Reduction of rejection of cylinder blocks in a casting unit: A six sigma DMAIC perspective

Abstract

Six-Sigma approach is a systematic and scientific operations management methodology aimed at achieving major enhancements in production process through the elimination of waste. In this case, a casting unit manufacturing cylinder blocks has been selected which was experiencing a rejection rate as high as 30% due to formation of blowholes, other than the surface. The main objective of this paper is to identify various causes of occurrence of blowholes and recommend corresponding remedies to counter these defects by systematic implementation of DMAIC cycle. Both preventive and corrective actions have been recommended to reduce the blowholes and overall improvement is validated through two-proportion test. Results of investigation demonstrated the net significant reduction of blowholes defect from 28,111 to 9,708 parts per million, which results in the net annual savings of INR 12,56,640.