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