ch-1 engineering design

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Engineering Design

What is Design ?

As many definitions as many there are designs because process of design is such acommon human experience

As perWebsters Dictionary

To fashion after a plan

Is this definition complete?

IfYes..What is missing in it.?

the essential fact that to design is to create something that has never been

Engineering Designer, artist, sculptor, a composer, a playwright and other creative

members practice design by this definition

Professional practice of Engineering is concerned with Design

Conclusion

Essence of Engineering is DESIGN

Then what is the .Formal Definition of Design..?

Design establishes and defines solutions to and pertinent structuresfor problems not solved before or new solutions to and which have

previously been solved in a different way

Ability to Design is both aScience and anArt

Science : is learned through techniques and methods used

Art : is best learned by doing Design

Discovery :

o Is getting the first sight of, or first knowledge of something

o Wecan discover what has already existed but has not been known before

Design should not be confused with Discoveryo Design is the product of Planning and Work

Invention :

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Design may or may not involve invention as some are truly inventive but

most are not

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What is a Good Design ?

Good design requires both Analysis and Synthesis Analysis

o

Decomposing problem into manageable parts To understand performance/behavior of parts in service using appropriate

discipline of science/engineering and computational tools

Usually involves simplification of real world problems though models

Synthesis

o Identification of Design Elements that will comprise

Product

Its decomposition into parts

Combination of part solutions into a total workable system

What is a Real World Problem that you intend to design ?o Rarely neat and defined

o May need many engineering (fluid, solid mechanics etc) and non-engineering

discipline (economics, finance, law etc)

o Input data may be best but out of the scope of the individual

o Constraints may be time, money, societal, environmental or energy regulations etc.

What is Final Design ?o Is it the best, most efficient..Only time will tell.!!!!!

o Rarely known the correct answer

o One is hopeful that His Design will Work

Conclusion

Engineering Design extends beyond the boundaries of Science

As Design Engineer during professional career you may have the

opportunityo To create dozens of designs

o Have satisfaction of seeing them become working reality

As Scientist during professional career you may have the opportunityo To make one creative addition to human knowledge in your whole life and many

never do so

o Can discover a new star bur\t can not make one

o Have to ask anEngineerto do it for him

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DESIGN PROCESS

IMPORTANCE OF PRODUCT DESIGN

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Product Design Consumer goods

Appliances, missiles,

Complex Engineering

System Electric power generating

system

Petrochemical plants

Building/bridge design

Emphasis in this Course As many Engineers (YOU) will

apply your design Skills

Without extensive specializedknowledge you will be able to

ras roblems

5% = for design

95% = for material,

manufacture, labor, capital

70~80% = for Design

commitment

=


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Impact of Design

Decision made in the design process: Costs are very little in terms of the

overall product cost but have a major effect on the cost of the product

Quality can not be built into a product unless it is designed into it

Design process should be conducted so as to develop, quality cost competitive

products in the shortest time possible

Static Product Vs Dynamic Product

Static Product

A change in design concept takes

long time period

Incremental changes occur at sub-

system and component level

Examples: refrigerators,

automobiles etc

Exists in market where customer is

not eager to change and does not

demand significant improvement

Fashion or styling play a little role

Market characterized by stable

number of large producers

High price competition and little

research

Product are similar to each other

Technology is stable and mature

Users dont demand significant

improvements

Industries standards may even

restrict change

Because of importance of cost,

emphasis is more on process

research than on product research

Dynamic Product

Basic design concept varies

frequently as the underlying

technology changes

Examples: telecommunication

systems, software etc

Customers may even drive change

Customer seeks to reduce product

cycle time

Market is characterized by many

small producers

Involves active market research

Companies seek new product

Technology is rapidly advancing

There is a high product

differentiation and low industrystandardization

More emphasis is placed on product

research than on process research

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PROBLEM SOLVING METHODOLOGY IN DESIGN PROCESS

PROBLEM DEFINITION (CH-2)

