Failure cost reduction in Dioctyl Phthalate manufacturing process using Six Sigma approach

Abstract

This objective of this research is to reduce the failure cost production in Dioctyl Phthalate (DOP) manufacturing process by using Six Sigma approach. Six Sigma approach consists of 5 phases which are Define phase, Measure phase, Analyse phase, Improve phase, and Control phase. In the Define phase, the problem of failure cost in DOP finished product and objective of the project were identified with the scope focusing on reducing failure cost regarding two types of defects: high colour and low resistivity. Then, in the Measure phase, process capabilities of DOP finished product were calculated the measurement system evaluation and verification were performed by calibration and Gage R&R method. After that, in the Analyse phase, the causes of the defects were identified by brainstorming and organized by the Cause-and-Effect diagram. Then, the causes of defects were prioritized by applying Failure Mode and Effects Analysis (FMEA). Then, in the Improve phase, Design of Experiment (DOE) was applied to determine significant causes that affect the quality of DOP finished product colour and low resistivity value. Then, optimum factor operating conditions were determined. After implementing the new operating conditions, control charts were used to monitor a process and to inform when to take corrective actions in the Control phase. The results of this research are that the process capability of colour parameter was improved from 0.92 to 1.48 and from 1.03 to 1.57 for resistivity value parameter. Thus, the failure cost of DOP reprocessing was reduced from 1,327, 368 baht quarterly in 2007 to 0 baht in the first quarter of 2008.