Computer Aided Drafting Chapter-1 PDF

TOPIC I: INTRODUCTION TO COMPUTER AIDED DRAFTING Introduction: People in manufacturing understand the importance of technical drawings. Good technical drawings can often reduce the risk of significant delays in production as well as guard against the danger of ending up with an inaccurate g...

TOPIC I: INTRODUCTION TO COMPUTER AIDED DRAFTING Introduction: People in manufacturing understand the importance of technical drawings. Good technical drawings can often reduce the risk of significant delays in production as well as guard against the danger of ending up with an inaccurate gear. Technical drawings must be accurate, and drafted according to industry standards. Drawing is the principal / universal language that everyone could understand. Drawing or illustrating techniques vary in style. However, a standard method of drawing is observed in making industry grade illustrations for constructions, manufacture and architectural purposes. This is called Computer-Aided Drafting. In this modern age, Technical Drafting is produced with the use of different computer aided design software such as: AutoCAD, Solid Works, and CATIA. These are commercial software that are generally available in the market but there are also similar software available for free like Google SketchUp. Being proficient with AutoCAD and its user interface can help make drafting tasks easier based on how familiar you are with all the tools that are just a click away. The exercises in this chapter give you an understanding of how to use the various interface elements that AutoCAD has to offer to make sure you have the tools available when you need them. Computer-aided design (CAD), also known as computer-aided drafting (CAD) or computer-aided design and drafting (CADD), is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design. Computer aided drafting describes the process of creating a technical drawing with the use of computer software. CAD software is used to increase the productivity of the designer, improve the quality of design, and improve communications through documentation and to create a database for manufacturing. CAD output is often in the form of electronic files for print or machining operations. CAD software uses either vector based graphics to depict the objects of traditional drafting, or may also produce raster graphics showing the overall appearance of designed objects. CAD often involves more than just shapes. As in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as: materials, processes, dimensions, and tolerances, according to application specific conventions. CAD may be used to design curves and figures in two-dimensional (2D) space; or curves, surfaces, and solids in three-dimensional (3D) space. CAD is an important industrial art extensively used in many applications, including automotive, shipbuilding, and aerospace industries; industrial and architectural design; prosthetics; and many more. CAD is also widely used to produce computer animation for special effects in movies, advertising and technical manuals. Because of its enormous economic importance, CAD has been a major driving force 2 for research in computational geometry, computer graphics (both hardware and software) and discrete differential geometry. Modern electronic drafting tools are often specialized computer-aided design packages. Basic drafting tools are included in all CAD programs, but some offer advanced automation specifically designed for drafting and architectural design. The tools that are right for you will depend on your budget. AutoCAD Architecture is the most capable, but also the most expensive. Computer Aided Drafting is a process of preparing a drawing of an object on the screen of a computer. There are various types of drawings in different fields of engineering and sciences. In the fields of mechanical or aeronautical engineering, the drawings of machine components and the layouts of them are prepared. In the field of civil engineering, plans and layouts of the buildings are prepared. In the field of electrical engineering, the layouts of power distribution system are prepared. In all fields of engineering use of computer is made for drawing and drafting. The use of CAD process provides enhanced graphics capabilities which allows any designer to: 1. Conceptualize his ideas. 2. Modify the design very easily. 3. Perform animation. 4. Make design calculations. 5. Use colors, fonts and other aesthetic features. REASONS FOR IMPLEMENTING A CAD SYSTEM 1. Increases the productivity of the designer: CAD improves the productivity of the designer to visualize the product and its component, parts and reduces the time required in synthesizing, analyzing and documenting the design. 2. Improves the quality of the design: CAD system improves the quality of the design. A CAD system permits a more detailed engineering analysis and a larger number of design alternatives can be investigated. The design errors are also reduced because of the greater accuracy provided by the system. 3. Improves communication: It improves the communication in design. The use of a CAD system provides better engineering drawings, more standardization in the drawing, and better documentation of the design, few drawing errors and legibility. 3  4. Create data base for manufacturing: In the process of creating the documentation for these products, much of the required data base to manufacture the products is also created. 5. Improves the efficiency of the design: It improves the efficiency of the design process and the wastage at the design stage can be reduced. APPLICATION OF CAD There are various processes which can be performed by use of computer in the drafting process. 1. Automated drafting: This involves the creation of hard copy engineering drawings directly from CAD data base. Drafting also includes features like automatic dimensioning, generation of cross – hatched areas, scaling of the drawing and the capability to develop sectional views and enlarged views in detail. It has ability to perform transformations of images and prepare 3D drawings like isometric views, perspective views etc. 2. Geometric modeling: concerned with the computer compatible mathematical description of the geometry of an object. The mathematical description allows the image of an object to be displayed and manipulated on a graphics terminal through signals from the CPU of the CAD system. The software that provides geometric modeling capabilities must be designed for efficient use both by computer and the human designer. BENEFITS OF CAD The implementation of the CAD system provides variety of benefits to the industries in design and production as given below: 1. Improved productivity in drafting. 2. Shorter preparation time for drawing. 3. Reduced man power requirement. 4. Customer modifications in drawing are easier. 5. More efficient operation in drafting. 6. Low wastage in drafting. 7. Minimized transcription errors in drawing. 8. Improved accuracy of drawing. 9. Assistance in preparation of documentation. 10. Better designs can be evolved. 4  11. Revisions are possible. 12. Colors can be used to customize the product. 