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Do we need to do Lean before we do Six Sigma?
Is there a 'best sequence' to rolling out Lean and Six Sigma in a business improvement programme?
I sometimes get asked about this question by those thinking about business improvement because they are concerned that their organisation is not yet ready for the complexity of Six Sigma, and that the standard and relatively simple disciplines of Lean will be easier to implement. They are also concerned that they don't really need a statistical approach because their volumes are low, or their basic processes simple. It is an interesting question, but in order to answer it you need to go right back to the roots and rationalities behind these two seemingly different approaches to improvement.
Lean originated in Toyota and has been evolving over the last 50 years. It has spread widely through Japan and has been adopted, in one form or other, across the globe in many organizations, sectors and industries. Although originally a manufacturing philosophy it has been successfully adapted to suit transactional processes in service industries. Its main focus is on time, seeking to reduce how long it takes to complete a task, or perhaps more importantly, how longs it takes to complete all the tasks in the Value Stream in order to satisfy a customer. (Value Stream is the entire process required to complete the transformation your organisation offers to customers or clients). In order to complete the transformation quickly you need to:
- Minimize inventory (the ideal state is single piece flow),
- Create small specialist areas or teams (called cells),
- Eliminate all but necessary tasks (waste elimination),
- Work only when requested by the 'pull' of the customer (as triggered by Kanbans),
- Create work standards and methods which will deliver the tasks in the most consistent and speedy manor,
- Introduce systematic error proofing to ensure defect free operations.
These disciplines will nearly always decrease cycle times and lead times, whilst increasing flexibility and capacity.
Six Sigma originated at Motorola in the late 80's and was made global by GE in the 90's. Like Lean it was originally a manufacturing discipline but it has been adapted and adopted by organisations of all shapes and sizes and is still going strong decades after its inception. It is essentially a statistical approach focusing on process capability; the ability of a process to deliver defect free outputs in the eyes of the customer.
In order to achieve Six Sigma process capability you need to:
- Understand what the customer truly requires (voice of the customer),
- Validate measurement systems,
- Gather data over time to understand the causes of variability in the process,
- Get to true root causes,
- Implement lasting fixes to ensure the process stays in control thereafter.
These disciplines usually lead to lasting defect reductions of the order of 70% to 80% and very satisfied customers.
So with this in mind do you need to do Lean before you do Six Sigma, and can you get away without Six Sigma? Let's deal with each of the common arguments in turn.
It is quicker and cheaper to train Lean Facilitators than Six Sigma Green and Black Belts
Both approaches require facilitators with skill sets needing training and nurturing over time. Six Sigma Green and Black Belts require more sophisticated training over a longer period of time, but successful Lean facilitators cannot be 'knocked out' by a few days training. It takes years of practice to really learn the skills necessary to transform processes successfully by the implementation of Lean systems.
Lean is easier for your people to accept than Six Sigma
Both approaches require a radically different approach to how we currently operate. Six Sigma demands valid data and an understanding of the causes of variation, but the standardisation and discipline of Lean is usually a million miles away from the way we currently work in the west. In many ways the mindset change required to implement Lean is more of a stretch than that required to implement Six Sigma. It also requires more people to adopt this mind set as it affects every operator and case worker. In the West we tend to have a pathological opposition to the fundamental tenants of Lean; minimize inventory and work to standard operations.
Lean is less radical than Six Sigma
To implement a pull system with minimal inventory requires very high levels of quality and reliability in our equipment and transport systems. This can only be brought about by the systematic introduction of standard operations and mistake proofing. The creation of cells may require the reorganization of workforce, equipment and workplace. Serious amounts of retraining may be required for your workforce. Six Sigma, on the other hand, requires that the Belts are properly supported by trained and motivated Champions within the organisation to ensure that the right projects get selected, that necessary time is devoted to projects, and that the necessary data collected to get to real root causes.
Six Sigma requires the volume of data only achievable from an automated production line and that it is not suitable for low volumes or long cycle times
You will be amazed by how little data a skilled Six Sigma Black Belt can get away with (especially with the early projects in a deployment where defect levels are relatively high), and in most cases processes repeat within an organisation even if products or processes don't. With Lean, don't forget, the foundation disciplines of standardisation and cell formation require repeatable processes and predicable volumes and mixes.
Lean projects are quicker than Six Sigma projects
This is often the case but this is usually because Lean projects are usually conducted in a short, sharp improvement activity called a Kaizen, and Six Sigma projects are usually carried out piecemeal. It is true that data collection does take some time in a Six Sigma project but there is no reason why the rest of the activities need take a long time. Many enlightened organisations are now carrying out their Six Sigma projects using the kaizen approach to overcome the long cycle time issue.
Summing up the arguments
So having addressed some of the issues can we now address the questions of which is best, Lean or Six Sigma, and which should be introduced first?
I would argue both Lean and Six Sigma are equally powerful but that that it is really a question of 'horses for courses'. Lean is best at resolving issues of excessive lead time or inventory and lack of capacity, whilst Six Sigma is best at fixing issues of poor quality or variability.
In any organisation of any size or complexity you will have both issues at the same time, and rounded problem solvers should be able to put their hand to both issues equally well.
Lean certainly can be said to lay the foundation for improvement, but it doesn't happen overnight, and whilst you are going through this transformation (which will take years!), the Black Belts can be hitting the really big and strategic issues of quality and variability within your organisation.
Lean can be seen as a 'tommy-gun approach', whilst Six Sigma can be seen as the 'sniper approach'. * Both are valuable and both have their place in an organisation embarking on the war against mediocrity.
Each discipline is suited to different problem types which will almost certainly exist simultaneously in any organisation of any size. You can certainly make a case for Lean first, but you can also make such a case for Six Sigma first.
The truth is that both Lean and Six Sigma require the introduction of new skills, mindsets and disciplines which are a challenge to any organisation. Each discipline is suited to different types of issue or problem, and both types are almost certainly present in your organisation now.
Both require a real commitment to change within the leadership (the workforce are not really an issue when it comes to deployment) and this is the real bottom line. Lean is definitely not easier to implement than Six Sigma and Lean is rarely enough ether.
My suggestion is first make the real commitment necessary to bring about lasting improvement within your organisation, and then implement Lean Six Sigma simultaneously.
Foot note: Although perhaps an unfortunate analogy the 'tommy-gun' V 'sniper' approach is a powerful way of looking at the deployment of improvement strategies. The 'tommy-gun' approach is akin to spreading bullets round in a more or less haphazard way hoping to take out some enemies (problems) along the way. Lean deployments sometimes utilize this mindset with their sheep dip approach to training and deployment. The 'sniper' approach utilizes much fewer but more highly trained individuals working on fewer but more strategically orientated projects which seek to 'take out' only the most troubling aspects of the process. A good Six Sigma deployment should adopt this approach with their Black Belts.
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