The Epic of Lean Six Sigma Terminology

2 August 2022

Getting started with Lean Six Sigma

An exploration of Lean Six Sigma’s terminology from a historic perspective. What is Lean Six Sigma? Is it a method? A philosophy? And how does the Toyota Production System relate to Lean Six Sigma? Is Kaizen something different than Lean?

Misconceptions surrounding Lean Six Sigma are prime examples of Babylonian confusion. Everyone is generally speaking about the same thing, namely process improvement, but all refer to it by different names. Still, there is merit to getting our definitions straight so that we can properly formalize continuous improvement throughout organizations. Hence this article, in which we attempt to illuminate the terminology from a historic perspective. We apologize in advance for the amount of jargon we are about to unleash.

The concept of Continuous Improvement can be traced back to the dawn of mankind. While this is a reassuring affirmation of its historic importance, it also means that we could technically start our Lean Six Sigma timeline anywhere in history. To make it easier on you, and ourselves, we chose to start our timeline at the Toyota Motor Company in the 1950’s.

The emergence of Lean

Toyota Motor Company and the Toyota Production System

Taiichi Ohno, along with a group of likeminded experts at the Toyota Motor Company, is inspired by the Ford Production System (FPS). The essence of the FPS is striving for a constant flow in production. Ford primarily achieved this by introducing standardized components and the assembly line. In the fifties Taiichi Ohno starts incorporating the FPS into the Toyota Production System, and gives this companywide improvement programme its name: Total Quality Control (TQC).

Introducing an exact copy of the FPS is not possible due to cultural differences, which sets the foundation for a couple of important adjustments in management. For example, monotonous assembly line work on the shop floor is not considered acceptable in Japan, and Toyota lacks the financial means to build large factories.

Kaizen: the revised Ford Production System

Aside from striving for constant flow in the FDS, Taiichi Ohno also introduces the principles of low volumes and Just-in-Time to the management of the Toyota Production System. The advantage of these principles is that it makes the organization agile and flexible. The disadvantage is that they carry risk and only work if the entire organization cooperates with Kaizen, which translates to Continuous Improvement. Kaizen is a word that carries a lot of history, but was made popular to the mainstream by Masaaki Imai as a general term for ‘continuous process improvement’.

Genryou Management

The management of this production process is dubbed ‘Genryou Management’ within Toyota. Therefore, Genryou is the term that describes the way in which the production process is designed. To this day Genryou Management is integral to the Toyota Production system and its 14 management principles.

Kata and Kaizen

Kata literally translates to ‘routine’. For Toyota this means that the improvement kata(routine) is executed in small incremental steps forward. Kaizen (continuous improvement) is done by way of ‘Kata’ within Toyota. This is in stark contrast to the prevailing ideas of large-scale innovation and improvement projects in the West. Later on this Kata-philosophy was also applied in the Scrum project management method.

Genryou goes West and becomes ‘Lean’

As we stated earlier, Toyota’s management style is called Genryou (Japanese: 源量). Genryou can be loosely translated to ‘Reduce weight’. Later on Taiichi Ohno starts playing with words a little, and changes the term to 限量, which translates to ‘limited volume’, because he believes this is more accurate. This is where the term ‘Lean’ originates from. In 1988 Taiichi Ohno publishes a book in which the translators choose to translate Genryou to ‘Lean’. Moreover, they choose to translate the former version (reduce weight) rather than Taiichi Ohno’s later revision (limited volume).

The machine that changed the World

In the meanwhile, in 1986 the Massachusetts Institute of Technology (MIT) starts a large scale research project into the differences in the automobile manufacturing industry. Researches such as James Womack, Daniel Jones, Daniel Roos and John Krafcik spend four years working on this global research project.

In 1988, in the middle of his research, John Krafcik publishes an article with the title: ‘Triumph of the Lean production System’. This article and the book ‘The Machine that changed the World’ export the term ‘Lean’ to a western audience. Due to later publications of researchers in the 90’s, the term ‘Lean Thinking’ becomes even more popular, causing Taiichi Ohno’s terms of ‘Genryou management’ and ‘TQC’ to fade into the background.

