Dağıtımda stok sistemleri ve hedef programlama uygulaması

Abstract

Günümüzde kuruluşlar pazar etkinliklerini arttırmak için dağıtım sistemlerini geliştirmek yoluna gitmişlerdir. Marka bağımlılığinın yerini marka bilincine bıraktığı pazarlarda, rekabet gittikçe artmıştır. Birinci bölümde, genel olarak dağıtım sisteminden bahsedilmiştir. İlk olarak dağıtımın tanımı yapılmıştır. Dağıtım sisteminin işlevlerinden, dağıtım zinciri ve dağıtımın değeri gibi kavramlardan bahsedilmiştir. Daha sonra dağıtımm amaçlan, dağıtımın maliyeti ve dağıtım operasyonları anlatılmıştır. Dağıtım planlama ve dağıtım planlamanın prensiplerini takiben dağıtım sistemlerinin geliştirilmesi, dağıtımm analiz edilmesi, üretim ve pazarlamanın maliyetler üzerinde etkileri, bir dağıtım sisteminin planlanmasi ve tasarlanması açıklanmıştır. Son olarakta, sistematik bir metot olan Dağıtım Kaynak Planlama'mn (DRP) aşamaları belirtilmiştir. İkinci bölümde, dağıtımda stok sistemleri yönetiminden bahsedilmiştir. Dağıtımda stok yönetimi sistemlerinin, çekme ve itme sistemleri olarak, ikiye ayrıldığı açıklanmıştır. Daha sonra, çekme sistemlerinin içerdiği sipariş noktası sistemi, periyodik gözden geçirme sistemi, çift sipariş noktası sistemi, satışı yerine koyma sistemi ve çekme sistemlerinin avantajları, dezavantajları ve temel stok sistemi anlatılmıştır. DRP, tahsisat ve itme sistemleri açıklandıktan sonra itme sistemleri ile ilgili bazı önemli noktalar belirtilmiştir. Üçüncü bölümde, karar analizlerine ve karar destek sistemlerine giriş yapılmış, çok amaçlı karar verme yöntemlerinden Hedef Programlama tanıtılmıştır. Daha sonra, Hedef Programlama çözüm yöntemleri grafik yöntem ve Simplex yöntemi örneklerle açıklanmış ve hedef programlada ileri teknikler anlatılmıştır. Dördüncü bölümde ise, dağıtım planlama ve çok amaçlı üretim için bir matematiksel programlama modeli açıklanmıştır. Sırası ile modelin amaçlan ve hedefleri, modelin yapısı, modelin değişkenleri, modelin kısıtlan ve hedef denklemleri tanımlanmıştır. Beşinci bölümde ise, uygulamanın yapıldığı şirket olan Grünberg Ticaret A.Ş.'den bahsedilmiştir. Firmanın Profilo Holding kuruluşu olduğu belirtilmiştir. Aynca firmanın tarihçesi ve dağıtım sistemi özetlenmiştir. Firmanın dağıtım sisteminin hedef programlama modeli kurulmuş ve mevcut verilerle çözülmüştür.

