Reliability Centric Six Sigma Evaluation Approach for Manufacturing Process

The inability to achieve the intended design reliability due to variations in manufacturing quality can significantly increase defect rates, ultimately leading to customer dissatisfaction. This concern underscores the critical need for a reliability-focused quality assessment methodology. In this work, an integrated Six Sigma-based evaluation framework is introduced to estimate the potential rise in product failures across a fleet of one million units over a defined period t, specifically when design reliability targets are not met. The approach begins with determining the system’s design reliability through component-level reliability modeling. Subsequently, the actual achieved reliability is assessed using a mathematical model that factors in the quality variations caused by component non-conformance and assembly errors. The gap identified between the design and achieved reliability is then translated into a Six Sigma quality performance measure for the manufacturing process. Additionally, a modified bathtub curve is proposed to depict the interplay between quality and reliability, with a particular focus on estimating the extra failures likely to occur during the product’s burn-in phase due to manufacturing inconsistencies. To further validate the approach, a sensitivity analysis is performed, illustrating how the defects per million opportunities (DPMO) vary with the hazard rate when manufacturing variations are present.