COMPUTER AIDED DESIGN
1. Define CAD;
Computer aided design can be defined as any design that involves the effective use of computers to create, modify or document an engineering design.
2. CAD system;
The cad system consists of two basic components; they are;
· Computer Hardware;
- It consists of graphic workstations,
- Graphic input devices like keyboard, mouse etc.,
- Graphic output devices like printer and plotters.
· Computer Software;
- It consists of operating system for basic operations,
- Software package used for geometric modeling,
- Application software for design, analysis and synthesis.
3. Elements of CAD; (or) Various phases of CAD;
The design process in a CAD system consists of 4 stages / phases, they are;
§ Geometric modeling,
§ Design analysis and optimization,
§ Design review and evaluation,
§ Documentation and drafting.
4. Drawing entities;
A drawing is created using a no. of entities. A large no. of options are provided to draw the entities depending upon the requirements.
Common entities are;
• Point, * Line, * Arc, * Ellipse,
• Circle, *Polygon, *Spline, *Rectangle, etc.,
5. Drawing Utilities;
Drawing utilities include several functions to have the creation and storage of drawings. Common utilities are;
*Screen size, * Line type, * Scaling * Layers,
*Grid, *Snap,, *Units, , *file utilities, etc.,
6.Editing commands in CAD;
It is necessary to make the corrections and alterations to the entities of a drawing. Editing commands are used for this process.A few editing commands are
*Erase, *Move, *Array, *Fillet, * Chamfer
*Mirror *Rotate, *Trim, *Copy *Scale, etc.,
7. Geometric modeling;
Geometric modeling involves the use of a CAD system to develop a mathematical description of the geometry of an object.
The mathematical description, called a geometric model is contained in computer memory. These operations include creating new geometric models from basic building blocks available in the system.
8. Geometric modeling techniques;
These are various types of geometric models used in CAD,
• Based on the dimensioning, - Two dimensional modeling, - Three dimensional modeling.
• Based on the modeling,
- Wire frame modeling,
- Surface modeling,
- Solid modeling.
9. 2D Vs 3D;
2D models are best utilized for design problems, such as flat objects and layouts of building.
3D models are capable of modeling an object in three dimensional according to user instructions.This is helpful in conceptualizing the object since in true 3D models can be displayed in various views and form different angles.
10. Advantages of CAD;
• High productivity and reduced lead time,
• Accuracy in design,
• Better central over the complete project process,
• Modifications in design relatively easy,
• Simulations of the computer generated model can reduce or eliminate prototype testing,
• Effective creation of manufacturing documentation,
• Optimized solution can be received,
11. Various 2D transformations;
In computer graphics drawing are created by serious primitives which are represented by the coordinates of their end points.
Certain changes in these drawings can be made by performing some mathematical operations on these coordinates. The basic transformations are Scaling, Rotation, translation, etc..,
12. Applications CAD software package;
The CAD system is applied, wherever we need to draw, design, and any facilities related to that.
· Automated industries,
· Manufacturing companies,
· Aerospace designs,
· Civil engineering plans,
· Electrical circuits, etc..,
13. CAD software package;
Auto CAD, CATIA, Iron CAD, Pro-E, Turbo CAD, Solid Edge, etc..,
14. Advantages of Wireframe Modeling;
· Simple to construct,
· Designer needs little training.
· It needs less memory space,
· It takes less manipulation time,
· It is best suitable for manipulation as orthographic, isometric and perspective views.
15. B-rep – Boundry representation;
B-rep construction consists of entering all boundary edge for all surfaces. This is similar or copying an engineering drawing into the computer, line by line, surface by surface, with one important qualification. The lines must be entered and surfaces oriented in such a way that they create valid volumes.
16. CSG – Constructive Solid Geometry;
CSG technique uses Boolean combinations or primitives solids to build a part. The Boolean operations are addition (+), subtraction (-), as illustrated in three dimensions.
17. Advantages of Solid Modeling;
· It is complete and unambiguous.
· Suitable for automated applications like creating part program without much human involvement.