cad unit1.pptx

8/20/2019 CAD unit1.pptx

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Presented byR. Hemanth Kumar

Asst. Professor

Mechanical Engineering

CAD


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MET71 COMPUTER AIDED DESIGN (3 1 0 4)Unit – I

Design process - Morphology of design, Types of design models,Application of design models, concurrent Engineering – CADsystem architecture.CAD Hardware wor!station – C"#, mass storage, input de$ices%!ey&oard, light pen, thum& wheel 'oy stic!, mouse, digiti(eretc.,) and output de$ices %printers, plotters) Display De$ices storage tu&e – raster scan , $ector refresh, plasma panel and

*CD.%+ hours)Unit – II

resenhams line and circle algorithms. Transformation in/raphics co-ordinate system used in /raphics and windowing

and $iew port transformations, Clipping , hidden line elimination,D transformations – rotation, scaling, translation, mirror,re0ection and shear - homogeneoustransformations – concatenation, 1D Transformation –orthographic and "erspecti$e "ro'ections.

%+ hours)


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Unit – III

Classi2cation of /eometric Modeling – 3ire frame, 4urface and4olid Modeling, applications –representation of cur$es and surfaces – "arametric form –Design of cur$ed shapes- Cu&ic spline –e(ier cur$e – -spline – Design of 4urfaces - features of 4urfaceModeling "ac!age - 4olid"rimiti$es, C4/, -rep and description of other modeling

techni5ues li!e "ure primiti$einstancing, cell decomposition, spatial occupancy enumeration,oolean 6perations %'oin, cut,intersection), Creating 1D o&'ects from D pro2les %e7trusion,re$ol$ing etc)

%+ hours)


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Unit – IV

4tandards for computer graphics %/84) and Data e7changestandards – 9/E4, 4TE". Datastructures for Entity storage – Data structures for interacti$emodelling- :elational data&ases –introduction to 4;* language . :ole of 66"4 in CAD. %+hours)Unit – V

E7pert 4ystems –strategies for 8nowledge Ac5uisition,representation of !nowledge – 9nferenceschemes."arametric and $ariational modeling,


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Text Boo! "

+. Chris Mcmahon and =immie rowne - CAD>CAM –

"rinciple "ractice and Manufacturing Management,nd Edition, Addision 3esley England, ???.. 4adhu 4ingh - Computer Aided Design and

Manufacturing, 99 Edition, 8hanna"u&lishers, @ewDelhi, ??.

Re#e$en%e Boo!"1. ".:adha!rishnan et al - CAD>CAM>C9M, @ew Age

9nternational " *td., @ew Delhi, ??B.. M."./roo$er and E.3.immers - CAD>CAM

Computer Aided Design and Manufacturing, TataMc/raw Hill "u&lishing Co. *td., @ew Delhi, ??B.

F. 9&rahim eid - CAD>CAM Theory and "ractice, TataMc/raw Hill "u&lishing Co. *td., @ew Delhi, ??F.


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UNIT – I

INTRODUCTION TO CAD

CAD = Mechanical and Computertechnology

CAD - models

by geometrical parameters - altered by changing releantparameters.

Uses

CAD - designers - vie o!"ects variety o# representations - test !

simulating real$orld conditions.

Aid - design process li"e Modelling# Assembly# Drafting# DieDesign# $ool Design# %heet metal# analysis of products.

Computer Aided Design %CAD& & assist - engineering processes

such as creation# optimi'ation# analysis and modifications.


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Design 'rocess(

consists of si( identifiable steps or phases)

*. Recognition of need#

+. Definition of problem#

,. %ynthesis#

. Analysis and optimi'ation #

. Ealuation#

/. Presentation


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The general design process !y shiegly


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)* Recognition o# need

• problem e(ists for 0hich some correctie action ta"en

•

defect in a current machine design+* De#inition o# pro!lem

• specification of the item to be designed

•

physical and functional characteristics# cost# 1uality andoperating performance

+, -, .* /ynthesis, Analysis and optimi0ation

•

highly iterati$e in the design process• conceptuali(ed, su&'ected to analysis, impro$ed

redesigned

• design optimi(ed within the constraints imposed on


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1, 2* 3valuation and 'resentation

• Ealuation is concerned 0ith measuring the design against the

specifications in +.

