Implementation of Six Sigma DMAIC Methodology for Defect Reduction in Automotive Component Manufacturing: A Multi-Plant Empirical Study

Abstract

Defect reduction and process quality improvement remain central strategic imperatives for automotive component manufacturers competing in an era of intensified global competition and increasingly demanding Original Equipment Manufacturer (OEM) quality specifications. This paper presents a rigorous empirical investigation of the implementation and outcomes of Six Sigma DMAIC (Define, Measure, Analyse, Improve, Control) methodology across seven automotive component manufacturing plants located in India, Russia, and Mexico. Using a longitudinal study design spanning 18 months, the research documents pre- and post- implementation performance across four key quality metrics: Defects Per Million Opportunities (DPMO), Process Capability Index (Cpk), First Pass Yield (FPY), and Cost of Poor Quality (COPQ) as a percentage of revenue. The findings demonstrate that structured DMAIC implementation achieves statistically significant improvements across all four quality metrics, with a mean DPMO reduction of 74.3%, a mean Cpk improvement from 0.87 to 1.54, and a mean COPQ reduction of 38.7% of revenue. A novel Quality Improvement Effectiveness Index (QIEI) is introduced to enable standardised cross- plant comparison of Six Sigma programme outcomes. Critical success factors and implementation barriers specific to multi- plant, multi- country deployments are identified and discussed, offering practical guidance for quality engineers and manufacturing executives undertaking Six Sigma programmes in diverse industrial contexts.