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CAD/CAM, CNC sistemleri ve CNC torna tezgahları için CAD/CAM programı uygulaması

Başlık çevirisi mevcut değil.

  1. Tez No: 55493
  2. Yazar: ERTUĞRUL ŞENSOY
  3. Danışmanlar: Y.DOÇ.DR. MUZAFFER ERTEN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Makine Mühendisliği, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1996
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 69

Özet

ÖZET Mühendisliklerin bütün dallarına girmiş olan Bilgisayar Yardımı ile Tasarım (Computer Aided Design) geniş anlamda bir parçanın, bir binanın, bir haritanın, daha doğrusu belli kurallara göre çizilen resimlerin bilgisayar ortamında gerçekleştirilmesi, Makina Mühendisliği dalındaki dar anlamı ise parça ve kalıp tasannu olarak tanımlanabilir. Bilgisayar Yardımıyla İmalat (Computer Aided Manufacturing) ise, bilgisayar ortamında tasarlanmış parçalara (geometrik bilgilere) dayanarak gerekli teknolojik bilgiler alındıktan sonra bilgisayar kontrollü tezgahların anlayabileceği bir dilde NC programlarının hazırlanması için bilgisayar kullanılması işlemidir. Bilgisayar kontrollü tezgahlarda imal edilen bir çok parça çok karmaşık şekilli olduğundan dolayı, elle programlama aşın derecede zorlaşmakta ve bu iş için özel bilgisayar programlarının gerekliliği artmaktadır. Bu programlar sayesinde hem zamandan tasarruf hem de işlem hasasiyetinde bir artış sağlanmaktadır. Tabii ki bu özel programlar fiyat açısından imalatçılara belirli bir yük getirmektedir. Bu çalışmada Türkiye'de gelişmesi gereken bir konu olarak düşündüğüm CAD/CAM ve CNC sistemleri ile ilgili bilgiler vererek, CNC tornalar için basit bir CAD/CAM programım en son geliştirilen Visual Basic programlama dili ile yazdım. Bu program CNC tezgahlarının elle programlanması hakkında yeterli bilgiye sahip olmayan fakat teknolojik bilgiye sahip olan elemanlar tarafından kullanılmak üzere yazılmıştır. Bu program sayesinde program içinde çizilmiş olan parçalar değişik dosyalarda saklanarak sonradan değişik işlem parametreleri ile yeniden gerekli olan G ve M kodlan elde edinilebilinir. Program, içindeki postprosesör sayesinde G-kodla- nm Absolute (Mutlak) koordinat sistemine göre çıkarır, fakat tasarım sırasında, mutlak veya eklemeli koordinat sistemi kullanılarak geometrilerin girilmesine izin verir. xıı

Özet (Çeviri)