Most critical step

True problem is not always as it seems at first glance

As this step takes a very small time so often overlooked

Formulation starts by writing down problem statement

Should include

o

Objectiveso Goals

o Current state of affairs and the desired state

o Any constraints placed on solution of the problem

o Definition of any special technical terms

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ProblemDefinition

GatheringInformation

Generation ofalternativesolution

Evaluation ofalternatives

Communicationof Results


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GATHERING INFORMATION (CH-4)

Most frustrating

Problem may be of in the area not related to your previous background or single reference

mat not be available related to subject

You may get a mountain of reports of previous work

So whatever the situation, the immediate action is to identify needed pieces of informationandfindor develop that information

Questions concerned with obtaining information

o What do I need to find out?

o Where can I find it and how can I get it?

o How credible and accurate is the information?

o How should the information be interpreted for my specific need?

o When do I have enough information?

o What decisions result from the information?

GENERATION OF ALTERNATIVE SOLUTIONS (Ch-5) It is vital to a successful design

Involves

o Use of creativity

o Application of physical principles and qualitative reasoning

o Ability to find and use information

EVALUATION OF ALTERNATIVES (Ch-5, 12, 14)

Selecting systematically the best among several designs, often in the face of incomplete

information

Evaluation basis involveo Engineering analysis (about service performance)

o Cost estimation (cost comparison)

o Design for manufacture (life cycle)

o Simulation and simulated service testing

o Experimental testing of full sized prototypes

COMMUNICATION OF RESULTS (Ch-17)

Purpose of design is to satisfy the needs of a customer or client

Final design must be communicated properly

Communication is usually oral or in written design report form

A per recent survey design engineers spend

o 60% time in discussing designs and preparing written documentation of designs

o 40% time in analyzing design and doing designs

Deliverables: detailed engineering drawings, computer programs, working models

Not only one time occurrence but a continual oral and written dialogue

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DETAILED DESCRIPTION OF DESIGN PROCESS

Morris Asimow at first gave a detailed description of complete design process

SEVEN PHASE OF DESIGN PROCESS

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Phase-1

Conceptual DesignPhase-2

Embodiment DesignPhase-3

Detail Design

Phase-7

Planning for

Retirement of

Phase-4

Planning forManufacture

Phase-5

Planning forDistribution

Phase-6

Planning for Use


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ORGANIZATION FOR DESIGN

Organization is arranged based on Function

Project

Functional Organization

Each individual has only one boss

All reports to single vice president

Economics of scale, deep expertise develop, clear career paths for specialists

Organizational links are between people of similar functions

Interactions are forced at level of unit manager

Acceptable for a business with a narrow and slowly changing set of product line

Can be a problem for a dynamic product situation

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Project Organization

People with different functional expertise are grouped together for product development

(development team)

Each development group reports to a project manager (Overall responsible)

Chief advantage is that it focuses the needed specialty talents on attainment of goals of theproject

Often project organization is time limited

People are reassigned back to the functional units after the goal is achieved

Disadvantages of Project Organization

Experts tend to9 loose their cutting edge functional capabilities with such intense focus

on project goal

Less economical than functional organization

Very common in start up companies where indeed company project are synonymous

Large corporations establish project organization for large critical projects

Matrix Organization

Combines the advantages of both functional and project organizations

Each person is linked according to the function and project they work on

Each individual has two supervisors ( Functional manager &Project manager)

One always is predominates

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Light Weight Project Organization (Functional)

In this functional links are stronger than project links so called functional organizations

Works well in stable business environment where product pre-dominates in market due to

technical excellence

Project Manager

Responsible for

Scheduling

Coordination

Arranging meetings

Functional Manager

Responsible for

Budget

Personnel matters

Performance evaluation

Heavy Weight Project Organization (Functional)

Has the advantage in introducing radically new products, especially where speed is important

Project Manager

Has complete budgetary authorities

Make most of the resource allocation

decisions

Functional Manager

Although each person belongs to functional

unit but has little authority and control

Plays a strong role for personal

evaluation

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Light Weight Project Organization Heavy Weight Project Organization


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CONCURRENT ENGINEERING

Conventional Engineering (Serial Design Process)

