COMPUTER AIDED DESIGN / COMPUTER AIDED MANUFACTURING (CAD/CAM

CAD/CAM/CAE
THIRD YEAR
SEMESTER VI - MECHANICAL ENGINEERING
(BAMU AURANGABAD)
DR. BABASAHEB AMBEDKAR MARATHAWADAUNIVERSITY,
AURANGABAD
PREPARED BY,
Prof. Shishir R. Rathod
AS PER DR. BABASAHED AMBEDKARMARATHAWADA
UNIVERSITY SYLLABUS
INTERNATIONAL CENTRE OF EXCELLENCE IN ENGINEERING
AND MANAGEMENT, AURANGABAD

MED 354 – COMPUTER AIDED DESIGN / COMPUTER AIDED
MANUFACTURING
(CAD/CAM)
Teaching Scheme
Lectures: 4 Hrs/Week
Credit: 4
Examination Scheme
Theory Examination: 80 Marks (3 Hrs)
Class Test: 20 Marks (1 Hr)
Objectives:
• To give an overview of CAD/CAM technology
• To understand use of computers for product design and manufacturing
• To develop 3D modeling skills required for product design
• To develop programming skills required for CNC manufacturing
• To understand the need and use of robotics and rapid prototyping
Unit 1: Introduction to CAD/CAM (5 Hrs)
Definition and history of CAD/CAM; PLM Flow chart for CAD and CAM; Concurrent
engineering used for Product Development; CAD/CAM applications like CAAP (Computer
Aided Assembly Planning), CAI (Computer Aided Inspection), RP (Rapid Prototyping) and
CAPP (Computer Aided Process Planning)
Unit 2: Hardware and Transformations (6 Hrs)
Hardware configuration required for graphics software, Functions of graphics system,
Ground rules for selection of graphics software; 2D transformations of geometric models like
translation, Scaling, Rotation, Reflection and Shear; Composite transformations:
Homogeneous and Concatenated representation; 3D Projections: Orthographic, Axonometric,
Oblique and Perspective projections (Numericals on 2D Transformations)
Unit 3: 3D Modeling Techniques (9 Hrs)
Wire frame, Surface and Solid modeling; Modern solid modeling techniques, feature based
modeling, parametric modeling, constraint based modeling; Solid Representation: boundary
representation, constructive solid geometry, sweep representations, primitive instancing, cell
decomposition, Parametric representation of Beizer curve, B-Spline curve; Introduction of
Surfaces like Beizer, BSpline; Capabilities of modeling software like Creo, CATIA, Solid
Works, UG/NX
Unit 4: CNC Machine Tools (9 Hrs)
Basic components of NC, CNC and DNC system, NC motion control systems, drive of NC
systems; Coordinate System of CNC Lathe Machine, CNC Drilling and CNC Milling
Machine; Tool Compensations in CNC Drilling, Lathe and Milling Machines; Different CNC
Machining Centers like three, four and five axes; ISO codes (G & M Codes), CNC Part
Programming like Manual and APT; Automatic Tool Changer (ATC) Arrangement in CNC

Unit 5: Manufacturing Automation (5 Hrs)
Definition, Types, Advantages and Limitations of Automation; Flexible Manufacturing
System (FMS), Elements of FMS, Applications of FMS, Merits and Demerits in FMS;
Computer Integrated Manufacturing (CIM); Group Technology, Merits and Demerits of
Group Technology Part classification and coding system; CAPP
Unit 6: Robotics and Rapid Prototyping (6 Hrs)
Robotics: Physical configuration, basic robot motion, technical features of a robot, methods
of robot programming, end effectors, industrial applications
Rapid Prototyping: Stereolithography, Selective Laser Sintering, Laminated Object
Manufacturing, Fusion Deposition Modeling, Solid Ground Curing and 3D Printing
Section A: Unit 1, 2 and 3
Section B: Unit 4, 5 and 6
Reference Books:
1. CAD/CAM – M. P. Grover and E. W. Zimmer, Prentice Hall of India Pvt. Ltd.
2.CAD/CAM – Principle Practice and Manufacturing Management, Chris McMahon and
Jimmie
Browne Addision Wesley England.
3. CAD/CAM Theory and Practice – Ibrahim Zeid, TMH.
4. CAD/CAM Principles and Application – Rao P. N., - TMH.
5. Automation, Production Systems and Computer Integrated Manufacturing – Grover M. P.
–Prentice
Hall of India.
6.Mathematical Elements for Computer Graphics – Rogers, D. F. and Adams, A., McGraw
Hill Inc.
7.CAD/CAM/CIM – P. Radhakrishnan, S. Subramanayan and V.Raju, New Age International
8. Computer Aided Manufacturing – P. N. Rao, N K Tewari and T K Kundra
9. Numerical Control Machines – P. S. Pabla, PHI Pub.
10. Numerical Control machine tools –Yoran Koran/ JosephBen, Khanna Publication.
11. Robotics - Control, Sensing and Intelligence – K.S. fu, RC. Gonzalez, Lee
12. Rapid Prototyping – M. Adithan, Atlantic Book House
Pattern of Question Paper:
The units in the syllabus are divided in two equal sections. Question paper consists of two
sections A and B. Section A includes first three units (1, 2, and 3) and Section B includes
remaining three units (4, 5 and 6). Question paper should cover the entire syllabus.
For 80 marks Paper:
1. Five questions in each Section
2.Question no. 1 and 6 are compulsory for 10 marks each which contains short answer
questions of 02 marks each
3. From remaining four questions, attempt any two questions from each section

MED 374 – LAB - VIII: COMPUTER AIDED DESIGN / COMPUTER AIDED
MANUFACTURING (CAD/CAM)
Teaching Scheme
Practical: 2 Hrs/Week
Credit: 2
Examination Scheme
Practical Exam: 50 Marks
Performing minimum 7 experiments out of the following and preparing record of the
experiments.
1.Creating 2-D model of any two components on any drafting tool which should contain
dimensions, tolerances and get its hardcopy output
2.Creating Solid model and its Drafting of any two components which should contain
dimensions, tolerances using any higher end CAD software and get its hardcopy output
3.Building a composite assembly consisting of at least five components using any higher end
CAD software and get its hardcopy output
4. Developing and executing a part program for contouring on CNC milling machine
5. Developing and executing a part program for CNC lathe machine
6. Developing and executing a part program for point to point on CNC drilling machine
7. Assignment on Unit 5
8. Assignment on Unit 6
Practical Examination
The Practical Examination will consist of performing an experiment based on practical work
done during the course and viva voce based on the syllabus and term work. The practical
examination will be assessed by two examiners, one will be the subject teacher and other
examiner appointed by Dr. B.A.M.U. Aurangabad.

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UNIT 1
INTODUCTION
CAD/CAM
CAD/CAM is a term which means computer-aided design and computer-
aided manufacturing. It is the technology concerned with the use of digital computers
to perform certain functions in design and production. This technology is moving in
the direction of greater integration of design and manufacturing, two activities which
have traditionally been treated as distinct and separate functions in a production firm.
Ultimately, CAD/CAM will provide the technology base for the computer-integrated
factory of the future.
Computer-aided design (CAD) can be defined as the use of computer
systems to assist in the creation, modification, analysis, or optimization of a design.
The computer systems consist of the hardware and software to perform the
specialized design functions required by the particular user firm. The CAD hardware
typically includes the computer, one or more graphics display terminals, keyboards,
and other peripheral equipment. The CAD software consists of the computer
programs to implement computer graphics on the system plus application programs
to facilitate the engineering functions of the user company. Examples of these
application programs include stress-strain analysis of components, dynamic response
of mechanisms, heat-transfer calculations, and numerical control part programming.
The collection of application programs will vary from one user firm to the next
because their product lines, manufacturing processes, and customer markets are
different. These factors give rise to differences in CAD systemrequirements.
Computer-aided manufacturing (CAM) can be defined as the use of
computer systems to plan, manage, and control the operations of a manufacturing
plant through either direct or indirect computer interface with the plant's production
resources. As indicated by the definition, the applications of computer-aided
manufacturing fall into two broad categories:

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1. Computer monitoring and control. These are the direct applications in
which the computer is connected directly to the manufacturing process
for the purpose of monitoring or controlling the process.
2. Manufacturing support applications. These are the indirect applications
in which the computer is used in support of the production operations in
the plant, but there is no direct interface between the computer and the
manufacturingprocess.
The distinction between the two categories is fundamental to an
understanding of computer-aided manufacturing. It seems appropriate to elaborate on
our brief definitions of the two types.
Computer monitoring and control can be separated into monitoring
applications and control applications. Computer process monitoring involves a direct
computer interface with the manufacturing process for the purpose of observing the
process and associated equipment and collecting data from the process. The
computer is not used to control the operation directly. The control of the process
remains in the hands of human operators, who may be guided by the information
compiled by thecomputer.
Computer process control goes one step further than monitoring by not only
observing the process but also controlling it based on the observations. The
distinction between monitoring and control is displayed in Figure. With computer
monitoring the flow of data between the process and the computer is in one direction
only, from the process to the computer. In control, the computer interface allows for
a two-way flow of data. Signals are transmitted from the process to the computer,
just as in the case of computer monitoring. In addition, the computer issuescommand
signals directly to the manufacturing process based on control algorithms contained
in itssoftware.
In addition to the applications involving a direct computer-process interface for the
purpose of process monitoring and control, computer-aided manufacturing also
includes indirect applications in which the computer serves a support role in the
manufacturing operations of the plant. In these applications, the computer is not
linked directly to the manufacturing process.

