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Integrating Lean Six Sigma and TOC Part 1

Integrating Lean Six Sigma and TOC Part 1

By Bob Sproull

The Integrated Improvement

At the end of my last post I set the stage for a discussion on how to implement the integration of the Theory of Constraints, Lean and Six Sigma in a manufacturing setting. Actually, this subject will take several posts to complete.

First, I will answer the question I asked in my last post about the speed and thickness of the extruded plastic product. As a reminder, here is the question I asked you:

Based upon the data collected, the equation and the graphic, what would be the best setting to achieve a thickness of 7.0 mm? The speed is only accurate to the nearest whole number.

  1. 500 (42.86 chose this answer)
  2. 525 (19.05% chose this answer)
  3. 509 (33.33% chose this answer)
  4. 515 (4.76% chose this answer)

There are actually several ways you can answer this question. The quickest way would be to observe the Scatter Plot, locate 7.0 mm on the y-axis, draw a horizontal line to the line of best fit and then draw a perpendicular line to the x-axis and read the approximate speed to achieve a thickness of 7.0 mm. This action would give you a plot that looks like the following:

Speed Line Fit Plot Solved

So based on this method, you might say that your speed should be somewhere around 500. The best way to determine the right speed would be to use the formula from Excel and calculate the speed. The formula is y = 0.074x + 3.2333, so you set y equal to 7.0 and solve for x. When you do so, you find that the optimal speed setting is a speed of 509 which is the correct answer to the question. Does this mean that every measurement will yield a thickness of 7.0 mm? The answer is no, because your R2 value is 0.908 which effectively means that roughly 90 % of the time you will be at 7.0 mm. Okay, on to our discussion on TLS.


TLS is the acronym for our integrated Theory of Constraints, Lean and Six Sigma improvement methodology. I have used this methodology for quite a few years with outstanding success in a variety of industries, but especially in manufacturing companies. The principal reason why TLS works so well is because this methodology provides the user with the improvement focus that is missing from the other popular improvement methodologies such as Lean, Six Sigma or combined Lean/Six Sigma. Before I explain my TLS concept, I want to emphasize that there is nothing wrong with the other methodologies, but without defining the focal point for improvement, results are often much less than they could be and frequently come at a much slower pace than with TLS.

The Basics of TLS

As the name suggests, TLS combines the best attributes of Lean and Six Sigma with the focusing power of TOC. And once we know where to focus our improvement effort, we apply the waste reduction power of Lean and the variation reduction and control of Six Sigma directly on this improvement focal point. So why is this focusing power so important? In order to answer this question, let’s explore each of the TLS components as though they are being used in isolation from the other two.


In the graphic below, we see the Lean improvement cycle which starts by defining value. As defined in the Lean vernacular, value means any activity that satisfies the following three requirements:

  1. The activity must move the product through the process and change it somehow
  2. The customer must see it as an activity they will pay for
  3. The activity must be done right the first time

If the activity doesn’t satisfy all three of these conditions, then Lean teaches us that it should be removed and replaced with a value-adding activity.

Lean Improvement Cycle

In the next step of the Lean improvement cycle we are told to identify the value stream. What exactly is a value stream? In the context of manufacturing, a value stream is a sequence of activities required to produce and sell a specific product along with the information and materials flows. The next step tells us to make value flow. In this step, Lean tells us to eliminate wait times everywhere in the process. The next step in the Lean process tells us to pull to customer demand. Pull moves the organization from producing for inventory to the desired state of producing for customers. This action results in inventory cost reductions and moves companies away from making product that the market may not want now or in the future. In the final step of the Lean improvement cycle we are told to pursue perfection. The intent of this cycle is that improvement is a journey and we should repeat the first four steps.

While I believe in and support the Lean Improvement Cycle, my one problem with it conceptually is that Lean tells us to “work on” the entire process. My belief is that there are key leverage points within a company that are much more in need of our attention and without identifying these leverage points, much of the work we accomplish is wasted effort.

Next Time

In my next post we will discuss the second component of TLS, the Six Sigma Improvement Cycle. As always, if you have any questions or comments about any of my posts , leave a message and I will respond.

Until next time.

Bob Sproull

Bob Sproull

About the author

Bob Sproull has helped businesses across the manufacturing spectrum improve their operations for more than 40 years.

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