Six Sigma (6σ)
6σ is a disciplined, data-driven approach and methodology for reduction of variation in any process – from manufacturing to transactional, product to service and in many organisations, 6σ refers to a measure of quality that continually strives for near perfection (minimal variation in all processes).
The idea behind 6σ is that if you understand your processes you can systematically establish all sources of variation and work to reduce the variation.
Useful Resources: Sigma Conversion Chart, DMAIC Structure, Six Sigma Blog
6σ Fundamentals
Six Sigma is based on some fundamental principles, these are:
- Y=f(X) - All process outcomes (the Y) are a function of the inputs (the Xs) and the process itself. This takes into account the known variation
- To reduce variation in the process output (the Y), you have to focus on the inputs (the X’s) and the process itself (the f)
- Variation is everywhere, it is a fact of life but must be understood and managed. The point of utilising 6σ tools and techniques is to understand the variation and minimise it!
- Valid measurements and data are required foundations for consistent improvement.
- Only a critical few inputs and process steps have significant effect on the output. Concentrate on the critical few
6σ Measures
The measures for 6σ that are used are:
- DPMO – defects per million opportunities
- Yield – percentage yield of the process
- Process σ – the measure of dispersion of the process output about the mean
Having a process sigma value of 6σ (+/- 6σ) will reflect a process that will, over time, produce no more than 3.4 defects per million outcomes.
DMAIC – Define, Measure, Analyse, Improve, Control (plus Replicate)
The DMAIC project method is a formalised problem-solving process. The five steps to can be applied to any procedure of a business to improve effectiveness.
- Define: Set the context and objectives for your improvement project.
- Measure: Determine the baseline performance and capability of the process or system you’re improving.
- Analyse: Use data and tools to understand the variation in the process, their root causes and effects on other processes
- Improve: Develop the modifications that lead to a validated improvement at root causes level in your process or system.
- Control: Establish plans and procedures to ensure that your improvements are sustained, the new way.
PLUS – Replicate: Take the lessons learnt to improve similar products or processes
6σ Hierarchy
6σ is driven via a tiered system of technicians, whose level of authority and responsibility is denoted by their belt colour’ –Yellow Belt, Green Belt, Black Belt, Master Black belt
Yellow Belt – active member of a project team with a basic understanding of the Six Sigma tools and familiar with the DMAIC process. The Yellow Belts main function is data collection and problem solving and they will be heavily involved during the project testing and implementation stages of a project.
Green Belt – are more conversant with each of the five steps (DMAIC) and the tools and techniques used. They are supervised by the Black Belt and will assist at all stages of a project, but are heavily involved at the implementation stage of any project in their operational area. Green Belts may also lead teams on small improvement projects
Black Belt – will have a clear working understanding of and the ability to use Six Sigma principles, tools and techniques. They provide the lead on improvement project teams in areas outside their own operational area as they have a good understanding of the organisation as a whole. They will possess leadership skills and understand the dynamics of a team, able to assign roles and responsibilities within their teams as appropriate and required, with the ability to motivate these teams through the DMAIC process to accept and implement the required changes. They will lead teams and projects to drive through improvements in product and service delivery processes. They will also participate in the training and development of the Yellow and Green Belts in the required tools and techniques required.
Master Black Belt – experts in the tools and techniques of Six Sigma, and responsible for the planning of the improvement projects, normally in conjunction with the Senior Management Team (sometimes supported by a Champion / Sponsor). In order to attain Master Black Belt status they will have completed at least three projects at Black Belt level and the role is normally full time with the Master lack Belt managing several concurrent projects cross functional teams
We will be launching a series of articles during the next couple of weeks that aim to provide a foundation understanding of SPC and it's application, this will hopefully help you make an informed choice about whether SPC is the correct tool for you!
The articles will be broken down into small bite size offerings that can be used for future reference. We will also be making available the relevant resources, including an SPC chart, calculation sheets and a table of constants along with some recommended further reading.
From my perspective, this is a very welcome development as it emphasises the language of business, basing all projects on a sound business case using proven tools and techniques to deliver: