Application of Six Sigma to Reduce Waste from Wire Spokes Production Process: A Case Study on Motorcycle Parts Factory

Abstract

This research aimed to decrease the amount of wastes in the production process of motorcycle parts by implementing the 5 steps of Six Sigma and 7 QC tools. First, the problems were identified through the Pareto Diagram; the problems were then assessed based on the data on damaged parts collected from the production process. The problems were analyzed by applying failure modes and effects analyses to determine the importance of causes, which led eventually to risk priority number that should be followed when selecting the problems to solve. Based on our analysis, the problem related to spokes with incorrect sizes, which is caused by mold wear as well as the problem related to marked wire spokes, which is caused by mold breakage, strongly affected the product quality. The cause of wastes was the mold of the spokes forming machine. Measures for improvement in order to reduce the risk of the problems were identified; one-point-lesson document to disseminate the knowledge for improvement was also prepared and provided. The results illustrated that when the problem of incorrect size spokes was solved, the risk priority number (RPN) decreased; the value prior to maintenance was 384, while it decreased to 85 after the maintenance (or 77.86 percent decrease). Additionally, when the problem of marked wire spokes was solved, RPN decreased from 324 to 75 (or 76.85 percent decrease). The number of incorrect size spokes was also reduced by 71.92 percent; prior to the maintenance, there were 12,964 pieces of incorrect sizes from January to March 2019, while after the maintenance, there were only 3,639 pieces. The number of marked wire spokes reduced by 84.74 percent, from 9,519 pieces from January to March 2019, to 1,453 pieces.