Esnek imalat sistemleri ve alternatif rotaları göz önünde bulundurarak esnek ortamlar için üretim hücrelerinin dizaynı
Flexible manufacturing systems and design of manufacturing cells for flexible environmental
- Tez No: 39871
- Danışmanlar: PROF.DR. GÖNÜL YENERSOY
- Tez Türü: Yüksek Lisans
- Konular: Endüstri ve Endüstri Mühendisliği, Industrial and Industrial Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 152
Özet
ÖZET Bu çalışmada. Esnek imalat Sistemlerinin (EiS) genel bölümleri tanıtılıp, bu bölümlerin işlevleri ve kurulması anlatılmıştır. Çalışmanın birinci bölümünde EiS genel yönleriyle tanıtılmıştır. ikinci bölümde, otomasyon ve otomasyon sistemleri anlatılmış ve otomasyon sonucu doğan Robotsal üretim ve bilgisayar destekli sistemler tanıtılmıştır. Üçüncü bölümde ise Esnek imalat Sistemlerine giriş yapılıp, bu sistemlerin tanımlamaları, işleme yapısı ve bu sistemlerden beklenen hedefler anlatılmıştır. Dördüncü bölümde, EiS' deki esneklik anlatılıp, imalat açısından esnekliğin üzerinde durulmuş ve çeşitli esneklik tanımlamaları yapılmıştır. Beşinci bölümde, EiS 'de Malzeme Taşıma Sistemleri 'ne duyulan gereksinim belirtilmiş ve bu sistemlerin çeşitleri anlatılmıştır. Altıncı bölümde, EİS 'de çizelgeleme ve bu çizelgelemede çeşitli sistem yaklaşımları üzerinde durulmuştur. Yedinci bölümde, maliyet modeli kurulup, maliyetlerin çeşitli açılardan sınıflandırılması yapılmıştır. Sekizinci bölümde, EiS'nin sosyal bilimciler ve teknolojistler açısından değerlendirilmesi yapılmıştır. Dokuzuncu bölümde, yaptığımız yatırımların değerlendirilmesi ve bu değerlendirmedeki aşamalar anlatılmıştır. Onuncu bölümde, EiS 'deki yerleşim problemi ve çeşitli yerleşim tipleri anlatılmıştır. Onbirinci bölümde ise, benzerlik katsayısından faydalanılarak alternatif rotalara sahip parçalar için makina hücrelerinin oluşturulması ile ilgili bir örnek problem tanımlanarak, çözümü aşamaları anlatılmıştır. ıx
Özet (Çeviri)
SUMMARY FLEXIBLE MANUFACTURING SYSTEMS AND DESIGN OF MANUFACTURING CELLS FOR FLEXIBLE ENVIRONMENT The implementation of the new manufacturing technologies into the existing manufacturing facilities requires a great deal of capital investments. Therefore, it is very important to perform the feasibility studies to justify it. The main advantages of using the new manufacturing tecniques are; the improvement in the quality of products, lower scrap rate, less dependability on labor skill and lower manufacturing costs. The lower manufacturing costs are mainly due to the less direct labor requirement which means the new techniques provides flexible automation. Automation is a technology concerned with the application of mechanical, electronic and computer-based systems to operate and control production. We can classified automation into three basic types; 1- Fixed automation 2- Programmable automation 3- Flexible automation Fixed automation is a system in which the sequence of processing (or assembly) operations is fixed by the equipment configuration. The operations in sequence are usually simple. It is the integration and coordination of many such operations into one piece of equipment that makes system complex. In programmable automation, the production equipment is designed with the capability to change the sequence of operations to accommodate different product configurations. The operations sequence is controlled by a program which is a set of instructions coded so that the system can read and interpret them. Flexible automation is an extension öf programmable automation. The concept of flexible automation has developed only over the last 15 or 20 years and the principles are still evolving. A flexible automated system is one that is capable of producing a variety of products (or parts) with virtually no time lost for changeovers from one product.Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters and other symbols. The numbers, lettes and symbols are coded in an appropriate format to define a program of instructions for a partial workpart or job. When the job changes, the program of instruction is changed. The capability to change the program is what makes NC suitable for low and medium-volume production. It is much easier to write new programs than to make major alteration of the processing equipment. Direct numerical control (DNC) and computer numerical control (CNC) represent a marriage between computer technology and NC technology. Direct numerical control was introduced in the commercially offered during the early 1970s. Direct numerical control involves the use of a large central computer in DNC is to download the NC part programs to the individual machines as required. In NC, the result of trend toward miniaturization was that it became economical for one computer (a minicomputer or a micro computer) to be used to control each machine tool. CNC denotes a numerical control system that uses a dedicated, stored program computer to perform some or all of the basic NC control functions. Then we can explain industrial robots. An industrial robot is a general-purpose, programmable machine possesing certain characteristics. In present- day robots, the most obvious character it ic is the robot's mechanical arm which is used for performing various industrial teska. Typical robot applications include spot welding, material transfer, machine loading, spray painting and assembly. The definition of an industrial robot given by the Robotics Industries Association (RIA) is the following;“An industrial robot is an reprogrammable, multi-functional manipulator designed to move material, parts or special devices through variable programmed motions for the performance of a variety of tasks.”At the other hand, the robots are reprogrammable multifunctional manipulators that move material, parts and tools. The primary function of robotin flexible cell and systems is to load and unload parts. According to this definition, robots can be xiclassified as programmable automation. The actions of the controlled