Mekanik Endüstride Cad/cam Sistemlerinin Seçimi Ve Etkin Kullanımı

Abstract

Firmalar, tasarım ve üretim süreçlerini gözden geçirerek, daha verimli ve uygun performansta çalışarak, daha az maliyetli, ve yüksek kalitede ürünler almasını sağlayacak Bilgisayar Destekli Tasarım (CAD, Computer Aided Design) ve Bilgisayar Destekli Üretim (CAM, Computer Aided Manufacturing) sistemlerinin getirdiği avantajlardan faydalanmak için sisteme geçmek istemektedirler. Ancak, ülkemizde bu geçiş süreci ve kullanım aşamasına gereken önem verilmeyerek, yapılan yanlış yatırımlarla firmalar zarara uğramaktadır. Söz konusu hataların başladığı nokta seçim aşaması olup, ihtiyaçların, amaç ve hedeflerin sağlıklı bir şekilde belirlenmemesi, yöneticilerin gerek firma, gerekse de konu hakkında yeterli bilgiye sahip olmamaları ve araştırma da yapmamaları sebebiyle sistemden yararlanmak bir yana, eski sistemi arar duruma gelinmektedir. Tüm bu nedenlerden ötürü, son derece hassas olan bu konu üzerine eğilip, öncelikle CAD/CAM kavramlarına açıklık getirilerek, sistem genel olarak tanıtılmış, faydalarından bahsedilmiş ve sistemin Bilgisayarla Bütünleşik Üretim (CİM) anlayışının bir parçası olduğu vurgulanarak, sistemden maksimum fayda almanın diğer CİM öğelerini de kazanarak gerçekleşeceği belirtilmiştir. CAD/CAM Sistemleri hakkında genel bir fikir verildikten sonra, üretim sektöründe makina endüstrisi ele alınarak, sistemin sektördeki yeri hakkında bilgi verilmiş ve sisteme geçiş kararı alan bir firmanın sağlıklı seçim yapabilmesi için geçmesi gereken aşamalar, yapması gereken faaliyetler ele alınmıştır. Burada tüm faaliyetler ile hesaplama ve değerlendirme yöntemlerinden bahsedilerek, konu gerçek örneklerle desteklenmiş, yapıcı önerilerde bulunulmuştur. Sonraki bölümde, gereksinimlerine uygun CAD/CAM sistemine, doğru ve isabetli kararlar alarak geçiş yapan firmanın, sistemden gerektiği gibi verim alabilmesi için yapması gereken faaliyetler olan başta eğitim ve organizasyon çalışmaları üzerinde durulmuş ve dünya üzerindeki saygın firmaların yaptığı araştırma sonuçları ile konunun önemi çarpıcı bir şekilde ifade edilmiştir. Bir başka bölümde CAD/CAM yazılımları üzerinde ayrıntılı bir şekilde durularak, tüm özelliklerinden bahsedilmeye çalışılmış ve daha sonra üretim sektöründen CAD/CAM yazılımı seçimi uygulamasıyla gerçek bir örnek verilerek, konu netleştirilmiştir

