An Effective Vendor Management System (VMS) - Enhanced Just In Time Implementation Panyaluck Udomleartprasert 1), Chatriwat Sommechai 2) 1) Assumption University, Graduate School of Computer and Engineering Management (panyaluckud@actth.com) 2) Atotech (Thailand) Company Limited, Senior Account Manager (Chatriwat@atotech.co.th) Abstract The supplier performance has a significant effect on the competitiveness in implementation Just-In-Time and entire supply chain. In this paper, the supplier performance effected in Just-In-Time implementation was described, the supplier must be introduced and developed before being an approved Just-In-Time supplier. Considering, the importance of supplier performance as a part of Just-In-Time implementation, the Just-In-Time will not be successful if no good cooperation from supplier in term of quality and business point of view. This paper proposed the strategies in managing vendor called Vendor Management System (VMS), which shown in the management flow model for development the supplier performance to reach ready state before entering the Just- In-Time. The Vendor Management System (VMS) identifies five phases starting from qualification, measuring, analyzing, implementing and maintaining the supplier performance. The Vendor Management Team (VMT) will implement each VMS phase as proposed steps at a periodic timeframe. The suppliers who reach the ready state level as company goal and expectation will be selected to enter the Just-in-time program. An example of vendor management model in an electronics manufacturer in Thailand showed the effectiveness of the system through the yearly performance and incoming quality lot acceptance rate. Keywords: Vendor Management System, Just-In-Time, Supply Chain Management, Vendor Management Team, Quality Manufacturing Excellent, Ready state 1. Introduction As the growing popularity of just in time and supply chain management, the supplier seems to be more significant role for manufacturing to achieve their customer satisfaction in terms of quality, delivery and business point of view. The smooth running of production line could be interrupted by the poor quality of material. The schedule to delivery will be effected by both poor quality of material and poor delivery performance. Also the manufacturing will get less profit if they select the non-reasonable price of material, as of the material is the cost of manufacturers. In order to achieve the Quality Manufacturing Excellence (QME), the Vendor Management System (VMS) is the one mo st important factor of success. The vendor/ supplier is the partnership that concerned to manufacturer not only the quality but also other business issues [1]. As Vendor Partnership Relation (VPR), it is necessary to work closely between manufacturer and supplier as a team working such as training a supplier s staff about quality techniques, including a design review meeting to gain ideas on how supplier parts can best be used, providing sale projections/ forecasts with supplier to support their production scheduling, sharing information of accept/ reject criteria for manufacturer and supplier, etc. Such this VPR, it leads to establish the Vendor Management Team (VMT) at Manufacturer to assess, work, and coordinate with the vendor partnership at a first stage of production. The supplier development is a vehicle that can be the important factor to increase the competitiveness of the entire supply chains [2]. The supplier development had been studied since the supplier selection phase, the quality of materials, good delivery performance and cost are some of major criteria in selection suppliers [1, 3, 4, 5]. Other than these 3 criteria, AHP was developed to set priorities involving subjective judgements in supplier selection [5,6] and also AHP was to solve the supplier selection problem in supplier management process [7]. The excellence methodology to select the supplier is important phase for VMS, but it is not enough to guarantee whether the supplier will send the excellence quality of product as manufacturer s requirement all along and every shipment. As of the supplier is the Vendor Partnership Relation to manufacturer, the fully cycle to development suppliers must be performed to know and involve the between this Manufacturer-Supplier Relationship (MSR). The supplier development among several researches now are more emphasized on the supplier selection and evaluation [8]. In this paper we have proposed the fully system of Vendor Management System (VMS) program and its model to support the Just In Time and Supply Chain Management that this Vendor Management System (VMS) will cover the supplier development from selection, measure, improve until the supplier achieve the excellent quality. The Vendor Management System (VMS) will also provide the recommendation the Ready Status (RS) of supplier before they enter to the Just In Time (JIT) and Supply Chain Management (SCM). The VMS is included 5 phases as specified in section 3.
