The question is asked under what conditions Lean Manufacturing or Six Sigma should be applied. Examining the strategy of the two methodologies might help with answering this question. Lean strategies focus on elimination of waste by using tools such as KANBAN, 5S, Kaizen and Total Productive Maintenance. The roots of lean are footed in the Toyota Production System. Meanwhile Six Sigma strategies are targeted for the elimination of variation within processes. Six Sigma focuses on a structured system of Master Black Belts, Black Belts, Green Belts armed with tools such as SPC, Capability Analysis, Process Mapping and Quality Function Deployment. In their article “Lean Sigma”, Antony, Escamilla and Caine (2003) suggest companies today are seeking to identify what strategy fits the culture of their organizations the best. In some cases the authors suggested a blended or mixed approach would be beneficial.
There are cultural differences between the two methodologies that suggest one might choose Lean vs. Six Sigma or vice versa. In “Where Lean Meets Six Sigma”, Drickhamer (2002) indicates lean programs are firmly rooted in a teamwork centered culture while Six Sigma has an “elitist” factor utilizing highly trained black belts and specialist working on long projects in distant offices from the factory floor. The author also suggests benefits from a blended or mixed approach.
The proper sequence to apply a blended approach might be with Lean first and then bringing in Six Sigma tools as needed. This approach is suggested in a Works Management article (Anonymous, 2003). The statement is made that “the key lean principles generally offer the broader base from which to assess current performance…and will be the best starting place”. Six Sigma can be a final pillar for a Lean program.
Finally, there is no clear answer to the question about when to apply lean and when to apply Six Sigma. Recent literature is recommending a blended or mixed approach to gain greater benefits by using the best elements of each approach.
Anonymous (2003), Does Six Mix?, Works Management, 56(6), p14-16
Antony, J., Escamilla, J.L., and Caine, P. (2002), Lean Sigma, Manufacturing Engineer, 82(2), p40.
Drickhamer D.,(2002) Where Lean Meets Six Sigma, Industry Week, 51(4), p55.