All functions carried out serially in distinct and separate departments with little interaction

between them Easy to see how design teams will make decisions

Cost for serial design process is high (large percentage cast is committed at conceptual and

embodiment stage when changes become necessary)

Actual process is more in the nature of spiral

Concurrent Engineering (Systematic Integrated Product Design Approach)

Shortens product development time

Improves quality

Reduces product life cycle costs

Main objective: to bring in as many view points and talents at Design Phase so that decisions

will be valid for downstream parts of product development cycle like mnfg & field service

Main elements of Concurrent Engineering

Cross-functional teams

Parallel design

Vendor partnering

Cross-functional teams

It is a heavy weight project organization used most frequently with Concurrent Engineering

Skills from functional areas embedded in design teams provide

quick and easy decision making

communication with functional units

Must be approved by the managers of the functional units with decision making authorities

Functional units and cross-functional teams must build mutual respect and understanding for

each others needs, requirements and responsibilities

Parallel Design (Simultaneous Engineering)

Refers to each functional area Implementing their aspect of design at the earliest possible time roughly in parallel

All groups provide input to the development of product design specifications

Nearly continuous communication between functional units and design teams is necessary

Decidedly different from the old practice

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Vendor Partenering

It is a form of parallel engineering

Technical expertise of vendor for certain components is employed as an integral member of

cross-functional design teams

In conventional process vendors are selected by a bidding process after the design has been

finalized

In CE, key vendors, known for proficient technology, reliable delivery and reasonable costs

are selected only in design process before parts have been designed

So a strategic partnership is developed

It reduces the amount of part design that must be done in house

Integrates vendors manufacturing expertise into the design

Ensures a degree of allegiance and cooperation that should minimize the time for receipt of

parts

Computer Aided Engineering (CAE) in Design

Engineers were the first professional group to use computer

FORTRAN (first high level language)

Drafting automation, 3-D Solid modeling, conversion to 2-D engineering drawings, FEA,

design optimization, simulation, rapid prototyping and CAM, Interaction between CADCAM

Data base management system (DBMS), spread sheet software, MathCAD, MatLab,

Mathmatica, Maple etc



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DESIGN TO CODES AND STANDARDS

Much designs are not very different from what has been done in the past

CHIEF ASPECTS

1. Makes the best practice available to everyone, ensuring efficiency and safety2. Promotes interchangeability and compatibility

CODE

Collection of laws and rules that assists a

Government agency in meeting its obligation

to protect the general welfare by preventing

damage to property or injury or loss of life to

persons

Tell the engineer what to do and when

under what circumstances to so it

Usually are legal requirements, e.g.

building code, fire code etc.

Often incorporate national standards into

them by reference

STANDARD

A general agreed upon set of procedures,

criteria, dimensions, materials and parts

Tell engineer how to do it

Usually regarded as recommendations,

that do not have force of law

This way standards become legally

enforceable

TWO BROAD FORMS OF CODE

PERFORMANCE CODE

Stated in terms of specific requirements

i.e. expected to be achieved However methods to achieve results is not

specified

PERSPECTIVE/SPECIFICATION CODE

States requirements in terms of

specific details in specific situations Leaves no discretion to the designer

TYPES OF DESIGN STANDARDS

PERFORMANCE

STANDARDS

Published for many

products

e.g. seat belts, auto crash

safety etc.

TEST METHOD

STANDARDS

For measurement of

properties

e.g. Yield strength,

thermal conductivity,sensitivity etc.

CODE OF PRACTICE

Provides detailed design

methods for a repetitivetechnical problem

e.g. design of piping, heat

exchanger Pressure vesseletc. ASME, BS (PD)



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STANDARDS PREPARATION

1. Often prepared by individual companies for their own proprietary use e.g. dimensions,tolerances, forms, processes etc.