Physical distribution is a matter of economic priority on a national scale and its importance is increasing. Recently, there is a tendency of globalization of economies in conjunction with declining duty taxes. Therefore, in this heavily competitive global market, companies are forced to have better planned, controlled and quality finished products which must be distributed in the most efficient way. Furthermore, companies have to review their public relations, image, quality and distribution policies due to this competitive environment. In this perspective, it is clear that the companies having their distribution strategies and policies based on their products' specifications, types, quantities and market condition, are increasing their influence in the market. In the past, cost reduction effort tended mainly to be directed to the control of direct labor and production plant cost in manufacturing and processing. Some techniques, such as value analysis, have demonstrated the relative economic significance in the different functional areas; in the more progressive firms, top management is directing attention to the greater economies to be derived from well-planned warehousing and transportation. The distribution system covers the whole range of operations and movement of goods between the producer and the consumer. The requirements of maximum performance in each different area of activity are often conflicting and the operational system will be that compromise which produces the best overall result. This is achieved when a distribution system automatically coordinates the actions of the managers controlling each area of the activity and can test the effect of changes in one area on the performance of others. The main function of a distribution system is to provide the customer with goods in the right condition, at the right time, at the right place, in the right quantities and at an economical cost. As the market is likely to be continiously changing, the performance of the system in this dynamic situation should be tested at regular intervals for efficiency in operation and robustness against the predictable and unforeseen changes. Only in this way can the investment be safeguarded. Distribution systems can be greatly affected by both internal and external changes, often outside the control of management. Typical internal changes are growth, change in commodity mix, technological opportunity and rationalization after take-over or merger. External changes can be caused by national and international legislation, technological development, competitors' activity and market shift. Therefore, there is a need for a planning, design, management and communication system which will detect these changes and react to them as they occur. IX In the first chapter, the following topics are covered: - Function of distribution; the objective of a distribution system is to match the production output to the market demand by holding goods until they are required and delivering them when demanded. According to these objectives, there are two basic functions of distributing; warehousing and delivering products. - Objective of distribution; the overall objective of distribution is to provide a service to the marketing and production functions by holding and delivering the products efficiently and economically. Secondary objectives can be related to warehousing, delivering and planning the distribution system. - The cost of distribution; it is related to these three objectives, but they will vary according to the number, sizes and locations of warehouses which influence the numbers, sizes and types of vehicle and the personnel employed. - Distribution operations; there are two kinds of operations in distribution, the physical movement of products and the transmission of products for the purpose of control. - Influence of warehousing factors on plans; the major objective of warehousing is to provide the " surge capacity ". That is needed to overcome fluctuations in supply or demand. Planning the number and locations of warehouses will depend upon the distribution objectives and the distribution variables of a system. - Distribution planning principles; the purpose of a distribution system is to move products from the point of manufacture to their market for the least cost consistent with providing good service. The type and the size of distribution system will be determined by the character of products and the geographical area served. The basic components of distribution system are; types of products, range and volume of products, geographical spread, level of service expected, number and types of customer, relatives costs and finance available for investment. One measure of distribution performence is the analysis of the average and greatest length of time that elapses between an order being placed and goods being received. Some examples showing the different ways that service level can be improved are; direct delivery from factory to customers, trunking delivery to warehouses, local delivery to retail outlets, intermittent delivery to the public and continious delivery direct costumers. The analysis of the design of distribution systems must be made in three broad production categories; group manufacture of a wide range of products, group products of narrow range of products and sole manufacture of a single product. Production considerations and marketing considerations; production considerations are least when the factory is sited near the raw materials. An efficient distribution system is necessary for promoting more sales and there must be mutual relations between marketing and distribution systems. Planning a distribution system must be a joint venture that considers the overall needs rather than individual needs alone. Thus production and marketing needs can be satisfied optimally. Long term planning has to provide answers to questions concerning the type of system to be operated, the sites for supply points, the allocation of manufacturing plants to factories and goods to warehouses. The near future will be considered in short term plans which include a detailed examination of operations over the length of a cycle, a season or a year. The design of distribution system can be thought in four stages; the policy making stage, the long term planning stage, the short term planning stage and the controlling stage. - İn this part, a systematic method of distribution resources planning in 12 steps is stated. In the second chapter, the management of distribution inventory and the integration of administrative and physical control systems with the inventory planning system are discussed. In this chapter the following topics are covered: - The traditional pull system is to order without regard for the needs of other warehouses, the inventory available at the central warehouse or the production schedule. Pull systems include the order point system, the periodic review system, the double order point system and the sales replacement system. The base stock system, which may exhibit some push systems characteristics, is primarily a pull system. The advantages of a pull system are; ability of operating autonomously and having low data processing and communication expenses. The disadvantage of a pull system is that orders are submitted without regard to available inventory, production schedules, shipping plans and combination of shipments, or irregular occurences. In the base stock system, as these deficiencies in pull system have been recognized, communication between regional warehouses and the central supply has increased and greater control of shipping quantities has been placed at the central supply. Thus, the base stock system with the basic characteristics of a pull system have taken on some characteristics of a push system. XI - Push systems, as the names implies, are based on centralized control with a push of stocks down to the lower echelons based on system-wide viewpoint. This broad viewpoint and elimination of "surprise" large replenishement orders should reduce the costs to achieve a given customer service level or improve the service level for a given total stock investement. The push system goes beyond the base stock system in two important ways. First is tendency to project actual requirements at any particular branch well into the future rather than using forecasting procedure. Second, the allocation decision is based on the system stock level and all of the projections. The methodology of Distribution Requirements Planning (DRP) is similar to the methodology of Push system in the sense that actual requirements are projected at each branch. The important differences is that lot sizes in DRP are established locally by the branches themselves. DRP ties production and distribution planning together by determining aggregate time-phased net requirements at the same point in the material flow as the Master Production Schedule (MPS). DRP avoids problems by projecting branch warehouse requirements by period and generating planned orders on the central warehouse. DRP is especially beneficial when shipping cost factors make it advisable to ship in large quantities at relatively infrequent intervals. A push allocation system works especially well when there are regular shipments to branch warehouses or when shipping costs do not require the shipment of relatively large quantities. Push allocation can combine the projection of branch warehouse and central supply requirements by period. In the third chapter, the decision making process is defined and 'Multiple Criteria Decision Making' (MCDM hereon) is discussed. The mathemetical analysis of 'Linear Goal Programming', one of the techniques used in MCDM, is made and linear goal programming modelling is analyzed in detail. The MCDM solution techniques can be classified as Graphics Method and Modified Simplex Method. Finally, advanced topics in goal programming are mentionned. In the fourth chapter, it is concerned with the development of a model for aiding management decision making in a multiple processing environment. The situation considered is one with several manufacturing locations and transshipment points over several time periods. A multiple goal model is developed to aid decision makers in determining both production and shipment patterns while considering various goals, such as : (i) minimization of the deviation from the desired level of total costs; (ii) minimizing the deviations from the goal levels for final inventories; (iii) mmimizing the deviations, from their desired goal levels, of the amounts of certain items that are produced at various plants and/or shipped over certain routes. In the fifth chapter, we discuss an application made in Grünberg Tic. AS. This company, which is a member of Profilo Holding, is the general distributor of AEG and XU Telefonken durable consumer goods in Turkey. It is also stated in the chapter about the history of the company and the distribution system of the company is described. Later in the chapter, a problem related to the distribution system at Griinberg is explained. This problem is modelled via 'Goal Programming' approach and applied to an existing computer application.