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Do Lean and Six Sigma Complement One Another?
Set-up as rival methodologies, this article explores ways in which Lean and Six Sigma may be compatible bed fellows
What has today become known as Lean, originated in the Toyota Motor Company in the late 1940's and developed to become known as the Toyota Production System (TPS). So successful was TPS at transforming Japanese companies into industrial powerhouses, that Western companies were forced to respond.
Many tried to adopt the TPS Lean system, but because of the cultural differences between the East and West, the lack of teachers, called Sensei in Japanese, and the fact that Western companies tended to use the tools only, rather than adopt the underlying philosophies and management principles, the adoption had limited success.
In 1987, the US electronics giant, Motorola developed a methodology they called Six Sigma. Aimed at reducing variation, Six Sigma is more than a project and statistical tools based problem solving methodology. The smart thing about Six Sigma is that it has a roadmap and a set of tools which can be learnt in a reasonably short space of time. Also it recognises the importance of cultural acceptance of change in an organisation and includes tools and techniques for engaging organisational process stakeholders.
As Lean matured and Six Sigma leaked out to other organisations, they both became successful but competing methodologies for business improvement. Today, many companies still cling to either Lean or Six Sigma. Smart companies however are finding ways to integrate both methodologies, under the banner Lean Six Sigma (LSS). This article looks at ways in which Lean and Six Sigma complement one another.
The TPS or Lean system can be crudely represented as a triangle with the three sides being; i) long term consistent ideals and philosophies, ii) good practise management principles which support these philosophies and iii) technical problem solving competencies and tools focused on the elimination of waste in-line with the ideologies and philosophies (see Fig. 1).
The scientific method for improvement was first postulated by Ibn al-Haytham Alhazen (965-1039) and later developed by William Whewell (1794-1866) and Ludwik Fleck (1896-1961). This method states that a solution or validated theory can be found by; first observing and collecting evidence, then developing a hypothesis and testing this hypothesis by rigorous experimentation. If the tests support the hypothesis then the theory or improvement is validated, and if not then start again and adjust the hypothesis.
The Lean system is underpinned by the problem solving method; Plan Do Check Act (PDCA), invented by Walter A. Shewhart in the 1930's but made famous by W. Edwards Deming who introduced it to the Japanese in the 1950's. PDCA follows the scientific method (see Fig. 2).
The Six Sigma scientific improvement methodology is based on the DMAIC (pronounced de-may-ik) process, which stands for Define, Measure, Analyse, Improve and Control (see Fig. 3).
Both PDCA and DMAIC can be used to solve problems and make improvements. However, the DMAIC methodology of Six Sigma follows a structured roadmap with clearly defined milestones, activities and a choice of tools for each phase. It is a project by project methodology. Following the roadmap helps to ensure success.
The DMAIC methodology can be taught in a structured way, which enables consistency and a good level of competency in a reasonably short timeframe. The structured learning in Six Sigma is graded into belts, fashioned after the martial arts grading system. A Yellow Belt is the entry level qualification and used mainly for support or to run small improvement projects. Green Belts are intermediate level practitioners and typically part time improvement specialists, whilst Black Belts are high level technical exponents who usually work full time on process improvements. The highest level is a Master Black Belt and these are the technical experts who generally work with both management and other Belts to ensure project success.
The Lean PDCA method relies on the skill and experience of the leader or team guided by a Sensei to coach and teach. The methodology is less directed and is underpinned by ideals, philosophies and principles, known in Toyota as ‘The Toyota Way'. The Lean Way can be understood at deeper and deeper levels but a high level of proficiency comes only after years of guided practice.
When solving problems one of the most important assets a project manager or leader can have is to know when to use the right tool for the job. Lean tools can be used within a Six Sigma project and Six Sigma tools can be used within a Lean improvement.
Six Sigma is data centric and incorporates many practical statistically based tools focused on variation reduction and quality improvement. Lean concentrates on creating process flow, the removal of bottlenecks and the reduction of waste.
Many Lean tools are now embedded in the DMAIC process and it is said (ref. Jeffrey K. Liker) that Toyota have used every Six Sigma tool available but just not under the Six Sigma banner.
The fundamental objective of Lean is to reduce waste and the fundamental objective of Six Sigma is to reduce variability.
In the TPS, there are three kinds of waste, defined by the Japanese words mura, muri and muda, which mean unevenness (or variation), overburden (or stress) and non-value added work (waste) respectively. Unevenness in the form of lumpy production schedules, unbalanced processes etc... can cause over burden and non-value added work in the system. Overburden can cause break downs and quality problems, which lead to unevenness and non value added work, and non-value added work can create overburden and unevenness in the system. Therefore mura affects muri affects muda affects mura in a vicious circle (see Fig. 4).
Often in Lean the focus is only on the reduction of waste and the affects of variation and overburden are not tackled. Six Sigma helps address this weakness because it has a very effective roadmap and set of tools for analysing and reducing variability. The two methodologies are therefore complementary.
Six Sigma recognises the importance of cultural acceptance of changes and has tools for supporting change within an organisation. Jack Welch, of GE fame, developed a change effectiveness formula to demonstrate that cultural acceptance of change was just as important as the quality of the technical solution. This was expressed as an equation as shown in Fig. 5.
Six Sigma's approach to changing the culture of a company comes through the development of the belt structure within the organisation, and the management of stakeholders during projects. However, long term culture change cannot be achieved on a project by project basis alone and must be underpinned by a set of ideals and philosophies. The Lean system of figure 1 is structured on the principle of creating the right culture through ideals, philosophies and management principles to enable improvement to happen continuously. Continuous improvement is achieved by involving people throughout the organisation in team based improvement activities called Kaizen.
Both Lean and Six Sigma methodologies are data centric with operational and process improvements as their ultimate goal. We have seen that both Lean and Six Sigma are based on the fundamental scientific principle and that tools can be readily exchanged.
Six Sigma has a strong data centric tool kit and a rigorous methodology guided by a roadmap and focused on variation reduction. Lean is based on creating the right culture for continuous improvement to happen and focuses on process flow and the removal of waste.
The combination of the Lean and Six Sigma approaches brings together a strong set of tools, rigorous methods and cultural ideologies that enable organisations to tackle a range of problems, whether these are to do with waste or variability. It enables the strategic gaps of today to be addressed whilst at the same time creating a culture of continuous improvement for tomorrow.
SigmaPro were one of the first companies to offer an integrated Lean Six Sigma approach. SigmaPro work with organisations to plan improvement strategies, helping them to identify, select and run Lean Six Sigma projects, and support and coach staff to get the best out of their processes. Call us now for help in implementation of Lean Six Sigma and improving your business critical processes.
Author Biography
Dr David Cowburn
David has 25 years of running companies to Managing Director level and is experienced in utilising Lean Six Sigma in a wide variety of businesses including, manufacturing, process industry, service, and administrative.
In a people based hands-on style, he works and trains at all levels in an organisation from Board to shop floor to bring about rapid measurable step changes in performance. David was originally trained in the Toyota Production System and has since developed a high level blend of Lean and Six Sigma philosophies and tools through working with businesses all around the World.Quick Enquiry or Call Back
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