Bir kalıp üretimi sisteminde alternatif rota esaslı grup teknolojisi uygulaması

Abstract

Geçtiğimiz on yıl süresince imalat Kaynakları Planlaması, Tam Zamanında Üretim felsefesi ve Esnek imalat. gibi yöntemlerin kullanılması ile imalat planlama ve kontrolünde önemli değişimler gerçekleşmiştir. Hücresel imalat ise, küçük parti imalatına olanak tanıması ile bir yandan kütle üretimine benzer ekonomik faydaların kazanılmasını sağladığı bir yandan da atölye üretimindeki esnekliği muhafaza ettiği için gerek akademisyenler gerekse uygulayıcılar tarafından yoğun bir ilgi görmüştür. Hücresel İmalatın ilk ve en önemli adımı, parçaları benzer -tasarım özelliklerine ya da proses gereksinimlerine göre "parça aileleri" seklinde, ailelerin üretiminde kullanılan makinaları ise "makim hücreleri" seklinde kümelendirmektir. Bu tezin ilk bölümünde genel hatları ile Grup Teknolojisi tanıtılmakta ve atölye tipi üretime etkilerinden bahsedilmiştir, ikinci bölümde, grup teknolojisindeki parça ailesi ve makina grupları bulma yöntemleri ile ilgili olarak yapılmış olan bir literatür araştırması sonucu bulunan algoritmalar kısaca tanıtılmıştır, üçüncü bölümde, 'alternatif rota ve makina kapasitesi' esaslı bir kümelendirme yöntemi ile söz konusu yöntem için hazırlanan bilgisayar programı hakkında bilgi verilmiştir. Dördüncü ve son bölümde ise bölüm 3 'de bahsedilen yöntemin bir kalıp imalatı sisteminde uygulanması sırasında izlenen yol, karşılaşılan güçlükler ve elde edilen sonuçlar hakkında bileri sunulmuştur.

Group technology is an organizational technique to improve manufacturing productivity by exploting the underlying commonality between parts and manufacturing prosses. With more effective design rationalization and manufacturing standardization, the efficency associated with flow-line production is sought while the flexibility of a job shop manufacturing system is maintained. These features are essentials for a firm to remain competitive in the current manufacturing environment, in which more special orders are demanded, production life cycles are reduced, and competition is focused on factors like delivery speed, quality, design flexibility, delivery reliability as well as price. Firms have to manufacture products in a larger product mix. smaller volume, increased part complexity and shorter production period. Cellular manufacturing is the application of GT to manufacturing In cellular manufacturing, a firm's manufacturing system is organized into cells. Each cell (a machine cell) includes a number of dissimilar machines to process a family of parts (a part family). A part family is a collection of parts which are similar either because of geometric shape and size or because similar processing steps are required in their manufacture. The parts within a family are xii different, but their similarities are close enough to merit their identification as members of the part family. A machine cell in GT, determines a group of machines located close to one another. As explained previously each cell consists of dissimilar types of machines and possesses specific manufacturing capabilities to process one or more part families. In the first chapter of the thesis, GT is introduced. The elements of GT are explained and the one that simplifies the material flow system is widely examined. Then the advantages and disadvantages of GT are discussed. Compared with the functional layout in the job shop, the results of succesfull application of GT in manufacturing ensure as follows :. Reduction in machine set-up times,. Smooth work flow due to possibilty of small batch manufacturing,. Reduced in-processes inventories,. Reduction in throughput times,. Reduction in handling cost,. Reduction in tooling investment,. Simplication in production planning,. Increased quality. All of the these advantages are mainly realized by simplifying the work-flow in machine shop applied to GT principles. However some disadvantages occur in GT. The major disadvantages are:. Extensive analysis, along with the accompanying difficulties in the selection of the appropriate methodolgy, is required for the formation of parts families and machine groups. xiii . The purchase of additional machines may be required in order to realize the gains inherent in the group (cell) structure. Especially if the machines which are few in number are required in a greater number of cells than their present number, this results in decreased work loads and extra machines are required.. Another subject explained in this chapter is about the affects of GT on the dominant costs - such as direct work force cost, capital cost, material cost, and WIP cost - in the manufacturing system. The initial stages in the implementation of cellular manufacturing involves the determination of part families and machine cells. So, in the second chapter, some clustering methods are introduced. There has been a considerable amount of work done in this area. Diverse clustering algorithms have been employed as effective tools in formatting manufacturing cells. Basically, they can be classified into two major classes. A design-oriented approach relies on the design features of parts to perform the necessary analyses. The production-oriented approach, on the other hand, is based on routeing information to group parts or machines. The latter can be further divided into several categories with recpect to the differences in clustering logic. These categories are :. Array-based clustering techniques. Hierarchical clustering techniques,. Non-hierarchical clustering techniques,. Mathematical programming based clustering techniques. Graphic theoretic approach. Heuristics xiv In the third chapter, "Multiple routeings and capacity considiration based clustering method" and its computer application are introduced. The originality of this method lies in considering both the manufacturing system as well as projected product icon, and distributing the demand among the alternate routeings in order to optain a better manufacturing cell design. The proposed heuristic determines manufacturing cells to minimize the material flow within the shop, and solves problems : (i) the selection of routeings, and (ii) the formation of manufacturing cells. The procedure is iterative, until a set of working routeings and manufacturing cells are optained with minimal inter-cell traffic. The first problem is formulated as a linear programming problem, while second is solved by the inter-cell traffic minimization method (ICTMM). ICTMM is a bottom-up aggregation procedure which aggregate work centers to cells based on 'normalized inter-cell traffic', and then validates the assignment of work centers. The aggregation-validation procedure is continued until cells are formed and no further reduction in traffic is possible under the prescribed cell size constraint. The computer program writen in QUICK-BASIC consists of seven stages. These are:. Information about clustering method,. Entering new problem,. Reading of existing problem from disk (ette),. Displaying or printing input data,. Solving problem,. Modification of problem,. Displaying or printing final solution. xv In the last chapter, the system which will be converted to cellular manufacturing system is introduced. After this, the procedure of collecting production data which will be used in the analysis, and difficulties that occure during the procedure are explained step by step. These steps are:. Determination of general part sequences,. Pre-grouping of parts,. Selection of best machines for the operations,. Determination of route ings,. Determination of operations time,. Determination of machine capacities and. Determination of part importance weights. Finally, the part families and machine cells are determined by using a computer program of the clustering method introduced in the third chapter.