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Computer monitoring versus computer control: (a) computer monitoring;
(b) computer control.
Instead, the computer is used "off-line" to provide plans, schedules,
forecasts, instructions, and information by which the firm's production resources can
be managed more effectively. The form of the relationship between the computer and
the process is represented symbolically in Figure. Dashed lines are used to indicate
that the communication and control link is an off-line connection, with human beings
often required to consumate the interface. Some examples of CAM for
manufacturing support that are discussed in subsequent chapters of this bookinclude:
Numerical control part programming by computers. Control programs are
prepared for automated machine tools.
Computer-automated process planning. The computer prepares a listing of
the operation sequence required to process a particular product or component.
Computer-generate work standards. The computer determines the time
standard for a particular production operation.
Production scheduling. The computer determines an appropriate schedule
for meeting production requirements.
Material requirements planning. The computer is used to determine when
to order raw materials and purchased components and how many should be ordered
to achieve the productionschedule.
Shop floor control. In this CAM application, data are collected from the
factory to determine progress of the various production shop orders.
In all of these examples, human beings are presently required in the

application either to provide input to the computer programs or to interpret the
computer output and implement the required action.
CAM for manufacturing support.
THE PRODUCT CYCLE AND CAD/CAM
For the reader to appreciate the scope of CAD/CAM in the operations of a
manufacturing firm, it is appropriate to examine the various activities and functions
that must be accomplished in the design and manufacture of a product. We will refer
to these activities and functions as the product cycle.
A diagram showing the various steps in the product cycle is presented in
Figure. The cycle is driven by customers and markets which demand the product. It
is realistic to think of these as a large collection of diverse industrial and consumer
markets rather than one monolithic market. Depending on the particular customer
group, there will be differences in the way the product cycle is activated. In some
cases, the design functions are performed by the customer and the product is
manufactured by a different firm. In other cases, design and manufacturing is
accomplished by the same firm. Whatever the case, the product cycle begins with a
concept, an idea for a product. This concept is cultivated, refined, analyzed,
improved, and translated into a plan for the product through the design engineering
process. The plan is documented by drafting Ii set of engineering drawings showing
how the product is made and providing a set of specifications indicating how the
product shouldperform.
Except for engineering changes which typically follow the product
throughout its life cycle, this completes the design activities in Figure. The next
activities involve the manufacture of the product. A process plan is formulated which
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specifies the sequence of production operations required to make the product. New
equipment and tools must sometimes be acquired to produce the new product.
Scheduling provides a plan that commits the company to the manufacture of certain
quantities of the product by certain dates. Once all of these plans are formulated, the
product goes into production, followed by quality testing, and delivery to the
customer.
Product cycle (design and manufacturing).
The impact of CAD/CAM is manifest in all of the different activities in the
product cycle, as indicated in Figure. Computer-aided design and automated drafting
are utilized in the conceptualization, design, and documentation of the product.
Computers are used in process planning and scheduling to perform these functions
more efficiently. Computers are used in production to monitor and control the
manufacturing operations. In quality control, computers are used to perform
inspections and performance tests on the product and its components.
As illustrated in Figure, CAD/CAM is overlaid on virtually all of the
activities and functions of the product cycle. In the design and production operations
of a modem manufacturing firm, the computer has become a pervasive, useful, and
indispensable tool. It is strategically important and competitively imperative that
manufacturing firms and the people who are employed by them understand CAD/
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CAM.
Product cycle revised with CAD/CAM overlaid.
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(2) Computer Aided Assembly Planning
Computer aided assembly planning involves automatically determining a sequence
of motions to assemble a product from its individual parts. The motions can include
part motions, grasping locations, tool access, fixture planning, factory layout, and
many other issues, all of which have complex geometric components that use
computational geometry techniques. A number of technical issues that must be
addressed for assembly automation includes following;
(2.1) Representation of assemblies and assembly plans
A computer representation of mechanical assemblies is necessary in order to
automate the generation of assembly plans. The main issue in this stage is to
decide what information about assemblies is required, and how this information is
represented in the computer. An assembly of parts can be represented by the
description of its individual components and their relationships in the assembly.
Assembly data base stores the geometric models of individual parts, the spatial
positions and orientations of the parts in the assembly, and the assembly or
attachment relationships between parts. One of the widely used methods for
representation of assemblies is based on graph structures. In this scheme, an
assembly model is represented by a graph structure in which each node
represents an individual part or a sub assembly. The branches of the graph
represent relationship among parts. Four kinds of relationships exist: part-of (P),
attachment (A), constraint (C) and sub assembly (SA).
(2.2) Generation of Assembly Sequences and Assembly plans
For usefulness, an assembly planning system must generate correct assembly
plans. Further, to solve problems that require optimization, such as selection of best
assembly alternative, one must be able to traverse the space of all candidate
solutions. The number of distinct feasible assembly plans can be large even for
assemblies made of a small number of parts therefore complete enumeration is not
possible in most cases real applications. Finding systematic ways to narrow down
alternatives is crucial for the automatic planning of assembly..
(2.3) Integration with CAD programs
A mechanical assembly is a composition of interconnected parts. Frequently, the
parts are being designed using CAD programs therefore the shape of each part and
geometric information are already available in computer database. The assembly
planning will be more efficient if these CAD databases can be directly integrated with
programs that generate assembly models.
(2.4) Integration with task and motion planners
With the progress of digital electronics, the programmable robots are introduced in
manufacturing. These robots can be adapted to execute different operations by
changing their internal programs. Task and motion planners that will facilitate robot
programming are constantly getting developed. With a view toward future
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integration, the output of assembly planners should compatible with what is required
by task and motion planners. It is also desirable that assembly planners also take
into account the capabilities and limitations of task and motion planners.
(3) Benefits of Computer Aided Assembly Planning
 Accelerate new product introductions
 Shorten time-to-production
 Optimize production management
 Decrease operating costs
 Ensure overall product and process quality
 Allow engineers, designers and shop floor personnel to collaborate
interactively
Computer Aided Inspection
Computer Aided Inspection (CAI) is a new technology that enables one to develop a
comparison of a physical part to a 3D CAD model. This process is faster, more
complete, and more accurate than using a Coordinate Measuring Machine (CMM) or
other more traditional methods. An automatic inspection method and apparatus using
structured light and machine vision camera is used to inspect an object in conjunction
with the geometric model of the object. Camera images of the object are analyzed by
computer to produce the location of points on the object’s surfaces in three dimensions.
Point-cloud data is taken from a laser scanner or other 3-D scanning device. During a
setup phase before object inspection, the points are analyzed with respect to the
geometric model of the object. The software provides a graphical comparison of the
manufactured part compared to the CAD model. Many points are eliminated to reduce
data-taking and analysis time to a minimum and prevent extraneous reflections from
producing errors. When similar objects are subsequently inspected, points from each
surface of interest are spatially averaged to give high accuracy measurements of object
dimensions. The inspection device uses several multiplexed sensors, each composed of
a camera and a structured light source, to measure all sides of the object in a single
pass.
Computers are used in many ways in inspection planning and execution also.
Computer controlled inspection equipment
Coordinate Measuring Machine (CMM) is a 3-dimensional measuring device that uses a
contact probe to detect the surface of the object. The probe is generally a highly
sensitive pressure sensing device that is triggered by any contact with a surface. The
linear distances moved along the 3 axes are recorded, thus providing the x, y and z
coordinates of the point. CMMs are classified as either vertical or horizontal, according
to the orientation of the probe with respect to the measuring table.
Computer aided inspection setup planning
Computer-Aided Inspection Planning (CAIP) is the integration bridge between
CAD/CAM and Computer Aided Inspection (CAI). A CAIP system for On-Machine
Measurement (OMM) is proposed to inspect the complicated mechanical parts efficiently

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during machining or after machining. The inspection planning consists of Global
Inspection Planning (GIP) and Local Inspection Planning (LIP). In the GIP, the system
creates the optimal inspection sequence of features in a given part by analyzing the
various feature information. Feature groups are formed for effective planning, and
special feature groups are determined for sequencing. The integrated process and
inspection plan is generated based on the series of heuristic rules developed. The
integrated inspection planning is able to determine optimum manufacturing sequence for
inspection and machining processes. Finally, the results are simulated and analyzed to
verify the effectiveness of the proposed CAIP.
Rapid Prototyping
Rapid prototyping is the idea of quickly assembling a physical part, piece or model of a
product. This is often done using sophisticated computer-aided design or other assembly
software, and physically implemented using 3-D printers.
The term rapid prototyping originally described only the methods for fast production of
models, patterns or simple prototypes by using generative production methods. The initial
point was a digital, three-dimensional design data. For the implementation of this technology,
the development of a data interface was important. The data interface can give exact
descriptions of the geometries of the object and can be used by rapid prototyping
mechanisms. This was possible with the development of data format STL
(STereoLithography). The STL interface was originally developed for the stereolithography
process and has proved its worth as a data standard. Over time Rapid Prototyping also
included the terms Rapid Tooling and Rapid Manufacturing.
Rapid Tooling is the rapid production of tools and tooling inserts by using the same
procedures as in Rapid Prototyping. Rapid manufacturing produces compared to RP and RT,
functioning final products. Also here, like it is with the other two, generative methods are
used. Rapid Tooling is especially for areas, where individualized products, components or
customer-focused and small numbers of products are needed, interesting.
Example Prototype of a grab hand, produced with Polyjet
ManufacturingMethodsofRapidPrototyping
 Colorjet: Many tenth millimeter layers of full-colored plaster are glued together. Because
of the ability to print full- colored it is especially used for visual models or models for
exhibition models.
 Fused Deposition Modeling (FDM): The object is built up with melted plastic which
comes out drop by drop out of a extruder. Quickly robust plastic models are possible.
Leading method by home printing.
 Stereolithografie (SLA): A liquid resin is hardened via laser. Vers detailed models are
possible and it is also used for production of individual products.
 PolyJet: A print head applies small drops of photosensitive polymer on a platform. This
drops are hardened immediately with UV-laser. While printing, a combination of
multiple materials is possible. So very realistic prototypes can be produced.
 Selective Laser Sintering (SLS)/Selective Laser Melting (SLM): With the aid of a highly
productive laser, the raw material in powder is molded by melting/ sintering. Both

