Fundamentals of Engineering Design
F IRST E DITION
Nadeem Akbar Najar, CEng(I)
BSc.(Mathematics),BSc.(Applied Sciences)
AMIE (Mechanical Engineering),M.Tech(Thermal System & Design)
Shayesta Abdullah
BSc(IT), MCA
Published by
JKERT FOUNDATION
F UNDAMENTALS OF E NGINEERING D ESIGN
B Y: NADEEM A KBAR NAJAR , CE NG (I), S HAYESTA A BDULLAH
Copyright c 2017, Nadeem Akbar Najar, Shayesta Abdullah
P UBLISHED B Y: J K E R T F OUNDATION , J & K
ISBN 978-93-5291-564-4
First Edition, 2017
Preface
The book titled "Fundamentals of Engineering Design" is an effort towards providing an effective
guidance to the students of B Tech or BE in general and Associate Membership examination of
Institution of Engineers (India) in particular. Since AMIE students mostly rely on self study therefore,
a need was felt to provide a book for the subject which could be studied without the help of any
teacher.
This book covers the most of the concepts of engineering design which are necessary before going
for advanced designing procedure of respective stream. Usually, it is common practice to teach the
general design principles to undergraduate engineering students during the commonalities section of
the programme, whether it is B Tech or BE or AMIE.
No book is complete and there is always a scope for improvement. We shall be happy if errors are
brought to our notice and suggestions are welcome at following mail ID:
♥❛❞❡❡♠❝❡♥❣❅❣♠❛✐❧✳❝♦♠
Nadeem Akbar Najar
Shayesta Abdullah
Contents
1
Engineering Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.1
Engineering Design Process and its structure
1.2
Need: Identification and Analysis
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6
Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types of needs . . . . . . . . . . . . . . . . . . . . . . . . .
Need Identification . . . . . . . . . . . . . . . . . . . . .
Need Analysis . . . . . . . . . . . . . . . . . . . . . . . . .
Principles of Need Analysis . . . . . . . . . . . . . . .
Need Identification and Analysis: An Example
1.3
Design Specifications
1.3.1
1.3.2
1.3.3
1.3.4
Performance Specification . .
Product Design Specification
Manufacturing Specification .
Sales Specification . . . . . . . . .
1.4
Standards of performance and constraints
16
1.5
Product Life Cycle
17
1.6
Aesthetics
19
1.7
Role of Aesthetics in Engineering Design
19
2
Methods of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1
Searching for Design Concept
2.1.1
Tests to Qualify Design Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9
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2.2
Evaluation of Design Concepts
2.2.1
2.2.2
2.2.3
Physical Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Physical Realisability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Economic Feasibility and Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3
Design through Morphological Analysis
2.3.1
Seven Phases of Morphological Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4
Brainstorming Technique
2.4.1
2.4.2
Rules for Brainstorming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Procedure for Brainstorming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.5
Other Design Methods
2.5.1
2.5.2
2.5.3
2.5.4
2.5.5
Design by Innovation
Design by Evolution .
Design by Evaluation
Routine Design . . . . .
Creative Design . . . .
3
Detailed Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.1
Introduction
35
3.2
Design for Manufacture
35
3.3
Design for Assembly
38
3.4
Design for Shaping
39
3.5
Design for Maintenance / Maintainability
39
3.5.1
Modularity and Lines of Repair:
3.6
Design for Use
42
3.7
Design for Recyclability
42
3.8
Design Checks
42
3.8.1
3.8.2
3.8.3
3.8.4
Clarity . . .
Simplicity .
Modularity
Safety . . . .
3.9
Standardization and Size Ranges
3.9.1
3.9.2
3.9.3
Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Preferred Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Range Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4
Reliability and Robust Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.1
Introduction
47
4.2
Design for Reliability
47
4.3
Reliability and Quality
48
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32
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7
4.4
Reliability in Series and Parallel
48
4.5
Failure Types in Reliability Engineering
50
4.5.1
Bath-Tub Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.6
Robust Design
4.6.1
Taguchi’s Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5
Design Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.1
Introduction
55
5.2
Design Organization
55
5.3
Communication
56
5.4
Technical Report
58
5.5
Drawings
59
5.6
Presentation
61
5.7
Models
61
6
IT and its Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.1
Introduction
63
6.2
Definition of Information Technology
63
6.3
Characteristics of Information Technology
64
6.4
Importance of Information Technology
64
6.5
Application of IT in Design Organizations
65
6.6
Database Systems
67
6.7
Characteristics of Database Systems
67
6.8
DBMS
68
6.8.1
Component Modules of DBMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.9
Advantages of Using the DBMS Approach
69
6.10
Database Security
70
52
1. Engineering Design Process
1.1
Engineering Design Process and its structure
Engineering design has been defined by The Accreditation Board for Engineering and Technology
(ABET) as "the process of devising a system, component or process to meet desired needs."
ABET emphasizes that design is an iterative decision-making process, in which natural sciences,
mathematics, and applied sciences (engineering) are applied to meet a stated objective in an optimal
manner.
The engineering design process is a series of steps that engineers follow when they are trying to
solve a problem and design a solution for something; it is a methodical approach to problem solving.
This is similar to the “Scientific Method” which is taught to young scientists. There is no single
universally accepted design process. It seems as though most engineers have their own twist for how
the process works. The process generally starts with a problem and ends with a solution, but the
middle steps can vary. One can think of the engineering design process as a recipe for banana bread;
it can be made a lot of different ways but it’s usually going to start with bananas and it’s going to end
with a loaf of bread. One such “recipe” for the engineering design process will be outlined in this
unit; this is not the only correct version of the process, it is just one example. It will provide a good
starting point for students to explore the engineering process. In figure 1.1, the eight stepped design
process is shown, although the design process varies from industry to industry, but there remains a
10
Chapter 1. Engineering Design Process
consistent sequential progression at the heart of the most design processes. The steps involve:
• Identify the need / problem
• Analyze the need / problem
• Develop the possible solution
• Select the best possible solution
• Construct a prototype
• Test and evaluate the solution
• Communicate the solution
• Redesign
Figure 1.1: Stepwise flow of design process
Figure 1.2: Block diagram of a design process
1.2 Need: Identification and Analysis
1.2
11
Need: Identification and Analysis
1.2.1 Need
A need has been described as a gap between “what is” and “what should be".
1.2.2 Types of needs
Direct Needs
Needs are expressed by the customers to the designer during various processes of need identification.
The direct needs are those needs of the consumer which are apparent and evident from the very
purpose for which the artifact is to be produced.
Latent Needs
While preparing a list of needs in consultation with the customers during need identification there
are various hidden needs which may arise in future as soon as the customer starts using the product.During need identification process the customer may not be able to express the hidden needs due
to inexperience or short term thought process. Therefore, it is the duty of the designer to identify the
hidden / latent needs of the customer and incorporate the same in the design.
Constant Needs
The basic purpose for which the product is to be designed can never change although there may be
modifications to the design arising out of various factors. For example, the basic purpose of a chair is
to let the people sit in it, a customer may demand a cushioning or wheeling feature into the existing
design but the basic purpose of the chair remains the same. Such needs which do not change with
the time are termed as constant needs.
Variable Needs
The variable needs keep on changing with the time due to various factors which may compel the
user to demand for the varying features to be incorporated into the product from time to time.
1.2.3 Need Identification
Customer Needs Identification is the process of determining what and how a customer wants a
product to perform. Customer needs are non-technical, and they reflect the customer’s perception of
12
Chapter 1. Engineering Design Process
the product, not the actual design specifications, although frequently they are closely related.
Customer Needs Identification has two major goals:
1. To keep the product focused on customer needs.
2. To identify not just the explicit needs of the customer, but also the latent needs. The latent
needs are the hidden needs.
These customer requirements should be independent of any particular product or potential solution.
After all, it’s only after identifying customer needs that one can begin to meet them.
So with that in mind, the goal is to find out precisely what the customer wants. Here is a four-step
method for identifying customer needs:
1. Gather raw data from customers
2. Interpret the data in terms of customer needs
3. Organize the needs
4. Reflect on the Process
Need identification is the most important step in the design process, because it is directly related
with the satisfaction of the customer. It is of worth to mention here that “the greatest defect a product
can have is not satisfying the customer”.
1.2.4 Need Analysis
Needs analysis is defined as a formal process focus on how a product addresses the needs of a human.
It is not an official business development tool, but is considered a valuable analytical technique
to better gauge the marketability of a product or a service to a human consumer. It is often used
across many industries, such as software development, automobiles, consumer products and banking
services. Needs analysis was originally used for software developers, who used the system in tandem
with requirements analysis - a study of the elements represented within a system.
1.2.5 Principles of Need Analysis
• The opinion of end users is essential to unify a diverse, opinionated design team, and their
opinion should transcend the desires of your design team.
• Market research is essential to unify end user opinions, and to use quantitative and qualitative
1.2 Need: Identification and Analysis
13
research to find the best direction for product or service designs.
• Appeal to the lowest common denominator in end user needs. Marketing to the lowest skill
levels results in the largest potential market.
• Do comprehensive beta tests of your products over a long period of time to allow adequate
adjustments before "freezing" your product for the final manufacturing stage.
• Continue to monitor user feedback after the product launch, and address defects quickly and
keep an accurate record to apply to future releases, if they cannot be addressed immediately in
the current product.
• Elegant designs are the end product of successful needs analysis, and will put your product
head and shoulders above industry peers.
1.2.6 Need Identification and Analysis: An Example
Al Nadeem Inc. , a well-established tool manufacturer (renamed for the purpose of this example), was
looking to enter the growing market of handheld power tools by developing a cordless screwdriver.
Al Nadeem Inc. conducted 30 interviews to get a precise idea of what their customers wanted.
Here are some sample responses from the customers:
• I need to drive screws fast
• I like the pistol grip
• I want to be able to use it when the batteries are dead
• I can’t drive screws into hard wood
Based on these responses, and many, many others, Al Nadeem Inc. was able to create a list of
Interpreted Needs. Here are the interpretations used to design the screwdriver:
• The screwdriver drives screws faster than by hand
• The screwdriver grip is comfortable
• The user can apply torque manually to the screwdriver to drive a screw
• The screwdriver drives screws into hard wood
All of these interpretations, which are written in an affirmative style, helped to guide the engineers.
