Grup teknolojisi imalat sistemi ve bu sistemin tasarımına yönelik yeni bir metot

Abstract

ÖZET Günümüzdeki pazar talepleri, mamullerin daha küçük parti miktarı ve artan çeşitlilikle imal edilmelerine açık bir eğilim göstermektedir. Böyle bir durumda yetersiz kalan geleneksel ima lat sistemleri farklı bir organizasyonel yapı için zorlanmakta dır. Bu derişik yapı, Grup Teknolojisi ( GT ) İmalat Sistemi üze rinde yoğunluk kazanmaktadır. GT imalat 5istemi tasarımında önemli aşama iş parçası ve makina gruplarının (grup düzenlemesi nin) oluşturulmasıdır. Bu çalışmada grup düzenlemesi sorunu çok boyutlu bir görüş açısı altında incelenmeye çalışılmış ve çözümü için yeni bir et kileşimli metot önerisi yapılarak bu metodun aşamaları anlatıl mıştır. Çalışma beş bölüm halinde toplanmıştır: Birinci bölümde, önce sistem yaklaşımı ile üretim sistemle ri tanımlanmış ve imalat sistemlerinin yeri belirlenmiştir. Daha sonra imalat sistemleri sınıflandırılmış ve bunlardan gelenek sel imalat sistemi çeşitleri biribirleriyle karşılaştırmalı ola rak açıklanmış ve neden GT imalat sistemi gereklidir sorusuna cevap verilmiştir. Ardından GT tanıtılarak aşamaları, yararları, uygulama zorlukları ve ekonomisinden bahsedilmiştir. Tezin ikinci bölümünde, GT'de ilk aşama olan grup düzenle mesi, başka bir deyişle iş parçası aileleri ve makina grupları nın veya makina hücrelerinin oluşturulması amacı ile kullanılan yaklaşımlar tanıtılmıştır. Bu yaklaşımlardan öncelikle parça sı nıflandırma ve kodlamanın, firmanın tasarım, üretim planlama ile üretim fonksiyonlarına etkileri anlatılmış, ancak üretimde maki na gruplarının oluşturulması aşamasında yetersiz kaldığı vurgu lanmıştır. Daha sonra parça sınıflandırma ve kodlama sistemle rinden Brisch ile Opitz Sistemlerinin özellikleri tanıtılmıştır. İkinci yaklaşım olarak üretim akış analizi ele alınmış ve bu yaklaşımın ilk iki aşaması olan fabrika akış analizi ile grup analizi ayrıntılı bir şekilde anlatılarak parça-makina grupları na nasıl ulaşılabileceğinin yolları gösterilmiştir. Son olarak bir Japon yaklaşımı olan Tam Anında (TA) Üretim tanıtılarak ge rek grupların oluşturulması ve gerekse diğer GT tasarımı aşama larına etkileri belirtilmiştir. Üçüncü bölüm, ikinci bölümde anlatılan grup düzenleme yak laşımları ile ilgili yayın taramasını kapsamaktadır. Üretim akış analizi çalışmaları, uygulanan metotlar yönünden iki ana grupta toplanmış ve açıklanmıştır. Bunlar; makinalar arasında geçen iş parçaları miktarları yönünden bir ilişkinin göstergesi olan ben zerlik katsayıları esasına dayanan metotlar ile iş `parçası-maki- na matrisinde diyagonal dizili gruplar oluşturan metotlardır.Ayrıca bu bölümde iş parçası kodlama çalışmaları ve iş parçası ile makina istatistiklerini bir arada kullanan ve grup tasarımı nı amaçlayan bir metot tanıtılmıştır. Çalışmanın dördüncü bölümünde, GT sistemi tasarımı için ye ni ve etkileşimli bir metot önerisi yapılmıştır. Metot öncelikle ele alınma ve gösterim kolaylığı bakımından seçilen düşünsel bir örnek üzerinde tüm aşamaları ve akış diyagramları yardımıyla an latılmıştır. Metodun ilgili yayınlardan farklı olan özgün tarafı, karar verici ile etkileşime girebilecek özelliklere sahip bir şekilde birçok alternatif türetebilmesidir. Ayrıca metot simülasyon ça lışmaları ile bütünleştirilmiştir. Bu arada GT'de simülasyon üzerine yapılan yayın taraması ile araştırmaların başkaca hangi noktalarda toplanması gerekeceği gösterilmiştir. 5on olarak metot endüstriyel bir mühendislik firmasına uy gulanmış ve elde edilen sonuçlar yorumları ile açıklanmıştır. Sonuncu bölümde ise, bu çalışmada elde edilen belli başlı, sonuçlar onüç madde halinde özetlenmiştir.