13. Production of orthographic projections with dimensions and tolerances. 14. Hatching of all sections with different filling patterns. 15. Preparation of assembly or sub assembly drawings. 16. Preparation of part list. 17. Machining and tolerance symbols at the required surfaces. 18. Hydraulic and pneumatic circuit diagrams with symbols. 19. Printing can be done to any scale LIMITATIONS OF CAD 1. 32 – Bit word computer is necessary because of large amount of computer memory and time. 2. The size of the software package is large. 3. Skill and judgment are required to prepare the drawing. 4. Huge investment CAD SOFTWARES The software is an interpreter or translator which allows the user to perform specific type of application or job related to CAD. The following software are available for drafting. 1. AUTOCAD 2. Pro – E 3. CATIA 4. MS OFFICE 5. PAINT 6. ANSYS 7. MSc.NASTRAN 8. IDEAS 9. SOLID WORKS 10. HYPERMESH 11. FLUENT – GAMBIT 12. SKETCH UP The above software is used depending upon their application. 5  AUTO CAD AutoCAD package is suitable for accurate and perfect drawings of engineering designs. The drawing of machine parts, isometric views and assembly drawings are possible in AutoCAD. The package is suitable for 2D and 3D drawings. AutoCAD is a commercial product made by Autodesk, with many versions, including one called AutoCAD Architecture. AutoCAD Architecture has purpose built features specifically designed for architectural drafting. In addition to design tools for initial architectural conceptualization, it offers tools to make building renovations faster and easier. Productivity tools include those that reflect the actual design of walls and other structures. AutoCAD is able to maintain precise dimensional spacing among components such as walls, beams, columns, and doors. AutoCAD Architecture offers a library of pre-built components to help speed up and automate the design and construction process. THE AUTOCAD INTERFACE Let’s start your AutoCAD and get familiar with the AutoCAD interface elements, what they do, and where you can access them. Look at the figure at the bottom of this page. You can see where the interface elements are by clicking the next/previous button on the menu. If you can’t see the image, you need to install flash player for your browser. LAUNCHING AUTOCAD AutoCAD is one of the most popular computer-aided drafting applications on the market today. You can use it to design plans for residential homes and complex drawings such as paper- converting machines and circuit boards. To become efficient with AutoCAD, you should get to know as many methods of launching the program as possible. HOW CAN YOU START AUTOCAD? 1. In your Computer, click the “START” button and all programs in the computer will appear. 2. Look for “Autodesk”, click it and more options will appear. 6  3. Finally, click the “AutoCAD” (Icons may differ on the versions installed in the computer) and the computer will start to run the AutoCAD software then the interface will appear just like in figure 1.1. NAVIGATING THE USER INTERFACE The AutoCAD user interface — or UI as it’s often referred to — can be very overwhelming, but it doesn’t have to be. All you need is some understanding of how things are laid out and what the various UI elements are. AutoCAD, like other Windows-based applications, has pull-down menus, toolbars, a document area, and a status bar area. However AutoCAD also has some unique user interface elements that aren’t found in a lot of other applications. Some of the unique interface elements are a Command Line window, dynamic input tooltips and dock able windows. (Figure 1.1). Figure 1.1 The AutoCAD User’s Interface 7  Table 1.1 Parts and Functions Parts Functions It is a representation of Drawing 1 Template. This is the 1. Drawing Area part of the AutoCAD software that handles all of the object to be created. It is the part of the AutoCAD software wherein the user 2. Command Line can type the command to be executed. It is a basic X-Y-Z (Z Is not visible) axis. In which it 3. UCS Icon could be a Universal Coordinate System or World Coordinate System. It contains all icon tools that can be useful on creating a 4. Toolbar design. The crosshairs serve as the pointer on giving a direction 5. Crosshairs/Cursor for every command especially for the direct distance entry. This is the part of the AutoCAD wherein the user can 6. Ribbon turn On or Off the tools that could help in creating a certain object. This is the part of the AutoCAD wherein the user can 7. Drawing tools/status turn On or Off the tools that could help in creating a bar certain object. 8. Cascading Drop Down It is another way to access commands in AutoCAD. Menu A layout figure area wherein the user can identify the 9. Model space tab/mode possible output of the object. Note: There are other areas of AutoCAD environment that the coordinate system appear and because this is a free scaling system that can also use the annotation tools near the lock and clear screen icon buttons. DRAWING WINDOW The drawing window (see Figure 1.1) is the main area in the middle of AutoCAD where you add and modify objects in the designs that you create. When you create a new drawing or open an existing drawing, a drawing window appears. Each open drawing has its own drawing window. Along the bottom of each drawing window, you find these items: A series of tabs similar to those found in a spreadsheet program. These tabs represent where you create your model (Model tab) and the layouts used for plotting different views of your model. 8  The drawing status bar along the bottom displays settings specific to the drawing, such as the current annotation scale. If you disable the drawing status bar, the options are displayed in the status bar area of the application window instead. The Command Line window by default is displayed between the drawing window and the status bar area. If you don’t like its position, you can dock it above or along the left or right side of the drawing window. The Command Line window plays a key role in inputting commands, options, and values to create and modify objects. It also displays command prompts and messages to let you know what AutoCAD is waiting for. If you want to gain additional room in the AutoCAD application window, you can close the Command Line window. Press Ctrl+9 to toggle the display of the Command Line window on and off. When the Command Line window is hidden, command prompts and options are displayed in dynamic tooltips. The Text window displays a running history of the commands and options that you previously entered in the Command Line window or at the dynamic input tooltip. You won’t need the Text window very often, but if you need to see what you did a few commands ago, press fn + F2 to bring up the Text window. (see figure 1.2) Figure 1.2 AutoCAD Text window The status bar allows you to quickly access drafting settings and other settings that are used for some of the features. Most of the settings on the status bar allow you to toggle drafting settings on or off without opening a dialog box or remembering a shortcut key combination. Also, you can right-click most buttons to access options that allow you to change the behavior of the drafting settings. 9