Reduction of Heat Seal Leak Defect in Lead Acid Battery Assembly Process by Using Structured Problem Solving Approach

The objective of this study is to reduce the heat seal leak rejection in the lead-acid battery assembly process using Six Sigma’s DMAIC (Define, Measure, Analyze, Improve and Control) methodology. In the DMAIC methodology, Shainin tools and techniques has been used to identify and validate the causes. It was found that material sticking to the hot plate and stringing of the melt is a cause of the problem. The melt that remains on the hot plate degrading and transferring to the subsequent welds, resulting in poor welding. This is suppressed by advanced chromium (Cr+) coating on heat sealing platen. After implementing the solution, the heat seal leak rejections are significantly reduced by 65 % and platen cleaning frequency reduced by 50 %.