2 The Supplier Performance effects Manufacturing JIT The Just In Time (JIT) characteristics are to reduce costs through simplification, improve efficiency by eliminating waste and unnecessary action, affect every function of the organization, can help improve the effectiveness and profitability of a manufacturer, reduce inventory and storage. JIT means changing from a push system of producing as much as possible at high capacity levels to a pull system that produced only to the extent dictated by demand acquired [9]. As the Manufacturing SCM-JIT model in Figure 1.it is represented a revolutionary concept to be strong quality commitment of vendor and manufacturer, continuous quality improvement to achieve the customer satisfaction. The JIT management activities should be included the Realigning supplier relationships such as supplier selection, working closely, continuous improvement on quality system, consistently high delivery performance. In this case if the supplier miss the delivery schedule or send the poor quality material, the assembly line will be disrupted. Also this will effect to the entire supply chains. The Supplier Manufacturing Customer, are always the member of one small business chain. The supply chain relation is the relation of several business chains, and it is incredible that they are effect each other between chain-by-chain. So the management system in each chain is influenced to how good of input to another chain. The Quality Manufacturing Excellence Model is proposed as figure 1, the keys success of this chain are as the followings; 2.1 Vendor Management System The vendor management system is for supporting the good quality of material, delivery on time, good service and cooperation, reasonable price, strong and close relationship to continuous improve, etc. 2.2 Manufacturing System The Manufacturing system is included internal manufacturing management system, quality management system, preventive maintenance, production scheduling and planning, capacity planning, supporting tools such as SPC, etc. All activities are conducted to achieve the customer satisfaction. 2.3 Customer and Customer satisfaction The customer requirement will be effect to the manufacturing system and vendor management system. The customer satisfaction is treated as the most important key success for company and customer feedback is important for company improving. In this research, we studied on the Vendor Management System (VMS), and propose the model for the full improvement system other than selection and evaluation process, we also included the maintaining process for supplier development that are proposed phase by phase. 3 The Vendor Management System Model (VMS) As the Vendor Management System (VMS) is the one of key success to Quality Manufacturing Excellence, several knowledge had been discovered to support and control to get the closer relationship from suppliers or vendor and manufacturer. Supply chain management is one of several ideas that try to point out the important of supplier manufacturing customer relationship. Just-In-Time is also the concept that attempt to get the better service from suppliers such as zero inventory in manufacturing, on-time delivery but more frequent, reduced lot size, setup time reduction, multifunctional workers, small group problem solving, preventive maintenance, pull system, etc. To implement the Just-In-Time, the firms that try to implement JIT by slashing inventory and demanding that their supplier make frequent deliveries to the firms and provide the accurate planning and projection. Supplier deliveries and Kanbans are some of the last elements of JIT to be implemented [9]. The quality of material and supplier s relationship are still the big issues that the firms need to concern, the firm need to introduce some basic knowledge before implementation. And the JIT program can not be successful if the incoming material still have a poor quality, it will stuck the JIT production, inventory planning and schedule and delivery planning to customer. Finally, the Just In Time (JIT) and Supply Chain Management (SCM) are not successful. The Vendor Management System (VMS) is proposed for selecting, measuring, analyzing, developing and maintaining the supplier s performance. The VMS included 5 phases of development starting from Supplier Qualification (SQ), Supplier Performance Measurement (SPM), Supplier Analysis for Improvement (SAI), Implement for Supplier Development and Improvement (IDI), and Maintaining of Supplier Performance (MP). The Vendor Management System should be conducted by the team, The Vendor Management Team (VMT) should include the purchasing, procurement section, quality section as incoming quality control or supplier quality engineer which direct approach to improve vendor s performance, surveillance audit, etc. Several firms try to development their supplier, some firms did evaluate the supplier performance such as measure incoming quality material by lot accept/ reject, some firms did select the supplier by AHP model or benchmarking, but none have fully developed the supplier as proposed VMS model. The followings are the fully system of supplier development that it is call Vendor Management System (VMS). 3.1 Phase I: Supplier Qualification (SQ) The supplier qualification phase will be included the selection of supplier in case the new supplier, the firms must have the system to select the appropriate supplier to deal business. The appropriate supplier is the supplier who has the
