Design for Six Sigma: A Model Partner for QbD

When the concept of Six Sigma was developed at Motorola in the 1980's, its practitioners soon realized it had an inherent flaw that would preclude many manufacturers achieving six sigma levels of performance. Once a process reached five sigma levels, there was often little financial incentive to push ahead to the six sigma threshold. As consultant Murray Adams explains in our recently posted article, "Design for Six Sigma: A Potent Supplement for QbD", "financial gain of further improvement is frequently outweighed by the cost of implementation." The dilemma was called the five sigma barrier.

In a heavily regulated industry such as pharma, however, settling for pretty good will not do. Adams continues: " . . . a 5 sigma process may not be sufficient for many critical process steps. In fact, in the pharmaceutical industry, even the 'world class' six sigma standard (3.4 dpm) is inadequate with respect to the occurrence of some critical defects. Given the limitations of the 5 sigma barrier, how can we achieve an appropriate level of process performance while maintaining a competitive operating cost?"

The answer that the Motorola folks came up with was to adapt some of the tools of Six Sigma for the early stages of product design--thus, Design for Six Sigma was born. There isn't a good understanding of the differences between DfSS and Six Sigma in the drug industry, Adams believes, but pharmaceutical development teams would be well served to incorporate more DfSS into their practices. Once they do, he says, they'll find that many of its tools--such as Monte Carlo Simulation, Parameter Design, and Tolerance Allocation--complement Quality by Design concepts and support initiatives being undertaken under the QbD umbrella.

Those interested in learning more on Monte Carlo Simulation should also read "Leaning on Six Sigma and Predictive Modeling in a New Industry Paradigm," by Oracle's John Danese and Fred Ciochetto. This PharmaManufacturing.com article also includes references to other resources on the topic.