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
listed below,
*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.
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