Six Sigma for improving the quality of the production process: a case study in the inverter manufacturing company

Purpose The development of new energy vehicles is conducive to environmental protection, and the inverter, as a key part of new energy vehicles, its quality level has an important impact on the endurance of the vehicles. The purpose of this study was to empirically demonstrate how Six Sigma (SS) methods were useful in identifying the key influencing factors of inverter quality defects, optimizing and controlling the value of key factors to improve inverse first pass yield (FPY%) and customer satisfaction. Design/methodology/approach A case study approach comprising SS with DMAIC (Define, Measure, Analyze, Improve, Control) was applied. The measurement system analysis, cause and effect matrix, failure mode and effects analysis, analysis of variance and Box-Behnken design of experiments methods were used in C enterprise in China to improve the inverter quality. Findings In this paper, the powerful improvement capability of SS was demonstrated. The experimental results showed that the vacuum reflow peak temperature, the ultrasonic welding frequency and ultrasonic welding amplitude were the key factors influencing the quality of the inverter production. This paper redefined the optimal standard for these three critical parameters, optimized the manufacturing process and increased the first pass yield from 95.84% to 99.6%,the SS level improved from 3.5 to 4.7, resulting in significant social and economic benefits for C enterprise. Originality/value In this case study, the SS methodology applied to the new energy vehicles inverter manufacturing field. It helps the company managers to solve the complex problems encountered in the production of inverters.