متدولوژی ترکیبی برای انتخاب تامین کننده و ارزیابی عملکرد

Today, organizations that wish to carry on the sustainable growing need a robust strategic performance measurement and evaluation system because of changing demands of consumers, reduced product life cycle, competitive and globalised markets. In this study, a new methodology is introduced and proposed for increasing the supplier selection and evaluation quality. The new approach considers both qualitative and quantitative variables in evaluating performance for selection of suppliers based on efficiency and effectiveness in one of the biggest car manufacturing factory in Turkey. This new methodology is realized in two steps. In the first stage, qualitative performance evaluation is performed by using fuzzy AHP (Analytical Hierarchical Process) in finding criteria weights and then fuzzy TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) is utilized in finding the ranking of suppliers. So, qualitative variables are transformed into a quantitative variable for using in DEA (Data Envelopment Analysis) methodology as an output called quality management system audit. In the second stage, DEA is performed with one dummy input and four output variables, namely, quality management system audit, warranty cost ratio, defect ratio, quality management. As a result, comparing with the present system applied by the car factory, the new method seems to be some advantages and superiorities for making the decision in buying the quality car luggage side part (panel) by selecting the suitable supplier(s) in an automotive factory of Turkey.

To choose the right supplier deals, with an important evaluation, and selection problems in the purchasing function of a business. A good supplier selection makes a significant difference to an organization’s future to reduce operational costs and improve the quality of its end products. There have been a lot of factors in today’s global market in which that influence companies to search for a competitive advantage by focusing on purchasing raw materials and component parts represents the largest percentage of the total product cost. For instance, high technology products such as motor vehicles, railroad&transport equipment, machinery&equipment components, purchased materials and services account for up to 80% of the total product cost. Therefore, selecting the right suppliers is a key to the procurement process and represents a major opportunity for companies to reduce costs. On the other hand, selecting the wrong suppliers can cause operational and financial problems (Weber, Current, & Benton, 1991). The traditional approach to supplier selection has been to select suppliers solely on the basis of price for many years. However, as companies have learned that price as a single criterion for supplier selection is insufficient, they have turned into more comprehensive multi-criteria decision making techniques. Recently, these criteria have become increasingly complex as environmental, social, political, and customer satisfaction concerns have been added to the traditional factors of quality, delivery, cost, and service. Apart from cost reduction, companies continuously work with suppliers to remain competitive by reducing product development time, improving product quality, and reducing lead times. For instance, a qualified base of suppliers helps a company achieve greater innovation through improved product design and increased flexibility. Some authors have identified several criteria for supplier selection, such as the net price, quality, delivery, historical supplier performance, capacity, communication systems, service, and geographic location, among others (Dempsey, 1978). These evaluation criteria involve trade-offs and are a key issue in the supplier assessment process since it measures the performance of suppliers. For example, one vendor may offer inexpensive parts of slightly below average quality, while another vendor may offer higher quality parts, with uncertain delivery thus setting up trade-offs. In addition, the importance of each criterion, varies from one purchase to the next and is complicated further by the fact that some criteria are quantitative (price, quality, etc.), while others are qualitative (service, flexibility, etc.). Thus, a technique is needed that can adjust for the decision maker’s attitude toward the importance of each criterion and incorporates both qualitative and quantitative factors (Bhutta & Huq, 2002). The overall objective of the supplier evaluation process is to reduce risk and maximize overall value to the purchaser. An effective supplier survey should have certain characteristics such as comprehensiveness, objectiveness, reliability, flexibility and finally, it has to be mathematically straightforward. It can be concluded that important savings can be realized through effective purchasing strategies. This study helps decision makers reduce a base of potential suppliers to a manageable number and make the supplier selection by means of multi-criteria techniques. This new methodology was applied to a car manufacturing facility in Turkey.