• fabrication and testing of a prototype model to assess operating

performance# 1uality# reliability and other criteria

• presentation of the design - documentation by - dra0ings#

material specifications# assembly lists 2 design data base

created

'roduct Development and Manu#acture(

Machines inoled & Computers

$as"s & information processing

3se & assist in the definition and processing of information

connected 0ith design of products


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'rocess involved in !ringing the product to Mar4et


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Models o# the Design 'rocess

4. %teps of the design process according to

Pahl and 5eit'6*789

44.$he design process according to

:hsuga


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I* /teps o# the design process according to 'ahl and 5eit0 %)67.&


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4n this model the design process is described by a flo0 diagram

comprising four main phases 0hich may be summari'ed as)


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I* The design process according to Ohsuga


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Application o# design models(

• $his may be diided into t0o main classification

i. Ealuating actions

ii. ;eneratie actions

• E(tract in#ormation 8 present model

• A design analyst might use this for the follo0ing assessments)

o.

A isual assessmento. An assessment of the mass of the components# by using the CAD model

o.An ealuation of loads in the components# by considering them as parts of a

mechanism

o.An ealuation of stresses# for e(ample using the finite element model.

o detailed dra0ings 0ith components of the design# and from these# manufacturing

engineers < information for tooling and for the control of production machines.

C i i


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Concurrent engineering(

• Concurrent engineering or %imultaneous Engineering - cross functional team

approach

• Adopted to improve the e##iciency of product design and reduce the productdeelopment cycle time.

• 'arallel 3ngineering.

• 5rings together a 0ide spectrum of people from seeral functional areas in the

design and manufacture of a product.• Representaties from R ! D# engineering# manufacturing# materials management#

1uality assurance# mar"eting etc. deelop the product as a team.

• All Depts do tas4s in parallel

• $he team reie0s the design from the point of ie0 of mar"eting# process# tool

design and procurement# operation# facility and capacity planning# design for

manufacturability# assembly# testing and maintenance# standardi'ation#

procurement of components and sub-assemblies# 1uality assurance etc as the

design is eoled

• !ottlenec4 in the deelopment process is thoroughly studied and rectified.


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• All the departments get a chance to reie0 the design and identify delays and

difficulties.

• $he departments can start their o0n processes simultaneously.

• e(ample# the tool design# procurement of material and machinery and recruitment and

training of manpo0er 0hich contributes to considerable delay can be ta"en up

simultaneously as the design deelopment is in progress. 4ssues are debated thoroughly

and conflicts are resoled amicably.

• 4t gies mar"eting and other groups the opportunity to reie0 the design during the

modeling# prototyping and soft tooling phases of deelopment.

• CAD systems especially ,D modelers can play an important role in early product

deelopment phases. 4n fact# they can become the core of the CE.

• CAD offers visual chec4 0hen design changes cost the least.

• Teamor4 bet0een product deelopment# production planning and manufacturing is

essential for satisfactory implementation of Concurrent Engineering.


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Teamor4 Advantages

• the co-operation bet0een arious specialists and systematic application of special

methods such as =>D 6=uality >unction Deployment9# D>MA 6Design for Manufacture

and Assembly9 and >MEA 6>ailure Mode and Effect Analysis9 ensures 1uic"

optimi'ation of design and early detection of possible faults in product and production

planning.

• Reduction in lead time 0hich reduces cost of production and guarantees better 1uality.


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Comparison o# Concurrent 3ngineering and /e9uential 3ngineering

A comparison of concurrent and se1uential engineering based on cost is attempted in

this section. $he distribution of the product deelopment cost during the product

deelopment cycle is sho0n in >ig. $his figure sho0s that though only about *? of the

budget is spent at the time of design completion# 0hereas the remaining 8? is already

committed.deelopment cost and product cost can be

reduced by proper and careful design


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IM':3M3NTATION O; CONCURR3NT 3N


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CAD system architecture(

ardare( the computer and associated peripheral e1uipment

/o#tare( the computer programs running on the hard0are

Data( the data structure created and manipulated by the soft0are)

uman >noledge and activates


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CAD /ystem Architecture

• Model de#inition( to add geometric elements to a model of the #orm of a

component@

• Model manipulation( to moe# copy# delete# edit or modify elements in models@

• 'icture generation( to generate images of the design model

• User interaction( to handle commands input by user and to present output to the

user about the operation of the system@• Data!ase management( for the management of the files that ma"e database

• Application( these elements of the soft0are do not modify the design model# but

use it to generate information for ealuation# analysis or manufacture@

• Utilities( a catch$allB term for parts of the soft0are that do not directly affect the

design model# but modi#y the operation of the system in some 0ay 6e.g to set the

color to be used for display# or the units to be used for construction of a part

model9.


