing reduced Assembly Method Variety from the original Manifest Variety.; Finally, automobile industry practices are qualitatively compared with those in other industries, by reviewing manufacturer's reasons for providing variant products and then outlining the four strategies commonly used to handle product variety viz. Delayed differentiation, found to be more important in electronics than in the automotive industry because of high demand uncertainty coupled with rapid product obsolescence and greater customer sensitivity to delivery lead times; Modular design; Component commonality, and Manufacturing system flexibility, the dominant strategy in the automotive industry, where product life cycles are longer and where means of reducing the impact of variety on the manufacturing chain are therefore emphasized.