Six Sigma was first developed by Motorola in 1986, but has since grown rapidly into a world-wide Business Excellence quality program used by many of the world's top companies. These companies include General Electric, Allied Signal, 3M, and Honeywell. Like all effective programs, it is sponsored and supported by senior management, and the position of Six Sigma Black Belt is aspired to by most of the best professionals in the company.
Six Sigma and Lean Manufacturing
Six Sigma is very closely related to Lean Manufacturing, and the two are often combined within a company to a Business Excellence function, sometimes called Lean Six Sigma. As a guide, Six Sigma deals with improving product quality, whereas Lean Manufacturing deals with product speed and quantity. The Kepner-Tregoe business tools are also sometimes included in the Business Excellence function.
Six Sigma Black Belt
Those chosen to be Six Sigma Black Belts need to be excellent leaders and agents of change. They are dynamic, self-motivated individuals, and set stretch goals for themselves. They are trained to a high level in Project Management, Change Management, and Advanced Statistics.
Six Sigma Black Belt Project Selection
The Six Sigma strategy is not continuous improvement, but break-through improvement. The most difficult, intractable problems are assigned to Six Sigma Black Belts. At a given time, Black Belts have one project each, and work full-time on that project.
Six Sigma Project Principles
The most fundamental principle in Six Sigma is that there is variation in every process output, and that this variation is a function of shifts in the process inputs. The objective in a Six Sigma Black Belt project is to determine what the key process input variables are, investigate how they affect the output, and then choose a set of values for these inputs that give the "best" output. The key input variables are then set to a fixed value, and so the variation in process output is greatly reduced.
The Importance of the Normal Distribution Curve in Six Sigma
Six Sigma Black Belt projects often make use of the Normal Distribution Curve. Sometimes called the "Gaussian" Curve, or "Bell-Shaped" Curve, it has some features that make it very useful. For example, around 68% of the population lies within one standard deviation of the mean, 95% of the population lies within two standard deviations of the mean, and around 99.7% of the population lies within three standard deviations of the mean. About 3 parts per million fall outside six standard deviations from the mean. This is the quality target for the Six Sigma program.
Six Sigma Black Belt Project Types
There are two types of Six Sigma Project. The first, and most common, deals with improving an existing product or process. The second type deals with product and process design, and is called "Design for Six Sigma", or DFSS. Only the first type is dealt with here.
The Six Sigma Project Phases ("DMAIC")
Define
This is a critically important phase in any Six Sigma project. The problem is stated and defined with a problem statement, objective statement or goal, estimated business benefit, and the project metrics.
Six Sigma Measure Phase
In this phase of a Black Belt Six Sigma project, the current process capability is calculated, the measurement tools are checked for gage capability, and a process map of the existing process is drawn up.
Six Sigma Analyse Phase
The Analyse phase of the Six Sigma project is where the advanced statistics are used. Existing data are analysed to check for variability due to machines, materials, processing methods, or operator. In the Analyse phase, the process map from the Measure phase is used as a source of ideas for possible input variables to the process output.
Six Sigma Improve Phase
This phase of a Six Sigma Black Belt project attempts to find out which of the process input variables are the key ones. Typically a Designed Experiment (DOE)is conducted to see the relationship between the input variables and the process output.
Six Sigma Control Phase
Along with the Define phase of the Six Sigma project, this phase is the most important. The "best" settings for the key process input variables are selected and controlled. Since the main factors that affect the output no longer change, then the process output has less variation.
Six Sigma Black Belt Project Summary
Six Sigma Black Belt projects allow the best people in the company to work on the most important problems. The problems are well defined, rigorously analysed, and the best process settings are controlled using the best available methods. Project cost savings are validated by the finance department.
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