Six Sigma is a set of techniques and tools for process improvement
Six Sigma seeks to improve the quality of process outputs by
Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified value targets,
for example:
This is based on the calculation method employed in process capability studies.
Capability studies measure the number of standard deviations between the process mean and the nearest specification limit in sigma units, represented by the Greek letter σ (sigma). As process standard deviation goes up, or the mean of the process moves away from the center of the tolerance, fewer standard deviations will fit between the mean and the nearest specification limit, decreasing the sigma number and increasing the likelihood of items outside specification.
In Six Sigma, mainly two methodologies followed:
1. DMAIC- Define, Measure, Analyze, Improve & Control
2. DMADV-Define, Measure, Analyze, Design & Validate.
Six sigma methodology can be applied in most of the fields i.e. production /manufacturing, service, IT, Administration, Quality, HR, Purchase, etc.
DPM= Defect per Million.
DMAIC- Define- Measure- Analyze- Improve- Control
Six Sigma seeks to improve the quality of process outputs by
- Identifying and removing the causes of defects (errors)
- Minimizing variability in manufacturing and business processes.
Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified value targets,
for example:
- Reduce process cycle time,
- Reduce pollution,
- Reduce costs,
- Increase customer satisfaction
- Increase profits
This is based on the calculation method employed in process capability studies.
Capability studies measure the number of standard deviations between the process mean and the nearest specification limit in sigma units, represented by the Greek letter σ (sigma). As process standard deviation goes up, or the mean of the process moves away from the center of the tolerance, fewer standard deviations will fit between the mean and the nearest specification limit, decreasing the sigma number and increasing the likelihood of items outside specification.
In Six Sigma, mainly two methodologies followed:
1. DMAIC- Define, Measure, Analyze, Improve & Control
2. DMADV-Define, Measure, Analyze, Design & Validate.
Six sigma methodology can be applied in most of the fields i.e. production /manufacturing, service, IT, Administration, Quality, HR, Purchase, etc.
What is Six
Sigma : 6σ
Sigma(σ)
·
Degree of variation;
·
Level of performance in terms of defects;
·
Statistical measurement of process capability;
·
Benchmark for comparison;
·
Process improvement methodology;
Business
Definition
A break
through strategy to significantly improve customer satisfaction and shareholder
value by reducing variability in every aspect of business.
Technical
Definition
A
statistical term signifying 3.4 defects per million opportunities
Sigma Level
|
DPM Opportunity
|
1σ
|
6,90,000
|
2σ
|
3,08,000
|
3σ
|
66,800
|
4σ
|
6,210
|
5σ
|
230
|
6σ
|
3.4
|
DMAIC- Define- Measure- Analyze- Improve- Control
Define
- Identify, evaluate and select projects for improvement
- Set goals
- Form teams.
The purpose of this step is to clearly
articulate the business problem, goal, potential resources, project scope and
high-level project timeline.
This information is typically captured
within project charter document.
Write down what you currently know.
Seek to clarify facts, set objectives
and form the project team
Define the following:
- A Problem
- The Customer
- Critical To Quality
- Project Target
- Project Boundry/scope
- A Project charter for Agreement between sponser and leader.
- Collect data on size of the selected problem,
- identify key customer requirements,
- Determine key product and process characteristic
The purpose of this step is to
objectively establish current baselines as the basis for improvement.
This is a data collection step, the
purpose of which is to establish process performance baselines.
The performance metric baseline(s) from
the Measure phase will be compared to the performance metric at the conclusion
of the project to determine objectively whether significant improvement has
been made.
The team decides on what should be
measured and how to measure it.
It is usual for teams to invest a lot
of effort into assessing the suitability of the proposed measurement systems.
Good data is at the heart of the DMAIC
process
Analyze
- Analyze data, establish and confirm the “ vital few “ determinants of the performance.
- Validate hypothesis
The purpose of this step is to
identify, validate and select root cause for elimination.
A large number of potential root causes
(process inputs, X) of the project problem are identified via root cause
analysis (for example a fishbone diagram).
The top 3-4 potential root causes are
selected using multi-voting or other consensus tool for further validation.
A data collection plan is created and
data are collected to establish the relative contribution of each root causes
to the project metric, Y. This process is repeated until "valid" root
causes can be identified. Within Six Sigma, often complex analysis tools are
used.
However, it is acceptable to use basic
tools if these are appropriate. Of the "validated" root causes, all
or some can be
- List and prioritize potential causes of the problem
- Prioritize the root causes (key process inputs) to pursue in the Improve step
- Identify how the process inputs (Xs) affect the process outputs (Ys)
- Data is analyzed to understand the magnitude of contribution of each root cause, X, to the project metric, Y.
- Statistical tests using p-values accompanied by Histograms, Pareto charts, and line plots are often used to do this.
- Process maps can be created to help pin-point where in the process the root causes reside, what might be contributing to the occurrence.
Improve
- Improvement strategy
- Develop ideas to remove root causes
- Design and carry out experiments,
- Optimize the process.
- Final solutions
The purpose of this step is to
identify, test and implement a solution to the problem; in part or in whole.
Identify creative solutions to
eliminate the key root causes in order to fix and prevent process problems.
Use brainstorming or techniques like
Six Thinking Hats and Random Word.
Some projects can utilize complex
analysis tools like DOE (Design of Experiments), but try to focus on obvious
solutions if these are apparent.
Control
- Establish standards to maintain process;
- Establish the controls, implement and monitor.
- Evaluate impact of the project
A Control chart can be useful during
the control stage to assess the stability of the improvements over time