modulation instituteendeavor is that suggested by morris asimow. engineering design is a...
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Modulation Institute
For video lectures call @ 9015781999 or visit www.modulation.in
Modulation Institute
For video lectures call @ 9015781999 or visit www.modulation.in
CONTENTS
Engineering design process and its structure.
Identification and analysis of need, product design specifications, standards of
performance and constraints.
Searching for design concepts, morphological analysis, brainstorming. Evaluation
of design concepts for physical reliability, economic feasibility and utility.
Detailed design:
Design for manufacture, assembly, shipping, maintenance, use, and recyclability.
Design checks for clarity, simplicity, modularity and safety. Standardization and
size ranges.
Reliability and robust design. Design organization and communication, . technical
reports, drawings, presentations and models.
Concept of manufacturing:
Classification of manufacturing processes. Fundamentals of casting.
Basic understanding of commonly used casting processes (sand casting,
investment casting and permanent mould casting processes).
Fundamentals of metal forming :
Hot and cold working, basic understanding of primary metal forming processes
(rolling, forging, extrusion and drawing processes, punching and blanking).
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Fundamentals of metal cutting:
tool-work interaction for production of machined surfaces.
Classification of machining processes. Basic machining operations (turning,
shaping, planning, drilling and milling processes).
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Introduction:
The economic future of India depends on our ability to design, make and sell
competitive products. Excellent design and effective manufacture are the pre-
requisites of a successive industry. There is a general impression that the quality of
Indian products can still be improved. The fact that consumers have lost their
confidence on Indian-made products cannot be denied. This problem can be solved
only by designing and manufacturing better products through improved
methodology. Keeping this in view, the subject “Design and manufacturing”
purpose to present the methods and procedures of design and manufacture.
Although engineers are not the only people who design things, the professional
practice of engineering is largely concerned with design. It is usually said that
design is the essence of engineering.
The ability to design is both a science and an art. The science can be learned
through procedures developed by eminent scholars. But the art can be learned only
by doing design.
Types of Products
A product is the tangible end result of a manufacturing process and is meant for
satisfying human needs. The product can be classified as follows: -
1. Convenience goods
These are less expensive and are clustered around shops and restaurants.
These can be purchased at consumer's convenience. E.g. Cigarette, Candy,
Magazines etc.
2. Shopping goods
These are expensive and people buy it less frequently.
E.g. Jewellary garments etc.
3. Specialty goods
These are purchased, taking extra pain..E.g. Rare objects like stamps.
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4. Industrial goods
These are items used in the production of other items.
Eg. Raw materials
Another way of classifying products is into
Continuous Products, and
Discrete products
The continuous products : are those which are produced in a continuous fashion.
For example, plates, sheets, tubes and bars etc are produced in very long lengths,
and then these are cut into desired lengths.
On the other hand
Discrete products are produced one after another, each in separate units.
On the basis of the output product, the Industry is usually named as continuous
industry and discrete industry.
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Requirements in a good product
• Customer Satisfaction
• Profit
To achieve customer satisfaction:
The product should function properly.
It must have desired accuracy
It must have desired reliability
It must be easy to operate
It must be serviceable
It must make minimum space utilization
It must withstand rough handling
Pleasant appearances.
Reasonable price.
How can it be profitable?
It must be easy to manufacture
The raw material must be cheap and easily available
The manufacturing process has to the decided on the basis of quantity to be
produced
It must use standard parts
It must be easy to pack and distribute.
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Definition of Design:
Designing is such a vast field that it is defined in several ways. Various definitions
of designing as pronounced by well-known designers are
“Design is that which defines solutions to problem which have previously been
solved in a different way”
“ Design is the conscious human process of planning physical things that display
a new form in response to some pre-determined need”.
“Design is an act of collecting all pertinent information for the production of
goods and services to meet some human need”.