The need with the asterisk denotes a latent need, something previously unnoticed but clearly
representing a problem many people would identify with.
14
Chapter 1. Engineering Design Process
Al Nadeem Inc. then organized the needs according to their level of importance, frequency of
appearance, etc., after which they developed a highly successful cordless screwdriver. Thanks to an
extensive customer needs identification process, Al Nadeem Inc. was able to clearly define the goals
and restrictions on the screwdriver so that engineers could implement a proper design.
1.3
Design Specifications
A design specification is a detailed document providing information about the characteristics of a
product to set criteria the developers will need to meet. Its use is called for where a structure or
product has to be specially made to meet a need. For example, a design specification must include
all necessary drawings, dimensions, environmental factors, ergonomic factors, aesthetic factors, cost,
maintenance that will be needed, quality, safety, documentation and description. It also tells specific
examples of how the design of the project should be executed, helping others work properly.
A design engineer formulates the design specification. These specifications can be divided into
following groupings:
1. Performance Specification
2. Product Design Specification
3. Manufacturing Specification
4. Sales Specification
1.3.1
Performance Specification
Performance or customer specification is prepared on the basis of market research information or the
specific requirement specified by a particular customer. The information involves:
• The determination of purpose of the product to be designed.
• From market survey, the degree of customer satisfaction from existing products in the market,
is obtained and also the limitations in the existing product are ascertained.
• Surveys also reveal the selling price of the existing product.
• It is also ascertained that whether the product is a luxury or a necessity.
• The information about the target users is also obtained.
• Aesthetic considerations are also given a thought.
1.3 Design Specifications
15
• Operational and environmental conditions to which the product will be subjected to.
• Operational safety requirements, limitations of use and associated hazards.
• Servicing and maintenance considerations are also specified.
• A mention of degree of variability of acceptance to the customer in terms of the parameters
associated with performance, appearance, shelf and design life, rate of deterioration, reliability
etc.
1.3.2
Product Design Specification
The product design specification specifies the characteristics, capabilities and limitations of the
product. Extreme care is to be exercised while preparing this specification as there is an ardent need
to compare the specification prepared by engineer with that of the customer’s specifications so as to
show the compliance. This specification gives a complete description of the product. The important
features of product design specification are as follows:
• Under specified operating conditions, the design life in terms of time (hours or days or months
or years) , number of operations or cycles of operation which can be expected from the product.
• Under specified operating conditions, expected rate of degradation of the product.
• The determination of performance parameters. For example, the manufacturers of a bike
specify the mileage as 70 Kilometer /Litre.
• Under specified design life and operating conditions, the reliability which can be expected
from the product.
• The variation of performance under various operation conditions like environment cycling,
vibration, saline environment, noise, fumes or any other biological factor.
1.3.3
Manufacturing Specification
It comprises of the information, whatever is necessary for the manufacture of the product. These
specifications are the most complex in nature involving:
• Drawings of components and assemblies (CAD Drawings).
• Tool details including jigs, fixtures and measuring equipments.
• Equipment calibration requirements.
16
Chapter 1. Engineering Design Process
Figure 1.3: Product design specification
• Specifications of the raw materials.
• Instructions for assembly, packaging, storage, transport and the final installation at end user
site.
• Details of the trade and respective standard.
1.3.4
Sales Specification
This specification includes the information related to performance, safety and reliability as claimed
by the manufacturer. The customer decides the final selection of a particular product on the basis of
this specification.
It includes the following features:
• Complete illustration of the product appearance.
• Dimensional details of the product usually external dimensions.
• Statement of performance in terms of characteristics and claims.
• After sales service, safety and reliability details.
1.4
Standards of performance and constraints
Standards of performance and constraints are a set of complex requirements which are a must to
ensure the matching of reliability level, cost, safety level and overall performance to that as expected
by the customer. The success of a system depends upon whether the design performs its function to
1.5 Product Life Cycle
17
Figure 1.4: Standards of performance and constraints
the desired level of requirement or not. If it performs well, we say the design is successful otherwise
the system fails. Figure 1.4, shows the standards of performance and constraints diagrammatically.
1.5
Product Life Cycle
A product has a life of its own and goes through cycles. Although different products have different
types of life cycles, the traditional product life cycle for most products is shown in Figure 1.5. If a
manufacturer is considering entering an industry and making a product, knowing where the product
is in its life cycle can provide valuable information of how to position its product in the market in
terms of price, promotion and distribution. Products typically go through four stages during their
lifetime. Each stage is different and requires marketing strategies unique to the stage.
Introduction Stage:
This stage involves introducing a new and previously unknown product to buyers. Sales are small,
the production process is new, and cost reductions through economies of size or the experience curve
have not been realized. The promotion plan is geared to acquainting buyers with the product. The
18
Chapter 1. Engineering Design Process
Figure 1.5: Product Life Cycle
pricing plan is focused on first-time buyers and enticing them to try the product.
Growth Stage:
In this stage, sales grow rapidly. Buyers have be come acquainted with the product and are willing to
buy it. So, new buyers enter the market and previous buyers come back as repeat buyers. Production
may need to be ramped up quickly and may require a large infusion of capital and expertise into the
business. Cost reductions occur as the business moves down the experience curve and economies of
size are realized. Profit margins are often large. Competitors may enter the market but little rivalry
exists because the market is growing rapidly. Promotion and pricing strategies are revised to take
advantage of the growing industry.
Mature Stage:
In this stage the market becomes saturated. Production has caught up with demand and demand
growth slows precipitously. There are few first-time buyers. Most buyers are repeat buyers. Competition becomes intense, leading to aggressive promotional and pricing programs to capture market
share from competitors or just to maintain market share. Although experience curves and size
economies are achieved, intense pricing programs often lead to smaller profit margins. Although
companies try to differentiate their products, the products actually become more standardized.
Decline Stage:
In this stage buyers move on to other products and sales drop. Intense rivalry exists among competi-
1.6 Aesthetics
19
tors. Profits dry up because of narrow profit margins and declining sales. Some businesses leave the
industry. The remaining businesses try to revive interest in the product. If they are successful, sales
may begin to grow. If not, sales will stabilize or continue to decline.
1.6
Aesthetics
The literal meaning of aesthetics is "a set of principles concerned with the nature and appreciation of
beauty or the branch of philosophy which deals with questions of beauty and artistic taste."
Aesthetics is concerned with how things look. This can be influenced by an objects’ appearance and
its style. The appearance of an object is the feature that people notice first. In some ways appearance
can be very personal and is influenced by things like the materials from which the object is made
and the type of finish applied to its surface.
It is important that products have visual appeal. In a world where many new products function in a
similar way, it is often the appearance which sells the product. Aesthetics is a pan of design which is
difficult to analyze and describe in words. However there are aspects of appearance which can be
considered separately.
1.7
Role of Aesthetics in Engineering Design
Aesthetics forms an important element of engineering design. Every engineering design gives
due consideration to the aesthetics aspect. No matter how best the design is, the final outlook of
the product should be eye catcher. A customer gets attracted to the aesthetically sound products.
Therefore, it is the duty of designer to incorporate the aesthetic aspects into the design. The
importance of aesthetics for engineering design can be summarized as follows:
1. Function
2. Form
3. Unity
4. Style
1. Function: The element of function in the concept of aesthetics underlines the form description
20
Chapter 1. Engineering Design Process
of the actual operative function of the product. The function is not confined to mechanical
function of the product but it also covers the cost function, environment function, user acceptance and familiarity, maintenance as well as aesthetics.
2. Form: A form comprises of elements like line proportion, colour and texture. A designer sets
a unique form by organizing the above elements of form, properly.
3. Unity: The word ’Unity’ signifies the harmonious combination of the components of the
product. Unity is worked out by the designer with the help of similar proportions and shapes.
A designer should be able to recognize and create a delicate balance of unity with variety
within the framework of the form of the product.
4. Style: The styling refers to ornamentation of the external look of the product to serve as an
eye catcher. The very purpose of the styling is to attract the consumer towards the product.
Styling is different from aesthetic quality which results from proper function, form and unity.
*
2. Methods of Design
2.1
Searching for Design Concept
Upon choosing a particular design idea, it is compulsory to validate the design idea so as to go ahead
with other steps of design process till commercial production. Design concept signifies the validity
of a design idea. While executing a design method,a large number of feasible solutions may arise. It
is not possible to study each and every solution due to time and cost constraints.Therefore, only a
best possible solution is selected subjected to the criteria specified by customer needs, that is, the
selected solution must comply with the customer needs.
Qualifying Design Concept
A solution is declared to have qualified the design concept or validation when it has been subjected
to testing rather model testing. Testing demonstrates the adequacy of a product or design by giving
direct or tangible results. Tests are used to investigate the ideas, check the feasibility of ideas or
concepts and also help in demonstrating the compliance of the product with specific requirements.
Figure 2.1, shows the attributes of a qualifying design concept.
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Chapter 2. Methods of Design
Figure 2.1: Attributes of a qualifying design concept
2.1.1 Tests to Qualify Design Concept
Scale Model Test
A scaled down or a small model of the original product is developed to investigate the feasibility of
the design. It also helps in evaluation of new concepts.
Development Test
New variables of new materials or new components or new systems are determined by development
tests. Development tests help in giving a practical shape to the products. These tests also enable one
to check the rigidity of design.
Prototype Test
A full size replica model of original product is developed to explore workability of the design. Doing
prototype testing is of paramount importance before proceeding for commercial production.
Proof Test
Proof tests bring out the degree of variability in the performance of the model with respect to
expected design performance. The importance of proof test lies in identifying failure modes and
weak links in the product.It can also give information about the maintenance strategy for a particular
design. Verification of a design depends upon the results obtained from proof tests.
2.2 Evaluation of Design Concepts
23
Acceptance Test
This type of test is carried out on final product to verify that whether the product meets the design
requirements or not.
