Introduction
Lean and Six Sigma are two of the most widely used process improvement methodologies. While both aim to improve efficiency and reduce waste, they differ in their approach and focus.
🔹 Lean: Focuses on eliminating waste and increasing speed.
🔹 Six Sigma: Focuses on reducing defects and improving quality.
Many organizations combine Lean and Six Sigma (Lean Six Sigma) to maximize benefits. Let’s dive into their key differences, similarities, tools, and real-world applications.
What is Lean?
Lean is a methodology that focuses on minimizing waste and maximizing value. Originally developed by Toyota (Toyota Production System - TPS), Lean ensures that every step in a process adds value.
Key Principles of Lean (5 Lean Principles)
- Define Value – Understand what the customer values.
- Map the Value Stream – Identify every step in the process.
- Create Flow – Ensure smooth workflow with minimal delays.
- Establish Pull System – Produce based on demand, not forecasts.
- Strive for Perfection – Continuously improve processes.
7 Wastes in Lean (TIMWOOD)
Lean focuses on eliminating the 7 types of waste (TIMWOOD):
| Waste | Example |
|---|---|
| Transportation | Moving materials between departments unnecessarily |
| Inventory | Excess raw materials or work-in-progress (WIP) |
| Motion | Unnecessary movement of employees or machines |
| Waiting | Delays in production or service |
| Overproduction | Producing more than needed |
| Overprocessing | Adding unnecessary steps to a process |
| Defects | Errors that require rework |
Example of Lean in Action
🔹 Amazon uses Lean principles to reduce warehouse waste and optimize deliveries.
Common Lean Tools
- 5S (Sort, Set in Order, Shine, Standardize, Sustain) – Organizes workplaces efficiently.
- Kanban – Visual workflow management system.
- Value Stream Mapping (VSM) – Identifies and removes waste.
What is Six Sigma?
Six Sigma is a data-driven methodology that aims to reduce defects and process variations. It was developed by Motorola in the 1980s and later popularized by General Electric (GE).
Key Principles of Six Sigma
- Customer Focus – Deliver quality products/services.
- Data-Driven Decisions – Use statistics to solve problems.
- Process Standardization – Reduce variations in outcomes.
- Continuous Improvement – Use structured problem-solving.
Six Sigma Levels (Sigma Levels & Defects Per Million Opportunities - DPMO)
| Sigma Level | Defects Per Million (DPMO) | Process Yield (%) |
|---|---|---|
| 1 Sigma | 690,000 | 30.85% |
| 2 Sigma | 308,000 | 69.15% |
| 3 Sigma | 66,800 | 93.32% |
| 4 Sigma | 6,210 | 99.38% |
| 5 Sigma | 230 | 99.977% |
| 6 Sigma | 3.4 | 99.9997% |
🔹 A process at Six Sigma level has only 3.4 defects per million opportunities (DPMO), meaning it is nearly defect-free.
Six Sigma Methodologies
Six Sigma uses two main approaches:
DMAIC (Define, Measure, Analyze, Improve, Control) – Used for improving existing processes.
DMADV (Define, Measure, Analyze, Design, Verify) – Used for designing new processes.
Example of Six Sigma in Action
🔹 General Electric (GE) used Six Sigma to save $12 billion in operational costs.
Common Six Sigma Tools
- Fishbone Diagram (Ishikawa Cause & Effect) – Identifies root causes of defects.
- Pareto Chart – Focuses on solving the most critical issues.
- Control Charts – Monitors process stability over time.
Key Differences Between Lean & Six Sigma
| Factor | Lean | Six Sigma |
|---|---|---|
| Primary Goal | Reduce waste & improve speed | Reduce defects & improve quality |
| Focus | Efficiency | Consistency & accuracy |
| Approach | Eliminates non-value-adding activities | Uses statistics to reduce variation |
| Methodology | 5 Lean Principles, 7 Wastes (TIMWOOD) | DMAIC, DMADV |
| Tools Used | 5S, Kanban, Value Stream Mapping | Fishbone Diagram, Pareto Charts, Control Charts |
| Origin | Toyota Production System (TPS) | Motorola (1980s) |
| Best for | Service industries, manufacturing | Quality improvement in any process |
Can Lean & Six Sigma Work Together? (Lean Six Sigma)
Yes! Lean Six Sigma (LSS) combines the speed and waste reduction of Lean with the quality improvement of Six Sigma.
How Lean Six Sigma Works
Lean eliminates waste to make processes faster.
Six Sigma reduces defects to improve quality.
Together, they create a streamlined, high-quality process.
Example of Lean Six Sigma in Action
🔹 Ford used Lean Six Sigma to reduce vehicle production defects and improve efficiency.
When to Use Lean, Six Sigma, or Both?
| Scenario | Best Approach |
|---|---|
| Slow processes & bottlenecks | Lean |
| High defect rates & quality issues | Six Sigma |
| Customer complaints about errors | Six Sigma |
| Long wait times or excess inventory | Lean |
| Need to improve efficiency & quality together | Lean Six Sigma |
Conclusion
✅ Lean is best for eliminating waste and increasing speed.
✅ Six Sigma is best for reducing defects and improving quality.
✅ Lean Six Sigma combines both to maximize efficiency and effectiveness.