Lean principles and methods have become so closely tied to Six Sigma tools, knowing which is which can often be confusing. Compressing the two approaches into the moniker, Lean Six Sigma, is common.
Although separate, Lean methods and Six Sigma tools can work together well. However, they do use different tools to achieve different (if complementary) objectives. Most articles that speak to the two initiatives don’t help much in that they just provide very general, very conceptual definitions of them.
Let’s explain the difference by visualizing an illustration
Imagine that you’ve been asked to help a candy manufacturer improve its processes. You dig into the company’s operations and find these issues:
- The shop floor is disorganized to the point that it seems unsafe
- The schedule is in chaos; no one seems to know what’s due, what’s on time, and what’s late
- Customer service is poor
- Inventory control is almost non-existent
- Scrap at all points of the production process is high
Lean tools are going to be the most effective here. The majority of the most important sources of variation are immediately apparent. It very well could be deeply hidden causes of the company’s problems but there’s no question that the company needs to improve the flow of materials and information. As such, the fundamental Lean tools of 5S: visual factory, value stream mapping, leader standard work, and operator standard work are essential. These will provide more benefits than will Six Sigma tools, at least initially.
Now let’s take a closer look at the scrap issue
Basic Six Sigma tools like Pareto analysis will help us determine which process steps create the most scrap or which products have the highest scrap. Other analysis tools can help us nail down the conditions that cause scrap to increase or decrease. All of this information is obviously helpful in developing process improvements that will reduce scrap. Advanced tools, such as Design of Experiments (DOE), can help determine optimal “settings” for each process step.
For example, a DOE project might tell us that one “cook temperature” setting is good when humidity is high, while another “cook temperature” setting is best when humidity is low.
There you have it. Lean and Six Sigma tools have different applications. When it comes to training, you can start with the Lean principles and methods then work your way to Six Sigma tools.
Authored by: Rick Bohan, business consultant for ERC and Lean expert.