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technologies are suitable for the production of functional models and small batch series.
Both provide the opportunity to treat metal.
 HP Multi Jet Fusion: A heat-conductive liquid („fusing agent‟) is ejected onto a layer of
powder. In a second step, a heat source is applied, which causes the fusing agent covered
areas to melt. When cooling down, the melted areas solidify to a physical object. The
technology allows high-throughput production of high-quality and high-accuracy plastic
parts.
TheadvantagesofRapidPrototyping
The great advantage of rapid prototyping is that you can get the model, prototype, or tool you
want really quick. The producing period depends on selected methods and the size,
complexity of the object, but also on the quality of the digital model you have. Generally, the
productions doesn‟t take longer than a few days. Thanks to this speed, models and prototypes
can be used more often and earlier. The printed objects can be used for visualizations or
exhibitions and help to reduce e.g. faulty designs. The earlier such defaults are found the
more cost-effectively they can be repaired.
In addition to speed, Rapid Prototyping technologies have another advantage. Due to the
generative construction of objects, by RP there is no large part of waste like in other
processes, such as cutting, milling, turning or grinding. This is not only to be considered for
reasons of cost but also to save resources. By methods which use a powder bed, the powder
can be used all right for further prints. In SLA and FDM and Polyjet processes, some forms
require support material (support) which has to be removed after printing. But by clever
modeling this can be reduced to a minimum.
Rapid prototyping will then get to its cost limits, when you want to a normal (above small
batch series) or serial production. But with single-digit numbers or a few dozen to a few
hundred pieces, the RP procedures offer you not only a speed but also a cost advantage,
compared to traditional manufacturing methods. Especially if you want to offer personalized
or individual products for your customers or create three-dimensional objects for yourself,
the processes, which are summarized under the term rapid prototyping, unfold their potential.
Another trend that is associated with the establishment of rapid prototyping is a beginning re-
regionalization. The sinking acquisition costs for rapid prototyping machines make it
possible for more and more companies to buy their own printer and and so produce their own
models, prototypes or end products. So they don‟t have to buy such services or products from
other suppliers. For private users, this technology makes it possible to manufacture spare
parts or gadgets by themselves, and to be independently from other manufacturers or
suppliers. Now, everyone can become a “manufacturer”, the only thing you need is a 3D
printer and a printable digital 3D model.
COMPUTER AIDED PROCESS PLANNING

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Process planning is concerned with determining the sequence of individual manufacturing
operation needed to produce a given product.
 The resulting operation sequence is documented on a form called as operation sheet.
Manufacturing planning, process planning, material processing, process engineering machine
routing are contents under process planning.
Activities
 Selection of processes and tools
 Selection of m/c tools and equipments
 Sequencing the operations
 Grouping of operations
 Selection of work piece holding devices
 Selection of inspection instruments
 Determining the tolerances
 Determining proper cutting conditions
 Determining the machining time and non machining time
 Editing the process sheets
Need of CAPP
In conventional planning the plan is created by planners who have their own ideas and
opinions about best routing.
 Thus it has different plans by the different planners for the same product process.
 It thus requires experienced planner for efficient planning.
 It requires lot of time
Introduction to CAPP
In recent years attempts have been made to capture logic, judgment and experience required
and incorporated them in computer.
Based on characteristics of the product automatically generates the sequence of
manufacturing operations.
The automation provides opportunity to generate production routings which are rational,
consistent and perhaps even optimal.
Requirements for CAPP
The input to system may be engineering drawing or CAD database. The other requisites are :-
 Part list
 Annual demand / batch size
 Accuracy and surface finish requirement
 Equipment details
 Data on cutting fluids, tools, jigs and fixtures, gauges.
 Standard available stock size
 Machining data, data on handling and setup
C. A. P. P. Can be classified as :-
 1.variant approach
 2. Generative approach

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THE DESIGN PROCESS
Before examining the several facets of computer-aided design, let us first
consider the general design process. The process of designing something is
characterized by Shigley as an iterative procedure, which consists of six identifiable
steps or phases:-
1. Recognition ofneed
2. Definition ofproblem
3. Synthesis
4. Analysis andoptimization
5. Evaluation
6. Presentation
Recognition of need involves the realization by someone that a problem
exists for which some corrective action should be taken. This might be the
identification of some defect in a current machine design by an engineer or the
perception of a new product marketing opportunity by a salesperson. Definition of
the problem involves a thorough specification of the item to be designed. This
specification includes physical and functional characteristics, cost, quality, and
operating performance.
Synthesis and analysis are closely related and highly interactive in the
design process. A certain component or subsystem of the overall system is
conceptualized by the designer, subjected to analysis, improved through this analysis
procedure, and redesigned. The process is repeated until the design has been
optimized within the constraints imposed on the designer. The componentsand

subsystems are synthesized into the final overall system in a similar interactive
manner.
Evaluation is concerned with measuring the design against the specifications
established in the problem definition phase. This evaluation often requires the
fabrication and testing of a prototype model to assess operating performance, quality,
reliability, and other criteria. The final phase in the design process is the presentation
of the design. This includes documentation of the design by means of drawings,
material specifications, assembly lists, and so on. Essentially, the documentation
requires that a design database be created. Figure illustrates the basic steps in the
design process, indicating its iterative nature.
The general design process as defined by Shigley .
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Engineering design has traditionally been accomplished on drawing boards, with the
design being documented in the form of a detailed engineering drawing. Mechanical
design includes the drawing of the complete product as well as its components and
subassemblies, and the tools and fixtures required to manufacture the product.
Electrical design is concerned with the preparation of circuit diagrams, specification
of electronic components, and so on. Similar manual documentation is required in
other engineering design fields (structural design, aircraft design, chemical
engineering design, etc.). In each engineering discipline, the approach has
traditionally been to synthesize a preliminary design manually and then to subject
that design to some form of analysis. The analysis may involve sophisticated
engineering calculations or it may involve a very subjective judgment of the aesthete
appeal possessed by the design. The analysis procedure identifies certain
improvements that can he made in the design. As stated previously, the process is
iterative. Each iteration yields an improvement in the design. The trouble with this
iterative process is that it is time consuming. Many engineering labor hours are
required to complete the designproject.
THE APPLICATION OF COMPUTERS FOR DESIGN
The various design-related tasks which are performed by a modem
computer-aided design-system can be grouped into four functional areas:
1. Geometricmodeling
2. Engineeringanalysis
3. Design review andevaluation
4. Automated drafting
These four areas correspond to the final four phases in Shigley's general
design process, illustrated in Figure. Geometric modeling corresponds to the
synthesis phase in which the physical design project takes form on the ICG system.
Engineering analysis corresponds to phase 4, dealing with analysis and optimization.
Design review and evaluation is the fifth step in the general design procedure.
Automated drafting involves a procedure for converting the design image data
residingincomputermemoryintoahard-copydocument.Itrepresentsanimportant

method for presentation (phase 6) of the design. The following four sections explore
each of these four CAD functions.
Geometric modeling
In computer-aided design, geometric modeling is concerned with the
computer-compatible mathematical description of the geometry of an object. The
mathematical description allows the image of the object to be displayed and
manipulated on a graphics terminal through signals from the CPU of the CAD
system. The software that provides geometric modeling capabilities must be designed
for efficient use both by the computer and the human designer.
To use geometric modeling, the designer constructs, the graphical image of
the object on the CRT screen of the ICG system by inputting three types of
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commands to the computer. The first type of command generates basic geometric
elements such as points, lines, and circles. The second command type is used to
accomplish scaling, rotating, or other transformations of these elements. The third
type of command causes the various elements to be joined into the desired shape of
the object being creaed on the ICG system. During the geometric modeling process,
the computer converts the commands into a mathematical model, stores it in the
computer data files, and displays it as an image on the CRT screen. The model can
subsequently be called from the data files for review, analysis, or alteration.
There are several different methods of representing the object in geometric
modeling. The basic form uses wire frames to represent the object. In this form, the
object is displayed by interconnecting lines as shown in Figure. Wire frame
geometric modeling is classified into three types depending on the capabilities of the
ICG system. The three types are:
1. 2D. Two-dimensional representation is used for a flatobject.
2. 2½D. This goes somewhat beyond the 2D capability by permitting a
three-dimensional object to be represented as long as it has no side-walldetails.
3. 3D. This allows for full three-dimensional modeling of a more complex
geometry.

Example of wire-frame drawing of a part.
Even three-dimensional wire-frame representations of an object are sometimes
inadequate for complicated shapes. Wire-frame models can be enhanced by several
different methods. Figure shows the same object shown in the previous figure but
with two possible improvements. 1be first uses dashed lines to portray the rear edges
of the object, those which would be invisible from the front. 1be second
enhancement removes the hidden lines completely, thus providing a less cluttered
picture of the object for the viewer. Some CAD systems have an automatic "hidden-
line removal feature," while other systems require the user to identify the lines that
are to be removed from view. Another enhancement of the wire-frame model
involves providing a surface representation which makes the object appear solid to
the viewer. However, the object is still stored in the computer as a wire-framemodel.
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Same workpart as shown in Figure 4.4 but with (a) dashed lines 10 show rear edges
of part, and (b) hidden-line removal. (Courtesy of Computervision Corp.)
Solid model of yoke part as displayed on a computer graphics system. (Courtesy of
Computervision Corp.)
The most advanced method of geometric modeling is solid modeling in
three dimensions. This method, illustrated in Figure, typically uses solid geometry
shapes called primitives to construct theobject.
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Another feature of some CAD systems is color graphics capability. By
means of colour, it is possible to display more information on the graphics screen.
Colored images help to clarify components in an assembly, or highlight dimensions,
or a host of other purposes.
Engineering analysis
In the formulation of nearly any engineering design project, some type of
analysis is required. The analysis may involve stress-strain calculations, heat-transfer
computations, or the use of differential equations to describe the dynamic behavior of
the system being designed. The computer can be used to aid in this analysis work. It
is often necessary that specific programs be developed internally by the engineering
analysis group to solve a particular design problem. In other situations, commercially
available general-purpose programs can be used to perform the engineering analysis.
Turnkey CAD/CAM systems often include or can be interfaced to
engineering analysis software which can be called to operate on the current design
model.
We discuss two important examples of this type:
Analysis of mass properties
Finite-element analysis
The analysis of mass properties is the analysis feature of a CAD system that
has probably the widest application. It provides properties of a solid object being
analyzed, such as the surface area, weight, volume, center of gravity, and moment of
inertia. For a plane surface (or a cross section of a solid object) the corresponding
computations include the perimeter, area, and inertia properties.
Probably the most powerful analysis feature of a CAD system is the finite-
element method. With this technique, the object is divided into a large number of
finite elements (usually rectangular or triangular shapes) which form an
interconnecting network of concentrated nodes. By using a computer with significant
computational capabilities, the entire Object can be analyzed for stress-strain, heat
transfer, and other characteristics by calculating the behavior of each node. By
determining the interrelating behaviors of all the nodes in the system, the behavior of

