Combining Lean Manufacturing and Six Sigma for Continuous Improvement

Six sigma is now the most common continuous improvement tool in business. It is often combined with lean manufacturing to form the lean six sigma improvement method. Six sigma has been in use by a select few companies for over 20 years. Lean manufacturing was made popular by Toyota in the Toyota Production System, and has also been in use for a couple decades.

Recently, the combination of both methods has proven successful. However, integrating the two disciplines is not always easy, as the approach to each method differs considerably. Lean manufacturing follows a system called PDCA (Plan-Do-Check-Act), which as the name implies, is a fairly quick implementation. It is more of a "just do it" philosophy. In other words, get an idea, implement it, see if it worked, then adjust to make it better.

Six sigma is more methodical. It follows a model known as DMAIC (Define-Measure-Analyze-Improve-Control), which as the model depicts, is more time consuming. Integrating both lean manufacturing and six sigma can be very powerful, especially when the strengths of both tools are utilized. For example, six sigma’s methodical approach minimizes wasted efforts on ideas that are misguided or unjustified, and lean manufacturing’s excellent improvement tools fit nicely into the Improve phase of the six sigma model.

Both lean manufacturing and six sigma have a set of tools that are used to solve business problems (opportunities). Combining both methods increases the tool set by nearly 100%. Although there are differences of opinion, it really doesn’t make sense to limit your business issues to only one set of tools. It doesn’t even make sense to limit it to two sets of tools, however, when you look at the toolbox of lean manufacturing and six sigma, almost any business problem could be solved with one of the tools.

There are many lean manufacturing tools, but the most popular are value stream mapping, 5S (workplace organization), SMED (setup reduction), kaizen (Japanese for incremental improvement), kanban, standard work, tpm (total productive maintenance), OEE (overall equipment effectiveness), one piece and continuous flow, theory of constraints, pull systems, takt time and line balance.

Six sigma has a huge collection of tools ranging from project define tools of prioritization techniques, house of quality, analysis of mean and variances, hypothesis testing, regression analysis, design for six sigma, DOE (design of experiments), FMEA (failure mode effects analysis), cause and effects analysis and matrix, and many others.

Just looking at the tools, for the continuous improvement professional, it becomes readily apparent that neither discipline should be left out. Business issues, opportunities, and problems should determine the tools necessary rather than the skills of the team members.

Both disciplines do require time to learn. Even more important is the application experience. Combine the skill set required and the "soft" skills of dealing with people, and implementing lean six sigma becomes a large initiative. However, when these tools are mastered, and the implementer utilizes the knowledge of those people with experience (such as employees), many problems can be solved swiftly, yielding huge gains in productivity, scrap, cycle time, inventory, sales, or any other metric.