2.2
Evaluation of Design Concepts
2.2.1 Physical Reliability
Reliability is defined as the probability with which a product will perform its desired function under
a set of specified operating conditions over a period of time. A design concept needs to be evaluated
for physical reliability , that is the reliability of the design should be as close as possible to 1.0 for a
design to be called as highly reliable. Reliability is an important design parameter which determines
the overall reliability of the product by computing the reliability of individual components. Should
the redundancy of components be increased in parallel, the reliability of the product increases many
folds. The physical structure of the product needs to be strong enough to enable the user to use the
product over a predetermined period of time under given set of operating conditions.
2.2.2 Physical Realisability
Physical realisability of alternative solution depends upon an inter-relationship between various
factors. In order to enable the designers to take a decision, it is necessary to develop a theory of
physical realisability which explains the effect of various factors that need to be considered in the
design.Every manufacturer has a level of confidence at the time of taking a decision whether they
can give the product final shape or not, in other words, whether the product is realizable or not. It
is the belief of manufacturer which compels him to start the project. Money and time is available
with every manufacturer still some products are realizable, some are not. The intensity of belief (that
a physically realizable design can be accomplished with given money and time ) is an important
factor while deciding physical realisability. These beliefs cannot be absolute, as there is always some
amount of uncertainty until the product is realized, this is given by confidence level using following
mathematical formula:
24
Chapter 2. Methods of Design
Confidence Level,
dE
L = f E.RB .
dR
(2.1)
where, E = amount of favourable evidence in decimals,
R= Current expenditure in rupees and it may vary from 0 to RB
RB =allowable budget of time and money,
dE
dR
= initial rate of increase in favourable evidence with expenditure.
2.2.3 Economic Feasibility and Utility
Ultimate goal of a manufacturer is to earn a profit and make an image in the eyes of the customer
through a well established brand. Therefore, the design team in consultation with a financial analyst
develops an economic model of the new product. The purpose of the development of the model
is to justify the continuation of product development program and resolve specific trade-offs, for
example, manufacturing and development costs. An early economic analysis is preferred before the
commencement of the project to anticipate the profits in advance. Economic worth of a product is not
measured from cost of the product only, but, the utility also plays an important role in determination
of economic worth of a product.Thus, the economic feasibility of a design is best measured by
product utility factor. More the utility of a product , the more is its economic worth. It can be best
understood from the following example.
Suppose two bulbs A and B are available to the customer from the market and the comparison of the
two is done on the basis of their corresponding illuminating ability and life in months as follows:
Bulb A has a total utility as follows:
Bulb
A
B
Illumination
6
7
Life (Months)
3.5
3
Utility
9.5
10
Table 2.1: Illuminating ability and life of two bulbs
UA = 6 + 3.5 = 9.5
Bulb B has a total utility as follows:
2.3 Design through Morphological Analysis
25
UB = 7 + 3 = 10
Thus, it is evident that bulb B has more utility than bulb A. Therefore, the economic worth and
economic feasibility of bulb B is more.
2.3
Design through Morphological Analysis
Morphology
The literal meaning of the word "morphology" with respect to a design concept, is a systematic search
for alternatives by looking at possible combinations of diverse and previously unrelated parameters.
Morphological Analysis
Morphological analysis refers to a method of searching for ideas. Generally, through a design
method a large number of solutions are generated against a particular problem and it is must to
reduce them to few feasible solutions. Therefore, some solutions are ignored by terming them
as incompatible and some are selected. The selected solutions termed as feasible solutions are
compared on time-cost requirement basis. In case of projects, the morphology of design refers to a
series of major phases. Normally, a new phase is never begun unless the preceding one has not been
finished.Thus, morphology of design ensures a chronological structure of a design project.
2.3.1 Seven Phases of Morphological Analysis
Phase 1:Feasibility Study
The purpose of feasibility study is to achieve a set of useful solutions to problem. In this phase
of morphological analysis, various elements of design, parameters , constraints and major design
criteria are identified.
Phase 2:Preliminary Design
The purpose of preliminary design is to look for a best design concept out of many alternatives. In this
phase of morphological analysis less wanted solutions are eliminated after determining superiority
or inferiority of various solutions. A surviving solution is subjected to close examination and a
synthesis study is initiated. Tolerances of various components and critical materials is established.
Finally, a projective type study is undertaken before going for next phase.
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Chapter 2. Methods of Design
Phase 3:Detailed Design
The purpose of this phase is to furnish the engineering description of a tested and a producible design.
The importance of this phase lies in the fact that a final decision (whether to continue or abandon) on
a particular design concept is taken. If a decision of continuation is taken, therefore a master layout
is prepared and experimental investigation is initiated by making a prototype. Finally, a prototype is
tested and evaluated taking into consideration, the fulfillment of customer needs.
Phase 4:Planning for Production Processes
First three phases of morphological analysis lie in the domain of design engineers and rest phases
are shared by other segments of management as well. In this phase, a proper planning of tool design
and production engineering department is carried out.Since, the decision of production involves
enormous economic commitment, therefore planning for production processes is a critical activity.
Following aspects of production planning are studied:
• A detailed planning of manufacturing processes is carried out.
• Planning about design of tools and fixtures is carried out.
• Planning about the need of designing new product and plant facilities is carried out.
• It also involves the planning for an efficient quality control system.
• Planning for production and personal job specification, standard times, labour costs, production
control, work schedule and inventory control, standard cost of labour, materials and services.
• Planning for information flow system is carried out.
• Since, production involves the major capital investment, therefore, an efficient financial
planning is an ardent need.
Phase 5:Planning for Distribution
The purpose of planning for distribution is to ensure the establishment of an effective and flexible
system for distribution of finished goods. The decision on the packing of the product is taken in this
phase. For an efficient distribution of the product, a warehouse plays an important role, therefore,
decision on warehousing system is also taken in this phase.It also involves the planning for promoting
the product before the target users, therefore an efficient and economical promotional activity is
undertaken. Usually, the products are to be transported from the premises of manufacturer to the
2.3 Design through Morphological Analysis
27
retail outlets or directly to the users, through rail, aircraft or ship, therefore, certain features are
added to the product by adding hooks, lugs or brackets to the body of product during design only to
ensure the safe and secure carriage.
Phase 6:Planning for Consumption
The purpose of this phase is to incorporate, in the design, adequate service features and to provide a
rational basis for product improvement and design. Following are the important steps involved in
this phase:
• Design for maintenance, that is, the product should involve least and easy maintenance.
• Design for reliability, that is the product should be reliable and dependable.
• Design for safety, that is, adequate safety features should be incorporated in the design.
• Human factor should be considered to ensure convenience in use.
• Sufficient aesthetic features should be included in the design.
• Design for operational economy ,that is, the running or operational costs should be as minimum
as possible.
• Design for adequate duration of service, that is, the product should not suffer frequent
breakdowns or out of service situations but should offer the services upto considerable duration
of time.
• Design for product improvement on the basis of service data and its incorporation into the
next generation designs.
Phase 7: Planning for Obsolescence
This phase of morphological analysis deals with the disposal of obsolete product. Following points
are to taken into the consideration while planning for obsolescence:
• It is the duty of designers and engineers to anticipate the problems associated with the
obsolescence and disposal of a product as they are aware of the constituent materials of the
product.
• Products should be designed in such a way that rate of obsolescence should be reduced by
taking into account the anticipated effects of technical developments.
• Designers should try to match the physical life of a product with the anticipated service life to
28
Chapter 2. Methods of Design
avoid any premature failure of the product.
• A product should be designed on the basis of several levels. If a higher level becomes obsolete,
the next sub level should ensure the further use of the product.
• Design of the product should involve the possible retrieval of reusable and long lived components from the product upon obsolescence.
Figure 2.2: Morphology of Design
2.4
Brainstorming Technique
Brainstorming is a tool used by teams to bring out the ideas of each individual and present them in
an orderly fashion to the rest of the team. The key ingredient is to provide an environment free of
criticism for creative and unrestricted exploration of options or solutions to a design problem.
Brainstorming helps a team break free of old, ineffective ideas. This free-wheeling technique for
generating ideas may produce some that seem half-baked, but it can lead to new and original solutions
2.4 Brainstorming Technique
29
to problems. Some of the specific benefits of brainstorming are that it:
• Encourages creativity. It expands our thinking to include all aspects of a problem or a solution.
A design team can identify a wide range of options.
• Rapidly produces a large number of ideas.By encouraging people to offer whatever ideas come
to mind, it helps groups develop many ideas quickly.
• Equalizes involvement by all team members.It provides a nonjudgmental environment that
encourages everyone to offer ideas. All ideas are recorded.
• Fosters a sense of ownership. Having all members actively participate in the Brainstorming
process fosters a sense of ownership in the topic discussed and in the resulting activities. When
the people on a team contribute personally to the direction of a decision, they are more likely
to support it.
• Provides input to other tools.You may want to affinitize the brainstormed ideas. And, if
appropriate, you can work with the team to reduce the number of ideas by multi-voting.
Brainstorming is useful when you want to generate a large number of ideas about issues to
tackle, possible causes of problems, approaches to use, or actions to take.
2.4.1 Rules for Brainstorming
For all participants to enjoy a creative and productive Brainstorming experience, the facilitator needs
to review and get team member’s buy-in on the ground rules for the session. These are the rules :
• Active participation by all team members. Everyone expresses his or her ideas, even if they
seem silly or far out.
• No discussion—criticisms, compliments, or other comments—during the brainstorm.
• Build on ideas generated by other team members.
• All ideas written exactly as presented and displayed where everyone can see them.
• Set a time limit.
• Clarify ideas.After the brainstorm, go over the list to make sure that all team members
understand the ideas. Remember that you are only clarifying the ideas, not making judgments
about them.
• Combine ideas.See whether two or more ideas that appear to be the same can be combined.
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Chapter 2. Methods of Design
2.4.2 Procedure for Brainstorming
The recommended sequence for conducting brainstorming and some suggestions for conducting the
session effectively are provided below:
• Review the rules for Brainstorming. Describe how this session will be conducted by going
over the points below.
• Set a time limit for Brainstorming, assign a timekeeper and data recorder, and start the clock.
Brainstorming should be a rapid generation of ideas, so do it quickly; 5-15 minutes works
well. If the time limit has expired and ideas are still being generated, you can extend the time
limit at five-minute intervals.
• State the topic to be brainstormed in the form of a question. Write it down and post it where
everyone can refer to it. Ensure that everyone understands it.
