Introduction & Overview of Auto CAD

By Prof Dileep Jigyasi

SIRT The SAGE Group

 

Learning to use a CAD system is similar to learning a new language. It is necessary to begin with the basic alphabet and learn how to use it correctly and effectively through practice. This will require learning some new concepts and skills as well as learning a different vocabulary. All CAD systems create designs using basic geometric entities. Many of the constructions used in technical designs are based upon two-dimensional planar geometry. The method and number of operations that are required to accomplish the constructions are different from one system to another, In engineering field, Computer-Aided Drafting (CAD) or Computer-Aided Design (CAD) and Computer-Aided Engineer (CAE) have been utilized in different fields of engineering and science. Manufacturing of a product is the main activity in engineering profession. The design of a product may start with trial design in the form of sketches on the paper. As the design improves and under goes changes, the final form of design must be the scaled manufacturing drawing with finer details included. These drawings can be two-dimensional and three-dimensional.

An engineering drawing may be prepared by means other than the use of conventional tools. Traditionally, drafting instruments have been used. The popular alternative now is to prepare the drawing with the aid of a computer. This method is known as Computer-Aided Design or Computer Aided Drafting.

Definition of CAD: Computer-Aided Design can be defined as, the process of preparing a drawing of an object on the screen of a computer. In other words, it can be defined as the use of computer system to assist in creation, modification, analysis or optimization of design. CAD is not suitable for design/drawing concept. It is only a tool that can be used to supplement traditional tools. The underlying basic concepts in engineering practice are orthographic projection, isometric projection, section of solids etc. There are various types of drawings required in engineering practice such as in the field of mechanical engineering drawing, the drawing of machine components and layout are prepared. The use of CAD process provides enhanced graphics capabilities which allow any designer to:

_ Concept utilize his ideas

_ Modify the design very easily

_ Perform animation

_ Make design calculations.

_ In latest CAD systems, interactive computer graphics (ICG) is used. ICG denotes a user oriented system in the computer and is employed to create, transform and display data in the form of pictures. The image is constructed out of the basic geometric element points, lines, circles etc. It can be modified according to the commands, can be enlarged, and reduced in size, moved

CAD applications in various fields of engineering are as follows:

_ Mechanical: Aerospace, Design of machine elements, CNC, VMC machine tools, Robots etc.

_ Automotive: Gear design, Kinematics, Hydraulics, Steering etc.

_ Electrical: Panel design, Circuit layout, Control system etc.

_ Electronics:  Mechatronics, Schematic diagrams of PCs, ICs etc.

_ Communication: Communication network, Satellite transmitting picture etc.

_ Civil and Architectural: Mapping, Building drawing, Structural design, Town planning,     Interior decorations, Multi- storied complex etc.

_ Aerospace: Design of spacecraft, Flight simulator lofting etc.

_ Automated-design: Automatic dimensioning, Generation of cross-hatched area, Scaling of drawing, Developed section view and Enlarged view in details etc.

_ Geometric modelling: Generation of points, Lines and Circles, Rotation of objects etc.

Software communication is a pattern of code called a language. The most primitive language is called machine code, which speaks, directly to the hardware equipment in either binary (two digit) signals. The writing of software is made much less involved with the aid of high level languages which are used in most areas of CADD. Software usually consists of a number of separate application package to perform the desired function. The size of computer depends on the number and size of packages and number of workstations

_ A wide range of standard software is available and generally it is not worth developing users own software. Basically software is an interpreter which allows the user to perform specific type of application related to CAD software. There are a number of 2D drafting software packages available in the market. Auto Desk, makers of AutoCAD is a leader in the 2D engineering CADD software industry. Although this course will focus on AutoCAD, there are other CADD software, packages available.

_  They include:

1. Corel Draw 2. CAD Std  3. Pro CAD+  4. Accucadd  5. CADD5

6. CADD 2002 7. Vector Engineer 8. Dexterpen  9. Corel CAD

_ All the above software are capable of creating drafting, but many of them do not have as many features as AutoCAD. The most important characteristic of CAD software is its three dimensional associative centralized and integrated data base known as 3D drafting. Such a data base is always richin information needed in design. Various 3D modelling packages are:

1. Pro\E 2. Unigraphics  3. CATIA 4. Ideas 5. Solid Works  6. Solid edge

Application software includes drafting and dimensioning software.

_ 3D geometric modelling,

_ Surface modelling,

_ Solid modelling, etc

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