Improvement of OEE performance using a Lean Six Sigma approach: an Italian manufacturing case study

Lean Six Sigma is a well-consolidated approach for improving processes. However, for some companies the use and project management of Six Sigma tools and Lean Production is unclear. The aim of this paper is to illustrate the use and project management of Six Sigma tools and Lean Production by discussing a novel case study dedicated to the improvement of overall equipment effectiveness (OEE). The case study was conducted in a medium-sized company which produces injection moulded parts in plastic using several presses. One of these machines had a poor OEE with a large variability. This led to the company not satisfying a customer in terms of on-time delivery performance. The poor OEE led to high costs in terms of work-in-process and re-inspections of the products. Following a typical define-measure-analyse-improve-control (DMAIC) pattern, a dedicated team of the company defined the set-up times and the internal diameter of the product as critical to quality characteristics (CTQs). The root causes of the variability of the CTQs were identified through a cause-effect diagram and a Chi-square test. Afterwards, the team removed the root causes and improved the CTQs which have increased the OEE from 40% to 61%, reducing its variability. Tools such as 5S, Single Minute Exchange of Die and poka-yoke were implemented to remove the root causes.