Improvement Study on Six Sigma Mechanical Design Tolerancing with Design of Experiment

Six sigma as an approach of business improvement has become a long strategy for many famous international enterprise. Six sigma mechanical design tolerancing proposed by Motorola Inc. is an effective method to achieve six sigma level. Although the approach has many advantages, it depends on many hypotheses and has some limitations. Then studies on how to improve it with the methodology of design of experiment are performed. The improved method overcomes the weakness of the original method. A cost function is developed to evaluate and show that the optimized results not only are robust to natural sources of manufacturing and material variation but also without cost increase. In order to validate its validity, an application study is demonstrated. On the basis of comparative analysis, it can be concluded that the improved method is more effective than itself and the total cost is reduced.