Application Of Lean Six Sigma Methodology In Defect Reduction: A Case Study Of Kalahari Ash Salt Bagging Plant

Abstract

The purpose of the current manuscript is to discuss the application experiences of Lean Six Sigma (LSS) process improvement methodology in defect reduction. The work discussed in the manuscript pertains to the results that were obtained in the quality control improvement project of the 50Kg Bagging Plant process of Kalahari Ash Processing Company, Botswana, to eliminate product defects. The defects in this case, were defined as the 50 kg filled salt bags not meeting the expected standard weight as per customer specifications. At any given month, these defects amounted to an average of 17.6% of the total production output with a yearly customer compensation loss of about US$40 000. Several LSS tools were applied within the DMAIC (Define-Measure-Analyze-Improve-Control) process improvement methodology from defining the problem through control and up to recommendations that could eliminate the process defects. Tools such as SIPOC (Supplier-Input-Process-Output-Customer) diagrams, Process Maps, Cause and Effect diagrams, Process Capability Analysis and Gage Repeatability and Reproducibility (Gage R&R) were applied in the project. A Solution Selection Matrix was then applied to provide concrete recommendations to eliminate the identified process defects. Through Stability, Linearity and Bias tests the results showed that the weighing equipment was a major source of process variation leading to the observed percentage defects. This variation was due to several factors, one of which was the frequency and timing of the calibration of the weighing equipment. The analysis showed that, by changing the frequency and timing of the calibration of the equipment, a significant defect reduction percentage and improvement in customer satisfaction ratings could be achieved.