SUMMARY Cad/Cam, CNC Systems and A Program Application For CNC Lathes The main aim for me to study this thesis is to write a simple CAD/CAM program and give some information about the basis of CAD/CAM and CNC machines. Engineering Design has been influced heavily by the CAD technology and tools available to designers. Similarly, manufacturing has undergone major changes with the introduction of numerically controlled (NC) and computer numerically controlled (CNC) machine tools. These replace conventional machines, thus offering increased flexibility, superior accuracy, and shorter production cycles. Despite, all of the benefits of CNC machines, I also studied the disadvantages of this system in my thesis. Computer-Aided Manufacturing (CAM) can be defined as the use of computer systems to plan, manage and control the operations of a manufacturing plant through either direct or indirect computer interface with the plant's production resources. A part production cycle by CNC operation includes different steps: 1-Part classification and identification: Parts are classified, numbered and coded to enable them to be identified, permit easy storage and retrieval and facilitate their production. 2-Process planning: In short, process planning is a complete time schedule that begins with a part design on paper and ends with a real product. 3-Design and procurement of new tools: A part process may reveal that new tools are needed to produce the part. If this is the case, the process planner initiates a request for design or purchase of new tools so that they become available at the time of manufacturing. XIV4-Planning and ordering of material: The process planner ensures that all the materials shown on the bill of material, developed by the part designer at the design phase, are in stock for part production. 5-NC programming: An NC programmer must develop the program needed to machine the part. 6-Production scheduling: Part production must be scheduled within the capacity and schedule of shops involved in producing the part as well as the availability of materials, tools, jigs or fixtures and other items needed to produce the part. 7-Manufacturing : The culmination of all the above activities is the manufacturing of the part. Various manufacturing processes exist and one or more of them would have been identified during process planning to manufacture the part. This identification is based on the tolerance and surface finish requirements specified by the designer. 8-Inspection: Inspections of produced parts are required by internal quality control and outside customers such as the government. Quality control inspects parts for dimensional accuracy, finish material, and other physical properties. Typically, statistical concepts of quality control are used to eliminate the need for inspection of every individual part. 9-Other activities: Parts that survive inspection and quality control equipments may follow different paths depending on various factors. If the company that produces a given part also produces the product the part belongs to, the next step after inspection is to assemble the part with others to form the product. If not, the part is packaged and shipped to prospective customers who assemble the parts into their products. Historically, CAD/CAM integration began with the development of the NC technology. NC machine tools have been improving steadily in both areas of hardware control and software developments. NC part programming and interactive computer graphics have contributed heavily to these developments. The integration of CAD and CAM places increasing emphasis on tools and paths for NC machines. It is interesting to note how independent developments (CAD and CAM) which began at completely opposite ends of the CAD/CAM spectrum during evolution of CAD/CAM systems have gradually approached each other. XVA CAD/CAM program is integrated software tool that prepares engineering details, finished blueprints, and numerical control (NC) programs. The use of these programs are the result of the complex shapes that had to be manufacture. For the people who has knowledge about the manufacturing processes but doesn't know how to write manual part programming will find the principles of writing block format of a CNC machine in this thesis. You will find a list of G and M codes that is showing the meaning of these. But this is not enough for finding the toolpath, at this point the mathematical formulas will help you. This computer program is written in a new programming language that is called Visual Basic. If you don't have too much about this programming language, you will have some introductry knowledge after reading this thesis. Before the program I want to tell the properties of a professional CAD/CAM program that is called Mastercam.This program has a very powerful design part. It allows the creation of the following entities in 3D or 2D : Points, lines, arcs, fillets, splines, ellipses, rectangles, chamfers and letters. IGES, VDA, DXF, CADL, NFL and ASCII are the data converters that is used in this program. Dimensioning in any plane or view, cross hatching, multiple viewports, dynamic rotation, panning and zooming, enhanced plotting capability and adaptabality to any International standard is the other properties of this program. The CAM features of this program are : 1-It has tool and material library 2-Cycle time estimation 3-Full tool description and simulation 4-Toolpath selection: Contouring,roughing, grooving, profiling, threading drilling and point to point machining supported. 5-Canned cycles support 6-C-axis support 7-Links to third party applications XVIIt has hundreds of library and custom postprocessors. Creating the part in my programme is similar to create a part in a CNC machine's CRT screen that is using dialogue method. There are five buttons to draw your part. You can draw part, by lines and arcs that can be in any angle and diameter. The creation begins from (0,0) and goes incrementally in Cartesian Coordinate System but when you are giving the points location in design time you can use Incremental Cartesian Coordinate System or Absolute Cartesian Coordinate System. The angles in this programme is positive in counter-clockwise direction. There is also zoom property. Dynamic zoom, zoom reset, zooming the part to fit the screen is the other properties of the program. After creating your part you can save it by using the File/Save property. If you want to open a file that includes your drawing, you only enter File/Open menu item after closing the program that you are dealing. As you draw, the program is taking the datas into a file and this file is used as a database because in a CNC lathe process the number of entities are too less than the milling operation. It is a good idea to learn database programs for the people who wants to write milling programmes. There are three choices in generation of toolpaths in this program. First is the roughing operation. When you click the concerned button a window will open. After getting the window you had to put some parameters to their places such as feedrate, spindle speed, number of programme. Also you had to choose some of the parameters such as Mm/Dev or Mm/Dak for the right G codes. Program asks you the depth of cut and according to these parameters, it writes the program in cycle (G71) form and simulates. Second is the finish operation and in this operation it doesn't use cycle. When you click the concerned button a window will open again. The parameters has small differences in this window such as toolnose radius compensation. The postprocessor can add G41 or G42 to your programme but you can want the programme to ofsett the toolnose in itself. Yes there is a property which offsets the toolnose in G42 form in this programme. The user can control first block's number and the increment number of the block number. The user can control the fluid, the spindle rotation direction. XVIIFigure 1. Toolpath for roughing Figure 2. Zoomed toolpath XVHIThe third operation is grooving. It is more complex than G75 x-axis grooving cycle. You can make different grooves with different sizes and in different dinstances and with different depth of cuts. After getting the G-codes if you want you can take them into text editor that is written for this programme. You can edit and save the necessary G-codes anywhere you want. In figure 1 you can see a toolpath for roughing and in figure 2 you can see zoomed toolpath for figure 1. XIX

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