the entire object can be assessed.
Some CAD systems have the capability to define automatically the nodes
and the network structure for the given object. 1be user simply defines certain
parameters for the finite-element model, and the CAD system proceeds with the
computations.
The output of the finite-element analysis is often best presented by the
system in graphical format on the CRT screen for easy visualization by the user, For
example, in stress-strain analysis of an object, the output may be shown in the form
of a deflected shape superimposed over the unstressed object. This is illustrated in
Figure. Color graphics can also be used to accentuate the comparison before and
after deflection of the object. This is illustrated in Figure for the same image as that
shown in Figure . If the finite-element analysis indicates behavior of the design
which is undesirable, the designer can modify the shape and recompute the finite-
element analysis for the reviseddesign.
Finite-element modeling for stress-strain analysis. Graphics display shows strained
part superimposed on unstrained part for comparison.
Design review and evaluation
Checking the accuracy of the design can be accomplished conveniently on
the graphics terminal. Semiautomatic dimensioning and tolerancing routines which
assign size specifications to surfaces indicated by the user help to reduce the
possibility of dimensioning errors. The designer can zoom in on part design details
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and magnify the image on the graphics screen for close scrutiny.
A procedure called layering is often helpful in design review. For example,
a good application of layering involves overlaying the geometric image of the final
shape of the machined part on top of the image of the rough casting. This ensures
that sufficient material is available on the casting to acccomplish the final machined
dimensions. This procedure can be performed in stages to check each successive step
in the processing of thepart.
Another related procedure for design review is interference checking. This
involves the analysis of an assembled structure in which there is a risk that the
components of the assembly may occupy the same space. This risk occurs in the
design of large chemical plants, air-separation cold boxes, and other complicated
piping structures.
One of the most interesting evaluation features available on some computer-
aided design systems is kinematics. The available kinematics packages provide the
capability to animate the motion of simple designed mechanisms such as hinged
components and linkages. This capability enhances the designer‟s visualization of the
operation of the mechanism and helps to ensure against interference with other
components. Without graphical kinematics on a CAD system, designers must often
resort to the use of pin-and-cardboard models to represent the mechanism.
commercial software packages are available to perform kinematic analysis. Among
these are programs such as ADAMS (Automatic Dynamic Analysis of Mechanical
Systems), developed at the University of Michigan. This type of program can be very
useful to the designer in constructing the required mechanism to accomplish a
specified motion and/or force.
Automated drafting
Automated drafting involves the creation of hard-copy engineering
drawings directly from the CAD data base. In some early computer-aided design
departments, automation of the drafting process represented the principal
justification for investing in the CAD system. Indeed, CAD systems can increase
productivity in the drafting function by roughly five times over manualdrafting.
Some of the graphics features of computer-aided design systems lend them-

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selves especially well to the drafting process. These features include automatic
dimensioning, generation of crosshatched areas, scaling of the drawing, and the
capability to develop sectional views and enlarged views of particular path details.
The ability to rotate the part or to perform other transformations of the image (e.g.,
oblique, isometric, or perspective views), as illustrated in Figure, can be of
significant assistance in drafting. Most CAD systems are capable of generating as
many as six views of the part. Engineering drawings can be made to adhere to
company drafting standards by programming the standards into the CAD system.
Figure shows an engineering drawing with four views displayed. This drawing was
produced automatically by a CAD system. Note how much the isometric view
promotes a higher level of understanding of the object for the user than the three
orthographic views.
Parts classification and coding
In addition to the four CAD functions described above, another feature of
the CAD data base is that it can be used to develop a parts classification and coding
system. Parts classification and coding involves the grouping of similar part designs
into classes, and relating the similarities by mean of a coding scheme. Designers can
use the classification and coding system to retrieve existing part designs rather than
always redesigning new parts.
CREATING THE MANUFACTURING DATA BASE
Another important reason for using a CAD system is that it offers the
opportunity to develop the data base needed to manufacture the product. In the
conventional manufacturing cycle practiced for so many years in industry,
engineering drawings were prepared by design draftsmen and then used by
manufacturing engineers to develop the process plan (i.e., the "route sheets"). The
activities involved in designing the product were separated from the activities
associated with process planning. Essentially, a two-step procedure was employed.
This was both time consuming and involved duplication of effort by design and
manufacturing personnel. In an integrated CAD/CAM system, a direct link is
established between product design and manufacturing: It" is the goal of CAD/CAM
not only to automate certain phases of design and certain phases of manufacturing,

but also to automate the transition from design to manufacturing. Computer-based
systems have been developed which create much of the data and documentation
required to plan and manage the manufacturing operations for the product.
The manufacturing data base is an integrated CAD/CAM data base. It
includes all the data on the product generated during design (geometry data, bill of
materials and parts lists, material specifications, etc.) as well as additional data
required for manufacturing much of which is based 011 the product design. Figure
4.10 shows how the CAD/CAM data base is related to design and manufacturing in a
typical production-oriented company.
FIGURE Desirable relationship of CAD/CAM data base to CAD and CAM.
BENERTS OF COMPUTER-AIDED DESIGN
There are many benefits of computer-aided design, only some of which can
be easily measured. Some of the benefits are intangible, reflected in improved work
quality, more pertinent and usable information, and improved control, all of which
are difficult to quantify. Other benefits are tangible, but the savings from them show
up far downstream in the production process, so that it is difficult to assign a dollar
figure to them in the design phase. Some of the benefits that derive from
implementing CAD/CAM can be directly measured. Table provides a checklistof
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1-24
1. Improved engineeringproductivity
2. Shorter leadtimes
3. Reduced engineering personnelrequirements
4. Customer modifications are easier tomake
5. Faster response to requests for quotations
6. Avoidance of subcontracting to meetschedules
7. Minimized transcriptionerrors
8. Improved accuracy ofdesign
9. In analysis, easier recognition of component interactions
10. Provides better functional analysis to reduce prototypetesting
11. Assistance in preparation ofdocumentation
12. Designs have morestandardization
13. Better designsprovided
14. Improved productivity in tooldesign
15. Better knowledge of costsprovided
16. Reduced training time for routine drafting tasks and NC part
programming
17. Fewer errors in NC partprogramming
18. Provides the potential for using more existing parts andtooling
19. Helps ensure designs are appropriate to existing manufacturing
techniques
20. Saves materials and machining time by optimizationalgorithms
potential benefits of an integrated CAD/CAM system. In the subsections that follow,
we elaborate on some of these advantages.
Productivity improvement in design
Increased productivity translates into a more competitive position for the
firm because it will reduce staff requirements on a given project. This leads to lower
costs in addition to improving response time on projects with tight schedules.
Surveying some of the larger CAD/CAM vendors, one finds that the
Productivity improvement ratio for a designer/draftsman is usually given as a range,
typically from a low end of 3: 1 to a high end in excess of 10: 1 (often far in excess
of that figure). There are individual cases in which productivity has been increased
by a factor of 100, but it would be inaccurate to represent that figure astypical.
TABLE Potential Benefits That May Result from implementing CAD as
Part of an Integrated CAD/CAMSystem.

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Productivity improvement in computer-aided design as compared to the
traditional design process is dependent on such factors as:
Complexity of the engineering drawing
Level of detail required in the drawing
Degree of repetitiveness in the designed parts
Degree of symmetry in theparts
Extensiveness of library of commonly used entities
As each of these factors is increased. the productivity advantage of CAD
will tend toincrease
Shorter lead times
Interactive computer-aided design is inherently faster than the traditional
design. It also speeds up the task of preparing reports and lists (e.g., the assembly
lists) which are normally accomplished manually. Accordingly, it is possible with a
CAD system to produce a finished set of component drawings and the associated
reports in a relatively short time. Shorter lead times in design translate into shorter
elapsed time between receipt of a customer order and delivery of the final product.
The enhanced productivity of designers working with CAD systems will tend to
reduce the prominence of design, engineering analysis, and drafting as critical time
elements in the overall manufacturing lead time.
Design analysis
The design analysis routines available in a CAD system help to consolidate
the design process into a more logical work pattern. Rather than having a back- and-
forth exchange between design and analysis groups, the same person can perform the
analysis while remaining at a CAD workstation. This helps to improve the
21. Provides operational results on the status of work inprogress
22. Makes the management of design personnel on projects more
effective
23. Assistance in inspection of complicatedparts
24. Better communication interfaces and greater understanding among
engineers, designers, drafters, management, and different project
groups.