The purpose of Industrial Companies invest on Computer Aided Design and Computer Aided Engineering (CAD/CAM) systems are to work more productive and appropriate performance and product high quality. However, selection and use of CAD/CAM systems are not considered in our country. Therefore, selection and use processes would generate wrong decision. The purpose of this study is to help companies how the CAD/CAM systems select properly and how the system use efficiently. The thesis contains five sections. The followings is a brief description of each station : In the first chapter, the general conceptions which is concerning about CAD/CAM were defined. To talk about these definitions briefly: Computer Aided Design (CAD), Computer Aided Manufacturing (CAM), Computer Aided Engineering (CAE), and Computer Integrated Manufacturing (CIM) describe four separate but closely related disciplines in computer graphics. The common goal of all these areas is to use the computer ' s huge memory capacity, fast processing speed, and user-friendly interactive graphics capabilities to automate and tie together otherwise cumbersome and separate engineering or production tasks, thus reducing the time, and cost of product development. CAD/CAM Systems involve the use of the digital computer to accomplish certain functions in design and productions. CAD is concerned with the use of the computer to support the design engineering function, and CAM is concerned with the use of the computer to support manufacturing engineering activities. The combination of CAD and CAM in the term CAD/CAM integrate the design and manufacturing functions in the industrial companies. Computer Aided Design can be defined as any design activity that involves the effective use of the computer to create, modify, or document an engineering design. CAD is most VUl commonly associated with the use of an interactive computer graphics system, referred to as a CAD system. The term CAD/CAM system is also used to support manufacturing as well as design applications. CAD is used to define some type of geometry for a mechanical part, architectural structure, electronic circuit, building layout, or other items. This information is stored in a computer database, from which it is as the basis for further work and to produce engineering drawings. There are several important reasons for using a CAD system to support the engineering design function: 1. To increase the productivity of the designer. This is accomplished by helping the designer to conceptualize the product and its components. In turn this helps to reduce the time required by the designer to synthesize, analyze, and document the design*. 2. To improve the quality of the design. The use of a CAD system with appropriate hardware and software capabilities permits the designer to do a more complete engineering analysis and to consider a large number and variety of design alternatives. The quality of the resulting design is thereby improved. 3. To improve design documentation. The graphical output of a CAD system results in better documentation of the design than what is practical with manual drafting. The engineering drawings are superior, and there is more standardization among the drawings, fewer drafting errors, and greater legibility. 4. To create a manufacturing data base. In the process of creating the documentation for the product design ( geometric specification of the product, dimensions of the components, materials specifications, bill of materials, etc.) much of the required data base to manufacture the product is also created. CAM systems provide the data and instructions to automated machines for making parts, assemblies, and circuits, often using the geometric data from CAD as a starting point. CAM includes applications that support manufacturing engineering, such as numeric codes generation, and simulation. The solid model generated by CAD softwares is important for representing part definition. M of me part's features can be defined and displayed in this model. There are other key factors paramount to successful manufacturing operation: Graphics, data management, associatively, and applications. IX CAE, computer software is available for performing a wide range of analysis and simulation. Such tools allow engineers to see how the product will behave under various conditions and catch any errors early in the design cycle, thus optimizing the design and reducing overall product development time and cost. Probably the most widely used method of computer analysis in engineering is the "Finite Element Method". Other types of tools include kinematics, dynamics, and rapid prototyping. As given below, there are several important benefits for using CAD / CAM / CAE system : - Qualified design : Evolved model is evaluated a lot of alternative, because of optimum result for the model, design is qualified, and fine tuned. - Design reliability : Using sensible analysis method and simulation techniques for the design, reliability border is increased. - Decrease of design and production time : Due to computerizability, design and production time is reduced. - Availability of documentation easily : Drafts, reports and graphics are prepared easily and quickly - Economy of material and labour : The result of making optimum design is to save material and labour. - Changing and evolving design easily : It can be applied to change on design and production methods quickly. In addition to correcting errors in a short time and producing new models can be possible. - Presentation of product in the market in a short time : Since design and production times are reduced, product is presented in the market quickly. Chapter two provides detail on a selecting process of CAD / CAM systems. Firms can choose CAD/CAM system in two ways. First, determined firm' s system; following scientific selection methods. Second, firms supported to choose a system which turn key project by other firms. According to recent research, the most way to choose CAD/CAM system in firms is to make their own decisions. Because, firms know their own necessities and goals. Also, when firms choose a system, firm get knowledge about CAD/CAM systems. The following is a proposed method of this dissertation for selecting CAD/CAM system. 1. Starting decision. 2. To organize a team which its goal is to select the CAD/CAM system. 3. To determine mission and goal for the company. 4. To define requirements and analyze the present system. 5. To receive proposal and pre-evaluate. 6. To evaluate remaining proposal with different methods, including demos. 7. Decision about selection. Facilities which started at took a decision on system' s investment and organized project team, attending to make a project planning about goals and necessities. It should be pointed out that needs determined correctly. If occurred any error in this part, selection process would generate wrong decision. While studying on selection, it should be taken into considering CAD/CAM systems which are required modern production and management methods and processes. This important point has been discussed in this chapter. In this thesis, it is asserted that make a system analysis and considering new production method are most important in order to system efficiency and for the return on investment in short time. Also, other important points can be arranged as the followings: 1) Reliability proposal 2) Service and support utilities 3) Delivery and implementation studies 4) Test installation 5) Software architecture In the other part of study, treat of evaluating CAD/CAM systems and some scoring models, economic analysis methods have been discussed. For example: - Scoring Models:. Unweighted 0-1 factor model. Unweighted factor scoring model. Weighted factor scoring model. Constraint weighted factor scoring model - Economic Analysis Methods:. Pay back period. Return on investment. Net present value a . Internal rate of return In chapter 3, return on investment for a short duration in order to reach a system efficiency have been studied. The following questions are answered in this chapter. 1) What does firm acquire with CAD/CAM system ? 2) How much money and time assigned for training ? 3) What is the return on investment in first year and in economic life ? 4) What is the minimum limit of investment ? 5) How much time is necessary for training from engineers and designers ? 6) How much productivity would loss during training ? 7) How can be planned on to productivity increase in long term ? 8) How can be organize ? Industrial companies which adopted the CAD/CAM system examined carefully later, studies about minimum productivity loss and loss time have been discussed with examples. After that, treat of training of CAD/CAM system. How system training can be given and purpose of training told. In another title, treat of organization concept and given an information about firms organizational structure which use CAD/CAM system. In chapter 4, commercial CAD/CAM softwares with their features, definition of important terms, and general characteristic of softwares have been explained. Also, showed all of CAD/CAM features. In this part, it has been pointed out that Product Data Management which is important for CAD/CAM systems. Furthermore data entrance, organization and control which is related to product and formation of product management told and it is a technology which is used for Product Data Management. In chapter 5, given an example which is a CAD/CAM system selecting in a industry and all explanations brought up concretely. In this part, selecting evaluation and calculation methods determined. At the end of this part, study about firms which produce CAD/CAM/CAE software. As a result, in this study, given general software features and definitions have given in many ways