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Lean and Six Sigma... Better Together

What is the link between Lean and Six Sigma? In this blog, Nick Brandwood, specialist Manufacturing Advisor at the GC Business Growth Hub explores the methodologies of Lean and Six Sigma and how they complement each other to produce real Quality, Cost and Delivery improvements and positive bottom line impacts for manufacturing companies.

You will often see in the comic strip Dilbert, or in office-based sitcoms, a graph of continuous improvement stuck to the wall to highlight the fact that we are in a modern office environment. This is invariably drawn as a time-based line graph – starting in the bottom left hand corner and then following a gradient to the top right hand corner – familiar? Good! My only problem is that continuous improvement, as a graph, doesn’t really look like that! In my mind, I prefer to visualise continuous improvement as two graphs:

  • The before graph is spiky, like a drawing of the Himalayas, reflecting the high level of day to day variability in QCD performance and highlighting that key parameters are out of control and nobody really understands why.
  • Contrast this with the after graph, which looks more like the flat lining heart monitor pulse on every episode of Casualty – this indicates that every day is the same, that key input parameters are identified and controlled, and this is reflected in consistent QCD performance and confidence.

Lean and Six Sigma practitioners will both make claims for this type of improvement. However, I argue below that Lean and Six Sigma are complementary and should be combined for maximum benefit - together they force you to confront problems, encourage you to value effective problem solvers and to pursue a robust, scientific methodology to identify and resolve the big issues.

Download our Concepts of Lean Manufacturing factsheet


Six Sigma

I first came across Six Sigma about 20 years ago and was intrigued by the promise of 3 defects in a million opportunities and what that meant in terms of Quality improvement, Cost savings and improved Customer Delivery performance. I was not alone; manufacturers, bankers, clinicians have all been tempted by this level of excellence and the process that delivers it.

Six Sigma is a five-step process that utilises a full and in-depth toolkit of inferential statistics to understand and eliminate the causes of variation within an activity. The five steps are known by the acronym DMAIC and are:

  • Define – Ensuring a common understanding of the start point and goal of the project and the financial benefit that makes the project a priority
  • Measure – Understanding the routine variability in the output to be improved (the Y or the effect) and the key input variables (the X’s or the causes) to be analysed
  • Analyse – Solving the equation Y=f(X1……Xn). This is the cause and effect equation and can be best understood as “what you get out (Y) is a function (f) of what you put in (the X’s). The analysis phase quantifies the effect the X’s (e.g. temperature, pressure, line speed) have on the Y (e.g. % yield), either individually or through interaction with each other. The X’s (inputs) are thus prioritised as points of focus to optimise the output during the improvement phase
  • Improvement – Optimise the output variable (the Y) and reduce the variability in the output variable by optimising and reducing the variability in the key input variables (the X’s)
  • Control – Standardise the process improvements so that the performance improvement is sustained, and the key learning points can be readily transferred

The first thing to note about DMAIC is that even without the utilisation of statistical techniques it is a thorough and robust project management tool. It ensures projects are prioritised on business benefit and decisions are made through recourse to data. It ensures activities are done in the right order and in a timely manner. Furthermore, the effectiveness of any improvement is then verified through data.


How does this fit with Lean Thinking?

An excellent read is the “Toyota Kata” by Mike Rother which characterises Toyota primarily as a learning organisation more than a lean organisation.

Lean systems are pull systems which are hard to sustain because the absence of a buffer WIP makes every problem a potential OTIF failure and consequently a big deal. One of the characteristics of Lean is this sensitising of the process, forcing organisations, teams and individuals to confront the big issues and address them.

This sensitivity is the unique identifier of Lean, it is also, conversely, the reason that most Lean implementations fail. WIP is the great safety net in manufacturing organisations, providing a buffer against the hidden causes of process variation, ensuring that whatever the problem there is always something to pass forward and to ship and, hey, the problem can be solved tomorrow.

Lean removes that buffer and forces you to solve that problem for good, now. You either embrace that and relish the challenge to improve your process and make it flow or find it unpalatable and hide behind the WIP and soak up the cost, the lead times and the lack of flexibility...becoming one of those organisations that says, “we tried Lean, it doesn’t work in our industry.”

Toyota embrace it, they are an organisation that values effective learning above anything else. Learning organisations relentlessly strive to increase knowledge of their processes and effective learning organisations are effective problem solving organisations. Effective problem solvers are scientific thinkers, they start with a hypothesis (a theory) of “what they expect to happen” and test this hypothesis through experiment and review “what actually happened” It is important to state within this scientific definition of problem solving that there is no such thing as a failed experiment – your hypothesis is proven, or it is disproven -either way you have learned something and the knowledge within the organisation is increased.

In this world of scientific thinkers hungry for knowledge, the important thing is the credibility of the knowledge because fundamental standardised improvements, not tweaks, will be made on the strength of it:

  • Are the right hypotheses being proposed?
  • Are statistically valid experiments being undertaken?
  • Are statistically significant conclusions being drawn?

Download our Problem Solving factsheet


Hopefully, in posing these questions, the role that Six Sigma has to play becomes clear as does the link between Lean and Six Sigma.

Lean sensitises our processes and forces us to resolve issues that were previously hidden or buffered by WIP to ensure the process flows. It forces us to problem solve or learn and to value effective problem solvers within our organisations.

Six Sigma is the mechanism of effective problem solving, I spoke early about the credibility of knowledge. Can we trust it? Can we act on it? Can we invest in it to give us significant QCD and bottom line returns? These are big questions with big risks associated with them. The Six Sigma methodology ensures that the right questions have been asked, that the biggest issues have been identified, that the root causes have been determined and that improvements have been implemented, verified and standardised.

As important though, it brings a scientific rigour to manufacturing. It ensures that effective problem solving, and effective problem solvers are valued within organisations. Continuous improvement is learning, and learning is structured, scientific problem solving. Six Sigma cautions people to follow the DMAIC process and to actually learn something new and to advance the threshold of knowledge rather than rushing in with the same old preconceptions and previously applied answers to previously experienced problems.

If you would like to speak to a Manufacturing Advisor about fully-funded onsite support or grant funding, please complete the form below or call 0161 359 3050.

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Nick Brandwood

Nick Brandwood, Manufacturing Advisor

Nick has over 20 years' experience of implementing Lean and overseeing Six Sigma Improvement projects. 

Originally employed as a graduate Polymer scientist he has subsequently been employed in technological, continuous improvement and senior line management roles in automotive, textiles and secure printing manufacturing organisations. 

Nick is very hands-on and likes to understand and analyse problems, questioning perceptions and speaking with data. He has significant experience in facilitating change having previously worked as a Manufacturing Advisory Service advisor and has undertaken Lean transformations in automotive, aerospace, food and textile manufacturing companies.  

He has also trained over 30 six sigma greenbelts, and specialises in understanding and controlling variation and risk within the manufacturing process.  

Most recently, Nick was employed as the Quality and OPEX manager in a secure print company – ensuring that the productivity, quality and process capability targets for the imminent £20 plastic banknote were achieved to the satisfaction of the client.

To view Nick's full profile including technical capabilities and industry experience, please click here.

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