APPLICATION OF DMAIC PRINCIPLES BASED ON THE CONCEPT OF SIX SIGMA TO REDUCE DEFECTS IN THE AUTOMOTIVE ASSEMBLY WELDING PROCESS Articles
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Abstract
The purpose of the research was to reduce the waste type of spatter defect in the automotive welding process to not more than 0.2 percent of the volume production per month. The problem is the type of spatter defect. Therefore, waste data was collected for the past 7 months from the total production of 48,260 automobiles. It was found that 490 pieces of waste were in the form of spatter defects, or more than 0.2 percent of the total volume of production per month. Therefore, DMAIC principles are applied as a problem-solving procedure and analysis of root causes with cause-and-effect diagrams. Bring the sub-causes from the analysis to a score level in order of importance. It was found that the sub-cause of scores greater than 80 percent was due to a non-optimal electrical current adjustment. Then, it was chosen to be improved by designing an experiment to find the optimal electrical current value for welding and assembly. The experiment consisted of three related variables: 1) force, 2) time for welding, and 3) welding electrical current value. A 3K factorial experiment was conducted, and the results were analyzed using the Minitab Statistics program. The results of the experiment found that the optimal electrical current value for welding was a pressure value of 3.6 kilonewton/meter, a welding time of 250 millisecond, and a welding current of 7.8 kiloampere, which resulted in the amount of spark generation equal to -0.197, which is a small and optimal amount of spatter. As a result, the average amount of waste before improvement was equal to 0.998 percent per month. After improvement, it decreased to an average of 0.023 percent per month. The Six Sigma level before adjustment was equal to 4.25, and after improvement, it increased to 5.33, indicating the quality level of a better process.
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