- VI - ABSTRACT GROUP TECHNOLOGY MANUFACTURING 5Y5TEM5 and A NEW METHOD ORIENTED TO THE DESIGN OF THESE SYSTEMS Market demands at the present time show a clear inclination towards producing goods in smaller lots and increased varieties. Traditional manufacturing systems which are insufficient in such a case, are forced into changing to a different organizational structure. This different structure concentrates on the Group Technology (GT) Manufacturing Systems. The most important stage in the design of an effective GT manufacturing systems is the formation of work piece families and machine groups (group layouts ). In this thesis the group layout problem has been studied in a multi-dimensional view and, by recommending a new inter active method for its solution, the stages of this method have been explained. The thesis has been organized in five chapters. In the first chapter, production systems are defined by the system approach and the role of manufacturing systems is determined. Afterwards, manufacturing systems are divided in two classes: 1. Traditional Manufacturing Systems 2. Cellular or GT Manufacturing Systems From these the traditional manufacturing systems appear in practice in four different types: i. Job Shop System ii. Flow Shop System iii. Project Shop System iv. Continous Process System In the thesis (study) these systems are examined in comparison with each other, especially from the point of view of work flow, and their advantages and disadvantages are explained. The job shop system is the one where work flow is- vıı - most complicated and therefore the one having the most problems. However, it is the one that is faced most frequently in practice. For this reason this system is considered and ways of improving its design are determined, and from this, leaving traditional manufacturing systems, the question of why cellular or GT manufacturing systems are necessary is answered. Then GT manufacturing systems are introduced; their stages, advantages and application difficulties are discussed. In addition, in this chapter explanations are made concerning manufacturing costs using the GT application, especially as to how the cost elements will be effected, and the importance of the cost efficiency of group layouts in the first stage of GT is emphasized. In the second chapter of the thesis the approaches to group layout, in other words, the formation of work piece families and machine groups or machine cells, which is the first stage in GT are introduced. These approaches are: i. Component classification and coding ii. Production flow analysis For the component classification and coding, definitions of classification and coding are made first; in addition, information about the code types are given. Then the purpose of classification and coding is discussed and its effects on the design, production planning and production functions of the firm are explained; but its insufficiency in the stage of formation of machine groups is also emphasized. In this chapter, moreover, the Brisch and Opitz 5ystems of classification and coding, whose fundamentals are opposite, are introduced. The following four steps of the production flow analysis, which is the second approach, are defined and explained briefly: - factory flow analysis - group analysis - inner-group layout analysis - tooling analysis Afterwards data required for the realization of production flow analysis in the manufacturing systems is listed and explained in detail. After this, the way factory flow analysis and group analysis, which are the first two steps of production flow analysis, utilize this data and bring about the machine cells is explained. Finally, a Japanese approach, Just-In-Time (JIT) production, is introduced and its effects on the- Vill - formation of groups as well as other GT design stages are explained. The third chapter covers the literature survey relating the group layout approaches explained in the second chapter. Here production flow analysis studies are gathered in two main groups with regards to applied methods, as follows: i. Methods taking the similarity coefficient as basis, ii. Methods forming diagonally formed clusters in parts-machine matrix. Each of these is described in detail from the point of different approaches presented. In addition, in this chapter, a method aiming at group design is also introduced, which uses component coding studies and machine statistics together. In the fourth chapter of the thesis, a new computerized method is proposed. The main characteristics of this original method are: i. It generates various alternative group layouts, ii. It developes an interactive decision making system^for choosing one of these alternatives, iii. A simulated model as an integrated sub-model of the main program aids the decision maker or programmer in choosing among these groupings and in finding a compromised solution if desired. iv. It demonstrates the interactions between group sizes and alternative inner-group flow lines. The method proposed in this thesis is explained together with a hypothetical example in order to assure explanation and demonstration ease. The stages of this method consists of the followings: 1. The formation of work piece families and machine groups in maximum number by main program: This program generates work piece families in maximum number and from this, machine groups, by processing routing data (information) taken generally from parts operation cards, with the help- IX - of an algorithm which takes set theory approach as basis. Determining of required machine number and work loads of existent system based on functional layout before grouping: Main group is the job shop system itself. In order to compare this group with other groupings alternatives, the required number of the machines in the group and work loads are determined in this stage. Determining the required machine numbers and work loads of generated groups based on functional layout, and extra machine requirements caused by groupings: This. is the completion steps of the second stage. In this way, the main group and generated groups are compared beforehand from the point of machine number and work loads, and the results are offered to the decision maker. Determination of the common machines recommended to each machine group and determination of production quantities which are the basis for the improvement of alternative marketing picture: The purpose of this stage is to increase the diminished machine work loads due to grouping to an acceptable level by determining common machines, and thereby calculating the values of the production quantities to be presented to the decision maker. Obtaining new groups by combining the groups: In the case that the decision maker is not satisfied with these groups, the method can combine the groups according to the desired criteria in order to offer to the decision maker different groupings. 6. Formation of the alt lines) of the machin help of this stage, through which the co families will be pas selection of the bes trade off between wo alternative flow lin becomes more involve advancing from the f result of this, the flow lines that are conditions. ernatives inner-group layouts (flow es in each group obtained: With the the best flow lines can be obtained, nsidered work piece or work piece sed. Alternative flow lines for the t flow line are formed seeking for a rk load. and work flow. Four es are tried in the method. Work flow d and machine work loads increase by irst line to the last ones. As a decision maker may choose the best favorable for his manufacturing7. Integration of the method with the simulation: The simulated model can be used at this stage for flow line evaluation, using different criteria, such as work piece throughput time, waiting time and machine idle time for different work piece batch quantities. As a result, it is very easy for decision maker to choose the best flow lines for his manufacturing conditions. In summary, the method uses b special heuristical search approach, set theory and simulation techniques as integrated parts of the main model, and the decision maker can influence the model interactively. In addition in this fourth chapter, additional subjects to be researched are indicated by the literature survey on simulation in GT. Finally, the method is applied to a manufacturing firm and very interesting results are found. The firm is divided first into nine processing units for the factory flow analysis and the passing frequencies of different inter unit parts are calculated end then work flow among units is simplified by combining two processing units. The combined units are determined as a main group and applied to the proposed method to realize both the group analysis and inner-group layout analysis. As a result for the layout of the main group, a number of alternatives are proposed to the decision maker along with the performance measures which simplify his selection. At the same time an opportunity has been created to try different strategies. Thirteen main results of this thesis are summarized in the conclusion chapter. Key words: Group technology, group layout, production flow line, interactive decision making.