Tam zamanında satınalma felsefesi ve bir simülasyon uygulaması

Abstract

ÖZET ikinci Dünya Savaşı' ndan sonra ağır bir yara alan Japon ekonomisi yeni teknolojik arayışlar içine girmiş ve üretimde kaliteyi arttırıp, maliyetleri düşürecek bir sistem üzerinde çalışmaya başlamıştır. Bunun sonucunda da Tam Zamanında üretim Sistemi (TZÜS) ortaya çıkmıştır. Tam Zamanında üretim sistemi sadece üretim alanında kullanılmakla kalmayıp, satınalma alanında da önemli sonuçlar elde edilmiştir. Birinci bölümde,. Tam Zamanında üretim ' in (TZÜ) kısa bir tanımından sonra, TZÜ kavramının ne olduğu ve ne şekilde yanlış kullanıldığı incelenmiştir. İkinci bölümde ise. Tam Zamanında üretim sistemi tanıtılacak, aşamaları belirlenecek ve Japonya' da ürün kalitesi ve verimlilik artışının sebepleri araştırılmıştır. üçüncü bölümde ise, geleneksel satınalmanın ana fonksiyonlarına, diğer organizasyonel fonksiyonlarla bağlantılarına, satınalma yönetiminin hedeflerine, satıcı ilişkilerine, satınalmanın sorumluluğununa, hedeflerinine ve stratejilerine değinilmiştir. Dördüncü bölümde. Tam Zamanında (TZ) satınalma kavramı açıklanmış, TZ satınalma sisteminin uygulanması ve TZ satınalma ile geleneksel satınalma arasındaki farklılıklar belirlenmiştir. Beşinci bölümde, Kanban sistemi tanıtılarak, kuralları ve sınırları belirlenmiştir. Tek ve çift kartlı Kanban sistemleri tanıtılarak, satınalma faaliyetine uygulaması incelenmiştir. Altıncı bölümde TZÜ sistemi içinde nakliyenin önemi ve organizasyonu incelenmiş ve nakliye maliyetlerinin azaltılması üzerine bir araştırma yapılmıştır. Yedinci bölümde, TZ satınalma faaliyetlerinin uygulanması sırasında karşılaşılan problemler belirlenerek, bunlara uygun çözüm yolları aranmıştır. Sekizinci bölüm olan uygulama bölümünde ise, TZ satınalma sistemine uygun bir simülasyon modeli geliştirilmiş. Bu sistem kullanılarak bir firma üzerinde yapılan uygulama açıklanarak sonuçlar yorumlanmıştır. -x-