There have been many definitions suggested to describe what is meant by
Engineering Design. One which m ay best summarize all the aspects of the field of
endeavor is that suggested by Morris Asimow. Engineering Design is a "purposeful
activity directed towards the go al of fulfilling human needs, particularly those
which can be m et by technological factor, of our civilization."
According to (M. Asimow- "Introduction to Design," Prentice Hall) :-
The emphasis is placed on three important phrases which tell us what Engineering
Design is
(i) A purposeful activity.
(ii) Aimed at the satisfaction of human needs.
(iii) Based on technological factors. It is most important that we fully realize the
implications of these three features whenever a design project is presented to
us. It is well known that the profession or engineering exists to solve
problems presented to its m embers by the sound application of scientific
principles. It is required that these problem s be solved, within a defined
time limit and taking due account of economic, human and legal factors.
The second aspect which is accentuated in the above description is that of
"fulfilling human needs." This is the most important consideration in design
and is the prim ary reason for the existence of engineering. These needs can
be manifest in many different ways but we must always realize who it that
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engineering should serve is. The third consideration separates Engineering
Design from other fields where hum an needs can b e satisfied by music,
literature, art, architecture and other artistic activities. Thus Engineering
Design is, by definition, limited to those areas where the logical
application of scientific principles is an essential method of solution. This
does not mean that artistic and aesthetic considerations are not taken into
account; merely that they are not the primary consideration in most cases.
Characteristics of Engineering Design :
There are a number of features which are necessary to recognize as constituting
the major characteristics of Engineering Design.
Engineering Design can be considered as being
1. Goal Oriented.
2. Variform
3. Constrained
4. Evolutive
5. Probabilistic
6.Value Comparative
7. Compromising
The Design Procedure :
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The major stages of engineering design may be listed as
• NEED
• IDEA
• DECISION
• ACTION
That there is a NEED is established and defined, followed by the development of
IDEAS, the DECISION as to which alternative will be translated to reality by the
ACTIONS of the production team. The early stages of this process are basically
the mental process of idea creation and decision making. These processes have
been studied by psychologists who have defined the stages involved. It is true that
some people are "born inventors" who seem to always have creative thoughts
whereas there are others who have "never had an original idea in their lives. There
are m any people, however, who have the cap ability f or originality, but for one
reason or another, have never developed the facility. It is for this reason that, in the
early stages of design practice, it is valuable to adopt a conscious approach to the
development of a creative attitude. This will obviously be more effective if the
conscious efforts are those which will become automatic and subconscious efforts
with the passage of time.
It appears that the stages of thinking followed by creative people are as follows
• DEFINITJON OF NEED
• PERIOD OF INCUBATION
• CONCEPTION OF SOLUTIONS
• ANALYSIS OF IDEAS
• DECISION
The design of any component includes two things:
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• Product design
• Process design
The product design involves the development of specification for a product that
will be functionally sound, good in appearance, and will give satisfactory
performance for an adequate life.
The process design involves developing methods of manufacture of the products so
that the component can be produced at a reasonably low cost.
History of Design Process
• Design by Single Person
• Over-the-wall design
• Simultaneous Engineering
• Concurrent Engineering
• Integrated design and Manufacture.
In olden times one person could design and manufacture an entire product. Even
for a large project such as the design of a ship or a bridge, one person had
sufficient knowledge of the Physics, Materials and manufacturing processes to
manage all aspects of the design and construction of the project. This period is
referred to as the period of design by single person in the history of design.
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By the middle of the 20th century products and manufacturing processes became
so complex that, one person could not handle all aspects of design and
manufacturing. This situation led to over-the-wall design process.
In this method each functional departments were separated from others, as shown
by wall. There was only one-way communications between Customer, Marketing,
Engg. Design and production department.
