A critical evaluation of Shingo's 'SMED' (Single Minute Exchange of Die) methodology

Shigeo Shingo's 'SMED' methodology has been at the forefront of retrospective changeover improvement activity since the mid-1980s. The 'SMED' methodology, which emphasizes that improvement should be sought primarily by rearranging changeover elements into external time, has been widely acclaimed and has been widely assimilated into academic texts and industrial training material. To date, no known critical evaluation of the methodology has been undertaken. This paper, in which a case study is also presented, argues that in the sequential application of stages, the 'SMED' methodology (including the sequential application of improvement techniques that are assigned to those stages) need not always represent an effective improvement route. The 'SMED' methodology's dominant objective of translating tasks into external time is also considered. The paper argues that the 'SMED' methodology does not sufficiently promote some important improvement options, particularly those that seek to reduce the duration of existing changeover tasks or eliminate them altogether. Opportunities for improvements of this type particularly arise when design changes to the existing manufacturing system are contemplated. The issue of design in the context of incremental kaizen improvement is also investigated.