Linking Logical Thinking Process to Critical Chain

In this short excerpt from Bill Dettmer‘s Logical Thinking Process training course, Paris June 2015 session, Bill explains how to switch from a Prerequisite Tree (PRT) to system-level change implementation with Critical Chain Project Management. All it takes is to rotate the PRT 90 degrees.


Logical Thinking Process training June 2016 opening speech

Paris, June 2016, day 1 of the Logical Thinking Process training course hosted by Marris Consulting, Philip Marris welcomes the participants with a speech.

Philip’s speech is a mix of teasing and testimony as well as an analysis of the growing relevance of Theory of Constraints (ToC). Philip also explains how the Logical Thinking Process tools help focusing, the core idea of ToC. Finally he shares his thoughts about why the participants are in the room that day: it takes a peculiar mindset to go the Logical Thinking Process way, people do not attend this course by chance.

After more than 16 minutes, Bill Dettmer finally can welcome the participants too.

I was fortunate to attend on the host side to facilitate the 6-day course, also taking care about video and photos of the venue. If you want to see how the 6 days unfolded in fastforward (2 mn), >click here<

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Performance improvement: simple things can earn big results

Silly things can cost a lot in terms of productivity and output.  In this video interview, Philip Marris  asks me about lessons learnt while helping a pharmaceutical plant to improve productivity and deliver drugs to patients faster.

It is about how simple actions solve those silly small problems and bring big results at literally no cost.

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TOC, Lean and aviation MRO

In a previous post, “CCPM helps shorten aircrafts MRO”, I explained the benefits of Critical Chain Project Management (CCPM) for reducing the aircraft downtime during their mandatory and scheduled MRO.

If CCPM is great and helps a lot meeting the challenge, it will not squeeze out every potential improvement, thus time reduction, on its own.

As I explained in my post Critical Chain and Lean Engineering, a promising pair, “What CCPM per se does not is discriminate added-value tasks and non added value, the wasteful tasks listed in a project in a Lean thinking way.

Conversely, if wasteful tasks remain in the project network, chance are they will be scheduled and add their load (and duration) to the project.

That’s why in aviation MRO (as well as in other businesses), Critical Chain Project Management will not be used as a stand alone but in conjunction with other approaches, like Lean and Six Sigma.

Lean mainly will help to discriminate value-added from non value-added tasks, especially those on the Critical Chain, making them high priorities to optimize, reduce or eliminate.

We did not differently when we started with our client Embraer and while in their service center, I placed Philip Marris in front of the camcorders to present, in situ, two books related to TOC, Critical Chain and Lean in aviation MRO (aircraft Maintenance, Repair and Overhaul).

Note: Critical Chain Project Management is part of the Theory of Constraints Body of Knowledge, hence the title of this post where “TOC” is referring to CCPM.

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What keeps TOC confidential? (and me angry)

It is one of the frustrations for Theory of Constraints (TOC) enthusiasts: why is their beloved business philosophy so barely known?

No other, neither Lean nor Six Sigma had such a visible high-flying banner like “The Goal”, the (probably) first business novel*, sold over 6 million copies so far. If readers have been so many and as it is reported so thrilled by the content, how come only very few people know anything about TOC?

*The Goal is a business novel written by Eliyahu Goldratt and Jeff Cox.

In this video interview, Nicolas Hennion shares his views, answering Philip Marris’ questions.

The first question about the name “Theory of Constraints” was also discussed with Bill Dettmer, another TOC expert with a pragmatic point of view.

I totally share Nicolas’ frustration about TOC Body of Knowledge being overprotected and monetized.

In my case, I stopped my learning journey in the mid-1990 when Internet was still young and not that populated with available free material as nowadays, Amazon did not exist and buying books from foreign countries (remember I am a Frenchman) was expensive and complicated. I resumed studying TOC and the Thinking Processes developed in between in around 2010, buying carefully chosen second-hand books, still shockingly expensive.

I estimate I’ve lost 10 years in my TOC learning journey, being disappointed about the difficulties and costs to get to the educational material. I turned to Lean instead, and did well.

When the TOC old guard wonders why TOC is still confidential, they should rewind Nicolas’ interview and try to understand the way the younger generations operate; networking, sharing, hacking open source style.

Food for thoughts…

Related: Theory of Constraints is something great, except for its name


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You are probably wrong when identifying your bottleneck

Things moved on since Eli Goldratt’s revealed Theory of Constraints through his business novel and bestseller “the Goal”. Most of today’s processes are more complex than 30 years ago: supply chains are stretched over the globe, new products are launched more frequently and batches are changed more often, among others. Thus identifying the bottleneck or capacity constraint is more difficult and must also be redone more often.

In this video, Philip Marris shares some “lessons from the road”, real case lessons learned from more than 30 cases in the last 10 years. Surprisingly, if companies were rather good identifying their bottleneck, it turned out that now, in 80% of cases companies are wrong about where their capacity constraint is.

Main learnings are:

  • companies are often confusing where the constraint should be with where it really is
  • ERP data is not a reliable way to identify constraints
  • companies tend to have an outdated / obsolete analysis of the situation
  • new quality requirements often create new capacity constraints
  • (bad) cost cutting decisions create new bad constraints

As a conclusion, he points out that being wrong about where a company’s constraints are is good news since it implies that there are significant opportunities remaining to improve performance drastically and rapidly.

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What is Little’s law? What is it good for?

Little’s law is a simple equation explaining how Waiting Time, Throughput and Inventory are related.

Wait Time = Inventory (or WIP) / Throughput

Here is a video about Little’s law:

Fine, what is Little’s law good for?

Well, if a process lead time is too long, chances are that work-in-progress (WIP) is too high. For a given processing rate (Throughput), the lead time will be equal to WIP/Throughput. To reduce the lead time the process Throughput must be increased or the WIP reduced.

Throughput is usually limited by some constraint: machining speed, resources available and so on. It may not be easy to increase Throughput.

WIP on the other hand can generally be controlled by limiting the inventory or the work to be done entering the system upfront.

In this video, Philip Marris explains how to reduce WIP by controlling the flow of work entering the system. Even he does not mention Little’s law, it is indeed used to reduce Inventory.

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The origins of Logical Thinking Process

The Logical Thinking Process is the name of a book from Bill Dettmer as well as the name of a complex problem solving process inspired by Goldratt’s Thinking Processes. Over time, while teaching the original Thinking Processes, Bill realized it can also  be used for strategy deployment, not only complex problem solving. In this video interview, Bill Dettmer tells Philip Marris about the origins of the whole.

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Beware of bottleneck hunting!

In the following video interview, Philip Marris (answering Clarke Ching‘s questions) states that the five focusing steps of Theory of Constraints are wrong!

Well it needs some more listening  to understand the wisdom behind the provocative statement.

First, the five focusing steps (5FS) are basically ok. What bothers Philip is the fifth step after the first iteration.

In his view, accepting to go through the 5FS over and over is just bottleneck hunting and accepting the fact that the organization’s “strategy” is defined by the newest or the next bottleneck.

Philip is advocating to select the most suitable bottleneck, in order to keep mastering it, and surround this bottleneck with excess capacity resources. In this way, the bottleneck remains in one’s span of control, instead of moving upstreams to a supplier or to market’s demand, and keeps at the same point for a longer period of time.

If the 5FS are taken literally, this could lead to an exhausting periodic rearrangement around a new bottleneck, reshuffling the cards regarding strategy, sales, operations and so on.

Organisations need stability, especially factories. Therefore, this approach works well in operations.

Check out Marris-Consulting Youtube Channel for more


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