1-26
concentration of designers, since they are interacting with their designs in a real-time
sense. Because of this analysis capability, designs can be created which are closer to
optimum. There is a time saving to be derived from the computerized analysis
routines, both in designer time and in elapsed time. This saving results from the rapid
response of the design analysis and from the tune no longer lost while the design
finds its way from the designer's drawing board to the design analyst's queue and
back again.
Fewer design errors
Interactive CAD systems provide an intrinsic capability for avoiding design,
drafting, and documentation errors. Data entry, transposition, and extension errors
that occur quite naturally during manual data compilation for preparation of a bill of
materials are virtually eliminated. One key reason for such accuracy is simply that
No manual handling of information is required once the initial drawing has
been developed. Errors are further avoided because interactive CAD systems perform
time-consuming repetitive duties such as multiple symbol placement, and sorts by
area and by like item, at high speeds with consistent and accurate results. Still more
errors can be avoided because a CAD system, with its interactive capabilities, can be
programmed to question input that may be erroneous. For example, the system might
question a tolerance of 0.00002 in. It is likely that the user specified too many zeros.
The success of this checking would depend on the ability of the CAD system
designers to determine what input is likely to be incorrect and hence, what to
question.
Greater accuracy in design calculations
There is also a high level of dimensional control, far beyond the levels of
accuracy attainable manually. Mathematical accuracy is often to 14 significant
decimal places. The accuracy delivered by interactive CAD systems in three-
dimensional curved space designs is so far behind that provided by manual
calculation methods that there is no real comparison.
Computer-based accuracy pays off in many ways. Parts are labeled by the
same recognizable nomenclature and number throughout all drawings. In some CAD
systems, a change entered on a single item can appear throughout the entire

documentation package, effecting the change on all drawings which utilize that part.
The accuracy also shows up in the form of more accurate material and cost estimates
and tighter procurement scheduling. These items are especially important in such
cases as long-lead-time material purchases.
Standardization of design, drafting, and documentation procedures
The single data base and operating system is common to all workstations in
the CAD system: Consequently, the system provides a natural standard for
design/drafting procedure -With interactive computer-aided design, drawings are
“standardized” as they are drawn; there is no confusion as to proper procedures
because the entire format is "built into" the system program.
Drawings are more understandable
Interactive CAD is equally adept at creating and maintaining isometrics and
oblique drawings as well as the simpler orthographies. All drawings can he generated
and updated with equal ease. Thus an up-to-date version of any drawing type can
always he made available.
FIGURE Improvement in visualization of images for various drawing types and
computer graphics features.
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1-28
In general, ease of visualization of a drawing relates directly to the
projection used. Orthographic views are less comprehensible than isometrics. An
isometric view is usually less understandable than a perspective view. Most actual
construction drawings are "line drawings." The addition of shading increases
comprehension. Different colors further enhance understanding. Finally, animation
of the images on the CRT screen allows for even greater visualization capability. The
various relationships are illustrated inFigure..
Improved procedures for engineering changes
Control and implementation of engineering changes is significantly
improved with computer-aided design. Original drawings and reports are stored in
the data base of the CAD system. This makes them more accessible than documents
kept in a drawing vault. They can be quickly checked against new information. Since
data storage is extremely compact, historical information from previous drawings can
be easily retained in the system's data base, for easy comparison with current
design/drafting needs.
Benefits in manufacturing
The benefits of computer-aided design carry over into manufacturing. As
indicated previously, the same CAD/CAM data base is used for manufacturing
planning and control, as well as for design. These manufacturing benefits are found
in the following areas:
Tool and fixture design for manufacturing
Numerical control part programming
Computer-aided process planning
Assembly lists (generated by CAD) for production
Computer-aided inspection
Robotics planning
Group technology
Shorter manufacturing lead times through better scheduling

1-24
Advantages of CAD:
1. Decrease in error percentage: As the CAD software makes use of some of the best
tools, the percentage of error that occurred because of manual designing is
significantlyreduced.
2. Decrease in effort: When it comes to the amount of effort that was needed for the
sake of designing the different models, it has been reduced significantly because the
software automates most of thetask.
3. Saves time: When you are using the computer aided design software, it will save your
time and you can make better and more efficient designs in shorter timeduration.
4. Easy to edit: When you are making designs, you may find the need to make
alterations. When you are using computer aided design software, it will be much
easier to make any changes because you can fix the errors and modify the drawings
easily.
5. Code re-use: As the entire task is carried out with the help of computer tools, it
removes the problem of duplication of labor, you can copy the different parts of code
and design which can then be reused multiple times over and overagain.
6. Improved accuracy: There is absolutely no doubt about the fact that the kind of
accuracy that CAD software will offer can never be achieved by opting for manual
drawings. You have tools to measure the precision, skill and accuracy level of the
designs.
7. Easy to share: The CAD tools make it easier to save the files and store it in a way
that you can use it time and again and send it without any unwanted hasslestoo.
Applications of CAD
1. Aerospace
When it comes to space shuttles, missiles and even high-tech aircrafts, it is CAD that
will turn out to be handy. Computer aided design software will come in handy in
designing some of the best models. When missiles and shuttles are designed, there is
immense need for having top accuracy. Further, the designing can be hugely complex
because there are various parameters that have to be borne in mind. It is the CAD
software that can be used for methodological planning and when implemented
diligently, it can aid in making some of the most meticulous and useful designs.
2. CivilEngineering
When it comes to construction of civil projects, there is a lot of designing that is
involved. Planning bridges and even towers and other structures needs special
consideration of some of the main points. Even a minor flaw in the design can be
problematic and it can create a big ruckus. This is why CAD software is put to use as
the different tools will come in handy in sketching the fine details of what you really
desire.
3. Landscaping
When you are designing landscapes, you need to be sure that you have a well thought
plan. The different outdoor detailing, floor plan and other aspects have to be judged
meticulously and once again, the need for accuracy is very high. In the field of
landscaping, one needs to be sure that all the main aspects have been taken care of
and there may be a lot of edits that may have to be made. Making a manual
landscaping plan can be a tedious job and very time consuming. On the contrary,
whenyoufallbackoncomputeraideddesignsoftware,youwillbeabletodesign

1-25
some of the best landscape models that will be apt and will serve the need diligently
too.
4. JewelryDesigning
Jewelry designing is one of the big booming businesses because there is a whopping
demand for some of the best jewelry pieces. When you use CAD software, you will
be able to come up with new and winning designs and the precision and details that
you can add to the pieces is worth a round of applause aswell.
There are different types of CAD software which can be used for designing jewelry
and even other accessories too. When it comes to fine imprint in jewelry, it is the
CAD software that will turn out to behandy.
5. Cartography
Cartography is the field of map making. There was a time when maps were made
manually by noting the details and carefully using the right scale and making the right
demarcations. It is needless to add that despite using the best scales, there was
provision for some errors. However, with the smart use of computer aided design
tools, you can now make some of the most accurate maps with ease. The CAD tools
can easily take in the details and distances and make some of the most accurate maps
that one can ask for.
These are some of the fields where CAD tools have found their use and it has become
an inseparable part of these industries no because too many people rely on computer
aided design tools.
Disadvantages of CAD
1. Costlystart-up:
When initially starting, factors like hardware, software and location may be required
which translates into high expanses.
2. Training:
Before proper operation, elaborate training may be required in order to ensure better
product quality.
ComputerAided Engineering:
Computer-Aided-Engineering (CAE) is the use of computers in modelling
engineering factors, processes, or systems, such as heat transfer, liquid and gas flows, stresses
andstrains.

Concurrent Engineering:
Concurrent engineering or Simultaneous Engineering is a methodology of
restructuring the product development activity in a manufacturing organization using a cross
functional team approach and is a technique adopted to improve the efficiency of product
design and reduce the product development cycle time. This is also sometimes referred to as
Parallel Engineering. Concurrent Engineering brings together a wide spectrum of people from
several functional areas in the design and manufacture of a product. Representatives from R
& D, engineering, manufacturing, materials management, quality assurance, marketing etc.
develop the product as a team. Everyone interacts with each other from the start, and they
perform their tasks in parallel. The team reviews the design from the point of view of
marketing, process, tool design and procurement, operation, facility and capacity planning,
design for manufacturability, assembly, testing and maintenance, standardization,
procurement of components and sub-assemblies, quality assurance etc as the design is
evolved. Even the vendor development department is associated with the prototype
development. Any possible bottleneck in the development process is thoroughly studied and
rectified. All the departments get a chance to review the design and identify delays and
difficulties. The departments can start their own processes simultaneously. For example, the
tool design, procurement of material and machinery and recruitment and training of
manpower which contributes to considerable delay can be taken up simultaneously as the
design development is in progress. Issues are debated thoroughly and conflicts are resolved
amicably.
Concurrent Engineering (CE) gives marketing and other groups the opportunity to
review the design during the modeling, prototyping and soft tooling phases of development.
CAD systems especially 3D modelers can play an important role in early product
development phases. In fact, they can become the core of the CE. They offer a visual check
when design changes cost the least.
Intensive teamwork between product development, production planning and
manufacturing is essential for satisfactory implementation of concurrent engineering. The
teamwork also brings additional advantages ; the co-operation between various specialists
and systematic application of special methods such as QFD (Quality Function Deployment),
DFMA (Design for Manufacture and Assembly) and FMEA (Failure Mode and Effect
Analysis) ensures quick optimization of design and early detection of possible faults in
product and production planning. This additionally leads to reduction in lead time which
reduces cost of production and guarantees betterquality.
Differentiate between concurrent engineering and sequential engineering:
Sequential engineering is the term used to describe the method of production in a linear
format. The different steps are done one after another, with all attention and resources
focused on that one task. After it is completed it is left alone and everything is concentrated
on the next task.
In concurrent engineering, different tasks are tackled at the same time, and not necessarily in
the usual order. This means that info found out later in the process can be added to earlier
parts, improving them, and also saving a lot of time.
Concurrent engineering is a method by which several teams within an organization work
simultaneously to develop new products and services and allows a more stream lined
approach.
1

The concurrent engineering is a non-linear product or project design approach during which
all phases of manufacturing operate at the same time - simultaneously. Both product and
process design run in parallel and occur inthe same time frame.
Product and process are closely coordinated to achieve optimal matching of requirements for
effective cost, quality, and delivery. Decision making involves full team participation and
involvement. The team often consists of product design engineers, manufacturing engineers,
marketing personnel, purchasing, finance, and suppliers.
Implementation of Concurrent Engineering:
The cycle of engineering design and manufacturing planning involves
interrelated activities in different engineering disciplines simultaneously, than sequentially as
shown in Fig. 2.9 (A). In addition, the activities necessary to complete a particular task
within a specific engineering discipline have to emerge wherever possible from their
sequential flow into a concurrent workflow with a high degree of parallelism as illustrated in
Fig. 2.9 (B). Concurrency implies that members of the multidisciplinary project team work in
parallel. This also means that there is no strict demarcation of jobs among various
departments. The multi-disciplinary approach has the advantage of several inputs which can
be focused effectively early in the design process. Presently engineering departments are
practicing this approach but still with a high degree of manual involvement and
redundancy. Planning scenarios experience a similar approach. One of the most critical links
in the entire product life cycle, i.e. the close interaction between design and
manufacturing has been made possible in concurrent engineering. Thus the product
development process has been freed from the large number of constraints arising from the
limitations of the sequential engineering. This has changed the way manufacturers
bring the products to market. For example, many manufacturers no longer view product
development as a relay race in which marketing passes the baton to R &D, which in
turn passes it to manufacturing. Representatives drawn from marketing, planning, design,
purchase, vendors, manufacturing, quality control and other department participate in
product development right from the beginning. Concurrent engineering is thus a cross-
functional approach to product design. Total quality management which is being
practiced by many companies is closely related to concurrentengineering.