SUMMARY JUST-IN-TIME PURCHASING AND A SIMULATION STUDY For a company, Purchasing is a window to the outside world. The prime function of purchasing, is that of being sensitive to the external supply market situation and also of feeding hack this information to the other function of the company. Purchasing has important links with most of the organizational functions. Purchasing has many benefits like, - To supply the organization with a steady flow materials and services to meet its needs; - To select the best suppliers in the market? - To protect the company' s cost structures - To maintain sound co-operative relationships with other department, providing information and advice as necessary to ensure the effective operation of the organization as a whole; - To monitor supply market trends; In the early 1950' s, a unique production system emerged in Japanese manufacturing companies that contributed substantially to Japan` s high product quality and productivity. During the past two decades, Japan' s annual productivity increase rate in manufacturing was 9.3 7. as compared with a 2.7 % increase in the USA. This distinctive Japanese system ie widely known as Just-In- Time <JIT) production. An important aspect of JIT that has had a great influence on product quality and productivity is JIT purchasing. JIT purchasing is an important element of this unique Japanese production planning and inventory control technique. JIT purchasing is effective for the f oilowinqs - Controlling the inventory system. - Reducing buffer inventories. - Reducing apace needed. - Reducing material handling. - Reducing wasted materials. This thesis consists of the following chapters? -3Sİ-In the first chapter, the definition of JIT is given. Then the misunderstanding of JIT and the right philosophy of JIT is explained. It' s clear that JIT iust be applied in all department of the company. The main idea and stage of JIT is explained in the second chapter. The elements of JIT can we list as below: - Uniform work loads, - Reduced set-up times, - Group technology, - Educated workers, - JIT delivery of purchasing goods, - Kanban system, - Total quality control, - The organization of JIT activity. These articles are constituted the philosophy of JIT. In the second chapter the reason of increasing of the quality and productivity in Japan is also investigated. The function of the traditional purchasing and it' s targets, the value analysis, the selection of the vendors, the relationships with the vendors are examined in the third chapter. After this it' s find out that the traditional purchasing has some deficiencies. In the 4th chapter, JIT purchasing and the applying of JIT purchasing system is tried to be explained. Purchasing activities include all of the functions involved in the procurement of material, from the time of need to receipt and use of the material. These activities vary considerably among organization depending on the size of the company. Generally, there are several major activities over which purchasing should have full responsibility, regardless of the organization' s size. The major activities of purchasing practice are as follows; - Determining the purchasing lot size. - Selecting suppliers. - Evaluating suppliers. - Receiving inspection. - Negotiating and bidding process. - Determining mode of transporting. - Determining product specification. - Paperwork. - Packaging. The difference between traditional purchasing and JIT purchasing can be listed as follows t -xii-Selection supplier Single source of supply for a given part in nearby geographical area with a longterm contract Rely on multiple source of supply for a given part and short-terra contract Evaluating supplier Receiving inspection Emphasis is placed Emphasis is placed on product quality,, on product quality delivery performance delivery perfor- and price, but no mance and price percentage of reject but about 2 % re- supplier is ject from Buppiier acceptable is acceptable Counting and re ceiving inspection of incaming parts is reduced and eventually eliminated Buyer's respomsi- blty for receiving counting and ins pecting ail incoming parts Negotiating and bidding process Primary objective is to achieve product quality through a longterm contract and fair price Primary objective is to get -the lowest possible price Determining mode Concern for both Concern for oat- of transportation inbound and outbound bound freight and freight and on time lower outbound delivery. Delivery costs. Delivery schedule left to schedule left to the buyer the supplier Product specification `Loose` specifica- `Rigid` specifica tions. The buyer tions. The buyer relies more on per- relies more on de- formance specifica- sign specifica tions than on tions than on product design and product performan- the supplier is ce and supplier encouraged to be have less freedom more innovative in design specifications -ssiii-Paperwork Less formal paper- Requires great work. Delivery deal of time and time and quantity formal paperwork, lever can be Changes in deliv- by telephone ery date and calls quantity orders Packaging Small standard Regular packaging containers used to for every part hold exact quantity type and part num- and to specify the ber with no clear precise specif ica- specifications on tion product content İt' s clear that there are too many differences between JIT purchasing and traditional purchasing. So JIT purchasing has many advantages and caused to spend time, money and material. In the fifth chapter, Kanban was explained. The techniques of Kanban have be&n pioneered by the Toyota Motor Company and have come to have an enviable reputation in Japan and elsewhere. Kanban is a `pull51 type technique that arranges the flow of materials, tools, parts, etc., through a manufacturing facility. Kanban works on the basis of a daily production schedule that is averaged out usually over a thirty day sales forecast for the entire facility. The main advantages of Kanban have been described as a decentralized control scheme which - allows each workstation to plan its own work in accordance with the orders it receives as Kanban tickets from its downstream neighbour! - has very low levels of data gathering and data processing costs ? and - has limited in-process inventories. The mean idea in the 6th chapter is 8 Transportation has a special mean for the JIT purchasing `. Delivery the raw material at the right time and at the right place is very important for the JIT purchasing philosophy. So the selection of the delivery firms and the agreements with them have a great effect on the planning of the purchasing. The more frequently the raw material is delivered, the less need there is to maintain an inventory position in a JIT system. Although each company must establish a range that best meets its particular needs, the goal is to minimise early deliveries and to eliminate late deliveries. The local suppliers usually have an advantage in being able to -xiv-deliver daily. Vendor relationships and shipping art have to be followed and by all problems roust be informed the other side by buyer or vendor. By usinq ail systems can we see some problems. JIT purchasing has some, too. These problems can we list as: missing the interest of the top managers, lower production quality, communication missing between buyer and vendor, and also communication missing between workers and managers. For using the kind of problems, dissecting and organizing are the best solutions. In the last chapter, a simulation model of JIT purchasing is constituted and with these model it's tried to be explained how the simulation day, stock costs and securing day effects the total cost of the product. JIT is a long-term solution to many inventory and quality problems. It is a cultural change that must be driven by top management if it is to succeed. It is not a way to solve the high costs and low quality at a short time period. JIT purchasing elements ares - Vendors - Quality - Quantity - Logistic It' found that applying JIT purchasing is not very easy, but not impossible, either. The benefits of JIT must be good understood and applied in all departments of the organization. To be successful, organizations must be patient, until from top to bottom all workers understand and appropriate the JIT philosophy, like people in Japan. When JIT purchasing is used by many organizations, it will be easier to adapt it. In Türkiye, some organizations are using JIT purchasing, but most of them don' t know what they do, it was. Some top managers say, that JIT purchasing applying in Türkiye is not easy because of the inflation and uncertainty of the economy. Applying a new technology bring some risks and uncertainty. -xv-