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Columnist: A. Blanton Godfrey

Photo: A. Blanton Godfrey


The Forgotten Science
Reliability methods are missing in many Six Sigma initiatives.

A. Blanton Godfrey


recently prepared a conference lecture titled “Six Sigma and Reliability: Is There Any Connection?” Because reliability is such a key part of design for Six Sigma and many opportunities exist to apply reliability methods in related projects, I was sure I could put together numerous examples of reliability’s role in most Six Sigma programs. To my surprise, I found very few applications.

Perhaps I shouldn’t have been so surprised. Most companies focus on cost reduction; very few have expanded their projects into design areas or top-line-growth efforts. It could be that companies are still in the early stages of their Six Sigma efforts and haven’t yet considered design or warranty problems or field failures. But why haven’t organizations implemented reliability methods more widely?

In many companies, the reliability function (if there’s one at all) is separate from the quality department or line management. A few years ago, while teaching a design for Six Sigma workshop in an aerospace company, I found that most designers didn’t know what a failure mode and effects analysis was. The company had a reliability department, which was responsible for completing FMEAs on new designs, but the results weren’t shared with the designers. Reliability engineering was considered a separate function.

Also, very little reliability engineering, estimation or prediction are covered in most four-week Six Sigma Black Belt courses. Most design for Six Sigma courses merely introduce these subjects, and most don’t cover life testing. Six Sigma courses have become very rigid. Almost everyone teaches the same topics, and few instructors customize their courses to meet their clients’ real needs. They have the packaged materials, the software, the case studies and the exercises, and they’re intent on going through all the material with no deviations. I suspect that very few Six Sigma instructors are even qualified to teach reliability.

Moreover, most of the time it doesn’t matter whether a Black Belt understands reliability because the company doesn’t have the data it needs for making estimates or predictions. In one company where improving throughput was critical, the only available numbers were hours that the production lines weren’t running. Very little useful information existed for estimating machine failure rates or complete production systems. At many companies, the different functions are so separated that collecting data from failures during or after warranty is almost impossible. Designers receive almost no information on how the products they’ve designed actually perform. Nor do they have information on competitive product performance. If the company lacks information on parts reliability, there’s little a designer can do to predict reliability. And if the company contracts out service and repair, it’s extremely difficult to get reliable information about field failures.

By splitting companies’ operations across many functions, we’ve also made it easy to blame someone else. The service department blames designers, purchasing, manufacturing or even shipping for problems they see every day. However, they don’t really have the information to determine where the problem originated. In many companies, the service function is quite profitable and there’s little motivation to reduce failures. When purchasing has little information on quality or reliability, we shouldn’t be surprised that it buys simply on lowest price. When manufacturing has little information on field failures caused by process changes or shortcuts, we shouldn’t be surprised to see these changes proliferate. When designers don’t receive reliable data about failures during tests or in the field, we should expect to see the same design errors repeatedly.

It’s easy to collect initial quality data on a wide variety of products. Organizations such as Consumers Union or J.D. Power and Associates provide useful quality studies and even make some attempt to portray a product’s reliability, at least during early months or years of use. But for many products, we have no idea of long-term reliability. Trade magazines generally describe the features and test results of only small samples of new product. Many companies find it’s far easier to replace failed items rather than repair them. I was shocked recently to learn that a garment meant to protect against chemical agents lost all protective ability after one washing. It seems that the buyer never bothered to test whether it met the specs of five washings.

So how do we encourage the use of reliability methods? One way is to expand the scope of initial Six Sigma projects. The best way to expand thinking is to provide organized lists of past projects and examples of results from other companies. Clients often recognize that the same problems exist in their companies. It’s also important to become more customer-centered in Six Sigma training and customize material to meet clients’ needs. For four or five people working on reliability problems, provide special sessions to introduce the right methods. Then offer one-on-one support to ensure they learn how to use the right method at the right time. Add follow-up workshops on advanced methods to expand their knowledge and get results in their organizations.

About the author

A. Blanton Godfrey, Ph.D., is dean and Joseph D. Moore Distinguished University Professor at North Carolina State University’s College of Textiles. Letters to the editor about this column can be e-mailed to letters@qualitydigest.com.