1introduction to cad
TRANSCRIPT
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vamsi
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.