Lean
Lean is a well-defined set of tools that increase customer value by eliminating waste (muda) and creating flow throughout the value stream. The following bullets describe lean improvements:
- Inexpensive to implement
- Focus on improving the process, not the people
- Address the batch and queue mentality of silos by following process flow
- Promote simple, error proof systems
Therefore, a Lean process is better (no defects, it is what the customer wants), cheaper (non-value added work is removed, there is no re-work or scrap), and faster (eliminates batch and queue, introduces flow, gets it right the first time).
The Lean Steps:
- Specify Value – from the customer’s perspective
- Map the Process – Process Map or Value Stream Map
- Identify Value Added and Non-Value Added Steps
- Examine Flow – continuous, minimally interrupted flow; single piece vs. batching
- Create Pull – do not produce until the next step downstream is ready for you
- Pursue Perfection – sustain improvement; change culture
Six Sigma
Six Sigma is a statistical model that measures a process in terms of defects. Six Sigma enables an organization to achieve quality by using a set of strategies, tools, and methods designed to improve processes so that less than 3.4 defects (errors) exist per million opportunities and processes are as near to perfect as possible. Sigma, or the Greek letter d, is the symbol for standard deviation in statistics. Standard deviation levels help us understand how much the process deviates from perfection.
Six Sigma is also a philosophy of management that emphasizes:
- The importance of understanding factors critical to quality and customer expectations
- The measurement and analysis of data
- The implementation of solutions designed to improve processes to affect the most statistically significant sources of variation
- Sustaining these solutions
In short, Six Sigma is several things:
- A statistical basis of measurement that strives for reduction of defects to 3.4 defects per million opportunities (DPMO)
- A philosophy or method of management
- A management goal: to perform as perfect as practically possible
- A symbol of quality
Motorola started using Six Sigma in the 1980s to improve its manufacturing processes. General Electric and others expanded its applicability to service processes with great success. Other users and innovators in the late 90s include DuPont, Dow Chemical, 3M, Ford, Amex, Bank of America, JP Morgan Chase, and United Health Care.
From Six Sigma For Managers, G. Brue, (2002)
Lean Six Sigma
Both Lean and Six Sigma have their weaknesses and their strengths. For example, Six Sigma will eliminate defects but will not address speed or optimize flow. Lean does not include the advanced statistical tools required to identify the sources of variation necessary to craft an intervention that is as simple and as focused as possible. Recognizing the complementary nature of the two methodologies, many companies have used Lean and Six Sigma concurrently, utilizing different pieces of the tool kit to address specific improvement problems along a value stream. This practice of combining different tool sets and playing to strengths is sometimes called the “blended approach.” The Center for Transforming Healthcare uses the Lean Six Sigma blended approach.