The customers ‘throw' their needs to marketing department. The marketing
department may throw the customer needs to the design department, in many
instances, orally. The Engg. Design department may conceive a design and hands
it over to the manufacturing sections. The manufacturing department interprets that
design and makes the product according to what they think suitable. Unfortunately,
often what is manufactured by a company using over-the-wall process is not what
the customers had in mind. This is due to lack of interaction between the different
departments. Thus, this single direction over-the-wall approach is inefficient and
costly and may result in poor quality products.
By the early 1980's the concept of simultaneous engineering emerged. This
philosophy emphasized simultaneous development of the manufacturing process-
the goal was the simultaneous development of the product and the manufacturing
process. This was accomplished by assigning manufacturing representatives to be
members of design team, so that they could interact with the design engineers
throughout the designs process.
In the 1980's the simultaneous design philosophy was broadened and called
concurrent engineering. A short definition of concurrent engineering is the
simultaneous progression of all aspects, at all stages of product development,
product specification, design, process and equipment etc. In concurrent
engineering the primary focus is on the integration of teams of people having a
stake in the product, design tools, and techniques and information about the
product and the processes used to develop and manufacture it. Tools and
techniques connect the teams with the information. Although many of the tools are
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computer-based, much design work is still done with pencil and paper. In fact,
concurrent engineering is 80% company culture and 20% computer support.
With the advent of computer technology, drastic changes have taken place in the
field of design and manufacturing. The result was a completely integrated design
and manufacturing system. This system makes a good use of technologies such as
CAD/CAM, FMS etc. The computer integrated manufacturing systems (CIMS)
moves towards the ‘Factory of the future'. CIMS is necessary for better quality,
efficiency and productivity.
Type of Designs:
The design can be classified in many ways. On the basis of knowledge, skill and
creativity required in the designing process, the designs are broadly classified into
three types
• Adaptive Design
• Variant Design
• Original Design
• Adaptive Design
In most design situations the designer's job is to make a slight modification of the
existing design. These are called adaptive designs . This type of design needs no
special knowledge or skill. E.g. converting mechanical watches into a new shape.
1. Variant Design
This type of design demands considerable scientific training and design ability, in
order to modify the existing designs into a new idea, by adopting a new material or
a different method of manufacture. In this case, though the designer starts from the
existing designs, the final product may be entirely different from the original
product.
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E.g. converting mechanical watches into quartz watches. Here a new technology is
adopted.
2. Original Design
Here the designer designs something that did not exist previously. Thus, it is also
called new design or innovative design. For making original designs, a lot of
research work, knowledge and creativity are essential. A company thinks of new
design when there is a new technology available or when there is enough market
push. Since this type of design demands maximum creativity from the part of the
designer, these are also called creative designs.
On the basis of the nature of design problem, design may be classified as:
1. Selection design
2. Configuration design
3. Parametric design
4. Original design
5. Re-design
6. Selection Design.
It involves choosing one or more items from a list of similar items. We do this by
using catalogues.
Eg.
• Selection of a bearing from a bearing catalogue
• Selection of a fan for cooling equipment
• Selecting a shaft.
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Configuration / Layout / Packaging Design
In this type of problem, all the components have been designed and the problem is
how to assemble them into the completed product. This type of design is similar to
arranging furniture in a living room.
Consider the packing of electronic components in a laptop computer. A laptop
computer has a keyboard, power supply, a main circuit board, a hard disk drive, a
floppy disk drive and room for two extension boards. Each component is of known
design and has certain constraints on its position. For example, the extension slots
must be adjacent to the main circuit board and the keyboard must be in front of the
machine.
Keyboard
Main Circuit board
Extension slots
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Floppy drive
Power supply
The different components are shown above. The designer's aim is to find, how to
fit all the components in a case? Where do we put what? One method for solving
such problems is to – select a component randomly from the list and position it in
the case so that all the constraints on that component are met.
Let's take keyboard first. It is placed in the front. Then we select and place a
second component. This procedure is continued until we reach a conflict, or all the
components are in the case. If a conflict arises, we back up and try again. Two
potential configurations are shown above.
Parametric Design