"A Preliminary Note on Comparative Analysis of Lean Production Systems - A Case of Automobile Body Buffer Management -"(in Japanese)

This paper is preliminary note on an empirical analysis that compares different interpretations and implementations of so called lean production system, by different automobile manufacturers in the world. This paper outlines an analytical framework and hypotheses by which the author tries to explain why significant inter-firm differences in manufacturing activities exist among the firms that are apparently all moving toward a similar manufacturing paradigm, generally called "lean production". The present research focused on a specific area in manufacturing management where a large quantitative and qualitative differences have been actually observed in recent years: body buffers that the auto assembly makers carry at their assembly plant, including welding, painting, and final assembly processes. This research attempts to introduce a framework by which we compare different logic or policies (i.e., a set of logically consistent routines) in manufacturing among the firms that are apparently oriented to the same paradigm, such as lean production. For example, several different patterns of activities for body buffer management have been identified among the European assembly plants, including some Japanese transplants in Europe: Random sequence assembly, Random paint sequence, Emphasizing keeping planned sequence, Emphasizing Levelization (Very low pained body buffer levels); Lot assembly sequence, Lot paint sequence, Emphasizing keeping planned sequence, De-emphasizing levelization, Keeping sequence between the upstream and downstream(Relatively low pained body buffer levels); Random assembly sequence, Small lot paint sequence, Deviation from planned sequence allowed, Emphasizing levelization, Emphasizing avoidance of assembly line stops, Emphasizing product variety(Relatively low pained body buffer levels); Random assembly sequence, Lot paint sequence, Deviation from planned sequence allowed (Relatively large pained body buffer levels); Random assembly sequence, Random paint sequence, Emphasizing keeping planned sequence, De-emphasizing levelization, Keeping sequence between the upstream and downstream(Moderate pained body buffer levels), and so on.