Raw Material Suppliers/ Vendor Management System (VMS) Training Quality Control/ Assurance Quality System Process Planning/ Instruction JIT Manufacturer Production Improvement Tools - SPC Management system Preventive Maintenance Customer Satisfaction (CS) Fig. 1 Supply Chain Activity Single Chain Table 1 Phase I Activities Activities Description 1. Information Interchange - Specification defining the product requirements: By firm - Specification defining what quality-related activities are expected of the : By Firm - Constrain of material production from provided specification: By supplier - Inventory plan, delivery plan and scheduling 2. Assessment of Supplier - On capability to meet quality requirements and to qualify the supplier s design through the evaluation of product samples - On Quality System or supplier survey that can be done by visiting supplier site or questionnaire Mailed - On manufacturing process such as the process capability analysis to see how consistency of supplier s production [1] 3. Quotation Process - Provide the quotation as the required time: By supplier 4. First Submission Sample Process - Provide the first sample submission as required specification: By supplier 5. Selection Supplier - Collect the supplier data as above items - Select the supplier by using the firm s techniques such as benchmarking, scoring, etc.
good quality systematic as the firms require, sells the product in the reasonable price with the conformance specification and on time delivery. This phase is a starting phase in supplier development program, both supplier and firm must conduct the joint quality planning, economic planning and technical planning [1]. The firm shall provide the specification, quality requirements, contact persons and other technical information to supplier. The qualification phase for new supplier, the firm can use the benchmark and decide upon to the skills, facility, capacity (that can show indirect about the ability to meet the delivery schedule), expected cost/ pricing, communication channel, etc. If there are more than 1 supplier all above factors can be used by comparing among several suppliers in the meantime. The activities exercised in this phase are in Table 1. Phase I: Supplier Qualification Phase (SQ) Phase IV: Implement for Supplier Development and Improvement Phase (IDI) Phase II: Supplier Performance Measurement Phase (SPM) Phase III: Supplier Analysis for Improvement (SAI) Phase V: Maintaining the Supplier Performance Phase (MP) Fig. 2 Proposed Vendor Management System Model 3.2 Phase II: Supplier Performance Measurement (SPM) After the selecting process of qualified supplier, the business dealing now is started. The suppliers who are the partnership of the company must be measured. The incoming quality control/ assurance is the most important role of this phase. The major purpose of this phase is to know the performance of supplier in term of mass production, shipment, delivery, price, etc other than the quality system as first qualification phase. In this report, we proposed 2 aspects of measurement (1) Quantitative Aspect or Product Aspect The product aspect is included all criteria concerned to product lot by lot submission such as (a) Incoming performance is the lot by lot performance as time to time acceptance. (b) The first sample submission performance is the first time that the company accept the product from supplier and inspect after provide them the requirement and specification. In the other way, if the first submission is always fail and resubmit several times, the company should revise those supplier capability again. Also the resubmission process cause the delay submission time of company to customer that also caused the delay to the entire chain. (c) Cost of poor quality, the poor product quality can cause the higher cost to customer such as the sorting cost of poor quality product. The cost of poor quality also included the defective finished goods in case the poor quality of product were used, the late delivery to customer due to the poor quality of material, etc. All this cost, the company should consider in rating the performance of supplier. (d) The Delivery Performance is one of the most important of measuring the supplier performance as of the late delivery can cause the late submission to all entire supply chain. The examples in calculation are shown in Table 2.
