Six Sigma Approach for Rejection Analysis in a Bearing Manufacturing Company through DMIAC Methodology: A Case Study

Abstract

This paper presents a Six Sigma approach undertaken within a needle bearing manufacturing company, by reducing rejection rate of assembly line and improvement in overall sigma level of bearing production with identification of different rejection criteria and reduction of cost of poor quality. The objectives accomplished by the application of Six Sigma approach to quality enhancement research work in the particular needle bearing manufacturing industry. Paper presents Six Sigma approach through five different phases: Define, Measure, Analyze, Improve, and Control (DMAIC). Some of the major findings while carrying out Six Sigma DMAIC tools and methodology on the assembly line of the company was: 1. the vital reason of the rejection of the bearing was due to needle missing from the bearings which is mainly due to loose pocket of welded cage. After repeatedly brainstorming session and applying DOE( Design of Experiment – L8 Orthogonal array), it is found that the reason is related to cage used in bearing. One more interesting finding was related to pocket where butt welding done where defect occurs more frequently. Hence, issues related to production of cage were minutely examined through DMAIC principle and sigma level of assembly line got improved. Six sigma tools used during the research work are SIPOC diagram, Measurement system analysis, Process mapping with identification of KPIV’S and KPOV’S, Current process sigma level, Pareto chart, Cause and effect diagram with cause validation table, Capability analysis, Control charts, DOE, Failure mode effect analysis(FMEA). This research work promotes the importance of six sigma and its application in the present day competitive manufacturing scenario. On the basis of one year data taken and one month after the research work, Increase in sigma level of assembly line was observed. This research work propose in exploring and providing a more clear view on an ongoing problem in the process of welded cage production and a suitable temporary solution was provided with a permanent long-term solution also proposed.