Cost Reduction in Automotive Parts Production by Applying Sampling Standards

Abstract

This study aims to improving the weld seam inspection sampling process in an automotive parts manufacturing facility, particularly for TAO model components. The improvement involves implementing the MIL–STD–105E sampling plan to replace the previous non–standard inspection method. Initially, three samples per lot were inspected, leading to high inspection costs due to the destructive testing nature, totaling 167,040 baht annually. The improvement strategy included historical data analysis, control chart implementation, and adjustment of the sampling plan. Results from the control charts indicated that the production process remained within control limits, allowing the application of switching rules from normal to reduced inspection. By adopting the MIL–STD–105E plan and negotiating acceptable risk levels with customers, the number of samples per lot was reduced from three to two. Consequently, annual inspections decreased from 1,392 to 1,008 pieces, cutting inspection costs to 120,960 baht—resulting in savings of 77,310 baht per year. These findings confirm that the process remains under statistical control while significantly reducing inspection costs in quality control.