Reducing Downtime Loss in the Automotive Parts Stamping Process Using Why-Why Analysis: A Case Study.

This research aims to reduce downtime in the production process of automotive part stamping and to enhance the overall efficiency of the machinery, the case study focuses on an 800-ton stamping press in a factory. Data were collected by analyzing the overall equipment efficiency (OEE) using the developed program named Thingworx and observing employees' operations from October to December 2022. The results showed that the OEE was below the target value set by the factory. Most problems occurred during mode change activities with waste investigation such as overprocessing and waiting. It was found that the main factors impacting downtime during the production process are issues from mold changeovers, problems with metal scraps stuck in the machinery, and mold repair issues. Why-Why analysis technique and lean tools including SMED, visual control, and continuous improvement, were used to decrease time spent on non-value added activities. The results from the research showed that the average time for mold changeovers decreased from 8.77 minutes to 3.51 minutes, a reduction of 60.22%. The average time for removing metal scraps decreased from 4.72 minutes to 0.81 minutes, a reduction of 82.76%. Additionally, the time for mold repairs decreased from 1,404 minutes to 448 minutes, a reduction of 68.09%. These improvements led to an overall equipment effectiveness of the 800-ton stamping press increasing from 55.85% to 65.65%, representing a 9.8 percentage point increase. Furthermore, it enabled a reduction in production downtime costs by 298,025 baht per month.