Theory of Constraints Handbook - James Cox Iii [692]
Analyze: It is important not to jump to improve before verifying why the problem exists. The main areas to look for causes of defects are data analysis, process analysis, and ultimately root cause analysis.
Improve: This step takes all the data from the D, M, and A steps and develops, selects, and implements solutions that will reduce the variation in a process.
Control: Sustain the new process through a robust monitoring plan.
The main purpose of the DMAIC process is for process improvement. When a process is at its “optimum” and still doesn’t meet expectations, a redesign or a new design is needed. This is called Design For Six Sigma (DFSS). DMADV (Define-Measure-Analyze-Design-Verify) is a common acronym used today for DFSS.
Motorola was one of the first companies to realize that a metrics and methodology approach was still not enough to drive “breakthrough” improvement. They continued the Six Sigma evolution into what is called the Six Sigma Management System. A Six Sigma Management System is a structured process to ensure that all improvement efforts are aligned to business strategy. Six Sigma has become a top down approach to execute strategy through the alignment of all improvement activities to assure fast, sustainable growth.
Theory of Constraints (TOC)
The basic concept of TOC is often introduced through the chain analogy. A chain is only as strong as its weakest link. Improvement that does not improve the performance of the weakest link most likely does not improve the system and can be considered waste. Many claim TOC is just common sense, but it is surely not common practice.
Introduced by Eli Goldratt in the mid 1980s, a wide awareness and understanding of parts of the TOC methodology was first accomplished through people reading the book, The Goal (Goldratt and Cox 1984). Although many of the TOC basic concepts were discussed in The Goal, the complete body of knowledge was not.
Some people think of TOC as simply finding and speeding up Herbie (the fictional Boy Scout in The Goal), the bottleneck. Then they find the next Herbie and the next Herbie, etc. TOC is not about chasing Herbies. More accurately, TOC is about how to improve and manage how the system constraint (Herbie) performs in the context of the total system. This is quite different. It is about managing the total system, which is comprised of interdependencies, variability, and constraints, to ensure maximum bottom-line results for the organization. TOC is about focusing first on the system’s leverage points and then on how all parts of the system impact the operation of the leverage points. This is the way to achieve total system improvement, not just localized improvements.
TOC applies the logical Thinking Processes (TP) used in the hard sciences—cause-and-effect—to understand and improve systems of all types, but particularly organizations. The process a doctor would follow if you went to him with an illness, first Diagnosis, then Design of a treatment plan, and then Execution of the treatment plan, is the same process followed by TOC with the use of three questions, What to Change, What to Change to, and How to Cause the Change.
One of the core beliefs of the hard sciences is that for many effects there are very few causes. Using the construct of “cause and effect” becomes increasingly important as we perform scientific analysis. All too often, we see organizations treating many “symptoms” instead of addressing the root causes. TOC looks for the core conflict that holds the root causes in place.
Think of an organization as a “money-making box” (see Fig. 36-3). It is first primed with investments in equipment and Inventory (I). Money is continually poured in as Operating Expense (OE) to pay for people and other ongoing expenses. The people process the Inventory and sell their products to make a larger amount of money called Throughput (T) (money generated by the system through sales).