in order for the manipulator to perform a desired motion cycle. A robot program can be defined as a path inspace to be followed by the manipulator, combined with peripheral actions that support the work cycle. In the robot-centered cell, the robot is located at the approximate center of the worcell, and the other pieces of equipment are aranged around it. A flexible manufacturing system consists of a group of processing stations ( predominantly CNC machine tools) interconnected by means of an automated material handling and storage system, and controlled by an integrated system. The initials FMS system are sometimes used to denote the term flexible machining system. A FMS consists of a group of machining centers, interconnected by means of an automated material handling and storage system and controlled by ab integrated control system. So a FMS can be defined as a computer controlled production system capable of processing a variety of part types. The objective of a FMS is to incorporate many individual automation concepts and technologies into a single production system. A FMS include automatic storage and retrieval systems, automatic material handling systems, robots, numerical control machine tools, group technology and hierarchical computer control systems. In a flexible manufacturing system, each part is first designed, then an NC-machine program is generated, a robot is programmed and finally the part is manufactured. All these processesare coordinated and supervised by a management system. In a FMS these processes require a high integration. The higher the degree of automation of a FMS, the greater the integration needed among the part-design, machine programming, robot programming and part-machining processed. In a FMS, the level of decision-making and information processing increased. This is because the human must match in information processing and decision making the tremendous speed at which computer process and present information. xiiThere are three basic components of a flexible manufacturing system: 1. Processing stations: In present-day applications, these workstations are typical computer numerical control (CNC) machine tools that perform machining operations on families of parts. However, FMSare being designed with other types of processing equipment, including inspection stations, assembly workheads, and sheet metal presses. 2. Material handling and storage: Various types of automated material handling equipment are used to transports the workparts and subassemblies between the processing stations, sometimes incorporating storage into the function. 3. Computer control system: Computer control is used to coordinate the aktivities of the processing stations and the material handling system in the FMS. One additional component in the FMS is human labor. Human beings are needed to manage the operations of the flexible manufacturing systems. The purpose of a material handling in afactory is to move raw materials, work-in-process, finished parts, tools and supplies from one location to another to facilitate the overall operations of manufacturing. The handling of materials must be performed safely, efficiently (at low cost), in atimely manner, accurately (the right materials in the right quantities to the right location), and without damage to raw materials. There is a great variety of material handling equipment available commercially. The equipment can be divided into the six catagories. These are hand trucks, powered trucks, cranes, conveyors, automated guided vehicle system (AGVS) and other handling eqipment. A conveyor system is used when materials must be moved in relatively large quantities between spesific locations over a fixed path. Most conveyor systems are powered to move the loads along the pathways. An automated or automatic guided vehicle system (AGVS) is a material handling system that uses independently operated, self-propelledvehicles that are guided along defined pathways in the floor. The vehicles are powered by means of on-board batteries that allow operation for xixiseveral hours (8 to 16 hours is typical) between recharging. Guidance is achieved by sensors on the vehicles that can follow the guide wires or paints. For a small facility or for a localized subsystem, material can be transported to and from a cell with conventional conveyors. For a large, complex facility, conveyors are too costly and inflexible. In these situation automated guided vehicles (AGVs) are finding widespread use. These trackless, self-propelled vehicles are automatically routed to provide a flexible means of transporting materials over random routes within a factory. AGVs are available in various configurations from handling pallets to moving assemblies and fixtures. There are two primary means of guiding AGVs. One method is by painting reflective stripes on the floor. This method offers low installation cost and an easy means of changing paths. Because the stripe is adversely affected by dirt and wear, this means of guiding is unacceptable in some facilities. The alternative is burying wire in the floor. This method is unaffected by dirt or wear but increases cost and difficulty during initial installation and changes. An automated storage/retrieval system (AS/RS)is a combination of equipment and controls which handles, stores and retrieves materials with precision, accuracy and speed under a defined degree of automation. The AS/RS consists of a a series of storage aisles that are serviced by one or more storage/retrieval (S/R) machines, usually one S/R machine per aisle. The AS/RS has one or more inpu/output stations where materials are delivered for entry into storage and where materials are picked up from the system. The final area of the factory to integrated in the automated factory is the warehouse. AR/RS have been in use for sometime; they provide the integration with balance of the automated factory that completely automates the material handling task. With these