• Collect everyone’s ideas.After allowing a few minutes for the participants to think about the
question, ask them to give their ideas. Establish either a structured or unstructured format for
calling out ideas:
- Structured: The facilitator establishes a rotation that enables each person in the group to
contribute an idea in turn. Any individual who is not ready with an idea when his or her turn
comes can pass until the next round, when he or she may offer an idea or pass again.
- Unstructured: Team members call out ideas as they come to mind. This method calls for close
monitoring by the facilitator to enforce the ground rules and ensure that all team members
have a chance to participate.
• Record ideas on a chart pack as they are called out, or collect ideas written by team members
on post-its . Display the ideas where everyone can see them. Having the words visible to
everyone at the same time avoids misinterpretation and duplication and helps stimulate creative
thinking by other team members.
- When recording ideas, ensure that they are written down exactly as spoken by the team
member. Don’t interpret. - Try to generate as long a list as possible. Keep Brainstorming until
all participants have passed or the allotted time has expired.
2.5 Other Design Methods
31
• Clarify each idea after all ideas have been presented, to ensure that all members have the
same understanding of it. Pointing to each idea on the chart pack in turn, ask the participants
whether they have any questions about its meaning. You may have to ask the contributor to
explain the idea in ac different way.
• Eliminate duplications. If two or more ideas appear to mean the same thing, you should try to
combine them or eliminate the duplicates. Before you can wrap the like ideas into a single
item or eliminate any items on the list, all of those who contributed the similar ideas must
agree that they mean the same thing. Otherwise, they remain as separate items.
2.5
Other Design Methods
Systematic Search
The purpose of this method is to solve a design problem using logical certainty. This method is also
referred to as systematic search method of designing.
Synectics
The purpose of this method is to direct the spontaneous activity of the brain and the nervous system
towards the exploration and transformation of design problem.
Quirk’s Reliability Index
The aim of this method is to enable the inexperienced designers to eliminate the unreliable components without testing.
Matchett’s Fundamental Design Method (FDM)
The aim of this method is to enable a designer to perceive and control the pattern of his thoughts and
to relate this pattern more closely to all aspects of a design solution.
Interaction Matrix
It works on the basis of establishing the connections between various elements within a problem.
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Chapter 2. Methods of Design
2.5.1 Design by Innovation
Innovative design is achieved by rapid scientific growth and technological discoveries as well as
competition among companies. Since, the needs of the society are evolving continuously and
growing relatively. The R & D teams of design organizations are consistently working towards
the betterment of existing designs by incorporating recent innovations in other fields of science
and technology. Innovation leads to the new designs to satisfy ever growing needs of the society.
Following are the key features of a successful innovative design:
• Competitive price
• Good appearance
• Sound functional design
• Better quality, both in material and workmanship
• Improved convenience in use
• Easy maintenance
• Use of new materials with relatively excellent qualities
• Eco-friendly nature of product
2.5.2 Design by Evolution
Evolutionary method of design is based on developments in the design of tools, equipment, processes
over a considerable period of time. Things get changed gradually with the passage of time and
each change was made to overcome some difficulty faced by the user. The main reason for slow
development was the absence of proper information and the design data. Figure 2.3, shows the
evolutionary design and development of telephone into smart phone.
Figure 2.3: Evolution of Telephone
2.5 Other Design Methods
33
2.5.3 Design by Evaluation
Once a prototype is made, it is studied in a careful manner before going for actual production to
ensure that it can be manufactured. The designer is expected to keep following constraints in his
mind:
• The total market value for the product.
• That portion of the total market which might demand a product like the one being designed.
• Market penetration, that is, that part of the reduced market which might demand the particular
design developed.
• The price at which the substitute competitive products are being sold in the market.
• The basic price of the product.
2.5.4 Routine Design
Routine design is such a concept, in which the design space of the function, expected behaviours
and structure variables are known and the problem is one of the instantiating values for the structure
variables.
2.5.5 Creative Design
Creativity is the ability to the synthesizing new combinations of ideas and concepts into meaningful
and useful forms. Engineering creativity is more akin to inventiveness than research.
Creative Process
The creative process can be viewed as moving from an amorphous idea to a well established idea,
from a chaotic idea to an organized idea or from an implicit to explicit idea.
Generation of creative ideas occur by a slow, deliberate process that can be cultivated and enhanced
with study and practice. Following is a four stage process, one should follow to become creative:
1. Preparation: The elements of the problem are examined and their inter-relations are studied.
2. Incubation:After the mind is fully prepared and is in a condition to recognize a solution, a
time gap or a period is observed to be existing between period of preparation and illumination,
during which the mind may be relaxed. This time period is called incubation period.
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Chapter 2. Methods of Design
3. Inspiration: A solution or a path towards the solution suddenly emerges. The sub-conscious
mind is always attempting at a solution by constantly rearranging various facts and experiences
stored within the memory. This stage is called inspiration.
4. Verification: Once the solution has struck to mind , it needs to be analyzed, tested and verified
for its correctness. It is the final process of a creative process.
Upon verification, we get a creative design.
*
3. Detailed Design
3.1
Introduction
3.2
Design for Manufacture
Consideration of manufacturing (also termed as production or fabrication) processes during the
design stage of a product is fundamental to successful design. Since selection of materials must
precede consideration and analysis of manufacturability, herein it will be assumed that this stage is
part of the definition of functional requirements (in response to customer needs) and thus will not be
addressed. Primary issues that do arise during material selection include product life, environmental
conditions, product features, and appearance factors.
Design for Manufacturing (DFM) and design for assembly (DFA) are the integration of product
design and process planning into one common activity. The goal is to design a product that is easily
and economically manufactured. The importance of designing for manufacturing is underlined by
the fact that about 70% of manufacturing costs of a product (cost of materials, processing, and
assembly) are determined by design decisions, with production decisions (such as process planning
or machine tool selection) responsible for only 20%. The heart of any design for manufacturing
system is a group of design principles or guidelines that are structured to help the designer reduce
the cost and difficulty of manufacturing an item. The following is a listing of these rules:
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Chapter 3. Detailed Design
1. Reduce the total number of parts:The reduction of the number of parts in a product is
probably the best opportunity for reducing manufacturing costs. Less parts implies less
purchases, inventory, handling, processing time, development time, equipment, engineering
time, assembly difficulty, service inspection, testing, etc. In general, it reduces the level of
intensity of all activities related to the product during its entire life. A part that does not need
to have relative motion with respect to other parts, does not have to be made of a different
material, or that would make the assembly or service of other parts extremely difficult or
impossible, is an excellent target for elimination. Some approaches to part-count reduction
are based on the use of one-piece structures and selection of manufacturing processes such as
injection molding, extrusion, precision castings, and powder metallurgy, among others.
2. Develop a modular design:The use of modules in product design simplifies manufacturing
activities such as inspection, testing, assembly, purchasing, redesign, maintenance, service,
and so on. One reason is that modules add versatility to product update in the redesign
process, help run tests before the final assembly is put together, and allow the use of standard
components to minimize product variations. However, the connection can be a limiting factor
when applying this rule.
3. Use of standard components: Standard components are less expensive than custom-made
items. The high availability of these components reduces product lead times. Also, their
reliability factors are well ascertained. Furthermore, the use of standard components refers to
the production pressure to the supplier, relieving in part the manufacturer’s concern of meeting
production schedules.
4. Design parts to be multi-functional: Multi-functional parts reduce the total number of parts
in a design, thus, obtaining the benefits given in rule 1. Some examples are a part to act as
both an electric conductor and as a structural member, or as a heat dissipating element and as
a structural member. Also, there can be elements that besides their principal function have
guiding, aligning, or self-fixturing features to facilitate assembly, and/or reflective surfaces to
facilitate inspection, etc.
3.2 Design for Manufacture
37
5. Design parts for multi-use: In a manufacturing firm, different products can share parts that
have been designed for multi-use. These parts can have the same or different functions when
used in different products. In order to do this, it is necessary to identify the parts that are
suitable for multi-use. For example, all the parts used in the firm (purchased or made) can
be sorted into two groups: the first containing all the parts that are used commonly in all
products. Then, part families are created by defining categories of similar parts in each group.
The goal is to minimize the number of categories, the variations within the categories, and the
number of design features within each variation. The result is a set of standard part families
from which multi-use parts are created. After organizing all the parts into part families, the
manufacturing processes are standardized for each part family. The production of a specific
part belonging to a given part family would follow the manufacturing routing that has been
setup for its family, skipping the operations that are not required for it. Furthermore, in design
changes to existing products and especially in new product designs, the standard multi-use
components should be used.
6. Design for ease of fabrication:Select the optimum combination between the material and
fabrication process to minimize the overall manufacturing cost. In general, final operations
such as painting, polishing, finish machining, etc. should be avoided. Excessive tolerance,
surface-finish requirement, and so on are commonly found problems that result in higher than
necessary production cost.
7. Avoid separate fasteners:The use of fasteners increases the cost of manufacturing a part due
to the handling and feeding operations that have to be performed. Besides the high cost of the
equipment required for them, these operations are not 100% successful, so they contribute
to reducing the overall manufacturing efficiency. In general, fasteners should be avoided and
replaced, for example, by using tabs or snap fits. If fasteners have to be used, then some guides
should be followed for selecting them. Minimize the number, size, and variation used; also,
utilize standard components whenever possible. Avoid screws that are too long, or too short,
separate washers, tapped holes, and round heads and flatheads (not good for vacuum pickup).
Self-tapping and chamfered screws are preferred because they improve placement success.
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Chapter 3. Detailed Design
Screws with vertical side heads should be selected vacuum pickup.
8. Minimize assembly directions: All parts should be assembled from one direction. If possible,
the best way to add parts is from above, in a vertical direction, parallel to the gravitational
direction (downward). In this way, the effects of gravity help the assembly process, contrary
to having to compensate for its effect when other directions are chosen.
9. Maximize compliance:Errors can occur during insertion operations due to variations in
part dimensions or on the accuracy of the positioning device used. This faulty behavior
can cause damage to the part and/or to the equipment. For this reason, it is necessary to
include compliance in the part design and in the assembly process. Examples of part built-in
compliance features include tapers or chamfers and moderate radius sizes to facilitate insertion,
and nonfunctional external elements to help detect hidden features. For the assembly process,
selection of a rigid-base part, tactile sensing capabilities, and vision systems are example of
compliance. A simple solution is to use high-quality parts with designed-in-compliance, a
rigid-base part, and selective compliance in the assembly tool.