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CAD ardare

?or4station & CP3

Mass storage – Magnetic tape storage# Magnetic Disc

%torage# Magnetic drum storage

Input devices - 6"eyboard# light pen# thumb 0heel# oy stic"#mouse# digiti'er# $ouch %creen# $rac" 5all9 Output devices -

6printers# plotters9

Display Devices- 6storage tube & raster scan# ector refresh#

plasma panel and CD9

C3NTRA: 'ROC3//IN< UNIT(


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C3NTRA: 'ROC3//IN< UNIT(

CP3 consists of three separate subsections

*. Control 3nit

+. Arithmetic ogic unit,. Memory


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Control Unit(

• $he control unit < administrator in a computer.

• 4t coordinates the operations of all other components.

• 4t controls the input and output of information through 4: deices#

synchroni0es the transfer of signals bet0een the arious sections.

• 3@ecutive program, 0hich is stored in memory.

Arithmetic :ogic unit

• $he A:U proides the circuitry re1uired to perform the arious calculations

and manipulations of data.

• Most A3Bs can add and su!tract# but latest A3Bs < capable of

multi#unctions and comple@ mathematical functions.• A3Bs 0ith simple@ circuits are capable of being programmed to perform these

more complicated operations# but more computing time is re1uired.

• $he more comple@ arithmetic logic units are faster# but these units are more

costly.


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Memory

• 5inary storage units# organised into !ytes.

• $he memory section stores all the instructions and data of a program.

• $herefore the C'U must trans#er these instructions and data. $0o types

of memory

Main memory 6primary storage9

Au(iliary memory 6%econdary storage9

Mass storage

$he most common deice used for computer storage technologies are

Magnetic tape storage

Magnetic Disc %torage

Magnetic drum storage


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Magnetic tape storage

• E(ample of se1uential access storage technology.

• Data are stored on magnetic tape# similar to that used in audio

systems.

• $he maor advantages of magnetic tapes are that is relatively

cheap 0hen compared 0ith other types of storage medium and

that it can easily hold large amount of data for its si'e.

• Magnetic tape unli"e punched paper tapes or cards can be used

again by simply overriting preiously stored data.

• %ince data are stored se1uentially access time is relatiely

slo.

• Ho0eer# the lo0 cost per bit and high capacity of magnetic

tape ma"e it ideal for system bac"up.

• 4t is most suitable for applications# 0hich may be re1uired in payroll# personnel

management# inentory control and customer inoicing 0here a large amount of data is

to be processed se9uentially

M i Di /


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Magnetic Disc /torage

• Magnetic dis" storage is also "no0n as a random access storage deice.

• $he storage medium is a magnetically coated dis". $here are seeral types and si'es

of dis"s each best suited to a particular set of applications.


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;loppy Disc

>loppy dis"s come in t0o standard si'es) the larger one is 8 inches in diameter and

smaller is F inches and is referred to as mini floppy.

Magnetic Drum /torage

$he magnetic drum is direct access storage deice 0ith high capacity and high

access rates. $he magnetic drum consists of a magnetically coated cylinder during

operation. $he drum is rotated at a constant speed and data are recorded in the form of

magneti'ed spots. $he drum can be read repeatedly 0ithout causing data loss.


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Input devices

Keyboard

Mouse

ight pen

$humb 0heel

Goy stic"

Digiti'er

$ouch %creen

$rac" 5all


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OUT'UT D3IC3/

Printers

Plotters':OTT3R/


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'RINT3R/

*. 4mpact printers

mechanical hammering deice

Printing mechanisms: (a) with typebars, (b) and (c) without typebars; (1) typebar,

(2) inked ribbon, (3) paper (recording medium), (4) paten !orpaper, (") spherica

printing head, (#) hammer, ($) numeric (aphabetic) whee


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+* In4"et printer


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-* :aser printer

CATOD3 RAB/ TU53(


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CATOD3 RAB/ TU53(

$he graphics display can be diided into t0o types based on the scan technology used to

control the electron beam.

Random %can

Raster %can

In Random scan graphics can be generated by dra0ing ectors or line segments on the


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g p g y g g

screen in a random order 0hich is controlled by the user input and the soft0are. $he 0ord

random indicates that the screen is not scanned in a particular order.

Raster /can system# the screen is scanned from top to bottom# left to right all the time to

generate graphics. $his is similar to home teleision scan system# thus suggesting the name

digital scan. $he three e(isting CR$ display that are based on these techni1ues are

i. Refresh display 6calligraphic9

ii. Direct ie0 storage tube

iii. Raster display

Re#resh Display(


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Re#resh Display( $he refresh !u##er stores the display file or program# 0hich contains points#

lines# characters and other attributes of picture to dra0n. $hese commands are

interpreted and processed by the display processor.