(2) Qualitative Aspect The qualitative aspect is included the service by supplier in term of customer satisfaction which can not directly identify in number such as the time response in request for quotation, the time response in term of action to solve problem, organization/ technology or quality system measuring. The activities of qualitative as aspects are shown in Table 2. This measurement Phase, the firms should weight the criteria as the order of important. Table 2. Phase II Activities: Aspect Activities Quantitative Aspect Qualitative Aspect 1. Incoming performance LAR = (# Lot Accept/ # Lot Rejected) x 100% The weight of total rating is upon to company setting 2. Cost of poor quality measurement For example: Deduct X % for sorting cost Y bath 3. The first submission sample - Approval Rate = #Approval samples x 100% # Submission - Commitment rate = 100 # of missed # of total submission 1. The time response of request for quotation 2. The time response in term of solving problem 3. Organization/ Technology and Quality system measuring The expectation time response or target date can be set by the company 3.3 Phase III: Supplier Analysis for Improvement (SAI) The supplier analysis phase can be done after the company measured the supplier performance in 2 aspects as proposed in Phase II, the analysis of supplier will be looking into the rating result from measurement that may be conducted every quarter, biannual, annual, etc. The company should analyze the weakness of vendor or what the company would like them to improve in both quantitative and qualitative measurements. The activities of this phase are shown in Table 3. Aspect Quantitative Aspect Qualitative Aspect Table 3 Phase III Activities: Analysis Activities 1. Notified defect from the incoming lot acceptance, company should discuss the majoring defect and get the corrective/ preventive action 2. Provide the summaries of quality performance, consider the overall Performance, discuss and find the solution to improve the performance 3. Statistical Process Capability (SPC) of vendor s process, Internal Yield of vendor, Quality system audit score. VMT and vendor should analyze the result together, correct and improve the weakness point, etc. Improvement aspect in term of qualitative result, such as faster response in request for quotation, fast response in solving problem. The mandatory factor that VMT should provide to supplier is the expectation of company such as how many days they want supplier reply corrective action report, or request for quotation. Then the supplier can improve their weak points. This analysis process should be done by all concerned sections that coordinate with the suppliers, this can be called Vendor Management Team (VMT) and the result of measurement should be review at a periodic of time or at least once a year. Vendor Management Team should also consider to the communication strategies of implementation for development as some of the implement is cost a lot, which VMT should consider to the consequence result whether it is reasonable to invest. If the implementation cases are not reasonable, it will cause the obstacle to the next phases. 3.4 Phase IV: Implementation for Supplier Development and Improvement (IDI) The development process is the process that the Vendor Management Team will implement the analysis result from Phase III to vendor system. The VMT should communicate to vendor what is their status of performance, what is the weakness or need improvement item. The detail should be in objective evidence that they can understand and perform the comment easily.