10. Minimize handling: Handling consists of positioning, orienting, and fixing a part or component. To facilitate orientation, symmetrical parts should be used when ever possible. If it is
not possible, then the asymmetry must be exaggerated to avoid failures. Use external guiding
features to help the orientation of a part. The subsequent operations should be designed so
that the orientation of the part is maintained. Also, magazines, tube feeders, part strips, and so
on, should be used to keep this orientation between operations. Avoid using flexible parts use slave circuit boards instead. If cables have to be used, then include a dummy connector to
plug the cable (robotic assembly) so that it can be located easily. When designing the product,
try to minimize the flow of material waste, parts, and so on, in the manufacturing operation;
also, take packaging into account, select appropriate and safe packaging for the product.
3.3
Design for Assembly
Assembly is a manufacturing process normally seen as an activity that does not add value to the final
product.Depending upon the number of components, sub-assemblies and complexities of the system,
3.4 Design for Shaping
39
the cost of assembly may soar too high thereby reducing the profit margin of the manufacturer. Thus
every effort should be made to minimize assembly costs by minimization of the total number of
parts, avoidance of several directions of assembly, and maximizing assemblability through the use of
following guidance features:
• Design parts with geometrical symmetry, and if not possible exaggerate the asymmetry.
• Avoid part features that will cause jamming and entanglement, and if needed add nonfunctional
features to achieve this objective.
• Incorporate guidance features to part’s geometry for ease of joining, such as chamfers; clearances should be configured for maximum guidance, but for minimum potential of jamming.
• Design products for unidirectional vertical (layered) assembly in order to avoid securing the
previous sub-assembly while turning it.
• Incorporate joining elements into the parts (such as snap fits) in order to avoid holding them in
place when utilizing additional joining elements (such as screws, bolts, nuts, or even rivets).
Snap fits can be designed to allow future disassembly or be configured for permanent joining
owing to potential safety hazards.
3.4
Design for Shaping
Shape and size of a product play an important role in the selection of the best solution to the problem.
A customer is more or less interested in choosing a product having a pleasant shape. A designer has
to maintain an aesthetically sound shape of the product throughout the design process.
3.5
Design for Maintenance / Maintainability
Maintainability is the degree to which a product allows safe, quick and easy replacement of its
component parts. It is embodied in the design of the product. A lack of maintainability will
be evident as high product maintenance costs, long out-of service times, and possible injuries to
maintenance engineers. One measure of maintainability is Time to Repair (TTR, also known as
‘turn-around time’). In large pieces of equipment, maintenance times might be listed for different
tasks on individual parts of the equipment. Two kinds of maintenance activity can be identified for
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Chapter 3. Detailed Design
any product:
• Preventive maintenance, for example replacing engine spark plugs every 30,000 km, or
changing the oil filter. Preventative maintenance requires the replacement of parts that are still
working but are expected to fail soon. It is also undertaken where degradation of a component
endangers components elsewhere in the product. For example an old oil filter may cause
serious engine damage by starving bearings of oil, or allowing abrasive metal sludge into clean
areas.This type of maintenance is also known by various names like; Condition monitoring,
predictive maintenance etc.
• Breakdown maintenance (repair), for example fitting a new vehicle starter motor where the
existing motor has burned out. Breakdown maintenance is performed after the product has
failed.
If the anticipated life of a component is known, failure can be avoided by scheduled replacement.
In certain instances, wholesale preventative maintenance is cheaper than piecemeal breakdown
maintenance. For example, replacing all the fluorescent lights in an office once a year can be
cheaper than replacing lights individually as they fail, because labor is used more efficiently. Since
maintainability is designed in, it is important to specify both reliability and maintainability targets
early in the design cycle. This in turn requires early knowledge of the anticipated life of the product
and its constituent parts, and the degree to which the parts are to be made replaceable.
3.5.1 Modularity and Lines of Repair:
A further consideration is where the components are to be replaced. This could be at the point of
use, at a repair depot, or at the point of manufacture. Car maintenance enthusiasts will replace spark
plugs at the point of use (their home). Most people will have them replaced at a repair depot (their
local dealer or garage). It would clearly be costly and inconvenient if the car had to be returned
to the manufacturer for replacement of spark plugs. These geographical points of repair are of ten
referred to as ‘lines of maintenance’ as follows:
• 1st line maintenance occurs at the point of use. It could be at home, wherever a vehicle
breaks down, on the tarmac in the case of an aircraft, or at the coalface in the case of mining
3.5 Design for Maintenance / Maintainability
41
equipment. It is appropriate to the replacement of small modular items that require a minimum
kit of tools and can be replaced within minutes.
• 2nd line maintenance occurs at a nearby maintenance depot. This could be railway workshops,
a car dealer, or your local domestic appliance service centre. It is appropriate where an
extended toolkit or special skills and processes are required, where adjustments must be made,
where special handling is required, where the time to repair may be lengthy, where reassembly
is complex, or where protection against the weather is important.
• 3rd line maintenance is undertaken by the manufacturer. It is rare for volume products to be
returned to the manufacturer for repair, but does happen in the case of bespoke equipment
or where the repair process requires skills and equipment beyond those available at the
local service centre. Examples would be aircraft re-wiring or engine rebuilds, and specialist
equipment servicing and repair. For volume products, 3rd line maintenance is not usually
economically viable.
This raises the issue of modularity. If the toolkit at 1st line is limited in size, then it may be more
convenient to replace not the failed component, but the entire module in which the failed component
is fitted. For example, a public address system consisting of separate mixer, CD player, amplifier
and loudspeakers is modular. The amplifier module can be replaced at 1st line without the need to
disturb other modules, and no special tools are required. The failed amplifier can then be sent to 2nd
or 3rd line for repair while the replacement is in use.
Modularity improves maintainability, but carries cost penalties. This is one reason why consumer
electronics manufacturers are moving away from separate modules towards ‘all-in-one’ entertainment
systems. There are also weight penalties to consider – modularity adds mass -a potential headache for
aircraft manufacturers. Software can also be made modular. A typical approach is that of ‘structured
programming’, where the main programme consists solely of a list of ‘go to subroutine’ commands,
each command pointing to a self-contained sub-routine or ‘module’.
42
3.6
Chapter 3. Detailed Design
Design for Use
While designing a product, a designer has to be careful while considering the needs of customers and
the convenience of use for all types of customers. A product should be usable with extreme dexterity
for everyone. Suppose a designer designs a seating chair for an examination hall which needs the
installation of writing pads at the hand rests of the chairs. Usually we find chairs having pads fixed
at the right hand rest of the chairs, but, the left-handed people can not use the chair for writing the
examination. Therefore,a flexible design needs to be carried out to take care of everyone.
3.7
Design for Recyclability
In the wake of concept of sustainable development, there has always been a thrust on environment
preservation in the manufacturing sector. Various government regulations and circulars have been
issued to employ the concept of design-for-recycling. The design guidelines for“green” products and
processes can be summarized as:
• Increase efficiency of energy use, while considering environmental impact.
• Minimize the amount of materials used.
• Use recyclable and biodegradable materials where possible. remanufacturing.
3.8
Design Checks
3.8.1 Clarity
Designer is supposed to have a clear thinking about shape, size, functions of a particular product. At
various stages of design process, design checks for clarity are to be carried out to ensure that the
shape, size and functions of the products are meeting the requirements of the design and customer.
3.8.2 Simplicity
A designer has to insist on simplicity of design. It means that the parts, components, assemblies of
the product should have a simple design functions. Simple design functions have following benefits:
• Maximize the life expectancy of the product (in materials as well as technology).
• Design a modular product for ease of disassembly and
3.8 Design Checks
43
• Simple parts are easy to assemble and disassemble.
• Simple parts entail easy maintenance.
• Simple design ensures ease of use.
• Cost of assembly and manufacture are reduced by opting for simple design.
3.8.3 Modularity
Modular design, or "modularity in design", is a design approach that subdivides a system into smaller
parts called modules or skids, that can be independently created and then used in different systems.
A modular system can be characterized by functional partitioning into discrete scalable, reusable
modules; rigorous use of well-defined modular interfaces; and making use of industry standards for
interfaces. With the increase in number of parts, components, sub-assemblies of the product, the
overall complexity of the design increases in terms of tedious maintenance practices, difficulty in
locating a fault, difficulty in troubleshooting, difficulty in assembling and disassembling, increase in
idle time upon breakdown etc. Therefore, every designer strives for a modular design. A modular
design divides a huge number of relevant components and sub-assemblies into few modules or
sub-systems. Modularity has following benefits:
• Ease of maintenance
• Ease of assembling/disassembling thereby reduction in cost of assembling/disassembling and
increase in profit.
• Easy installation
• Convenience in use
• Fault diagnosis becomes relatively easy
3.8.4 Safety
Safety aspect of design is of utmost importance. An unsafe product can, jeopardize the life of
operator, annihilate the material surrounding it. Therefore, a designer is bound to be extra cautious
while studying the safety aspects of the design. A designer should check the safety factor from all
possible angles after giving due consideration to following factors:
• Scope of use of product
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Chapter 3. Detailed Design
• Possible environment of use of product
• Population of users
• Human error involvement
• Chances of accidents
• User comfort
3.9
Standardization and Size Ranges
3.9.1 Standardization
A process of establishing standards or units of measure for the purpose of comparing quality, quantity
or performance is termed as standardization. Following points need to be considered while opting
for standards for designing:
• Material Standards: The physical properties , chemical composition of materials and the type
of heat treatment undergone by a material are the major criteria for material standard.
• Tolerance Standard: Standards for fits, tolerances and surface finish of the components.
• Geometric Standard: Different shapes and dimensions of commonly used machine elements
like nuts , bolts, rivets etc
3.9.2 Preferred Numbers
In industrial design, preferred numbers (also called preferred values, preferred series or convenient
numbers) are standard guidelines for choosing exact product dimensions within a given set of
constraints. Product developers must choose numerous lengths, distances, diameters, volumes,
and other characteristic quantities. While all of these choices are constrained by considerations of
functionality, usability, compatibility, safety or cost, there usually remains considerable leeway in
the exact choice for many dimensions.
