1introduction to cad

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I. INTRODUCTION TO CADI. INTRODUCTION TO CAD

Now it is the Era of Digital computers.

Computers are now used in industries to aid in design, manufacturing,

process planning, production management, quality control etc.

The popular acronyms CAD/CA/C! stand for Computer Aided Design/

Computer Aided anufacturing/ Computer !ntegrated anufacturing.

The new technology has !ntegrated the traditionally two distinct functions

i.e., design and manufacturing together.

CAD/CA forms the "asis for this new technology to lead to what is #nown

as $Computer !ntegrated !ndustries%.


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Definition of CADDefinition of CAD

The creation, modification, analysis and optimization of a

new component using a computer.

CAD involves three ma&or elements' CAD (ardware, )oftware and *ser

The primary functions of CAD involve design, analysis and application

to manufacturing.

!n an Engineering sense CAD also incorporates +inite Element

Analysis, )tress analysis, (eat Transfer analysis, +luid +low analysis,

etc


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CAD in a sense represents the evolution of graphical

representation of information on a computer.

The origin of CAD technology can be tracked back to the

development of Interactive Computer Graphics (ICG) and the

graphical representation of computers in turn can be tracked

back to the beginning of digital computers.

The milestone in the development of computer graphics !as

created by the pioneering !orks Ivan "utherland.


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In #$%& in his 'hD thesis describing a system called "ketch 'ad began

laying the theoretical basis for computer graphics.

That "ketch 'ad !as developed under the "AG* ("emi Automatic Ground

*nvironment) pro+ect a defense pro+ect of ,.". Air-orce.

'ictures could be displayed on the screen and manipulated by the user

!ith a light pen.

This proved the potential for a C/T as designer0s electronic dra!ing board

!ith graphical operations such as scaling translation rotation animation

and stimulation.


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"imilarly the evolution of CAD1CA2 systems has

occurred over the past three decades.

In #$%30s the first ever t!o-dimensional (4D) drafting

systems !ere developed.

5ater the 4D systems !ere e6tended to &D models and led

to the development of 7ire-rame modeling systems.

"urface and "olid 2odeling systems !ere developed onlyin the #$830s.


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5ater the "olid modeling led to the application programs

like numeric control (9C) codes and automated mesh

generation.

A volume representation of the part is re:uired for

performing Topological validity checks.

"ome of the popular soft!ares are I-D*A" (from "D/C)

'/;-*ngineer (from 'arametric Technology Corporation),nigraphics (from *D")


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Product cycleProduct cycle


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There are "asic reasons for using a CAD system

1. To improve the productivity of the designer:

2. To improve the quality of design:

. To improve communication:

!. To create a "ata#ase for $anufacturing

%. $ultiple&'roup (erformance


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1. To improve the productivity of the designer:

This is achieved "y assisting the designer to

visuali0e the product, its su" assem"lies, and

reducing the time required in synthesi0ing,

analy0ing and storing the design.

This reduces the time and cost involved in a

pro&ect.


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1.To improve the quality of design

A CAD system performs a thorough engineering

analysis, and selects the optimum design among the

various design alternatives.!t eliminates design errors and "rings in accuracy in

the design product, there"y resulting in a quality

product.


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2. To improve communication:

A CAD system also provides high quality engineering

drawings.

This results in standardi0ation, "etter

documentation, fewer errors and greater legi"ility.

This helps to read and implement the design into

production.


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3. To create a "ata#ase for $anufacturing

A CAD system is capa"le of producing the required

data"ase li#e dimensions, material specification, "ill

of material 4567, quantity if products required,

etc., while the product is "eing designed.

This data is essential in planning, manufacturing and

inspection activities.


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.$ultiple&'roup (erformance

A CAD system also has the capa"ility to allow for multi user or

mem"ers of the pro&ect group to perform on the same product.

8i#e for e9ample a component designed and stored in a li"rary

"y one mem"er can "e accessed "y another mem"er for use to

produce an assem"ly.

)imilarly, various users can access other:s design 4various

options availa"le to modify/not to modify a part created "y the

original designer7 and ma#e use to e9ecute the pro&ect.


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A designer performs the complete design process

by putting his capabilities into the CAD system.

A basic design process is an iterative procedure

which involves various stepsphases.


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!. "ecognition of need.

#. De$nition of the problem.

%. Synthesis.

&. Analysis and optimi'ation.

(. )valuation.

*. +resentation.


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/ecognition

of 9eed

Definition ofproblem

"ynthesis

Analysis and

;ptimi


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The first phase the recognition of need occurs either from market

demand or from a problem in an e6isting product.

These can be identified by the salesperson (market need) or by the

engineer (design change).

The definition of problem involves setting a definite

standard1specification.

The process is repeated to bring the problem to an optimal level

!ithin the constraints imposed.

Thus synthesis and analysis are essential to optimi


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*valuation is the process of comparing the design !ith the

specifications defined in the problem definition stage.

*valuation generally involves the fabrication and testing of

a prototype to assess the performance :uality reliability

etc.

'resentation is the final phase in the design process.

This includes documentation of the design using

engineering dra!ings material specifications =;2 etc.

This can be considered as the design data useful for further

activities.


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The documentation is the physical dra!ings and repots

produced manually.The later activities of the design process like the

process planning scheduling manufacturing etc. are

all again distributed to various groups !hich again

consumed a large amount of time.

9o! !ith the presence of CAD system the actual

design documentation process planning scheduling

manufacturing and all other activities re:uire lesser

manpo!er time and efforts.


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Pahl and beitz model


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Application of computer for design:

The various design activities that are performed on the CAD

system can be grouped into > categories namely?

#. Geometric 2odeling.

4. *ngineering Analysis.

&. Design /evie! and *valuation.

>. Automated Drafting.

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