The key success of this Phase is the Vendor Management Team (VMT) should set the target and objective of supplier improvement action and rate of improvement. The setting target should be realistic and commitment between the company and supplier. 3.5 Phase V: Maintaining the Supplier Performance (MP) The maintaining phase will be implemented when the supplier performance is achieved the Satisfied Level (SL). This Satisfied Level should be set up by the Company Goal of Supplier Performance, all the expectations should be communicated to vendor and the vendor should acknowledge themselves to reach this Satisfied Level. Even the vendor reached the Phase V Maintaining stage, it doesn t mean that the Vendor Management Team (VMT) will stop taking action. All the measurement process should be done to know whether all quality performance is really maintained and the periodical review is still necessary to perform. The closely working between company and suppliers is the one of key success to achieve the good supply chain performance. 4. Implementation steps of the Vendor Management System (VMS) to Supplier The supply chain management is still new management strategy in implementation to Thai organization, even we knew that this theory is not new in the world. In implementation to suppliers, the company must spend time to communicate, educate, well - train the suppliers to have the same understanding and commitment of the implementation. The planing steps in implementation of each company are different, but one thing there must be the same is the vendor partnership must be ready to provide the cooperation and get involves. Because the supply chain management is the commitment and cooperation between supplier and company to change their system starting from the stock keeping, foresee planning, cost reduction, etc that in long term the benefit will occurred to both company and suppliers. As we know that the company can not achieve all supply chain programs if the supplier still has a quality problems, delivery problem, etc. The material and delivery problem caused the difficult to forecast anything starting from launch the production till commit the delivery schedule to customer. The company will never know which incoming lot will be rejected or create the problem during production or if the delivery performance of the supplier is not consistently, some are on time or some are missed how can company commit to the customer. These are all the obstacles to develop the supply chain management in company. This VMS can be a strategic mechanism to manage and prepare the vendor system before entering Just In Time and the Supply Chain Management program. In this paper, we proposed the planning steps of VMS imp lementation as the followings and the flow chart is shown in Fig4. 4.1 Set up the Vendor Management Team (VMT) the Vendor Management Team should include (1) Procurement section: Concerned about the new source and suppliers (2) Quality section: Concerned about the quality information both receiving and provide the data, joint the specification, technical, testing methods, requirement in term of technical (3) Purchasing section: Concerned about the planing, delivery scheduling, pricing, etc. 4.2 Assign the Champion for each phase of Vendor Management System (VMS) The champion is the person who takes responsible to coordinate with the vendor management team to achieve the objective of phase. The others person will be the co-champion and support-champion upon to the important of role and activities. The followings are the guideline of champion responsibility for each phase and are shown in Table 4. (1) Phase I: Supplier Qualification (SQ) The general purpose of this phase is to select the vendor as company expectation. So the champion should be from the procurement side, quality side can be the co-champion to provide the information in term of technical. For the purchasing side, there is less concerned before there is still no any buy-sell activities in this phase. (2) Phase II: Supplier Performance Measurement (SPM) The general purpose of this phase is to measure the standing points in term of supplier s performance. The majority to measure are about the quality of product which quality section will be the champion in measuring the lot acceptance, also the delivery performance is the criteria in measuring that this performance will be measured by purchasing section. All data collection should be keep and tracking by the champion which in this phase is quality section. The procurement side will keep monitoring their selected supplier.
Table 4 Champion assigned in VMS activities Phase Champion Co-Champion Support-Champion I: SQ Procurement Section Quality Section Purchasing Section II: SPM Quality Section Purchasing Section Procurement Section III: SAI Quality Section Purchasing Section Procurement Section IV: IDI Procurement Section Quality Section Purchasing Section V: MSP Quality Section Procurement Section Purchasing Section (3) Phase III: Supplier Analysis for Improvement (SAI) The general purpose of this phase is to analyze the implementation program after studying the measuring result from phase II. The analysis must be the brain storming in the vendor management team which all the data must be provided by quality section as in phase II. Also in this phase the purchasing side is the co-champion to support data/ information of problem/ solution in term of response, delivery, etc. (4) Phase IV: Implementation for Supplier Development and Improvement (IDI) The general purpose of this phase is to implement the analysis result form phase III such as the quality program in term of increasing lot acceptance rate, how to achieve the 100% delivery performance, how to get faster response of request for quotation, how to get faster response what is the solution, etc. So in this phase the champion in term of quality is from quality section but the champion in term of delivery and response. In this phase, we set the procurement section to be the champion to follow up all activities that the team has implemented. Which the quality section will also implement the quality program directly to the supplier. (5) Phase V: Maintaining the Supplier Performance (MSP) The general purpose of this phase is to maintain the supplier performance for the supplier who reaches the saturated state as the company expectation. Although, the supplier has a excellent performance but the vendor management activities is necessary to continue, so the measuring phase II is still need to proceed to monitor the supplier performance. In this phase, the activities concerned are more on measuring and communicate the performance to supplier. So the champion should be from quality section, the procurement section should be the co-champion to cooperate and enhance the supplier for the opportunity about further business and relationship with company. 4.3 Set up the periodic review timeframe and schedule for each phase The timeframe for review and monitor the supplier performance is the support factor of succeed. It will create the discipline for both company and supplier to build up the continuous improvement. The followings are the proposed timeframe for each phase of vendor management system. The periodic review for each phase is shown in Table 5. Table 5 Periodic review for each phase Phase I Phase II Phase III Phase IV Phase V Qualification Measuring Summary Analysis Brainstorm Implement of Analysis Maintain Good Performance Starting Quarterly Quarterly Continuous Continuous 4.4 Communicate with supplier about the vendor management program Before implementation the Vendor Management System VMS, the company must introduce the course of the whole program such as How company measure the supplier performance, The expectation of company from supplier, The goal and objectives of the vendor management program, The timeframe of the project, etc. 4.5 Start measuring the current suppliers performance The Vendor Management Team (VMT) should perform this step, and all information should be reviewed and keep tracking by champion of each phase.