Preferred numbers serve two purposes:
1. Using them increases the probability of compatibility between objects designed at different
times by different people. In other words, it is one tactic among many in standardization,
whether within a company or within an industry, and it is usually desirable in industrial
contexts (unless the goal is vendor lock-in or planned obsolescence)
3.9 Standardization and Size Ranges
45
2. They are chosen such that when a product is manufactured in many different sizes, these will
end up roughly equally spaced on a logarithmic scale. They therefore help to minimize the
number of different sizes that need to be manufactured or kept in stock.
3.9.3 Range Sizes
A product needs to be produced in a variety of sizes to ensure a high level of standardization and
diversity in use. Extensively used sizes are produced in large quantities whereas odd sizes are
produced in limited quantities and as per demands only. *
4. Reliability and Robust Design
4.1
Introduction
The ultimate analysis of a product in terms of quality is carried out by checking the performance
under actual use and how it fulfills its functions over a period of time. A product is said to be reliable,
if its quality is consistent and it gives dependable results. For example, let us take an example of
performance of an aircraft which consists of thousands of parts and hundreds of sub assemblies . For
the aircraft to be airworthy and safe, it is must that all its critical parts perform well.
The customers always want to have high performance, adequate duration of service life without
failures and least possible maintenance of a product. Friction is a necessary evil which can not be
eliminated completely therefore, products undergo wear and tear but the thing which can improve a
product is that high performance can be coupled with low maintenance requirements to get a reliable
product.
4.2
Design for Reliability
Reliability may be defined as "the probability of product performing its purpose adequately for the
period of time intended under a set of specified operating conditions". Following are a few important
aspects of reliability:
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Chapter 4. Reliability and Robust Design
1. Reliability is a function of time. One can not expect on almost worn-out bearing to be as
reliable as new one recently put into service.
2. Reliability is a function of operating conditions. Hostile operating conditions can result into
frequent failures as compared to normal operating conditions.
3. Reliability being a concept of probability can be quantified for the purpose of optimization.
4.3
Reliability and Quality
Reliability and quality are two different aspects and should not be confused as to be same.The quality
of product is poor when it does not meet the specified requirements at the instant of the time it is
evaluated while as reliability is a projection of performance of a product over a period of time and is
usually designated as a quantifiable design parameter.
4.4
Reliability in Series and Parallel
Overall reliability of a product is dependent on the individual reliability of the components and
sub assemblies. The components may be connected in series or in parallel depending upon the
requirements.An overall system reliability prediction can be made by looking at the reliabilities of
the components that make up the whole system or product.
Reliability in Series
In a series configuration as shown in figure 4.1, a failure of any component results in the failure of
the entire system. In most cases, when considering complete systems at their basic subsystem level,
it is found that these are arranged reliability-wise in a series configuration. For example, a personal
computer may consist of four basic subsystems: the motherboard, the hard drive, the power supply
and the processor. These are reliability-wise in series and a failure of any of these subsystems will
cause a system failure. In other words, all of the units in a series system must succeed for the system
to succeed.
R(t) = R1 ∗ R2 ∗ R3 ∗ ........... ∗ RN
(4.1)
4.4 Reliability in Series and Parallel
49
Figure 4.1: Reliability in Series and Parallel Arrangements
Example: Series Arrangement
Three subsystems are reliability-wise in series and make up a system. Subsystem 1 has a reliability
of 99.5%, subsystem 2 has a reliability of 98.7 % and subsystem 3 has a reliability of 97.3 % for a
mission of 100 hours. What is the overall reliability of the system for a 100-hour mission? Since the
reliabilities of the subsystems are specified for 100 hours, the reliability of the system for a 100-hour
mission is simply:
Rs = 1 − (0.9950) ∗ (0.9870) ∗ (0.9730)
Rs = 0.955549245
Rs = 95.55%
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Chapter 4. Reliability and Robust Design
Reliability in Parallel
In a simple parallel system, as shown in the figure 4.1, at least one of the units must succeed for the
system to succeed. Units in parallel are also referred to as redundant units. Redundancy is a very
important aspect of system design and reliability in that adding redundancy is one of several methods
of improving system reliability. It is widely used in the aerospace industry and generally used in
mission critical systems. Other example applications include brake systems and support cables in
bridges.
R(t) = 1 − (1 − R1 ) ∗ (1 − R2 ) ∗ (1 − R3 ) ∗ ........... ∗ (1 − RN )
(4.2)
Example : Parallel Arrangement
Consider a system consisting of three subsystems arranged reliability-wise in parallel. Subsystem 1
has a reliability of 99.5 %, Subsystem 2 has a reliability of 98.7 % and Subsystem 3 has a reliability
of 97.3 % for a mission of 100 hours. What is the overall reliability of the system for a 100-hour
mission?
Since the reliabilities of the subsystems are specified for 100 hours, the reliability of the system for a
100-hour mission is:
Rs = 1 − (1 − 0.9950) ∗ (1 − 0.9870) ∗ (1 − 0.9730)
Rs = 1 − 0.000001755
Rs = 0.999998245
4.5
Failure Types in Reliability Engineering
Three types of failures are encountered in reliability engineering usually as follows:
1. Early failure stage: This is the period where relatively early failures occur following the first
operation of a device, and is characterized by a gradual decline in the number of failures over
time. This phenomenon is caused because products with latent failures cannot be completely
eliminated during the sorting process. These latent failures reveal themselves in a short time
4.5 Failure Types in Reliability Engineering
51
after first use of the device, due to temperature, voltage, and other stresses.
2. Random failure stage: Once the early failures have been eliminated, the failure rate stabilizes
at an extremely low level, but latent failures may reveal themselves at random over a long time
and thus their number does not decline to zero. Since failures occur at random, the failure rate
is almost constant.
3. Wear-out failure stage: This is the period where the devices fail due to wear, fatigue, and so
on, with the failure rate rising over time.
4.5.1 Bath-Tub Curve
The bathtub curve is widely used in reliability engineering. It describes a particular form of the
hazard function which comprises three parts:
• The first part is a decreasing failure rate, known as early failures.
• The second part is a constant failure rate, known as random failures.
• The third part is an increasing failure rate, known as wear-out failures.
The name is derived from the cross-sectional shape of a bathtub: steep sides and a flat bottom.
Figure 4.2: Bath-Tub Curve
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Chapter 4. Reliability and Robust Design
The bathtub curve is generated by mapping the rate of early "infant mortality" failures when first
introduced, the rate of random failures with constant failure rate during its "useful life", and finally
the rate of "wear out" failures as the product exceeds its design lifetime.
In less technical terms, in the early life of a product adhering to the bathtub curve, the failure
rate is high but rapidly decreasing as defective products are identified and discarded, and early
sources of potential failure such as handling and installation error are surmounted. In the mid-life of
a product—generally, once it reaches consumers—the failure rate is low and constant. In the late
life of the product, the failure rate increases, as age and wear take their toll on the product. Many
consumer product life cycles strongly exhibit the bathtub curve.
While the bathtub curve is useful, not every product or system follows a bathtub curve hazard
function, for example if units are retired or have decreased use during or before the onset of the
wear-out period, they will show fewer failures per unit calendar time (not per unit use time) than the
bathtub curve.
4.6
Robust Design
Robust product design is a concept from the teachings of Dr. Genichi Taguchi, a Japanese quality
guru. It is defined as reducing variation in a product without eliminating the causes of the variation.
In other words, making the product or process insensitive to variation. This variation (sometimes
called noise) can come from a variety of factors and can be classified into three main types: internal
variation, external variation, and unit to unit variation. Internal variation is due to deterioration
such as the wear of a machine, and aging of materials. External variation is from factor relating to
environmental conditions such as temperature, humidity and dust. Unit to Unit variation is variations
between parts due to variations in material, processes and equipment. Examples of robust design
include umbrella fabric that will not deteriorate when exposed to varying environments (external
variation), food products that have long shelf lives (internal variation), and replacement parts that
will fit properly (unit to unit variation). The goal of robust design is to come up with a way to make
the final product consistent when the process is subject to a variety of "noise".
4.6 Robust Design
53
Advantages of Robust Design
Robust design has many advantages. For one, the effect of robustness on quality is great. Robustness
reduces variation in parts by reducing the effects of uncontrollable variation. More consistent parts
equals better quality.
Another advantage is that lower quality parts or parts with higher tolerances can be used and a
quality product can still be made. This saves the company money, because the less variable the parts
can be the more they cost.
A third advantage is that the product will have more appeal to the customer. Customers demand a
robust product that won’t be as vulnerable to deterioration and can be used in a variety of situations.
This method is also good, because you are designing the robustness into the product and process
instead of trying to fix variation problem after they occur.
Disadvantages of Robust Design
One of the disadvantages of robust design is that to effectively deal with the noise, the designer must
be aware of the noise. If there is a noise factor that is affecting the product and the experiments run
do not address it (intentionally or not), the only way that the product will be robust to that variation
is by luck.
Another disadvantage to robust design done Taguchi’s way is that the problem becomes large
quickly. If you had a lot of different things to consider as control variables and/or noise variables,
it would take a great deal of time to run all the experimental trials. Controlling noise variables is
expense, and when lots of trials are required the dollars add up.
Another disadvantage is that by using orthogonal arrays, it assumes the noise factors are independent, which may be helpful in setting up the experiment, but is not necessarily a good assumption
4.6.1 Taguchi’s Methodology
Taguchi considers making a design robust in the parameter design portion of product or process
design. In parameter design the goal is to find values for controllable settings that minimize the
negative effects of the uncontrollable settings. Experiments are used to determine the impact of
particular settings on both the controllable and uncontrollable factors. The idea here is that by
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Chapter 4. Reliability and Robust Design
observing changes in a controllable factor (such as the thickness of boards), a value can be found
for that factor that reduces the effect (warping) of something that can’t be controlled (the humidity
outside). The ultimate goal is to find the optimal settings to minimize cost by minimizing variation.
When setting up these experiments, the factors that effect the product need to be determined.