$he electron beam accordingly e@cites the phosphor# 0hich glo0s for a short

period. $o maintain a steady flic"er & free image# the screen must be re#reshed

or redra0n at least - to 2 times per second# that is# at a rate of ,I to /I H'.

$he principal adantage to refresh displays is its high resolution 6I7/ ( I7/9

and thus its generation of high 1uality pictures.

the need to refresh the picture places a limit on the number of ectors that can be

displayed 0ithout flic"er

being a binary display# the refresh display is able to generate only to level of

color intensity.

4n some displays# the intensity of the electron beam can ary to proide !etter

color capabilities.

Re#resh Display(


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Re#resh Display(


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Direct ie /torage Tu!e %D/T&( Re#resh display 0ere ery e@pensive in the *7/Is due to the re1uired refresh

!u##er memory and fast display processor# and could only display a fe0

hundred ectors on the screen 0ithout flic"er.

At the end of *7/Is the D/T 0as introduced by $e"troni( as an alternatieand ine@pensive solution.

$he DJ%$ eliminates re#resh processors completely and conse1uently the

refresh buffer used 0ith refreshes display. 4t also uses a special type of phosphor that has a long – lasting gloing effect.

$he phosphor is embedded in a storage tube. 4n addition# the speed of the electron beam in the DJ%$ is sloer than in the

refresh display due to elimination of refresh cycle. 4n the DJ%$ the picture is stored as a charge in the phosphor mesh located

behind the screenBs surface.

$herefore# comple( pictures could be dra0n ithout #lic4er at highresolution. :nce displayed# the picture remains on the screen until it is e(plicitly erased. $his is 0hy the name Estorage tu!e 0as suggested. 4n addition to the lac" of selectie erasure# the DJ%$ cannot proide colors#

animation and use of light pen as an input deice.

Di t i /t T ! %D/T&


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Direct ie /torage Tu!e %D/T&(

Raster Display(


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Raster Display(

$he inability of the DJ%$ to meet the increasing demands by

arious CADCAM applications for colors# shaded images and

animation motiated hard0are designer to continue searching for

a solution.

During the late *7Is raster display based on the standard

teleision technology began to emerge as a iable alternatie.

$he drop in memory price due to adances in solid states made

large enough refresh buffers aailable support high resolutiondisplay.

A typical resolution of raster display is *+8I ( *+I 0ith a

possibility to reach I7/ ( I7/ as the DJ%$.

Raster displays are ery popular and nearly all recent display research


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Raster displays are ery popular and nearly all recent display research

and deelopment focus on them.

4n raster display# the display screen area is diided hori'ontally and

ertically into matri( of small elements called picture element or pi@el.

A pi(el is a small addressable area on the screen.

An N @ M resolution defines on a screen 0ith L ro0s and M Columns.

Each ro0 defines a scan line.

A rasteri'ation process is needed in order to display either a shaded

area or graphics entities.

4n this process the area or entities are conerted into their

corresponding pi(els 0hose intensity and color are controlled by the

image processing system.

R t Di l


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Raster Display(

?or4ing(


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g

4mages are displayed by conerting geometric in#ormation into pi@el alues

0hich then conerted into electron beam deflection through display processor

and deflection system.

4f the display is monochrome# the pi(el alue is used to control the intensity

leel or the gray leel on the screen.

>or color displays# the alue is used to control the color mapping into a color

map.

$he creation o# trans#er #ormat data from geometric information is "no0n as

scan conersion or rasteri0ation.

A rasteri'er that forms the image-creation system is mainly a set of scan

conversion algorithms.

Due to the uniersal need for these algorithms# the scan conersion or

rasteri'ation process is implemented.

T?O MAR>/(


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UNIT – I

*. Define design process.

+. Define morphology of design.

,. hat are the types of design modelsN

. hat are the applications of design modelsN

. Define concurrent engineering.

/. hat are the applications of concurrent engineeringN

. hat are the difference bet0een se1uential engineering and

concurrent engineeringN

8. hat are the adantages of concurrent engineeringN

7. hat are the steps in CAD system architectureN

*I.Define CAD hard0areN


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**.hat are the types of mass storage deicesN

*+.Lame some input deices.

*,.Lame some output deices.

*.hat are the types of display deicesN

*.Define raster scan.

*/.Define random scan.

*.hat are the adantages of storage tubeN

*8.hat are the disadantages of storage tubeN

*7.hat are the adantages of ector refreshN

+I.hat are the disadantages of ector refreshN

cad unit1.pptx

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