Dr. Salman Taghizadegan took nine years to complete “Essentials of Lean Six Sigma,” published in 2006 by Elsevier Inc. “When I started, there were no books on Lean Six Sigma,” recalls this Lean Six Sigma Master Black Belt and chemical engineer. He’s produced a textbook for academics and manufacturers that covers statistical theory and concepts, as well as the how-tos of engineering and implementing Six Sigma.
Lean thinking goes into Six Sigma and, wherever it finds the process needs acceleration, it does so, explains Taghizadegan, who is also process-quality improvement manager for Hunter Industries Inc. (www.hunterindustries.com), in San Marcos, Calif. An example he uses is a manufacturing process such as an extruder/molder, with which an engineer wants to experiment and whose variables are temperature, pressure and machine speed. “You vary input randomly,” he states. But because temperature takes so many cycles to stabilize, the experimenter could vary temperatures first before then varying pressures and speeds, or vice-versa. “That takes out some randomness,” Taghizadegan explains, emphasizing “the variables that take longest to stabilize should be done consecutively.”
Use a map
Vital to his approach is a road map to Lean Six Sigma continuous-improvement engineering strategies. Five phases comprise that process: Phase 0, process definition/projection selection; Phase I, process measurement; Phase II, process analytics; Phase III, process improvement; and Phase IV, process control and maintenance.
Each phase has unique tools or techniques. For example, in Phase 0, it’s the affinity diagram, used to generate ideas, and the quality function deployment, which Taghizadegan also calls the House of Quality. It develops a matrix that focuses on best opportunities and priority of actions. Phase 0 also has an overall business-process map, which is called SIPOC for supplier, inputs, processes, outputs and customer objectives.
Taghizadegan stresses, “Start with a clear project definition that will identify direction, goals and values of the project.” What he considers most important is the customer’s voice, a factor he calls critical quality. “It identifies issues or concerns important to customers. Customers set the boundaries of the process,” he says. Establishing upper and lower specification limits, or the quality of specification, is the other important aspect of project definition, he adds.
Phase 0 and all other phases and their respective tools focus not just on thinking, but on outcomes. “Phase 0 makes you understand the project goals and direction. Phase I collects data from the current process and measures it,” Taghizadegan explains. “In Phase II, you analyze it and find where you were, where you are and where you’re heading.”
In Phase III, “you take Phase II data and optimize it with any tool available in the world, whether scientific, engineering or otherwise. You can take any statistical and non-statistical tools and optimize your process,” Taghizadegan says. Those include physical and research tools, even preventive maintenance and total quality management. Then, Phase IV emphasizes maintaining the gains.
For companies seeking to move from One or Two Sigma to Six Sigma, Taghizadegan advises patience. “Three Sigma produces about 67,000 defects per million. It’s difficult to eliminate all those defects, in one step,” he observes. “If you have about 10 variables, or even five, you will find the top two to three variables have the highest impact. You try to eliminate their influence on defects, or optimize their positive influence first, before going to the least-impact variables.”
Noting that most companies operate at Two or Three Sigma, Taghizadegan believes that it takes at least five years to get to Six Sigma once the process begins. Facilitators must include an executive sponsor, champion and Master Black Belt. But, he adds, “Six Sigma methodologies require full integration of departments in the entire company.”
C. Kenna Amos, firstname.lastname@example.org, is an Automation World Contributing Editor.