Six Sigma vs Lean: A Comprehensive Comparison of Two Process Improvement Methodologies

The DMAIC Methodology

The heart of Six Sigma is its 5 phases, DMAIC: Define, Measure, Analyze, Improve, and Control. Here’s what they mean -

1. Define: Define the problem, improvement activity, opportunity for improvement, the project goals, and customer (internal and external) requirements.
2. Measure: Measure process performance using process maps, capability analysis, and pareto charts.
3. Analyse: Analyse the process using Root Cause Analysis, Failure Mode and Effects Analysis (FMEA), and Multi-vari charts, to eliminate root causes of variation and poor performance.
4. Improve: Improve process performance with tools such as Design of Experiments (DOE) and Kaizen events to address and eliminate root causes.
5. Control: Control the improved process and future process performance using tools like control plans, statistical process control, 5S, and poka-yokes.

Using Six Sigma to Control Defects and Eliminate Variation

As stated previously, Six Sigma is focused on eliminating variation. Variability in manufacturing can create manufacturing process problems which in turn leads to defects and production inconsistencies. The DMAIC methodology achieves variation elimination because it gets the manufacturer to scientifically and systematically do the following:

• Clearly understand how products are being produced and identify inefficiencies before working out the improvement steps.
• Develop a plan to understand the nature of the problem and how to address it.
• Implement the plan to cut waste to optimise value and achieve consistency in manufacturing processes by reducing the amount of variation that occurs.
• Collaboratively working with all stakeholders to identify variations that could have been missed.

When properly deployed, Six Sigma can achieve reduced scrap, shorter cycle times, improved on-time delivery, reduced operating costs, and greater customer satisfaction.

Real-World Applications

Six Sigma is used widely across all manufacturing industries. Incidentally, it has also become a general business process improvement tool and is used in non-manufacturing industries as well.

Principles of Lean Manufacturing

Lean's basis is built on numerous key principles:

• Identifying and Eliminating Waste (Muda): Lean identifies seven kinds of waste – defects, overproduction, ready, non-applied skills, transportation, stock, movement, and further processing – and seeks to put off them.
• Creating Value-Added Processes: Process activities should result in a product or service that the customer is willing to pay for. That is the meaning of value. Otherwise, this is considered as waste.
• Continuous Improvement (Kaizen): Lean encourages constant, incremental changes to enhance efficiency and excellence.
• Respect for People: Lean emphasizes appreciation for every person who contributes to the organisation and recognises that their insights are important for improvement.
• Involving All Levels of the Organization: Lean engages everybody, from the CEO to the manufacturing production workers, to pursue the highest production performance with maximum waste reduction.

Lean Tools and Techniques

To put into effect those principles, Lean makes use of several analytics tools:

• Value Stream Mapping (VSM): Value stream maps are similar to flowcharts but include additional information about various activities that occur at each step of the process. It is used to identify improvement opportunities and track performance.
• Kanban: A visual method for managing production workflows.
• Poka-Yoke (Mistake-Proofing): A process analysis tool used to make it impossible for errors to occur or to make the error immediately obvious once it has occurred.

Benefits of Lean in Manufacturing

When properly executed, Lean can result in greater manufacturing and business efficiencies.

Also, read about VDA 6.3 Process Audit

Key Differences

• Focus: Six Sigma is geared closer to lowering defects and minimizing variability in production. Its intention is precision and defects reduction. Lean, however, centres on getting rid of waste (muda) and streamlining procedures. It specializes on systems performance and process flows.
• Approach: Six Sigma relies heavily on statistical evaluation to identify and resolve troubles. Lean has a broader focus and looks at the organisation’s overall functioning.
• Applications: Both have been adapted widely to manufacturing and non-manufacturing industries.

Read about 5 Phases Of Six Sigma in detail.

Integrating Six Sigma and Lean: Lean Six Sigma

During the 2000s, Lean and Six Sigma were integrated together to become a separate process improvement tool. This hybrid technique leverages Six Sigma’s statistics-driven defect elimination methods and Lean’s efficiency and waste reduction techniques. It results in a holistic and factual approach to improving performance by removing operational waste and preventing defect.

Comparison Table