Application of lean six sigma methods to prevent crank defect in a hospital equipment company: A case study

Abstract

Crank is an important part of the bed to raise and lower the bed. Crank consists of outer pipes, threads, and nuts. Based on observations, crank defect mostly occurred in the production process of thread profiles. The defect is caused by variance in diameter minor and diameter major. This can make the crank stuck. The problem is caused by the carbide insert tool used has worn out because the optimal time of use of the tool has not been considered and process stages that are not in accordance with quality assurance management. The purpose of this research is to reduce defects in the crank production plan and prevent defects after usage by consumers. This paper provides recommendations for improvements in production process management. Lean six sigma aims to improve production line efficiency by reducing production costs, eliminating defects and establishing capability process so that the company can produce high quality product. In this paper define, measure, analyze, improve, control (DMAIC) is used as a lean six sigma tool to solve the problem. Therefore, DMAIC is used to identify, measure, and discover the causes of the problem and to suggest some solutions to control and reduce the defect. The use of simple mathematical model is proposed to determine the optimal used time of the carbide insert tool. The results show that the capability process increases from 3.8 to 4.1 sigma which lead to cost saving from 25-40% to 15-25% quality cost.