In this study, a new methodology is introduced and was applied in a car manufacturing factory for the selection and evaluation of quality supplier(s). According to the solution of aforementioned analysis, two suppliers (A2, A4) are defined as “non-efficient” vendors in manufacturing the luggage side part (panel). Hence, other five suppliers (A1, A3, A5, A6, A7) are the candidates which will be chosen for buying these components and will be able to join the bidding system for manufacturing luggage side panel. At the end of this evaluation process, the supplier which will be able to give the best price will be selected for luggage side panel production after the bidding and negotiation meeting. The OEM (Original Equipment Manufacturing) has its own supplier evaluation system as other OEMs have. According to the running system in the factory, after the yearly evaluation, suppliers should increase their performance and prove them with evaluation items. The most important evaluation item for the OEM is Quality Management System Audit which is qualitative, but this system audit is transformed into a quantitative result by a specific evaluation sheet on the basis of item points as shown in appendix (each supplier is audited once in a year). After performing an audit, improvement points are listed with a pictured audit report which is based on “Before–After” system. Supplier should reply the audit report within 15 days and put the pictures for closed actions. If an action closing requires more time, supplier needs a target date for unclosed actions and should close it on time. If not, the related audit item, Corrective&Preventive Actions Management, score will be “zero” and other related items, e.g. Quality and Environmental Management, will be low scored according to current audit situation. Hence, it will reduce next audit score and supplier will have disadvantages for the new projects. In general, the car company will ask for quotations from all seven suppliers and will have negotiation meetings with all of them. One supplier will be eliminated in each step and finally one supplier will be selected, but this will take almost two months which is very short duration for seven different quotation evaluations. Hence, supplier selection will be made in rush and some important cost and price items will be missed due to job stress caused by short supplier selection period. On the other hand, the car factory can prolong this period, but it will cause project to be delayed. At this point, our study will be a helpful sample for the other implementing businesses since ineffective suppliers (A2, A4) will be directly removed from part producer pool and quotation will not be requested from them. So, five suppliers will present their quotations and join the negotiation meetings. Consequently, two months quotation evaluation and supplier selection period will be used more effective. In the current running system, supplier quality level is used for supplier selection as qualitative when two suppliers have very close, similar quotation. For this reason, suppliers are informed and invited to present their final quotation. If there is not a reasonable difference between their prices given, supplier whose quality level is high is selected as part producer. Otherwise, supplier which gives the best price for the part is selected as supplier. In our application, current supplier for car luggage side part (panel) is supplier A7 for A type car. This situation shows that supplier A7 gave the best price for the part and got the project, but none of quality evaluation was done before project was given to the supplier A7 except pre-mass production. In the history, we see that suppliers A4, A6, and A7 presented their quotations. The price sequence is (from lower to higher) occurred like suppliers A7, A6, and A4. According to our study, supplier A4 would directly be eliminated from the list before company requested part quotations and suppliers A7 and A6 would be focused. Consequently; – Supplier A7 was chosen as the supplier for company. – Supplier A6 would be chosen as supplier according to our study. Quality performance of both suppliers in the year 2008 is shown in Table 15. Table 15. Quality performance indicator (PPM) of the year 2008. Suppliers Part reject status (2008) Accept Reject PPM A6 463,148 262 566 A7 260,633 348 1335 Table options Supplier A6 is better than supplier A7 according to quality performance indicator of the year 2008. If we think that the rejected parts are scrapped, this is a very important result because the loss of supplier A6 caused by rejected parts is reasonable to think provided that the production of luggage side part is feasible. As a matter of fact, part rejects are the biggest portion of problems as supplier looses money and it requests cost increase to be able to compansate its loss. This can take the company to make source change which is transferring the part to another supplier because OEMs do not want to increase part prices unless any unexpected things happen (e.g. raw material increase). Supplier assures part quality before starting the project and can not request any extra money (cost) about part defects and repairs. This analysis also shows us qualitative and quantitative outputs are not the exact decision making tools alone. According to the qualitative evaluation, company should choose A1 as supplier, but this time it should be ready to face with potential part problems such as PPM. On the other hand, according to quantitative evaluation, company should choose supplier A7, but that time it should be careful about the quality system of supplier and be ready to face with part problems, because PPM and warranty claim problems have direct connection with poor process development. Process development is placed in supplier quality system. If potential problems can not be caught during project development stage, it will bring lots of problems and concerns. Hence, before the supplier selection and evaluation, both qualitative and quantitative indicators should be considered together and combined. So, risks will be not only minimized and but also be analyzed efficiently and effectively.