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Integrating Lean Six Sigma and TOC Part 7

Integrating Lean Six Sigma and TOC Part 7

By Bob Sproull

The Answer

At the end of my last post, I asked you why I recommend identifying both the current and next constraint in the first step of the Ultimate Improvement Cycle.  The reason I do so is actually quite simple and logical.  When the current constraint is “broken” a new one will automatically appear to take its place, so by identifying the most likely next constraint early on, your improvement resources can be prepared to move your improvement efforts and resources to the new constraint without much delay.


Short Review

In my last post we discussed Steps 1a, 1b, and 1c, so today let’s finish that discussion and then move onto Step 2.  Just to refresh your memory on the UIC steps, here are the two figures I presented in my last post with their alpha-numeric steps listed.

The UIC Steps 1a, 1b and 1c continued

The entire purpose of Steps 1a, 1b and 1c is to analyze the value stream for opportunities to reduce waste and variation but not to take action.  The improvement actions don’t actually take place until Steps 2a, 2b and 2c. 

Another important action we take in Step 1a is the need to review the current method that we employ to schedule production within the plant. Why is this an important thing to know? The fact is, there is a right way and a wrong way to schedule a production facility. If you schedule it the wrong way, you will see excessive amounts of inventory, extended lead times, and due date performance much less than optimal. If you schedule it the right way, your throughput, inventory and operating expenses will be optimized and you have a much better chance of delivering products on time and maximizing profitability.

Using the tools of Lean, (e.g. Waste Walks, Time Studies, Spaghetti Diagrams, Flow Diagrams, etc.) we identify all existing forms of waste (e.g. downtime, unnecessary travel time, wasted motion, inventory, equipment changeover time, etc.) but, for now, only within or in front of the constraint. Waste in non-constraint operations is certainly important, and we’re not ignoring it, but remember, we are focusing our resources on improving only the constraint right now because the constraint dictates the system’s throughput and throughput, above all else, dictates profits. Notice in Steps 1a, 1b, and 1c we are using the first three elements of the typical Six Sigma roadmap (i.e. D – M – A – I – C) to evaluate our improvement options.


The UIC Steps 2a, 2b and 2c

In Step 2a, we will formally develop our plan on how to exploit the current constraint and, as such, we will spend time developing the specifics of our “attack plan.” Our plan will include: what to attack, when to attack it, how to attack it, identifying the resource requirements, and how our actions will help us move closer to our goal of making more money now and in the future. Our plan will include: identifying sources of waste and how best to eliminate them; the priority order of which defect problems to resolve; chronic downtime problems to eliminate; how we can reduce process variation; how we can reduce processing and cycle time variation, etc. In so doing, we will use all of the Lean, Six Sigma and Theory of Constraints tools and techniques at our disposal.

In Steps 2b and 2c our objective is to execute our improvement plan which is turn will reduce non-value-added waste, variation and defects in the current constraint. We are now taking definitive actions by executing the plan we developed in Step 2a. Because we want these steps to complement each other, we will carry them out in a concurrent manner. The plan that we developed in Step 2a will guide us through these two steps and will provide us with not only an automatic throughput gain, but reductions in operating and inventory expenses. In these two steps we should see many things happening within the constraint operation and the process in general. Examples include:

  1. All forms of waste being removed
  2. Variation being reduced
  3. Defects being reduced or eliminated
  4. Processing and Cycle times being shortened
  5. Lead times being reduced
  6. Manufacturing cells being developed
  7. Standardized work methods developed
  8. Process controls being implemented
  9. Error proofing devices being added to the process
  10. Changeover times being reduced
  11. Travel times and distances being shortened
  12. Downtime being reduced
  13. On-time delivery being improved


A Question to Ponder

In the Ultimate Improvement Cycle’s Steps 1a, 1b, and 1c I am suggesting that you not take any actions yet.  Why do you suppose that I have recommended this as a course of action?


Next Time

In my next post we will finish our discussion on Steps 2a, 2b, and 2c and then move on to Steps 3a, 3b, and 3c.  As always, if you have any questions or comments, just leave a message and I will respond. 


Until next time.

Bob Sproull



[1]  James P. Womack and Daniel T. Jones, Lean Thinking, Free Press – A division of Simon & Schuster, NY, NY, 1996


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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