Scrap Reduction in a Piston Manufacturing Industry : An Analysis Using Six Sigma and DMAIC Methodology

Six Sigma at many organizations simply means a measure of quality that strives for near perfection. It is a disciplined data-driven approach and methodology for eliminating defects in any process, from manufacturing to transaction and from product to service. This paper demonstrates the empirical application of Six Sigma and DMAIC to reduce product scrap within a piston manufacturing organization. The paper follows the DMAIC methodology to investigate defects and root causes, and provides a solution to reduce/eliminate these defects. The analysis employing Six Sigma and DMAIC indicates that the design of casting spoon and its material influence the amount of defective pistons produced. In particular, the why-why analysis and two sample t-Test are combined to statistically determine the correlation of the casting spoon design and its material with defects as well as to define their optimum values needed to reduce/eliminate the defects. As a result, a reduction of scrap percentage from 9.9% to 5% was achieved, which helped the studied organization to reduce its Defects Per Million Opportunities (DPMO) from 99,000 to 50,000 and thus improve its Sigma level from 2.86 to 3.2. Also, the process yield was improved from 90.1% to 95% and a saving of 52 lakh/year was obtained