2. By group of companies of the same industrial sector (Sponsored by Industry TradeAssociation) AISC, ANSI, ISO etc.

3. Government Specification Standards, as Govt. is the purchaser of large number of goods

and services

4. Defense Product Standards

ADVANTAGES OF STANDARDS

Standards play an important role for

Protecting public

Providing firm basis for negotiation and better understanding between buyer and seller

Reducing cost of design of products stock (standardized components and tools etc) One of the main Goal of Engineering Design Process

In new designs, 20% components are new, 40% are existing with minor modifications

and 40% are reused without modifications

ROLE OF CAE, GROUP TECHNOLOGY AND CADCAM IN DESIGN

STANDARDIZATION

CAEplays an important role in design standardization

Group Technology Provides formal way of recognizing and exploiting similarities in design (shape,

manufacturing process)

Coding and classification systems used to identify similarities

Computerized GT database provides quick methodology (so duplication avoided)

Provides standardization for creating parts and part features

Due to feed back of manufacturing costs, high cost design features are avoided

CADCAM

Interfacing and communication between various computer devices and manufacturing

machines

National institute of standards technology provided

Initial graphics Exchange Specifications (IGES) and Product Data Exchange Specification(PDES)

IGES and PDES represent a Neutral Data Format for transferring geometric data between

equipment from different CAD systems



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DESIGN REVIEW

Vital aspect ofDesign Process

Provides an opportunity for specialists from different disciplines to interact between

generalists to ask critical questions and exchange of vital information

Provides a systematic method for identifying Problems with design

Aids in determining possible courses of action

Initiates action to correct the problem areas

Design review teams consist of representatives from

Design, manufacturing, marketing, purchasing, quality control, reliability engineering and

field service Chairman (Project manager/Chief Engineer) of Design Review should

Have broad technical and products knowledge

Have not direct responsibility for design under review

Design Reviews should be held from 3~6 times in the life of the project

Minimum review schedule consists of Conceptual Reviews

(greater impact on design, changes can be made at this stage at lower costs)

Interim Reviews

(When embodiment design is finalized, product architecture, subsystems and

performance characteristics are established)

Final Reviews

(At the completion of detailed design and establishes whether the design is ready for

transfer to manufacture)

Two Aspects of Design Review

concerned with Elements of design itself (Product Design Specification PDS) concerned with Business of the product

Product Design Specification (PDS)

Essence of Technical Review of design is to compare the finding against detailed PDS

A detailed document that describes what design must be in terms of performance requirements,

environment in which it must operate, product life, cost, reliability and host of other designrequirements

Basic reference document for both product design and design review

Business Aspect Concerned with tracking the cost incurred in the project, design effect on marketing and sale,

maintaining time schedule

Review determines what changes in sources, people and money are required to produce

appropriate business outcome



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RE-DESIGN

A common situation in Design Process

As a result of Design Review

Details of design are changed many times as prototypes are developed and tested

Categories of Re-design

Fixes

Design modification required due to less than acceptable performance once the product has

been introduced into the market place

Updates

Usually planned as part of the products life cycle before the product is introduced to the

market

An update may add capacity and improve performance or incorporate its appearance to

keep it competitive

Most common situation in re-design is the modification of an existing product to meet newrequirements

e.g. banning of the use of fluorinated hydrocarbon refrigerants because of Ozone-hole

problem, required the extensive re-design of refrigeration system

Often re-design results from the failure of the product in service



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PRODUCT AND PROCESS CYCLES

Each product goes through cycle from Birth, into an initial growth stage, into a relatively

stable period, and finally into a declining state that eventually ends in the death of the product

Introductory stage: Product is new, consumer acceptance is low, so sales are low, rate of

product change is rapid as management tries to maximize its performance or uniqueness

Growth Stage: Knowledge of the product and its capabilities reaches to growing number of

customers

Maturity Stage: Product is widely accepted, sales are stable, grow at the same rate.

o Products at this stage experience considerable competition

o Great emphasis is on reducing the cost of a mature product

When product reaches at this stage, attempts should be rejuvinate it by incremental

innovation or development of still new applications Decline Stage: At some stage each product enters in this stage

o Sales decreasebecasue a new better product is in the market to fulfil the same

societal needs

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Birth Stage Initial Growth Stage Mature stage Decline stage

Expanded Product Life Cycle

Product Life

Cycle

ch-1 engineering design

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