An integrated approach for supplier selection in multi-item/multi-supplier environment

One of the important stages in supply chain management which regards all the activities from the purchasing of raw material to final delivery of the product is the supplier selection process. Since it is the first stage of the supply chain management, it is a critical process affecting the consecutive stages. It is simply desired to select the best supplier for a specific product. But since there are a lot of criteria and alternatives to be considered, numerous decision making models have been proposed to provide a solution to this problem. Within this study, an integrated approach including fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and a mixed integer linear programming model is developed to select the best supplier in a multi-item/multi-supplier environment. The importance value of each supplier with respect to each product is obtained via fuzzy TOPSIS in the first stage. Then in the second stage, these values are used as an input in the mathematical model which determines the suppliers and the quantities of products to be provided from the related suppliers. So as to validate the proposed methodology, an application is performed in air filter sector. (C) 2013 Elsevier Inc. All rights reserved

TEMPO RATING APPROACH USING FUZZY RULE BASED SYSTEM AND WESTINGHOUSE METHOD FOR THE ASSESSMENT OF NORMAL TIME

Tempo rating which aims to obtain the accurate tempo for the workers is an important process for time study applications. It is possible to reach the normal time after finding the precise tempo values. Westinghouse method, based on the factors of skill, effort, environmental conditions and consistency, can be considered as one of the well-known methods among tempo rating approaches. However, crisp numerical values with linguistic terms are used for evaluating each factor in Westinghouse method. In this study, a fuzzy rule based methodology is proposed due to the vague environment of decision making process of tempo rating. The developed methodology includes fuzzy rules for determining the evaluation scores of each factor. The proposed rating system is applied in a bus-bar production system so as to demonstrate its validity. The proposed rating system yields high level of conciseness on the basis of predetermined motion time system

A two stage approach for supplier selection problem in multi-item/multi-supplier environment with quantity discounts

Supplier selection, which is the basic process of finding the best supplier/suppliers to procure the items regarding various criteria, is an important decision problem to be studied. It becomes more complicated if there are various items and any supplier cannot provide all types of items individually. Such situations are called multi-item, multi-supplier environments and rarely studied in the literature. In addition, when quantity discounts are also considered, it gets more sophisticated. Although there are several studies dealing with these aspects separately, to the best knowledge of the authors, this study is the first candidate attempting to solve this type of problem with an integrated approach including Fuzzy Analytical Hierarchy Process (F-AHP) and Mixed Integer Linear Programming (MILP) model. This study mainly operates in two stages. In the first stage, the relative weights of each criterion for each type of item are determined via F-AHP technique. In the second stage, these outputs are used as inputs in the MILP model to determine the suppliers and the quantities to be provided. In order to validate the model, an application is performed in a gear motor company and numerical results of the problem are revealed to select the best suppliers among 6 alternatives, for the procurement of 5 items regarding 4 criteria, namely, price, quality, delivery time performance, and after sales performance, in case of quantity discounts. (C) 2015 Elsevier Ltd. All rights reserved