CHAPTER 3
A Framework for Applying Lean
Many structured approaches exist for improving processes and solving problems. The Plan, Do, Check, and Act (PDCA) approach has existed for a long time and provides one well-known framework as does Define, Measure, Analyze, Improve, and Control (DMAIC) which is used in the Six Sigma process improvement methodology:
1.Map the process: This is called the value stream map (VSM).
2.Analyze the current state VSM looking for unnecessary lead time and possible ways to reduce that wasted lead time using Lean tools.
3.Draw a new process map that reflects ideas for improving the process and reducing its lead time: This is called the future state VSM.
4.Determine from the revised process map how much lead time can be reduced.
5.Create a priority list that reflects the order in which the planned improvements will be made.
6.Implement the improvements and check how much the process lead time (and other metrics) has improved and whether the improvement met expectations.
7.Institute the improved process by standardizing on it and expecting adherence to the new process definition.
8.Repeat the steps above indefinitely.
Parallels can be drawn, however, between the steps of Lean improvement and both PDCA and DMAIC. Companies that use Lean most often also use Six Sigma, and so describing the Lean improvement process in the context of Six Sigma is most appropriate. This is done in Table 3.1, which demonstrates that DMAIC accurately describes the activities that are undertaken when the Lean methodology is used to improve processes.
Table 3.1 Analogy between Six Sigma and Lean activities
| Improvement phase | Six Sigma activities | Lean activities |
| Define | •Define product or service attributes most important to customers upon which to focus improvement. These are critical to quality (CTQs) •Construct charter which establishes the importance of improving the quality attributes that are selected |
•Establish metrics upon which improvement efforts are focused, one of which is usually lead time •Construct charter which establishes the importance of the project either to customers or internal customers if project is for internal efficiencies |
| Measure | •Measure process capability •Assess the measurement system competency •Collect data about the selected CTQs and process inputs most likely to be affecting them |
•Collect data to define the process steps •Draw VSM •Measure lead time and value-added ratio (VAR) |
| Analyze | •Analyze data to determine process inputs that most often cause defects or variation of the CTQs |
•Find nonvalue-added time (waste or muda) from the customers’ perspectives •Determine root causes of waste |
| Improve | •Design process changes to mitigate the effects of the most critical process variables identified in the Analyze phase •Conduct trials and do hypothesis tests to verify that the proposed process changes improve quality •If successful, institute the changes in a revised process description |
•Design process changes that will remove nonvalue-added time while not sacrificing quality •Implement changes, possibly using Kaizen events •Perform hypothesis test to confirm that lead time is reduced by the forecasted amount •Change process description documents to institute changes |
| Control | •Monitor quality using control charts to ensure improvements are sustained |
•Periodically audit process to ensure that it is being carried out according to the process descriptions |
Many types of maps can be used to map processes. The type of map used in Lean is called a VSM, and we will describe how to create one in the next chapter. We will also describe in that chapter how to analyze the process, via its map, to measure lead time and other process metrics. Part II of this book surveys some of the tools that are used within the Lean framework and how they reduce lead time and improve other business metrics. In Chapter 5, we also discuss the necessity of standardizing processes if process performance is to be improved. The last step in the list indicates that Lean is a continuous improvement process: Addressing a process just once with Lean does not reveal all the possible improvements. Processes can be analyzed and improved many times with Lean. The initial application of Lean addresses gross inefficiencies, and only after they are resolved can the minor inefficiencies be noticed and addressed. Even if lead time is reduced 70 to 90 percent in the initial application of Lean, improvements of the same order of magnitude can be made in the second and third applications.
The Lean framework outlined previously is similar to PDCA and DMAIC in that, first, the effort begins by measuring the process. Lean, like Six Sigma, is a data-driven methodology: Improvements are not based on hunches about how the process is executed, and it is not assumed that prospective changes in the process will actually result in improvement. Rather, time is spent to understand the process, map it, and analyze it, resulting in a high degree of confidence that the improvements identified will be successful. Thus both Lean and Six Sigma have an analysis component. All the process improvement frameworks end with the fix being institutionalized: If it cannot be guaranteed that the fix will continually be applied, then it cannot be guaranteed that the process will be improved.
Lean borrows a vast majority of its tools and terminology from the Toyota Production System (TPS). One tool that is used in Lean that is not part of the TPS repertoire is value stream mapping. Value stream mapping is an essential tool, however, because it is the mechanism that is employed to gain an overall understanding of the process and to point out where Lean tools can be implemented to the greatest advantage. On the contrary, process improvement in TPS is usually discussed in terms of its tools directly applied to problem areas rather than employing this overarching guiding mechanism. Value stream mapping is also advantageous because it brings about a great amount of awareness about how the process is really executed. Until such a map is created, no one person in a company is cognizant of how things are accomplished: Each person might know what role he or she plays in the process, but nobody knows the whole process or how the process steps interact. Furthermore, it is also often true that individuals cannot recite the sequence of tasks they follow to play their role in a process without thoughtful reflection, which can be motivated by value stream mapping.
Value stream mapping as mentioned in the Lean framework will probably suggest multiple actions that can be taken to reduce lead time. Therefore, some time might elapse between episodes of value stream mapping to allow for all those improvements to be implemented. Some of the improvements might be implemented through what are sometimes called kaizen events. The structure of kaizen events recognizes that some improvements can be made only if a sufficient amount of time is dedicated to the task. Kaizen events allow workers to be relieved of their everyday duties for multiple days (three to five days) in order to plan and implement an improvement. For example, a value stream mapping analysis might have identified that changeover time could be reduced at a particular machine. It is usually outside the scope of value stream mapping to make such an improvement, which would be implemented later via a follow-up kaizen project. During the time away from their jobs, a team would collect data about the changeover, find opportunities for improvements, and implement some of the improvements. Even with three to five days to work on the project, some of the improvements might need to be implemented over time if new equipment needs to be purchased or fabricated. Nonetheless, this discussion points out that making improvements using Lean does require an investment of time and resources. The inability to devote such resources because of the importance of daily deliverables and the resolution of ongoing crises is one of the most frequent barriers to implementing Lean and improving processes.