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IMPORTANT EXAMINATION QUESTIONS:
JUNE 2014
Q. Elaborate with suitable figure product design process and role of CAD in it. (07 M)
Q. Differentiate between sequential approach and concurrent Engineering approach to
product development. Why should later be adopted. (06Marks)
DEC 2014
Q. What is „Concurrent Engineering‟ approach for product development? Explain key
principles of Concurrent Engineering. (07 Marks)
Q. Elaborate role of manufacturing database in an integrated CAD environment with suitable
figure. (06 Marks)
JUNE 2015
Q. Define and explain the following terms :- (06 Marks)
1. CAD
2. CAM
3. CAE
Q. Explain the roll of CAD, CAM and CIM in product life cycle. (07 Marks)
Q. Write short notes on (14 Marks)
1. ConcurrentEngineering
2. Manufacturing database.
NOV/DEC 2015
Q. Explain the use of computers in product life cycle with the help of neat block diagram.
(07Marks)
Q. Explain the role of manufacturing data base in CIM. (07 Marks)
1. CAD and CAMsoftware‟s
2. Product designprocess
3. Concurrentengineering

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MAY/JUNE 2016
Q. Discuss in details the role played by the CAD, CAM and CIM in product life cycle
with help of neat block diagram. (13 Marks)
NOV/DEC 2016
Q. Define the term CAD and list down its advantages and disadvantages. (07 Marks)
Q. Explain the difference in scope between automation and CAD/CAM. (06 Marks)
1. ConcurrentEngineering
2. Need and use of different standards inCAD

Prof. Shishir R. Rathod Page 1
DEC 2014
Q. What are the ground rules for design for graphics software ? Explain inbrief.
(07Marks)
JUNE 2015
Q. Explain the ground rules and functions to be performed by a graphic
software for CADworksystem. (07Marks)
CAD/CAM/CAE
UNIT 2
Syllabus:
 Ground rules for graphics software
 Software and hardware configuration of graphicsystem.
 Functions of graphicssystem.
 2D and 3D transformations of geometric models like translation, scaling,
rotation, reflection,shear.
 HomogenousRepresentation
 ConcatenatedRepresentation
 Orthographicprojections.
Ground rules for graphics software:
The following are the “ground rules” that should be considered in designing graphics
software:
1. Simplicity: The graphics software should be easy touse.
2. Consistency: The package should operate in a consistent and predictable way to
theuser.
3. Completeness: There should be no inconvenient omissions in the set of
graphicsfunction.
4. Robustness: The graphics system should be tolerant of minor instances of
misuse by theoperator.
5. Performance: Within limitations imposed by the system hardware, the
performance should be exploited as much as possible by software. Graphics
program should be efficient and speed of response should be fast and
consistent.

CAD/CAM/CAE
6. Economy: Graphics programs should not be so large or expensive as to make
their useprohibitive.
Prof. Shishir R. Rathod Page
JUNE 2014
Q. Explain software configuration of graphics system. (07 Marks)
Software configuration of graphics system:
The software configuration of a graphics system:
In the operation of the graphics system by the user, a variety of activities take place,
which can be divided into three types:
 Interact with the graphics terminal to create and alter images on thescreen
 Construct a model of something physical out of the images on the screen. The
models are sometimes called as applicationmodels
 Enter the model into computer memory and/or secondarystorage.
Graphics software
The graphics software can be divided into three modules
 The graphicspackage
 The applicationprogram
 The application database
FIG. 2.1 Model of graphics software configuration

CAD/CAM/CAE
Application Program
 This software configuration is illustrated in figure 2.1. The central module is
the applicationprogram.
 It controls the storage of data into and retrieves data out of application
database.
 The application program is driven by the user through the graphicspackage.
 The application program is implemented by the user to construct the model of a
physical entity whose image to be viewed on the graphicsscreen.
 Application programs are written for particular problemareas.
 Problem areas in engineering design would include architecture, construction,
mechanical components, electronics, chemical engineering, and aerospace
engineering.
 Problem areas other than deign include flight simulators, graphical display of
data, mathematical analysis, and evenartwork
Graphics Package
 The graphics package is the software support between the user and the graphics
terminal.
 It manages the graphical interaction between the user and thesystem.
 It also serves as the interface between the user and the applicationsoftware.
 The graphics package consists of input subroutines and outputsubroutines.
 The input subroutine accepts the input commands and data from the user and
forwards them to the applicationprogram.
 The output subroutines control the display terminal (or other output device) and
convert the application models into 2D or 3D graphicspictures.
Application data base
 The database contains mathematical, numerical and logical definitions of the
application models, such as electronic circuits, mechanical components,
automobile bodies, and soforth.
 It also contains alphanumeric information associated with the models, such as
bills of material, mass properties and otherdata.
 The contents of the data base can be readily displayed on the CRT or plotted
out in hard copyform.
Page 3

CAD/CAM/CAE
Functions of graphics system:
JUNE 2015
Q. Explain the ground rules and functions to be performed by a graphic
software for CADworksystem. (07Marks)
OCT/NOV 2016
Q. Enlist and explain the functions to be performed by a graphic package.
(06 Marks)
Page 4
Following are the functions of a graphic package:
 Generation of graphicelements
 Transformations
 Display control and windowingfunctions
 Segmentingfunctions
 User inputfunctions
Generation of graphic elements:
 A graphic element in computer graphics is a basic image entity such as a dot
(or point), line segment, circle, and so forth.
 The collection of elements in the system could also include alphanumeric
characters and specialsymbols.
 There is often a special hardware component in the graphics system associated
with the display of many of theelements.
 This speeds up the process of generating theelement.
 The user can construct the application model out of collection of elements
available on thesystem.
 The term primitive is used in reference to the graphicselement.
 A primitive is a three-dimensional graphic element such as a sphere, cube, or
cylinder
 In 3D wire frame models and solid modelling, primitives are used as building
blocks to construct the three-dimensional model of the particular object of
interest to theuser.

CAD/CAM/CAE
Transformations:
 Transformations are used to change the image on the displayscreen.
 Transformations are applied to graphics elements in order to aid the user in
constructing an applicationmodel
 It includes enlargement and reduction of the image by a process
calledscaling, repositioning the image or translation, androtation.
Display control and windowing functions:
 This provides the user with the ability to view the image from the desired and
the desiredmagnification.
 Another aspect of display control is hidden-lineremoval.
 In most graphics systems, the image is made up of lines used to represent a
particularobject.
 Hidden-line removal is the procedure by which the image is divided into its
visible and invisible (or hidden)lines.
Segmenting functions:
 Segmenting provides user with the capability to selectively replace, delete or
otherwise modify portions of theimage.
 The term “segment” refers to a particular portion of the image which has been
identified for purposes of modifyingit.
 The segment may be defined a single element or logical grouping of elements
that can be modified as aunit.
 Storage type CRT tubes are unsuited to segmentingfunctions.
User input functions:
 User input functions constitute a critical set of functions in the graphics
package because they permit the operator to enter commands or data to the
system.
 The entry is accomplished by means of operator inputdevices.
Page 5

CAD/CAM/CAE
Hardware configuration of graphics system:
JUNE 2015
Q. Explain the hardware requirements and its specifications for CAD work
system. (06Marks)
NOV DEC-2015/MAY JUNE-2016
Q. Explain the hardware and software requirements for implementing
CAD/CAMfacilities. (07Marks)
A CAD system includes the following hardware components:
 One or more design workstations. These would consist of:
A graphicsterminal
Operator input devices
 One or more plotters or other outputdevices
 Central processing unit(CPU)
 Secondarystorage
These hardware components would be arranged in a configuration as illustrated in
figure 2.2.
Figure.2.2 Typical configuration of hardware components
Page 6

CAD/CAM/CAE
The Design Workstation:
A typical interactive graphics workstation would consists of the following hardware
components:
 A graphicsterminal
 Operator inputdevices
The graphics terminal:
A graphical terminal can display images as well as text. Graphics terminal is an
important component of CAD providing a window through which the communication
with the computer can be realized.
Graphics terminals are classified as
 CRT
 Flat Screen (Plasma panel andLCD)
Cathode Ray Tube (CRT):
Figure 2.3. Diagram of Cathode Ray Tube
 Nearly all computer graphics terminals available today use the cathode ray
tube (CRT) displaydevice.
 The operation of the cathode ray tube illustrated in fig.2.3.
Page 7

NOV DEC-2015
Q. Explain and differentiate the image generation techniques.
MAY JUNE-2016
Page 8
(06 Marks)
CAD/CAM/CAE
 A high-vacuum tube in which cathode rays produce a image on a fluorescent
screen, used in televisions and computerterminals.
 A heated cathode emits a high-speed electron beam into a phosphor-coated
glassscreen.
 The electrons energize the phosphor coating, causing it to glow at the points
where the beam makescontact.
 By focusing the electron beam, changing its intensity, and controlling its
points of contact against the phosphor coating through the use of a deflector
system, the beam can be made to generate a picture on the CRTscreen.
Image generation technique:
Q. Explain the various image generation techniques used in graphic display
device. (07Marks)
OCT NOV-2016
Q. Explain with suitable examples various image generation techniques used
in graphicdisplaydevices. (07Marks)
There are basically two types of image-generation techniques that are used in
graphic display.
 Strokewriting
 Rasterscan
Stroke Writing:
 Other names for stroke writing techniques include line drawing, random
positioning, vector writing, stroke writing, and directedbeam.
 In this technique, the electron beam is directed only to the part of the screen
where the picture is to be drawn rather than scanning from left to right and top
to bottom as in raster scan. It is also called vector display, stroke-writing
display.

