How Do I Choose Between Lean, Six Sigma, Theory of Constraints (TOC), and other Operations-Improvement Approaches?

Question guy (cartoon)Industrial Engineering is the optimization of systems of people and technology.  This can be as narrow as optimizing performance of a single machine, or as broad as optimizing performance of an entire company.  As with any field, over time, people have continually discovered better ways of doing things.  At certain points, authors and consultants—for better or worse—have coined new buzzwords for the current state of the art.  Over the last thirty years, some of these have been: Total Quality, JIT (Just-In-Time), World-Class Manufacturing, Lean, Reengineering, Six Sigma, TPS (Toyota Production System), and Theory of Constraints (TOC).  These are all just other names for…

The state of the art in industrial engineering

I can’t think of any aspect of the above philosophies that conflicts with any other.  Each iteration is just what came before it, combined with new findings.  So you don’t need to determine which to apply.  A competent industrial engineer will know all of them, and make use of all of their tools as appropriate.


Simitar, Inc. permits republication of all or part of this article, provided that (1) it is attributed to Robert Kotcher of Simitar, Inc., and (2) a link is provided to either the Simitar Home Page (if article is wholly republished) or to this article’s page (if the article is partly republished).

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    • “At Western Digital, I brought in Bob Kotcher based on his exemplary job performance, project management skills, academic & practical knowledge, and teamwork/communications skills, all of which Bob had repeatedly demonstrated to me when I had the opportunity to work with him prior to Western Digital. Bob brought with him world-class academic credentials and a simply outstanding knowledge of Factory Physics, including Capacity Modeling, Cycle-Time Simulation, and Lean Manufacturing. Bob is a great guy to work with and would be a valued member of any operations staff wanting to improve its productivity and/or lower operating costs. He won’t let you down.”

      Guy Harper – Engineering Projects Director
      Calisolar, Inc.
    • “At MMC, Bob initiated and led numerous cross-functional process improvement teams that made significant improvements to our production. For example, in one area, he linked together several disparate operations into a cell, reducing cycle time and WIP by 97% and saving $220,000 a year in labor and damaged product.”

      John Kim – Director, Thermal Reactor Process Engineering
    • “At Headway Technologies, we were planning a major capital investment in an additional photolithography stepper tool in order to improve throughput at this bottleneck. Bob did a Monte Carlo simulation analysis of this area and found something that none of us had suspected. The capacity at this work-center was actually operator-constrained, not machine-constrained. He showed us how, by adding operators, we could meet the required capacity increase. A few additional operators in the photolithography area kept these tools at an optimum utilization and this extra Opex was a small fraction of the capital depreciation that another stepper would have cost.” 

      Guy Harper – Engineering Projects Director
      Calisolar, Inc.
    • “At each company that he works with, [Simitar founder Bob Kotcher] strives to improve day-to-day operations, and thus to improve the bottom line.  Bob is not afraid to present politically unpalatable truths, if his work suggests that a change will lead to overall improvement.”

      Dr. Jennifer Robinson – Chief Operating Officer
      Fabtime, Inc.
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