Then the factors can be separated into controllable factors and uncontrollable factors and experiments
can be set up to test the effects of changing the values of each factor. There are many ways to set
up these experiments. Taguchi’s method involves finding correlation between variables. He uses
orthogonal arrays, with the inner array consisting of control factors and the outer array consisting of
"noise" factors. Each inner array is to be run with each outer array. (If six control factor experiments
and three "noise" factor experiments are needed, there will have to be (six times three) eighteen
experimental trials to get all the combinations).
5. Design Organization
5.1
Introduction
Engineering design today is very information-intensive. Information is required not only regarding
the knowledge and codes of practice within established disciplines, but also regarding the design
context. In addition, many engineering design organizations are realizing the need to draw on their
prior experience, especially where such experience has been at the interfaces of disciplines, and
hence not properly documented elsewhere. Because of the information-rich nature of engineering
design, and also the increasing need to focus on the design process, in addition to the product, the
study of information flow within engineering design organizations has become very important.
5.2
Design Organization
For the efficient functioning of a design team, the design specifications must be preserved for future.
It is the duty of an engineer to organize, improve, and transmit information. The information may be
relevant to any of the following items:
1. Drawings;
2. Specifications;
3. Performance predictions;
4. Bill of materials required;
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Chapter 5. Design Organization
5. Technical advice.
Organization of design involves organizing catalogues, files, data-books and operating manuals. The
designer should be able to gather any information as and when required. Design organization makes
it possible for the designers and engineers to design a product effectively.
5.3
Communication
The basic model of the communication process is exhibited in Figure 5.1. The communication begins
from a perception of the problem. The sender has information to communicate to the receiver. An
encoding process occurs when information is translated into a systematic set of symbols (language)
that express what the sender wishes to transmit. The product of encoding is a message. The form
of the message depends on the nature of the communication channel. The channel is the medium
through which the message will be carried from the sender to the receiver. The message may be a
written report, face-to-face communication, telephone call or transmission via a computer network.
When a message reaches the receiver, it is interpreted in light of receiver’s previous experience.
Feedback from the receiver to the sender indicates how the message has been transmitted. Feedback
presents the sender with an opportunity to determine whether the message has been received and
whether it has produced the intended effect – the adequate perception of the problem by the receiver
and transfer of the meaning.
The communications process encounters various difficulties that are related to psychological and
semantic interferences (barriers). Psychological interferences are associated with the communications
environment and can include the following:
• Non-identification of the purpose;
• Lack of respect by either party for the other (the sender and the receiver);
• Preconception of either party;
• Preoccupation of either party;
• Failure to establish the best channel;
• The sender is not clear;
• The sender/receiver is not open to feedback;
5.3 Communication
57
• Emotions are ignored;
Figure 5.1: Basic elements of the communication process
Semantic interferences are associated with improper selection for preparation. Common words from
a technical discipline take on a specialized meaning that can be completely unknown to the receiver.
Therefore, engineering students in communications must present basic word meanings that enable
proper engineering decisions. Word meanings must be thoroughly understood and applied in future
applicable courses. This basic mining task is known as Product Design Specification.
Product Design Specification involves a detailed listing of the requirements to be met in order to
produce a successful product or process. Elements of cover the formal means of communications
between all participants of the processes of planning and creating successful engineering design. All
elements of Product Design Specification should be determined and, whenever possible, expressed
in quantitative terms.
There is another important aspect: communication in the design process. This identifies with certain
specifics and requires an applicable strategy. The simple model presented in Figure 5.2 illustrates a
number of important aspects of the design process. Design starts with knowledge of the state of the
art information technology. The needs of society provide the impetus for design. When a need is
identified, a need must be conceptualized as some kind of structure.
The design concept must be subjected to a feasibility analysis until an acceptable product is produced,
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Chapter 5. Design Organization
or the project is abandoned. When the design enters the production phase, it begins to compete in the
world of technology. Each step of the design loop requires communication with all participants of
the design. Design is a creative process and all new creations are a result of communications strategy
of some kind.
Figure 5.2: A simple model of the design process steps
5.4
Technical Report
A technical report is a document that describes the process, progress, or results of technical or
scientific research or the state of a technical or scientific research problem. It might also include
recommendations and conclusions of the research. Unlike other scientific literature, such as scientific
journals and the proceedings of some academic conferences, technical reports rarely undergo
comprehensive independent peer review before publication. They may be considered as grey
literature. Where there is a review process, it is often limited to within the originating organization.
Similarly, there are no formal publishing procedures for such reports, except where established
5.5 Drawings
59
locally.
A formal technical report is usually written at the end of a project. Generally, it is a complete, stand
alone document aimed at persons having widely diverse backgrounds. The essential components of
a technical report are as under:
• Letter of transmittal, which serves as a covering letter, is provided so that the receiver of the
report gets introduced to the overall contents and purpose of the technical report.
• Summary of report,is provided at the beginning pages of the report giving an abstract knowledge about the report.It enables the reader to decide whether the report is worth-reading or
not.
• Introduction to the project, in order to acquaint the reader with the problem.
• Experimental procedures indicate the procedure followed for collecting the data relevant to
the project.
• Results and discussions
• Conclusion section states the conclusions drawn from the work undertaken.
• References / Bibliography section makes the mention of the persons and their corresponding
works, if some material is cited from them by the author of the technical report.
• Appendices are used for mathematical developments, simple calculations etc. The reason for
placing the appendices at the end is that it does not impede with the logical flow of the report.
Extensive mathematical calculations, if placed in the main body of the report would seriously
impede with the logical flow of thought.
• Tables
• Figures
5.5
Drawings
Technical drawing, drafting or drawing, is the act and discipline of composing drawings that visually
communicate how something functions or is constructed.
Technical drawing is essential for communicating ideas in industry and engineering. To make the
drawings easier to understand, people use familiar symbols, perspectives, units of measurement,
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Chapter 5. Design Organization
notation systems, visual styles, and page layout. Together, such conventions constitute a visual
language and help to ensure that the drawing is unambiguous and relatively easy to understand.
Many of the symbols and principles of technical drawing are codified in an international standard
called ISO 128.
The need for precise communication in the preparation of a functional document distinguishes
technical drawing from the expressive drawing of the visual arts. Artistic drawings are subjectively
interpreted; their meanings are multiply determined. Technical drawings are understood to have one
intended meaning.
A drafter, draftsperson, or draughtsman is a person who makes a drawing (technical or expressive).
A professional drafter who makes technical drawings is sometimes called a drafting technician.
Professional drafting is a desirable and necessary function in the design and manufacture of complex
mechanical components and machines. Professional draftspersons bridge the gap between engineers
and manufacturers and contribute experience and technical expertise to the design process.
Use of Drawing in Architecture:
The art and design that goes into making buildings is known as "architecture". To communicate all
aspects of the shape or design, detail drawings are used. In this field, the term plan is often used
when referring to the full section view of these drawings as viewed from three feet above finished
floor to show the locations of doorways, windows, stairwells, etc. Architectural drawings describe
and document an architect’s design.
Use of Drawing in Engineering:
Engineering can be a very broad term. It stems from the Latin ingenerare, meaning "to create".
Because this could apply to everything that humans create, it is given a narrower definition in the
context of technical drawing. Engineering drawings generally deal with mechanical engineered
items, such as manufactured parts and equipment.
Engineering drawings are usually created in accordance with standardized conventions for layout,
nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc.
Its purpose is to accurately and unambiguously capture all the geometric features of a product or a
component. The end goal of an engineering drawing is to convey all the required information that
5.6 Presentation
61
will allow a manufacturer to produce that component.
5.6
Presentation
Technical presentations serve engineering, scientific and high tech purposes, describing advances in
technology, problem resolution, product design and project status. In general, technical presentations
serve following purposes:
• To inform (e.g., knowledge transfer, classroom instruction) or
• To persuade (e.g., convincing others to adopt a design approach or accept the results of an
evaluation process).
• Design engineers communicate the detailed design to manufacturing engineers so as to
commence the production.
• Marketing team exhibits the striking features of the product to the clients before the launch of
the product.
5.7
Models
Modeling is the process of producing a model; a model is a representation of the construction and
working of some system of interest. A model is similar to but simpler than the system it represents.
One purpose of a model is to enable the analyst to predict the effect of changes to the system. On the
one hand, a model should be a close approximation to the real system and incorporate most of its
salient features. On the other hand, it should not be so complex that it is impossible to understand and
experiment with it. A good model is a judicious trade off between realism and simplicity. Simulation
practitioners recommend increasing the complexity of a model iteratively. An important issue in
modeling is model validity. Model validation techniques include simulating the model under known
input conditions and comparing model output with system output.
*
6. IT and its Elements
6.1
Introduction
Information Technology consists of two words – Information and Technology. Information refers to
any communication or representation of knowledge such as facts, data or opinions in any medium or
for including textual, numerical, graphic, narrative or audio visual forms.Technology is the practical
knowledge or the science of application of knowledge to practical. Thus Information Technology is
any equipment or interconnected system or subsystem of equipment that is used in the acquisition,
storage manipulation, management transmission or reception of data or information. IT refers to
anything related to computing technology such as networking, hardware, software, the internet or
the people that work with these technologies.
6.2
Definition of Information Technology
Information Technology can be defined as the technology involving the development, maintenance,
and use of computer systems, software, and networks for the processing and distribution of data. According to UNESCO Information Technology is a scientific, technological and engineering discipline
and management technique used in handing the information. Its application and association with
social, economic and cultural matters. IT is a field of engineering involving computer based hardware
and software systems , and communication systems, to enable the acquisition, representation, storage,
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transmission, and use of information. The hardware and software of computing and communication
form the basic too of technology. The web browsers, the operating systems, ERP’s and special
purpose applications are the software which is used in Information Technology.
6.3
Characteristics of Information Technology
• Acquisition, storage, manipulation, management, transmission o reception of data or information
• Real time access to information
• Easy availability of updated data
• Connecting geographically dispersed regions
• Wider range of communication media
6.4
Importance of Information Technology
• Information Technology is useful in ensuring the smooth functioning of all the departments
in accompany such as the human resource department, finance department, manufacturing
department and in security related purposes.