4.6 Start the next phase of VMS after get the result of measuring supplier performance 4.7 Discuss and communicate the measuring result and analysis result to vendor at a periodic time The discussion and communication of measuring result, in this paper we proposed every quarter. This step is in measuring and analysis phase. The duration of implementation should be the whole year project for implementation and maintaining phase. 5 Ready state of Supplier Performance to enter the JIT and Supply Chain Management Program The vendor management system is proposed to support the implementation of Just In Time and Supply chain management especially for supplier in Thailand which they are improving the quality and start implementing the Just in time and Supply Chain Management program. In implementation the JIT, the normal steps that company will proceed are slashing the inventory, pull in the material with more frequent delivery schedule, try to achieve the zero defect. In the criteria of achieving zero defective, the company should have the strategies to continuous improve the suppliers before launching the JIT. Definitely, the JIT will be stuck if there is a quality problem of material even it is only one defect piece because the company will have no more material stock and not spend time to inspect every lot of receiving material. The vendor management system should be implemented in the starting project of JIT and should be launch before slashing the inventory of each supplier. The supplier has different ready stage, some suppliers can be implemented the slashing inventory together with the pull in system, etc. The company must ensure whether they will not cause the obstacles of the project. This paper proposed the criteria to set the level of supplier performance before implementing JIT with those suppliers. The level of supplier can be categorized by the result of Measuring Supplier Performance Phase (MSP). They are 5 levels as shown in Table 6. Table 6 Supplier Performance Level Supplier Level Performance Level Status Level Certified Vendor 96 100% Satisfied Level or Ready State for JIT Preferred Vendor 86 95% Satisfied Level or Ready State for JIT Approved Vendor 60 85% Preparing state for JIT Improvement Need 30 59% Improvement need Disqualified 0 29 % Disqualified The supplier who are selected to enter the JIT program, we recommended they should be at least in the Level 2, with no quality problem of incoming lot 3 months consecutive. The supplier of Electronics Manufacturing in Thailand was selected to enter the JIT. They did not create the rejected lot for 3 consecutive months so the manufacturer can ensure the lot acceptance rate of incoming material that will not affect their JIT production line. For their overall performance in year 2001 are as the Fig. 3 Percentage(100%) 100 95 90 85 Packaging Vendor Performance Y2001 91.08 95.96 96.71 96.53 Q1 / 2001 Q2/ 2001 Q3/ 2001 Q4/ 2001 Quarter Fig. 3 Selected Supplier Performance to enter the Just in time of Electronics Manufacturing
Below is the flow chart in implementation steps of vendor management system to Thai supplier. (a). Set up the vendor management teams (VMT) (b). Assign the champion for each phase of VMT (c). Set the schedule for review each of VMS (d). Communicate about the VMS program to supplier (e). Start measuring the supplier performance (f). Start the next phase of VMS after getting the result of measuring supplier performance (g). Discuss and communicate the outcome of measuring, analysis and implement the improvement program Fig. 4 Implementation steps for Vendor Management System 6. Conclusion The vendor management system is a support tool to enhance the Just In Time program, it is included 5 phases in develop and improve the supplier. The Vendor Management System is started from Qualification phase, then measure the supplier performance and analyze the improvement program to develop and improve them in phase II and III. The improvement program