Design of Experiments Based Six Sigma DMAIC Application: Electrostatic Powder Coating Process

Six Sigma is a well-structured, data-driven and customer-centered quality engineering approach that focuses on improving product, process and service quality. Statistical engineering, which encompasses quality engineering, focuses on innovation and continuous business development. Being an essential Six Sigma a tool, design of experiments can be regarded as a crucial element of a process and is among the most powerful statistical techniques in statistical engineering. Accordingly, contribution of design of experiments to the firm's sustainable competitive advantage is huge. This study demonstrates how Six Sigma methodology incorporating design of experiments can be applied successfully within household appliances industry to address issues in electrostatic powder coating process. This study aimed to decrease low powder coating thickness defect rate of 47% to at least 20% and to increase the sigma level by using Six Sigma's Define-Measure-Analyze-Improve-Control (DMAIC) steps. The goals of the study were achieved by utilizing various Six Sigma tools and techniques such as workflow, Pareto analysis, measurement-system analyses, control charts, process-capability-analysis and cause-and-effect diagram. Z-test is conducted for different work shifts. For improvement, a two-level four-factor experimental design with two-replicates was implemented. As a result of this design of experiments based Six Sigma project, significant factors and their optimum levels have been determined. Through experimental design, defect rate is decreased from 47% to 17%, which is translated into significant financial savings. Finally, the process performance, which was initially at 3.9 sigma level, has been increased to 4.4 sigma level through the detailed implementation of the Six Sigma DMAIC steps.