Defect reduction using Lean Six Sigma and DMAIC

Purpose – Competitive pressures forces companies to seek solutions to eliminate wastes while improve product quality. Lean Six Sigma has been considered one of the most effective approaches for business transformation. This article aims to present an empirical case study where Lean Six Sigma and DMAIC methodologies are applied to reduce defects in an auto parts  manufacturer.

Design/methodology/approach – The study follows the DMAIC methodology to investigate the root causes of defects and offer the solutions to reduce them. Design of experiments and hypothesis testing were applied in a single case study with interviews in the DMAIC steps sequence.

Findings – The analysis carried pointed out the main defects in each of two manufacturing phases: die casting and machining. Mold temperature, metal temperature and second stage injection speed influenced the amount of defective die casting parts. On the other hand, the incidence of defects in machining process was affected by the fixation method. Solutions implemented reduced the defect incidence from a chronically high level to an acceptable one. The sigma level rose from 3.4 σ to 4σ sustainably.

Research limitations/implications – The study are limited to a single case study, without intention of generalizing the results to other types of industries.

Practical implications – This paper can be used for those who intend to use the same type of improvement methodologies.

Originality/value – This study describe in detail the entire process used in a structured improvement exercise.

Defect reduction, Lean Six Sigma, DMAIC