As the name implies, a lean Six Sigma methodology combines the principles of lean manufacturing (lean) with those of Six Sigma. But why would anyone want to do this? What are the advantages and disadvantages of combining lean and Six Sigma methodologies?

What Does Lean Contribute?

Lean is a process of continual improvement based on increasing value for the customer. The objective is to eliminate anything that does not contribute to what a customer is willing to pay for. This puts the focus on eliminating waste and streamlining the process of delivering the product or service.

Lean involves applying a number of principles and methods that include:

  • Kaizen – The principle of continuous improvement based on employee suggestions.
  • Kanban – Customer demand "pulls" the product through the production process.
  • TPM – Total productive maintenance is used to reduce equipment downtime.
  • TQM – Total quality management continually improves product and service quality.
  • 5S – Improving quality and efficiency through cleaning up and getting organized.
  • SMED – The principles of Single-Minute Exchange of Die reduce the time needed to change a machine or production line to produce a different product.
  • Poka-yoke – Used to eliminate the possibility of errors.

Lean is a tool used by businesses to streamline manufacturing and production processes. The main emphasis of lean is on cutting out unnecessary and wasteful step so that only the steps that directly add value to the product remain.

What Does Six Sigma Contribute?

Six Sigma is a quantitative method that focuses on improving quality in manufacturing using data collection and measurement, with the goal being to eliminate errors and variation. The result is improved product quality. Six Sigma addresses both the production and design of a product. The two approaches are represented by two acronyms: DMAIC and DMADV.

DMAIC

DMAIC is the Six Sigma acronym for the five steps used to improve an existing process or product. These are:

  • Define the Project — This is usually a problem to be solved. What are the goals, resources and limits of the project?
  • Measure – Collect data about the current system or process.
  • Analyze the Data — To find the root cause of the error.
  • Improve – Design and implement changes that will eliminate the error. Some techniques that are used include design of experiments, poka-yoke and standard work.
  • Control – Provide a system that allows monitoring and adjustments to maintain and improve on what was accomplished.

DMADV

  • DMADV is the Six Sigma methodology used to improve an existing a product or service, or for the creation of a new product or service. The steps in DMADV are:
  • Define – Establish the methods to be used and the goals of the project.
  • Measure — Identify characteristics such as those that are critical to quality (CTQ), required capabilities, production process capabilities and limits, and potential risks.
  • Analyze – Develop and test design alternatives.
  • Design – Select the best alternative, based on customer requirements.
  • Verify – Verify the design meets the goals of the project and make adjustments based on feedback and new data.

In many ways, the goals of lean and Six Sigma are similar, with lean having a broader scope and Six Sigma primarily focusing on eliminating errors and improving quality. However, both are based on a foundation of having a customer focus.

Synergism, Working Together in Lean Six Sigma

The differences in lean and Six Sigma are why they work together so well. For example, the two methods have similar goals, but they use different methods for identifying the root cause of waste and errors. Lean looks to optimize the production process. Six Sigma eliminates wastes that result from variations (errors) in the process. This means they can identify different types of deficiencies and waste.

Another difference is that lean is more of a bottom-up system, in which ideas for improvements (kaizen suggestions) flow up from the people doing the production work. Six Sigma is more of a top-down method employing experts to collect, analyze and act on data that is collected. This provides different viewpoints that will not only catch problems the other did not notice, but also come up with solutions the other had not considered.

Lean Six Sigma methodology is effective because the two methods complement each other, working together to identify errors and waste more efficiently than using just one method.

Drawbacks of Lean Six Sigma Methodology

There are some possible drawbacks to the lean Six Sigma methodology. One of the most significant is that both lean and Six Sigma involve major changes to the workplace. For example, most lean implementations are not successful because management underestimates the amount of time and effort required to implement and maintain lean.

In his book "Changing with Lean Six Sigma," A. Aruleswaran writes, "The most significant challenge is to change people and their mindsets."

It is not unusual for it to take more than two years to make the changes required just to implement lean. Implementing both lean and Six Sigma together means even greater complexity. If sufficient time and resources are not provided, the likelihood of failure is high.

On the other hand, it's easy to hire consultants and pour resources into lean Six Sigma methodologies, thinking you'll ensure success that way. While adequate resources must be allocated, the objective is not to spend a lot of money and waste resources. For example, Dr. Kaoru Ishikawa taught that 90 percent of all problems can be solved using simple graphical techniques he called the "seven tools of quality:"

  1. Cause-and-effects diagrams (fishbone diagram)
  2. Histograms
  3. Check sheets
  4. Pareto charts
  5. Stratification (flow charts)
  6. Control charts
  7. Scatter diagrams

Achieving the right balance to economically implement lean Six Sigma methodologies is a difficult challenge.

Other Possible Issues with Lean Six Sigma Methodologies

At times, lean and Six Sigma may give conflicting answers. A system must be in place to resolve differences and address situations in which conflicting "solutions" are championed. Babe Ruth's famous words apply when combining lean and Six Sigma: "The way a team plays as a whole determines its success. You may have the greatest bunch of individual stars in the world, but if they don't play together, the club won't be worth a dime."

In addition, lean Six Sigma methodology can result in using the wrong method for the problem being addressed. For example, Six Sigma is not appropriate for solving small problems that do not involve a significant number of variables. Lean techniques are much more efficient for solving these types of problems. Of course, this is also an advantage of lean Six Sigma methodology because both methods are available, and the best one or a combination of both can be used.

Results of Lean Six Sigma Methodology

In the forward to the book "Changing with Lean Six Sigma," V. S. Pandin writes: "Lean Six Sigma involves working on both the top line (revenue) as well as the bottom line (profits) of the enterprise. The attention to the top line is by being relevant to customer needs (voice of the customer), and the attention to the bottom line is through better quality, improved cycle times and lower costs."

Applying lean Six Sigma methodology throughout the workplace has a number of positive results, such as:

  • Both methods bring a focus on customer value and can reinforce each other to achieve a high level of customer focus that delivers value to both the customer and the organization implementing lean Six Sigma methods.
  • Waste is an unnecessary cost. By targeting waste directly, as well as targeting variation and errors, waste is more effectively eliminated.
  • Problems of all types and sizes are brought to light. Root causes are identified, and the problems are solved in an effective and efficient manner.
  • Products and services are delivered virtually defect-free, economically and on time.
  • Waste elimination, error elimination and a customer focus become the culture of an organization.

Visual Communication

Without clear, effective visual communication, implementing lean Six Sigma methods will be next to impossible. Visual communication using signs and labels delivers necessary information at the physical locations and times when it is needed most.