Defect reduction using DMAIC and Lean Six Sigma: a case study in a manufacturing car parts supplier

Abstract

Purpose Competitive pressures force companies to seek solutions to eliminate wastes while improving product quality. Lean Six Sigma (LSS) has been considered one of the most effective approaches for business transformation. This article aims to present an empirical case study where LSS and Define, Measure–Analyze–Improve–Control (DMAIC) methodologies are applied to reduce defects in a car parts manufacturer. Design/methodology/approach The study follows the DMAIC methodology. Design of experiments and hypothesis testing were applied in a single case study. Findings The main defects and the main factors that cause defective parts were indicated for die-casting and machining processes. Solutions implemented reduced the defect incidence from a chronically high level to an acceptable one. The sigma level rose from 3.4 s to 4 s sustainably. Research limitations/implications The study is limited to a single case study, without intention of generalizing the results to other types of industries. Practical implications This paper can be a useful guide of how to use DMAIC Six Sigma approach to defect reduction and can be applied in many sectors. Social implications This study offers the knowledge on how to apply the Six Sigma DMAIC methodology, reducing the dependence on specialization courses. Originality/value This study describes in detail the process used in a structured improvement exercise including sigma-level calculation, factorial experiments and hypothesis tests – a set of techniques still poorly combined in the literature.