Fuzzy Supplier Selection Method Based on Smaller-The-Better Quality Characteristic

Chun-Min Yu,Kuei-Kuei Lai,Chang-Hsien Hsu,Kuen-Suan Chen

doi:10.3390/app10103635

Abstract

Many important parts of tool machines all have the important smaller-the-better (STB) quality characteristics. The important STB quality characteristics will impact on the quality of the end-product. At the same time, supplier quality influences the quality and functionality of the end-product, so suppliers must be selected with caution. The six sigma quality index for the STB quality characteristics can directly reflect process quality levels. Besides, this index possesses a mathematical relationship with process yield. Nevertheless, the point estimation will cause the risk of misjudgment, due to sampling errors. As a result, this study applies the confidence interval of the index to a two-tailed fuzzy testing method, in order to select appropriate suppliers. Now that this method is on the basis of the confidence interval, the possibility of misjudgment caused by sampling errors will be reduced, while the precision of the selection will be enhanced. The method can help companies increase product quality, as well as the competitiveness of the industry chain as a whole. Finally, a numerical example is presented to show how to approach this method and its efficacy.

Highlights

Many important parts of tool machines all have important smaller-the-better (STB) quality characteristics, such as roundness, concentricity and verticality of gears, bearings and axle centers, etc
This study developed a two-tailed fuzzy testing method to select a proper supplier, which is more reasonable than the statistical testing method and more consistent with the discussions made in several studies [12,28,29,30,31,32]
To solve the practical limitation that the sample is so small that the traditional statistical testing accuracy is insufficient, this study develops the fuzzy testing method based on the confidence interval

Summary

Introduction

Many important parts of tool machines all have important smaller-the-better (STB) quality characteristics, such as roundness, concentricity and verticality of gears, bearings and axle centers, etc. The important smaller-the-better (STB) quality characteristics will decide the quality of the end product [1,2,3]. PCIs help manufacturers evaluate process quality during production, but are viewed as a useful tool of communication between engineers working for the same company. This has been confirmed by extensive research [4,5,6,7,8,9,10]. The project of six sigma quality improvement led by Motorola can effectively help companies enhance quality as well as reduce defect rates for production processes [11,12]. According to Linderman et al [13], six sigma assessment helped Motorola achieve its quality-control target of only

Objectives

Results

Conclusion