Case Study on the Application of Six Sigma DMAIC for Reducing Product Rejects in VRLA Battery Production

The high reject rate in the VRLA battery production process has become a critical issue affecting both efficiency and product quality. This study aims to reduce the reject rate by applying the Six Sigma methodology through the DMAIC approach (Define, Measure, Analyze, Improve, Control). The tools utilized include the Pareto diagram, DPMO and Sigma Level trend charts, and the 5 Why Analysis to identify root causes. The implementation results demonstrate a reduction in product mismatch rate from 4.2% to 1.1%. The average weekly DPMO decreased from 23,544.74 to less than 5,000, while the Sigma Level improved from 3.5 to above 4.0. The application of the Six Sigma methodology proved effective in enhancing process capability and reducing product defects.