CAD/CAM/CAE
 The stroke -writing system uses an electron beam which operates like a pencil
to create a line image on the CRTscreen.
 The image is constructed out of a sequence of straight-linesegments.
Figure 2.4 Stroke writing for generating images on computer graphics.
Raster scan:
Figure 2.5 Raster scan approach for generating images in computer graphics.
 Other names for the raster scan technique include digital TV and scan
graphics.
 In the raster scan approach, the viewing screen is divided into a large of
discrete phosphor picture elements, calledpixels.
 The matrix of pixels constitutes theraster.
Page 9

CAD/CAM/CAE
 The number of separate pixels in the raster display might typically range from
256 X 256 (a total of over 65000) to 1024 X 1024 ( a total of over 1000000
points).
 Each pixels on the screen can be made on the to glow with a different
brightness.
 Colour screen provide for the pixels to have different colours as well as
brightness.
Difference between Stroke writing and Raster scan:
Stroke writing Raster scan
1. In stroke writing display the beam is
moved between the end points of the
graphics primitives.
In raster scan display the beam is moved
all over the screen one scan line at a
time,fromtopbottomandthenbackto
top.
2. It has high resolution. It has a poor or less resolution.
3. It is costlier than raster scan system. It is less expensive than stroke writing
system.
4. It draws only lines and characters. It can draw areas filled with colours.
5. Mathematical functions are used to
draw an image.
Screen points/pixels are used to draw an
image.
6. Scanning is done between the end
points.
Scanning is done one line at a timefrom
top to bottom and left to right.
7. Scan is not converted to pixels. Scan is converted to pixels.
8. Video controller is not required. Video controller is required.
9. Cannot draw realistic shaded scenes. Used in systems to display realistic
images.
10. E.g. Pen plotter. E.g. TV sets, computer monitors.
Page 10

CAD/CAM/CAE
Liquid Crystal Display:
MAY JUNE-2016
Q. Write short notes on LCD and plasma panel.
Page 11
(05 Marks)
LCD (liquid crystal display) is the technology used for displays in notebook
and other smaller computers. Like light-emitting diode (LED) and gas-plasma
technologies, LCDs allow displays to be much thinner than cathode ray tube (CRT)
technology. LCDs consume much less power than LED and gas-display displays
because they work on the principle of blocking light rather than emitting it.
The liquid-crystal display has the distinct advantage of having a low power
consumption than the LED. It is typically of the order of microwatts for the display in
comparison to the some order of mill watts for LEDs. Low power consumption
requirement has made it compatible with MOS integrated logic circuit. Its other
advantages are its low cost, and good contrast. The main drawbacks of LCDs are
additional requirement of light source, a limited temperature range of operation
(between 0 and 60° C), low reliability, short operating life, poor visibility in low
ambient lighting, slow speed and the need for an ac drive.
A liquid crystal cell consists of a thin layer (about 10 u m) of a liquid crystal
sandwiched between two glass sheets with transparent electrodes deposited on their
inside faces. With both glass sheets transparent, the cell is known as transmittive type
cell. When one glass is transparent and the other has a reflective coating, the cell is
called reflective type. The LCD does not produce any illumination of its own. It, in
fact, depends entirely on illumination falling on it from an external source for its
visualeffect
LCDs are used in a wide range of applications including computer monitors,
televisions, instrument panels, aircraft cockpit displays, and indoor and outdoor
signage. Small LCD screens are common in portable consumer devices such as digital
cameras, watches, calculators, and mobile telephones, including smart phones. LCD
screens are also used on consumer electronics products such as DVD players, video
game devices and clocks. LCD screens have replaced heavy, bulky cathode ray tube
(CRT) displays in nearly all applications. LCD screens are available in a wider range

CAD/CAM/CAE
of screen sizes than CRT and plasma displays, with LCD screens available in sizes
ranging from tiny digital watches to huge, big-screen television sets.
ADVANTAGES OF LCD
1. LCD TVs are not affected by the increase or decrease in the airpressure
2. LCD‟s are lighter in weight with respect to the screensize.
3. Screens are perfectlyflat.
4. Consume little electricity and produce littleheat.
5. Energy efficient and lowpower.
6. Excellentcontrast.
7. Light weight andcompact.
8. Screens are available in a vast range ofsizes.
9. Used in battery powerelectronics.
DISADVANTAGES OF LCD
1. Considerably more expensive than comparableCRTs.
2. The colour and contrast from various viewing angles isinconsistent.
3. Fixedresolution.
4. Never technology costmore.
5. The aspect ratio and resolution arefixed.
6. Lower contrast than CRTs due to a poor blacklevel.
Plasma Panel Display:
A plasma display is a type of flat panel display that uses plasma, an
electrically charged ionized gas, to illuminate each pixel in order to produce a display
output. It is commonly used in large TV displays of 30 inches and higher. Plasma
displays are often brighter than LCD displays and also have a wider colour gamut,
with black levels almost equalling "dark room" levels. Plasma displays are also
known as gas-plasma displays.
Page 12

CAD/CAM/CAE
Operator Input Devices:
NOV DEC-2015
Q. Explain the data input devices in CAD.
Page 13
(07 Marks)
MAY JUNE-2016
Q. Explain with neat sketches the data input devices in CAD. (06 Marks)
OCT NOV-2016
Q. Write short notes on Data input devices used in CAD (05 Marks)
Following are the important input devices which are used in a computer:
 Keyboard
 Mouse
 Joystick
 Lightpen
 Trackball
 Scanner
Keyboard:
 Keyboard is the most common and very popular input device which helps in
inputting data to thecomputer.
 These devices may be used for entering graphic data in a convenient form or
for selecting an item from the menu displayed on thescreen.
 The keys on the keyboard are as follows:
Typingkey
Numeric key
Function key
Control key
Special purpose key

CAD/CAM/CAE
Mouse:
 Pointing devices like mouse because by mouse we can performs operations
graphically.
 The mouse is a most popular pointingdevice.
 The mouse operates on three basic principles: Mechanical, Optical, and Opto-
Mechanical. The mechanical mouse contains a free floating ball with rubber
coating on theunderside.
 Generally it has two buttons called left and right button and a wheel is present
between thebuttons.
 Mouse can be used to control the position of cursor on screen, but it cannot be
used to enter text into thecomputer.
Joystick:
 Joystick is also a pointing device which used to move cursor position in a
monitorscreen.
 It is a stick having a spherical ball at its both lower and upperends.
 The lower spherical ball moves in asocket.
 The joystick can be moves in all fourdirections.
 The function of joystick is similar to that of a mouse. It is mainly used in CAD
and playing computergames.
Figure 2.6 Joystick input device for interactive computer graphics.
Page 14

CAD/CAM/CAE
Track ball:
 Track ball is an input device that is mostly used in laptop, computer instead of
amouse.
 This is a ball which is half inserted and by moving fingers on ball, pointer can
bemoved.
 Since the whole device is not moved, a track ball requires space than amouse.
 A track ball comes in various shapes like a ball, a button and a square.
Page 15
Figure 2.7 Track ball input device for interactive computer graphics.

Transformations
• 2-DTransformations
• 3-DTransformations
Two-dimensionalTransformations
• To locate a point in a two-axis Cartesian system, the x and y coordinates arespecified.
• These coordinate can be treated together as a 1 x 2 matrix : (x, y), e.g. the matrix (1,4)
would be interpreted to be point which is 1 unit from the origin in the x-direction and 4
units from the origin in they-direction.
• This method of representation can be extended further to define a line as a 2 x 2 matrix
by giving x and y coordinates of the two end points of the line. The notation wouldbe,
Translation
•Translation involves moving the element from one location toanother
x‟= x+m, y‟= y +n
Where,
x‟, y‟ = coordinates of the translated point
x, y = coordinates of the original point
m, n= movements in the x and y direction
In the matrix notation this can be represented as,
(x‟, y‟) = (x, y) + T
Where,
T = (m, n), the transformation matrix

• Scaling
Scaling of an element is used to enlarge it or reduce its size. The scaling need not
necessarily be done equally in x and y directions. e.g. a circle can be transformed into
ellipse by using unequal x and y scaling factors.
The points of an element can be scaled by scaling factor asfollows:
(x‟, y‟) = (x, y)S
Where
• This would produce an alternation in the size of the element by the factor m in the x-
direction and by the factor n in the ydirection
• It also repositions theelement
• If the scaling factor is <1 , it is moved closer toorigin
• If the scaling factor is >1 , it is moved farther from theorigin
Rotation
In this transformation, the points of an object are rotated about the origin by an angle θ
For a positive angle, this rotation is in the counter clockwise direction
This accomplishes rotation of the object by the same angle, but it also moves the object. In
matrix notation the procedure will be as follows:
(x‟, y‟) = (x, y) R
Where

Example : Translation
Consider the line defined by,
Suppose the line to be translate in space by 2 units in x direction and 3 units in the y direction.
Example : Scaling
• Apply scaling factor of 2 to theline

The new line will be,
Example : Rotation
Rotate the line about origin by30°
The new line would be definedas:

• The new line willbe,
3 Dimensional Transformation
• Transformations by matrix methods can be extended to three dimensionalspace.
Translation
• The translation matrix for a point defined in three dimensional matrixwouldbe, T = (m,
n,p)
And would be applied by adding increments m, n and p to the respective coordinates of
each of the points defining the three-dimensional geometry elements