will be implemented to supplier after analysis in Phase IV, which the excellent supplier performance will be maintained in the last phase. All activities in vendor management system will be proceed by the vendor management team, normally included procurement who will be the champion in supplier selection and implementation for improvement in phase IV. The quality section who will be the champion in measuring, analyzing and maintaining the supplier performance, and the purchasing section will be the co-champion and support-champion in every phase. In implementation the Vendor Management System (VMS), the company must first set the vendor management team and responsible person to be a champion, co-champion, support-champion in vendor management system project then set the certain time for review the activities in each phase. It is necessary for vendor to acknowledge about the activities in vendor management system and criteria of measurement their performance. Then company can start the measuring and next phase of VMS which the result must be communicated to supplier and have agreed window. Before the JIT program is started, the vendor management should be launched to ensure the quality of material will not affect the JIT production. The supplier should achieve the preferred level or 86 percent of qualitative and quantitative measurement and the incoming lot acceptance should be zero defect for 3 consecutive months. The vendor management system had been implemented some phase in manufacturing in Thailand and the result influence the improvement in term of incoming performance measuring and measurement aspect phases.
In conclusion, this paper has set the systematic strategies and framework that can be used to manage the supplier in the quality aspect and business point of view. The system will contribute to improve the performance of both suppliers and manufacturer, and enhanced the competitive advantages through win-win partnership. 7. Acknowledgements This project can not be completed if there is no assistance from two persons. Firstly for my dear advisor, Dean of Comp uter and Engineering Management, Dr. Chamnong Jungthirapanich who empowered me to have the creative idea in this research. Hopefully, I would have an opportunity to be a co-author of his research paper in the future. Secondly for my boss, Mr. Akanit Boon-itt who always shared his wonderful experience in vendor management which it is very useful to extend the idea in this research. References [1] Juran J.M. and Gryna Frank M., Quality Planning and Analysis, McGraw Hill,Inc. Singapore, 1993. [2] J. Hartley and T. Choi, supplier development: customers as a catalyst of process change, Business Horizons, vol. 39 no.4, pp. 39-40, 1996. [3] C.A. Weber, J.R. Current, and W.C. Benton, Vendor selection Criteria and Methods, European Journal of Operation Research, Vol. 50, pp.2-18, 1991. [4] G.W. Dickson, An Analysis of Vendor Selection System and Decisions, Journal of Purchasing, vol. 2, no.1, pp. 5-17, 1966. [5] S.H. Ghodsypour and C.O Brien, A decision Support System for Supplier Selection using an Intergrated Analytic Hierarchy Process and Linear Programming, International Journal of Production Economics, vol. 56-57, pp. 199-212, 1998. [6] R.L. Nydick and R.P. Hill, Using the Analytic Hierarchy Process to Structure the Supplier Selection Procedure International Journal of Purchasing and Materilas Management, pp.31-36, Spring, 1992. [7] L.M Ellram, A managerial Guideline for Development: Reactive and Strategic Processes, Journal of Operation Management, Vol. 17, pp.39-58, 1998. [8] Purdy Lyn and Safayeni Frank, Strategies for Supplier Evaluation: A framework for Potential Advantages and Limitations IEEE International Research Journal on Management of Engineering and Technology, pp.435-443, 2000. [9] Russell, Roberta S. and Taylor III, Bernard W, Operations Management Focusing on Quality Competitiveness Prentice-Hall International, Inc. New Jersy USA, 1995pp. 734