It’s interesting to note that while the term ‘Lean Management’ has far surpassed ‘Genryou Management’ in popular usage, Kaizen has entered the Western jargon without much trouble.

The birth of Six Sigma

Six Sigma and improvement programmes

Toyota’s improvement programme is dubbed TQC and Philips names its improvement programme Company Wide Quality Control (CWQC). In this period companies increasingly give their improvement programmes distinctive names with which they can rise to fame. In 1970 Motorola follows up on this trend and develops its own unique quality programme called Six Sigma.

DMAIC projects lead the Six Sigma way

Most improvement programmes are born from necessity; a specific type of problem breeds a specific type of programme. For Motorola in 1970, this is a quality problem. Motorola surmises that their quality, which they translate to lack of defects, needs to increase tenfold. To achieve this, they set up their Six Sigma quality programme.

The programme consists out of a large number of improvement projects that are executed according to a predetermined cycle, namely the DMAIC cycle. The focus in these DMAIC projects is solving root causes of defects, substantiating these with statistical analyses and aiming for a process performance level of six sigma.

Simply put, this six sigma score indicates that roughly only 3.4 out of a million products are defects. To put it in a sports metaphor, imagine a football team that only misses 3.4 out of a million penalty shots.

Roles in a Six Sigma organization

The people executing DMAIC projects in the organization are called Green Belt and Black Belts. Besides these roles in a Six Sigma organization, there are also other roles, such as Yellow Belts, deployment managers, Champions, Sponsors and Master Black Belts.

When the General Electric Company decides to start working with Six Sigma as well, the programme becomes more widely known to the public.

Many people were involved in developing Six Sigma, but Bill Smith and Mikel J. Harry are the two engineers with the most known publications on the subject.

Lean and Six Sigma combined

Due to the similarities and overlap between Lean Management and Six Sigma, it is only a question of time before eventually a book is published about combining these approaches. In 2002, Michael L. George publishes the book ‘Lean Six Sigma, combining Six Sigma quality with Lean speed’.

While there are plenty of differences between Taiichi Ohno’s Lean management and Motorola’s Six Sigma Way, both methodologies contain a rich set of so-called ‘problem-solving techniques’, and share a customer and process-oriented perspective.

These ‘problem-solving tools’ include, but are not limited to risk analysis, statistical analysis, communication documents, brainstorm techniques, Kanban, Poka-yoke, 5S management and Visual Management. While the Lean Six Sigma philosophy is a constant, its repertoire of tools is continually expanded through new insights.

It could have been called Genryou Six Sigma

Today, Lean and Six Sigma are often considered inseparable. Green Belts and Black Belts are Lean Six Sigma Belts and the term ‘Lean Six Sigma’ resonates at the same level of the improvement programmes TQC en CWQC, with its own organizational structure, philosophy, project management methods and problem-solving tools. But Lean Six Sigma could just as well have been called ‘Kaizen DMAIC’ or ‘Genryou Six Sigma’. In the end, the name is merely circumstantial.

So what is Lean Six Sigma?

Lean Six Sigma is a quality management methodology that aims to continuously improve the speed and quality of processes in order to deliver what the customer wants as accurately as possible against the lowest possible operational costs and with the highest possible flexibility.

Continuous Improvement can be organized in various ways. Generally speaking, Toyota adhered to the theory of improvement in small incremental steps forward (Kata) whereas Motorola executed many DMAIC projects. But Kaizen events, improvement boards and DMADV projects are also ways to work on Continuous Improvement.

Successful Lean Six Sigma organizations have made Continuous Improvement (Kaizen) an important part of the way they work, and now situationally assess which improvement methods to use in order to reach their goals.

PS: Who really coined the term ‘Lean’…?

Only one question remains. Both The Productivity Press, the publishers of Taiichi Ohno’s book ‘Workplace Management’, and John Krafcik, writer of the article ‘Triumph of the Lean Production System’, claim to have coined the term Lean in 1988. In all fairness, The Productivity Press claims the term ‘Lean Management’, whereas Mr. Krafcik claims the term ‘Lean Production’. But the curious among us still wonder who was first…. 😉

If you’re interested in the Lean methodology, you could take a look at our Lean Thinking Pack!

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