• The companies are able to avoid any sort of errors or mistakes in the proper functioning of the
tools used for designing and manufacturing purposes.
• Due to the development of the information technology sector, the companies are being able to
keep themselves aware of the changes in the global markets.
• IT plays an important role in easily solving the mathematical problems and in the project
management system.
• It has a great use in the automated production of sensitive information, automated up-gradation
of the important business processes and the automated streamlining of the various business
processes.
• It has also played an important role in the areas of communication and automated administration of entire systems.
6.5 Application of IT in Design Organizations
6.5
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Application of IT in Design Organizations
IT has become a vital and integral part of every design organization. From multi-national corporations
who maintain mainframe systems and databases to small businesses that own a single computer,
IT plays a role. The important applications of information technology in the field of design and
manufacturing are given as follows.
• Product Development:
Information technology can speed up the time it takes new products to reach the market. Companies can now understand the requirements of consumers by collecting marketing intelligence
from proprietary databases, customers and sales representatives. IT helps businesses respond
quickly to changing customer requirements.
• Process Improvement:
Process improvement is another important IT application in business. Enterprise resource
planning system allow managers to review sales, costs and other operating figures on one
integrated software platform, usually in real time. An ERP system can replace a number of
traditional systems for finance, human resources and other functional areas.
• Communication:
At present, email is the principal means of communication between employees, suppliers and
customers. Communication by email is faster and costs less than sending a paper letter in the
mail. IT allows organizing email file folders by client or by type of communication, such as
orders or billing.
• Marketing:
One of the main applications of IT is in the area of marketing. Both large and small businesses
can now play on a same level and status on the internet. They can have a web site, take orders,
buy goods, sell excess or even operate some businesses entirely online.
• Inventory Management:
IT helps business to manage inventory effectively. Organizations are now able to maintain
enough stock to meet demand without investing in more than they require. Inventory management systems track the quantity of each item a company maintains, placing an order of
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additional stock when the quantities fall below a pre-determined reorder level.
• Customer Relationship Management:
Companies are using IT to design and manage customer relationships. Customer Relationship
Management (CRM) systems capture every interaction a company has with a customer. The
entire interaction is stored in the CRM system, ready to be recalled if the customer calls again.
• Data Management:
Through IT, companies are able to store and maintain a tremendous amount of historical data
economically and employees benefit from immediate access to the documents they need.
• Management Information Systems (MIS):
Storing data is only beneficial if that data can be used effectively. MIS enable companies
to track sales data, expenses and productivity levels. The information can be used to track
profitability over time, maximize return on investment and identify the areas of improvement.
• Globalization:
IT is at the core of operating models essential for globalization, such as telecommuting and
outsourcing. A company can outsource most of its noncore functions, such as human resources
and finances, to offshore companies and use network technologies to stay in contact with its
overseas employees, customers and suppliers.
• Competitive Advantage:
Cost savings, rapid product development and process improvements help companies gain and
maintain a competitive advantage in the market place. Companies can use rapid prototyping,
software simulations and other IT based systems to bring a product to market cost effectively
and quickly.
• Cost Effectiveness:
Although the initial IT implementation costs can be substantial, that resulting long term cost
savings are usually worth the investment. IT allows companies to reduce transaction and
implementation costs.
6.6 Database Systems
6.6
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Database Systems
Databases and database systems are an essential component of life in modern society: most of us
encounter several activities every day that involve some interaction with a database. For example,
if we go to the bank to deposit or withdraw funds, if we make a hotel or airline reservation, if we
access a computerized library catalog to search for a bibliographic item, or if we purchase something
online—such as a book, toy, or computer— chances are that our activities will involve someone
or some computer program accessing a database. Even purchasing items at a supermarket often
automatically updates the database that holds the inventory of grocery items. A Database is a shared
collection of related data which is used to support the activities of a particular organization. A
database can be viewed as a repository of data that is defined once and then is accessed by various
users. A database has the following implicit properties:
• A database represents some aspect of the real world, sometimes called the miniworld. Changes
to the miniworld are reflected in the database.
• A database is a logically coherent collection of data with some inherent meaning. A random
assortment of data cannot correctly be referred to as a database.
• A database is designed, built, and populated with data for a specific purpose. It has an intended
group of users and some preconceived applications in which these users are interested.
6.7
Characteristics of Database Systems
• Self-Describing Nature of a Database System:
A Database System contains not only the database itself but also a complete definition or
description of the database structure and constraints. This definition is stored in the DBMS
catalog, which contains information such as the structure of each file, the type and storage
format of each data item, and various constraints on the data.The information stored in the
catalog is called meta-data.
• Insulation between Program and Dataand Data Abstraction:
In the file based system, the structure of the data files is defined in the application programs so
if a user wants to change the structure of a file, all the programs that access that file might need
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to be changed as well. On the other hand, in the database approach, the data structure is stored
in the system catalog not in the programs. Therefore, one change is all that’s needed.We call
this property program-data independence.
• Sharing of Data and Multiuser Transaction Processing:
A multiuser database system must allow multiple users access to the database at the same. The
multiuser DBMS must have concurrency control strategies to ensure several users access to
the same data item at the same time, and to do so in a manner that the data will always be
correct – data integrity.The DBMS must include concurrency control software to ensure that
several users trying to update the same data do so in a controlled manner so that the result of
the updates is correct.
6.8
DBMS
A database management system (DBMS) is a collection of programs that enables users to create and
maintain a database. The DBMS is a general-purpose software system that facilitates the processes
of defining, constructing, manipulating, and sharing databases among various users and applications.
Defining a database involves specifying the data types, structures, and constraints of the data to be
stored in the database. The database definition or descriptive information is also stored by the DBMS
in the form of a database catalog or dictionary; it is called meta-data.
6.8.1 Component Modules of DBMS
A DBMS is a very complex software system that consists of many components, or modules, including
modules for implementing the catalog, query language processing,interface processing, accessing
and buffering data, controlling concurrency,and handling data recovery and security. The DBMS
must interface with other system software such as the operating system and compilers for various
programming languages.
The top part of the figure refers to the various users of the database environment and their interfaces.
The lower part shows the internals of the DBMS responsible for storage of data and processing
of transactions. The database and the DBMS catalog are usually stored on disk. Access to the
disk is controlled primarily by the operating system (OS), which schedules disk read/write. Many
6.9 Advantages of Using the DBMS Approach
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DBMSs have their own buffer management module to schedule disk read/write, because this has a
considerable effect on performance.
Three main components of DBMS are;
1. Data Definition Language (DDL):
The contents of database are created by using the DDL. It defines relationship between different
data elements and serves as an interface for application programmes that uses data
2. Data Manipulation Language(DML):
Data processed and updated by using a language called data manipulation language. It allows a
user to query database and receive summary or customized reports. DML is usually integrated
with other programming languages.
3. Data Dictionary:
Data dictionary contains schema of the database. It defines each data item in the database, lists
its structure, source, persons authorized to modify it etc. in other words it gives metadata ie,
data about data, through which the end user data are integrated and managed.
6.9
Advantages of Using the DBMS Approach
• Controlling Redundancy:
In traditional software development utilizing file processing, every user group maintains its
own files for handling its data-processing applications.This redundancy in storing the same
data multiple times leads to several problems such as duplication of effort, wastage of storage
space, inconsistency in data.
• Restricting Unauthorized Access:
When multiple users share a large database, it is likely that most users will not be Authorized
to access all information in the database.Hence, the type of access operation— retrieval or
update—must also be controlled.
• Providing Persistent Storage for Program Objects:
Databases can be used to provide persistent storage for program objects and data structures.
This is one of the main reasons for object-oriented database systems.a complex object in C++
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can be stored permanently in an object-oriented DBMS. Such an object is said to be persistent,
since it survives the termination of program execution and can later be directly retrieved by
another C++ program.
• Providing Storage Structures and Search Techniques for Efficient Query Processing:
Database systems must provide capabilities for efficiently executing queries and updates.
Because the database is typically stored on disk, the DBMS must provide specialized data
structures and search techniques to speed up disk search for the desired records. Auxiliary
files called indexes are used for this purpose.
• Providing Backup and Recovery:
A DBMS must provide facilities for recovering from hardware or software failures. The
backup and recovery subsystem of the DBMS is responsible for recovery.
• Providing Multiple User Interfaces:
Because many types of users with varying levels of technical knowledge use a database, a
DBMS should provide a variety of user interfaces.
• Representing Complex Relationships among Data:
A database may include numerous varieties of data that are interrelated in many ways. A
DBMS must have the capability to represent a variety of complex relationships among the
data, to define new relationships as they arise, and to retrieve and update related data easily
and efficiently.
• Permitting Inference and Actions Using Rules:
Some database systems provide capabilities for defining deduction rules for inference new
information from the stored database facts. Such systems are called deductive database
systems.
6.10
Database Security
Database security concerns the use of a broad range of information security controls to protect
databases (potentially including the data, the database applications or stored functions, the database
systems, the database servers and the associated network links) against compromises of their
6.10 Database Security
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confidentiality, integrity and availability.
Security risks to database systems include:
• Unauthorized or unintended activity or misuse by authorized database users, database Administrators, or network/systems managers, or by unauthorized users or hackers (e.g. Inappropriate
access to sensitive data, meta data or functions within databases, or inappropriate changes to
the database programs, structures or security configurations);
• Malware infections causing incidents such as unauthorized access, leakage or disclosure of
personal or proprietary data, deletion of or damage to the data or programs, interruption or
denial of authorized access to the database, attacks on other systems and the unanticipated
failure of database services;
• Overloads, performance constraints and capacity issues resulting in the inability of authorized
users to use databases as intended;
• Physical damage to database servers caused by computer room fires or floods, overheating,lightning, accidental liquid spills, static discharge, electronic breakdowns/equipment
failures and obsolescence;
• Design flaws and programming bugs in databases and the associated programs and systems,creating various security vulnerabilities (e.g. unauthorized privilege escalation), data
loss/corruption, performance degradation etc.;
• Data corruption and/or loss caused by the entry of invalid data or commands, mistakes in
database or system administration processes, sabotage/criminal damage etc.
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Figure 6.1: A simplified database system environment
6.10 Database Security
Figure 6.2: Component modules of a DBMS and their interactions
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