Scaling
The scaling transformation is given by,
For equal values of m, n and p, the scaling is linear
Rotation
• Rotation in three dimensions can be defined for each of theaxes
• Rotation about z axis by angle θ is accomplished by thematrix
• Rotation about y axis by angle θ is accomplished by thematrix

 Rotation about x axis by angle θ is accomplished by thematrix
Concatenation
• Singletransformationscanbecombinedasasequenceoftransformations.Thisiscalledas
concatenation, and the combined transformations are called concatenatedtransformations.
• Duringeditingprocesswhenagraphicsmodelisbeingdeveloped,theuseofconcatenated
transformation is quitecommon
• More than one transformations are usually requires to accomplish the desired
transformation
e.g.
1. Rotation of the element about an arbitrary point theelement
2. Magnifying the element but maintaining the location of one of its points in the same
location
• In the first case transformations would be: translation to the origin, then rotation about the
origin, then translation back to originallocation
• In the second case , the element would be scaled (magnified) followed by a translation to
locate the desired point asneeded
• The objective of the concatenation is to accomplish a series of image manipulations as a
singletransformation
• The concatenation is the product of the two transformationmatrix

• It is important that order of matrix multiplication be the same as the order in which the
transformations are to be carried out.
Example : Concatenation
• Apointtobescaledbyafactorof2androtatedby45°.Supposepointunderconsideration was (3,
1) . This may be one of the several points defining a geometricelement
• First accomplish the transformationssequentially,
First consider thescaling,
(x‟, y ‟) = (x, y)S
Next rotation can be performed
(x”, y”) = ( x‟, y‟) R
The same result can be accomplished by concatenating the two transformation matrices,
The product of the two matrices would be

Now applying this concatenated transformation to the original matrix
Examples
• A line is defined in 2 D space by its end points (1,2) and (6,4). Express this in matrix
notation and perform the following transformation in succession on thisline
1. Rotate the line by 90° about theorigin
2. Scale the line by a factor of 0.5 (Dec/Jan 04/05, 8Marks)
• A square of side 30 units has its coordinates A(10,10), B(40,10), C(40,40) andD(10,40),
Perform the following transformation in succession and show it on graphpaper
1. Rotate about origin 20°anticlockwise
2. Scale it by factor1.5
3. Perform the above sequence of transformationbyconcatenation
18Marks)
(May/June 04,

Homogeneous representation
• Inordertoconcatenatethetransformationsmatrices,alltransformationmatricesshouldbe
multiplicativetype.
• However,thetranslationmatrixisvectoradditivewhileallotherarematrixmultiplications.
• It is desirable, to express all geometric transformations in form that ,they can be
concatenated by matrix multiplicationonly.
• In homogeneousrepresentation,an n-dimensional space is mapped into
(n+1) dimensionalspace.
• Thus a 2 dimensional point [x, y] is represented with the homogeneous coordinate triple
(xh,yh,h)
Where,
• Thus, a general homogeneous coordinates can also be written as (h.x, h.y,h).
• For two-dimensional geometric transformations, homogeneous parameter h to be any
nonzerovalue.
• Thus , there is an infinite number of equivalent homogeneous representations for each
coordinate point (x,y)
• A convenient choice is simply to seth=1.
• Each two-dimensional position is then represented with coordinates (x, y,1)
• This facilitates the computer graphics operations where the concatenation of multiple
transformations can be easily carriedout.
• The translation matrix in multiplication form can be givenas,

The transformation operation can be written as
• The scaling matrix in multiplication form can be givenas,

The rotation matrix in multiplication form can be given as,

CAD/CAM/CAE
UNIT 3
Syllabus
 Wire framemodeling,
 Solid modeling
 Modern solidtechniques,
 Feature basedModelling
 Solid représentation : Boundary Representation & Constructive Solidgeometry.
 Beizer Curve & B-SplineCurve
 AssemblyModeling.
DATTA S. CHAPE T.E MECHANICAL
Wire frame modeling
• In construction of the wire-frame model, the edges of the object are shown aslines
• Theimageassumestheappearanceofaframestructuredoutofwire-soitiscalledasWire
framemodel
• Very often designers also build physical models to help in the visualization of adesign.
• This may require the construction of „skeleton‟ models using wires to represent the edges
of an object or component.
• Wire frame modeling, as used currently in computer-aided engineering techniques, is the
computer-based analogue of thisprocess.
• A wire-frame model consists of a finite set of points together with the edges connecting
various pairs of thesepoints,
• There are limitations to the models which use the wire frameapproach.
• These limitations are more prominent in case of three-dimensionalmodels.
• These models are more suitable for two-dimensionalrepresentation.
• Themoreremarkablelimitationisthatallthelinesthatdefineedgesofthemodelareshown in
theimage.
• Many of 3-D wire frame systems does not have automatic hidden line removalfeature.

CAD/CAM/CAE
• The image becomes much complicated to understand and in some cases it might be
interpreted in number ofways.
• There is also limitation in defining the model in CADdatabase
Wireframe ambiguity:
Is this object (a), (b) or (c) ?
(a) (b)
Solid modeling
• An improvement in the wire frame modeling, both in terms of realism to the user and
definition to thecomputer.
• In this models are displayed with less risk ofmisinterpretation
• When color are added the picture becomes realisticone.
• The solid modeling has wide range of applications other than CAD andmanufacturing.
• These includes color illustrations in magazines and technical publications, animation in
movies and trainingsimulators
(c)

CAD/CAM/CAE
The solid models are used widely because of following factors:
1. Increasing awareness among users of the limitation of the wire framesystems
2. Continuing development of computer hardware and software which makes solidmodeling
possible
• These models require high computational power in terms of both speed and memory, in
order tooperate
Modern solid techniques
1) SweepRepresentations
• When a curve /shape is moved along a curved path a new object created is called asweep
• When a 2D object is swept along a linear path, then the resulting object is known as
extrusion.
• Rotational sweeps are defined by rotating an area about anaxis.
• Sweepsofsolidsareusefulinmodellingtheregionssweptbyamachinetooloratoolpath.
• Sweeps whose generating volume or area changes in shape, size or in orientation as they
swept, are known as generalized sweeps.
• Sweep representation is useful in generating extruded solids and solids ofrevolution.
• The sweeping operation is based on sweeping a curve orsurface.
• Applications involves simulations of material removal due to machining operations and
interference detection of moving objects inspace.
DATTA S. CHAPE T.E MECHANICAL

CAD/CAM/CAE
• There are three types ofsweep
1. Linear
• Translational
• Rotational
2. Nonlinear
3. Hybrid
2) CellDecomposition
• An object can be modelled by decomposing its volume into smaller volume of cellswhich
are mutually continuous and do not penetrate into eachother.
• The shape in this need not be a cube nor they should beidentical.

CAD/CAM/CAE
• It can be seen that some cells are partly outside the boundary, while some of them are partly
inside theboundary
• This is approximate representation of an object.
• In such a case , a smaller hole or cavity gets neglected if the size of cavity is smaller of the
cells or other than squares in thisscheme.
• This difficulty can be overcome by permitting various shapes of cells other than squares and
rectangles, such astriangles.
Boolean operations
• Boolean operations are used to make more complicated shapes by combining simpler
shapes
• 3 types of operations arepossible:
1. union („U‟) or“join”
Prepared byS.G. NAGHATE T.EMECHANICAL

CAD/CAM/CAE
2. intersection(„∩‟)
3. difference („-‟) or“subtract”
Boolean operation on solids.
(a) Objects A and B, (b) A U B, (c) A ∩ B, (d) A - B, (e) B -A

CAD/CAM/CAE
Boolean operations applied to a cube and a sphere
Primitive Instancing
• In primitive instancing modeling approach, primitives are simple 3D solid shapes, which
form the base for creating a solidmodel
• These primitives are parameterized by geometric as well as physicalproperties.
• The solid model of any object can be created with different combinations of these
primitives.
• e.g. one primitive object may be a regular pyramid with a user defined number of faces
meeting at theapex.
• A parameterized primitive may be thought of as defining family of parts whose members
vary in few parameters, an important CAD concept known as grouptechnology.
• Primitive instancing is often used for relatively complex objects, such as gears , bolts,that
are tedious to define in terms of Boolean combinations of simplerobjects.
• e.g. A gear may be parameterized by its diameter or no. ofteeths.
• Primitive instancing is based on the concept of families of objects orparts
• All parts having same topology but different dimensions are grouped intofamily
• Each individual part in the family is called a primitiveinstance.
• e.g. a cylinder is represented by diameter(D) and height(h)

CAD/CAM/CAE
• Each primitive instancing is defined by specific (D) and(H)
• A number of such cylinder primitive instancing creates a family ofcylinders
• A group of such families can define asolid
Boundary representations (B-rep)
• Boundaryrepresentationsorb-repsdescribethesolidobjectintermsofitsboundaries,that is the
vertices, edges and faces.
• In this model, face is bounded by edges and each edge is bounded byvertices.
• The entities which constitute a B-rep modelare:
Geometrical Entities Topological entities
Point Vertex
Curve, line Edge
Surface Face
B – Rep Model
An Edge-Based Model

CAD/CAM/CAE
v4
e6
e5
e4
e3
Faces:
f1 e1 e4 e5
f2 e2 e6 e4
f3 e3 e5 e6
f4 e3 e2 e1
v1 e1
Edges:
e1 v1 v2
e2 v2 v3
e3 v3 v1
e4 v2 v4
e5 v1 v4
e6 v3 v4
v3
e2
v2
Vertices:
v1 x1 y1 z1
v2 x2 y2 z2
v3 x3 y3 z3
v4 x4 y4 z4
v5 x5 y5 z5
v6 x6 y6 z6
• Though B-rep models is constructed of surfaces of solids, computation of mass and
volumetric properties is possible.
• The range of models that can be modeled with B-rep technique is verylarge.

COMPUTER AIDED DESIGN / COMPUTER AIDED MANUFACTURING (CAD/CAM

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