considirations in mind it is clear that even a completely automated factory needs people to operate. Sucessful preventive maintenance and emergency repair are both critical to safely maintaining the smooth operationof an automated factory. In fact, while the number of people may be reduced, their roles are still xivcritically important, and their skill level must be higher. The interaction of automated machinery with humans places a new premium on safety. This applies not only to maintenance personnel, but also to any situation that causes people to interact with or work in close proximityto automated machinery. The automation of a facility will result in a drastic reduction in the number of persons directly involved in the production process. It will also result in an increase in the number of support personel and the skills required of them. Flexible manufacturing systems are considered to fill a gap between high-production transfer lines and low production NC machines. With automation complete, the production facility is ready to produce parts. That is, unless a machine failure occurs. In a manufacturing cell a single machine failure will often stop production from that cell. In the automated factory, one should be quick to realize that, much of manufacturing is no longer binary, so eff iciencyalone is not the answer. One must be able to produce upon demand. The high cost of owning and maintaining production machinery dictates that; it be kept working on regular basis. This call for equipment that is flexible. There are lots of problems occured while one decides to use and install a flexible manufacturing system. The most important problem to be solved seems to be the cost of a flexible manufacturing system. During the first installation, The installment cost is quite high. This is due to the essential need of numerical control equipment, machines, robots and automatic material handling equipments. Considering the operation and control of a FMS, the human can icrease system reliability by acting as a backup decision-maker. The function of a supervisior performs include planning, teaching, monitoring. The main functions of a supervisior are to monitor the information flow and to intervene in emergency situations. The performance of system monitoring and intervening relate to the human's information processing capabilities. The size of the FMS system and the amount xvof decision-making that has to be performed will affect the supervisior 's performance and the efficiency of the system. In flexible manufacturing system (FMS), it is common that most machines are multi-purpose and are capable of performing more than one operation, which makes parts reroueting possible. In addition, due to scheduling constraints, reroueting is often desirable. Machine grouping procedures do not consider alternative routeings that a part may go during the operational phase of system. When a part is rerouted, it adversely affects the cell performance. The existing procedures for machine cells formation in cellular manufacturing have not taken these factors into consideration. In this research, a new procedure is developed which provides the flexibility of incorporating alternative routeings in the system's design phase. Several appoaches have been developed to identify machine cells and their associated part families. These approaches can be classified into two groups; (1) based on part characteristics, and (2) based on production methods. The part-orientated techniques usually employ some coding and classification scheme. These algorithms are very flexible and can incorporate any relevant data that influences the grouping process. An FMS is designed to offer several types of flexibilities among which flexibilities in routeing, product mix and part volume are the important ones. The machine cell formation process for an FMS, therefore, should incorporate alternative routeing sequences and corresponding volumes for each part. The procedure developed in this research incorporates alternative routeing sequences, production volumes and operation times for each part in the machine cell formation process. A example is presented to demonstrate the effectiveness and special features. In this research, a new procedure based on a similarity coefficient is proposed that incorporates alternative routeing sequences in addition to production volumes and operation times for each part in the formation of machine cells and part families. The usage factors for alternative routes are determined for available production resources. The procedure uses a new similarity coefficient in the determination of machine cells and corresponding part families. XV 1A new machine-component clustering procedure based on similarity coefficient has been developed. The most important feature of this new procedure is the incorporation of alternative route ings for parts, and machine capacity constraints. The new similarity coefficient assigns similarity among machines with usage factors of all alternative routeings. The usage factors are determined by satisfying production and capacity constraints. The demand and processing times are assumed to be known with certainty. incorporation of requirements planning in the design of machine cells can significantly improve the performance of the cellular system at the operational level. The results from the example revealedthat the new procedure can improve machine component grouping solutions significantly, besides satisfying production and capacity constraints in the process of the cellular design for the system. Since flexible manufacturing systems are essential for the near future and in time the necessity for those kinds of systems arises engineers and competitors involved in todays rapidly changing demand market have to get into corporation to achieve a position in the ever improving technology and have the chance to get benefit of those technologies. xvi i
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