Lean and Six Sigma--Comparing and Contrasting the Process Steps
I have had the opportunity to be trained in both Lean and Six Sigma methodologies. While the outcomes of the two methodologies are similar (operational cost savings in one form or another), the actual process steps are in a different order, at least from my perspective.
| Steps: |
Lean Process |
Six Sigma Process |
| Step 1 |
Current State Assessment (Value Stream Map) |
Define Opportunities--identify, quantify, and prioritize process improvement opportunities. |
| Step 2 |
Future State Map (Value Stream projections after Waste Reduction Kaizens) |
Measure approved opportunities--current state measurements |
| Step 3 |
Identify, quantify, and prioritize process improvement opportunities |
Analyze--scenarios, what-ifs, design of experiments leading to an outcome result |
| Step 4 |
Kaizen--implement the change and remeasure |
Improve--implement the solution and remeasure |
| Step 5 |
Audits to sustain the gains |
Control--develop control system to sustain the change. |
With a Six Sigma approach, Master Black Belts, working with and through Senior Leaders, define in detail the various process improvement opportunities as the very first step used in the methodology. The define phase for a Six Sigma project is a very time consuming assessment that includes a clear definition of each problem or opportunity, the associated objectives to be accomplished (and how the accomplishments will be measured), the financial business cases worth $250,000 or more in savings, the projects' scopes defined, the expected benefits to the customers from each problem/opportunity, and a high-level implementation time line. Criteria are then used to select the process improvements that will be implemented, thrown out, and/or sent back for rework. The focus of a six sigma project may be a value-adding work process or non-value adding work. Note that all this work occurs at the Define stage (Step 1). Measure is where the baseline definition for a six sigma project occurs--very similar to the lean current state assessment (Step 2). The Analyze step (Step 3) in six sigma process looks at what the options are for improving the problem or exploiting the opportunity--very similar to the future state brainstorming within a lean process improvement engagement, but the six sigma analyze phase relies heavily on a lot of statistical calculations and on optimizing designs of experiments.
Lean process improvement, on the other hand, begins with an assessment of the current state using a technique called value stream mapping to identify the flow of information, materials and time through each process step that creates customer value (Step 1). Value adding work and non-value adding wastes are identified and quantified within the map. The current state is used to identify the presence of wastes within the value stream--these identified wastes then become the process improvement opportunities captured in the future state map (Step 2). After the future state map is developed, the opportunities are prioritized in a sequence for implementation. Project charters and goal documents are developed prior to each Kaizen event (Step 3).
Step 4 is very similar in each of the methodologies--six sigma names it "Improve" while Lean calls it "Kaizen." Step 5, under each methodology, aims to sustain the gains--six sigma develops a control system while Lean uses on-going managerial audits.
I invite each of my readers to share their thoughts and impressions about these two methodologies.
Best regards.
