یک رویکرد فازی-QFD برای انتخاب تامین کننده

This article suggests a new method that transfers the house of quality (HOQ) approach typical of quality function deployment (QFD) problems to the supplier selection process. To test its efficacy, the method is applied to a supplier selection process for a medium-to-large industry that manufactures complete clutch couplings. The study starts by identifying the features that the purchased product should have (internal variables “WHAT”) in order to satisfy the company's needs, then it seeks to establish the relevant supplier assessment criteria (external variables “HOW”) in order to come up with a final ranking based on the fuzzy suitability index (FSI). The whole procedure was implemented using fuzzy numbers; the application of a fuzzy algorithm allowed the company to define by means of linguistic variables the relative importance of the “WHAT”, the “HOW”–“WHAT” correlation scores, the resulting weights of the “HOW” and the impact of each potential supplier. Special attention is paid to the various subjective assessments in the HOQ process, and symmetrical triangular fuzzy numbers are suggested to capture the vagueness in people's verbal assessments.

Leading business management publications emphasize the need to understand manufacturing decisions and practices for a firm to improve its competitive position. Various publications argue that manufacturing decisions and choices have to be consistent with the corporate strategy for effective operations management. The aim of this study was to get a better understanding of a particular, strategic operating decision area, i.e. the supplier selection process. As more manufacturing organizations are adopting TQM and JIT concepts, the role of the supplier and supply chain management become increasingly important (Verma and Pullman, 1998a and Verma and Pullman, 1998b). In a time of global markets such as ours, the success of an enterprise often depends on its ability to choose its suppliers. Supplier selection is sometimes highly complex, since it incorporates a great variety of uncontrollable and unpredictable factors that affect the decisions involved. All in all, this should prompt careful attention to the way in which such decisions are reached and justified, and would consequently suggest (among other things) the use of decisional models to support procurement decision-making. Moreover, supplier assessments or ratings should be done routinely to ensure that incoming materials meet relevant quality standards (Li et al., 1997). There is much discussion on this topic in the literature and various procedures have been proposed to help deal with the problems posed by supplier selection. Several factors that may complicate the decision-making process, such as incomplete information, additional qualitative criteria and imprecise preferences, are often not taken into account (De Boer et al., 1998). In this article, we propose and illustrate a decisional model for supplier selection that is based on TQM methods such as quality function deployment (QFD), adopting an analysis based on fuzzy logic. The paper is organized as follows: in Section 2, we illustrate some of the topics that are considered strategic in the suppliers selection. In Section 3 the QFD methodology and fuzzy logic are discussed. In Section 4, a case study of an industry that manufactures complete clutch couplings is used to illustrate the application of the proposed method. Finally, a discussion of the fuzzy-QFD methodology and the conclusions are presented in 5 and 6.

The QFD multi-attribute decisional method, designed to support the development of products conforming to the customer's needs and requirements, was applied to the problem of clutch plate supplier selection for an industry that manufactures complete clutch couplings. In this general picture, the QFD—and the HOQ in particular—have demonstrated their potential as key tools for reconciling conventional needs (which remain important) with assessment criteria of the suppliers’ attributes. The fuzzy logic proved to be useful because the main variables neither quantitatively defined nor attributable to specific sets, were expressed as linguistic variables instead and because the general “if–then–else” rules were fundamental tools for linking the input linguistic variables with the system's outputs. The proposed method is therefore used in the selection of semi-processed part suppliers of strategic importance to the company. For the business of the company, the benefits associated with having a formal system in place to identify and continually measure supplier performance are various. First of all, this method offers a tangible means by which to evaluate suppliers. In the light of the heterogeneous capabilities of suppliers, the decision-makers can objectively assess each supplier interface and detect when corrective action may be necessary. Secondly, the information can be used to derive baseline levels of acceptable supplier operational performance. Thirdly, the information captured can be used to identify ‘‘preferred’’ suppliers. Given that ‘‘preferred suppliers’’ have graduated to that status through their exemplary efforts, more future business can be allocated to them. The implication is that less time and lower costs will be required to screen and develop new exchange partners. Fourthly, tracking these metrics can provide the information necessary to prune under-performing vendors from the supplier base. Given that the firm is trying to reduce the breadth of its supplier portfolio in an attempt to increase quality and reduce costs, operational metrics provide the means to accomplish that end (Criterion 6 for the evaluation of the decision models, De Boer, 2003). Some extensions and improvement could be accomplished starting from this methodology. This ordering method could be extended to multi-purpose evaluation, e.g. employee selection, appraising performance of individuals or departments, etc. In the near future this method could be applied effectively to various issues such as policymaking, business strategies and performance assessment and not only to supplier selection. An improvement could be the introduction of variables that take into consideration the inventory management of the items purchased. As De Boer et al. (2001) observed, in existing literature only a few models incorporate the decision to schedule orders over time with the vendor selection decision, although it can be argued that ordering policy and supplier choice influence one another. Some values such as the minimum purchasable quantity and the lot sizing policies of the suppliers can significantly influence the way of managing the purchased goods and the indirect costs to the buyer.