Lean
The focus of Lean is to reduce waste, identify non-value-added activities(NVA) in the process through tools such as 8 major wastes, ECRS, and value stream map, and minimize or eliminate NVA as much as possible.
Lean originated in the 1980s from Toyota Production System(TPS), which focuses on reducing Muda(Waste) through Kaizen methods. After this concept spread to the world, it subverted many traditional manufacturing concept.
Lean’s architecture consists of two pillars, namely JIT (Just-In-Time) and Jidoka (Automation).
JIT emphasizes the stability and smoothness of the process, and ensures the reduction of eight major wastes through takt time control, one-piece flow, and pull production.
Jidoka represents that personnel need to have quality awareness training, so operators need to stop production line when defect is generated. It can be achieved through automation system, Andon, or Kanban.
There are many common tools can be used to reduce waste, for example:
- 5S (or 6S nowadays)
- SMED (Single Minute Exchange of Die)
- Heijunka
- Cell production
- Value Stream Map
- 5-why
8 wastes are common inefficient sources in the production line. The first English letter of these 8 wastes is DOWNTIME, which means that these wastes cannot add value to products, but will cause inefficiency, cost and inventory problems.
- Defects
- Overproduction
- Waiting
- Not utilizing talent
- Transportation
- Inventory excess
- Motion waste
- Excess processing
Six Sigma
The focus of Six Sigma is to reduce variation. Six Sigma combined descriptive statistics, inferential statistics, probability theory, and other quality tools such as SPC and MSA to control process variation and further reduce variation through experimental design or other problem solving methods to approach the goal of Zero defect.
Six Sigma originated from Motorola in 1986. At that time, in order to improve product quality, Bill Smith formulated a series of methods, which were then vigorously promoted by companies such as General Electric and Honeywell.
Six Sigma is deeply influenced by other quality improvement theories, such as Statistical Process Control(SPC), Total Quality Management(TQM), PDCA, etc. Six Sigma is compatible with statistics and quality management, and has developed into a set of problem solving methodologies.
At the beginning, DMAIC roadmap was used to improve production problem, and then more processes are derived according to the type of problem, such as DMADV or CDOV.
DMAIC
- Define, Measure, Analyze, Improve, Control
- Focus on improve existed process
CDOV
- Concept, Design, Optimize, Verify
- Focus on new product design
DMADV
- Define, Measure, Analyze, Design, Verify
- Focus on new process design
There is no standard scope for Six Sigma body of knowledge, but below content should be involved generally.
- Project charter definition
- Project tools (VOC, QFD, Process map…etc.)
- QC 7 tools and New QC 7 tools
- Descriptive statistics
- Central Limit Theorem
- Statistical Process Control
- Hypothesis Testing
- ANOVA
- Measurement System Analysis
- Correlation and Regression
- Design of Experiment
- Full Factorial Design
- Fractional Factorial Design
- Response Surface
I summarized a Mind map based on DMAIC flow to show a whole picture of these tools.
Conclusion
In recent years, Lean and Six Sigma, as the main methods of continuous improvement, are often collectively referred to as Lean Six Sigma.
The purpose of Lean Six Sigma is to integrate Lean and Six Sigma, absorb the advantages of the two management modes, make up for the deficiencies of a single management mode, and achieve better management effects. The key point is that Lean Six Sigma is a comprehensive methodology that complements each other and improves technology. It is hoped that through many statistical and quality tools, waste and variation can be reduced, and customer value can be realized quickly and efficiently.
Regardless of the name, the focus should be on continuous improvement, and through the use of different tools, the following Continuous Improvement Process can be achieved
- Identify problem
- Define project
- Measure status quo
- Analyze root causes
- Generate countermeasure
- Implement action
- Control and monitor result
- Horizontal deployment
