Lean Theory or Description
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Lean: Theory or Description

During my recent doctoral studies, I wanted to understand whether a theory underpinned Lean or whether it was simply a descriptive of the Toyota Production System. Scouring the lean literature led to me to think at first that Lean is pretty much devoid of theory. However I then stumbled on a paper by Schmenner and Swink. In it, the authors describe the theory of Swift and Even Flow which they define in the following way:

the more swift and even the flow of materials through a process, the more productive that process is

(Schmenner, R. and Swink, M. 1998, On theory in operations management, Journal of Operations Management , 17, p. 102).

The theory consists of three main concepts: The first is value-added and non-value-added work which, as we know, is central to Lean Thinking (Womack and Jones, 1996, Lean Thinking, Simon and Schuster, NY). The second is that materials can move swiftly only if there are no bottlenecks which, as we know, is central to Goldratt’s Theory of Constraints (ToC). The third is that for materials to flow more evenly, it is necessary to narrow the variability associated with either the demand on the process. Variability in demand is central to John Seddon’s Systems Thinking while variability in process steps is central to Six Sigma.

It appears then that, although the authors do not use the term itself, there is a theoretical basis for Lean. Furthermore the theory units Lean with other complementary (but also competitive) process improvement methodologies that have emerged alongside Lean over the last two decades.


S A Partners themselves operate a very structured approach via their Delivery Model to Lean or Continuous Improvement. The process applied comprises of:

  1. Assessing
  2. Delivering
    1. Leadership consulting
    2. Systems consulting
    3. Improvement training
  3. Programme Governance (measuring the outputs v targets v time)

The delivery model is made up of 3 triangles, encircled with the programme governance ring, and each element has a specific purpose.

The middle triangle represents the systems that are present in all organisations, without systems running effectively, organisations can not function, regardless of how well your people are trained. The left triangle represents the leadership in an organisation. All organisations require good leadership, whether at the operational level, or at the strategic level, and this triangle makes sure that you have good leaders in all those levels. We then have the improvement triangle. Quite simply, if you have no people in your organisation who are trained in continuous improvement, then improvement will never take place. In reality, this means having the right number of green and black belt qualified practitioners.

Finally, the Programme Governance part of the framework ensures implementation is on time, and in budget.


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