Operating Window Experiments: A Novel Approach to Quality Improvement

The operating window method is a novel tool in quality engineering. It has been practiced in some industrial sectors but has received scant attention in academic research. If a critical factor for competing failure modes can be identified, the probability of failures can be reduced by widening the operating window of this factor, thus improving the system's quality and reliability. A rigorous foundation is given for some existing practice, particularly the operating window signal-to-noise (SN) ratio. A new strategy is given for design, analysis, and system optimization, which is an improvement over existing practice. We illustrate our approach with the analysis of a wave soldering experiment.