PROCESS CAPABILITY ANALYSIS OF WORK PROCEDURES TO REDUCE WASTE : A CASE STUDY OF AN AUTOMOTIVE PARTS MANUFACTURING PLANT

Abstract

This study focuses on analyzing and improving the process capability for waste reduction in an automotive parts manufacturing plant. A cause-and-effects diagram was employed to investigate and identify the root causes of defects. Process capability analysis was then applied to evaluate the effectiveness of improvements of the Work Procedures. The initial defect rate was 2.9 percent, consisting mainly of surface scratches, dents, discontinuous surfaces, and poor surface finishes. The primary causes were inappropriate insert selection and cutting direction, leading to inadequate tool strength and premature wear. Prior to the improvement, the process capability index (Ppk) was 0.67. After implementing the proposed improvements, the three-step modification process includes altering the cutting tool path direction, adjusting the feed rate, and changing the cutting insert. The defects were completely eliminated, tool life was significantly extended, the process capability index increased to 1.39, and production costs were reduced by 5.10 percent