Chapter 5 Introduction to Design What Is Design? Engineering

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Chapter 5

• Introduction to Design

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What Is Design?

• Engineering design is a systematic process by
  which solutions to the needs of humankind are
  obtained
• Examples
• Efficient lawn mulching machine
• Lightweight,compact wireless communication
  devices
• High-temperature resistance material for reentry
  vehicle

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What Is Design? cont

• Teamwork with engineers, scientists,
  environmentalists, economists, sociologists,
  legal personnel, marketing personnel, etc
• Public sentiments as executed through government
  regulations and political influence (e.g. new
  transportation vehicle banned in downtown, etc)
• Engineers must be beware of the impact of our
  actions on society and the environment

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What Is Design? cont

• General term of design objects aesthetic
  appearance Like clothes
• The process of applying the various techniques
  and scientific principles for the purpose of
  designing a device, a process or a system in
  sufficient detail to permit its realization
• Example Define, calculate motions, forces, and
  changes in energy ? sizes, shapes, materials
• Failurestress and deflection analysis needed
• Applied, inertial loads Parts geometry Analysis
  of the forces, moments, and torques Dynamics of
  the system

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Machine Design

• Designare To designate, mark out
• To outline, plan or plot, as action or work To
  conceive, invent, contrive
• Mechanism
• A device which transforms motion to some
  desirable pattern and typically develops low
  forces and transmits little power
• Machine
• Contains mechanism which are designed to provide
  significant forces and transmit power

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Engineering Design (Mechanical Engineering)

• Pencil sharpener
• Camera shutter
• Analog clock
• Folding chair
• Adjustable table
• Lamp
• Umbrella
• Hood linkage

• Food blender
• Bank vault door
• Transmission
• Bull dozer
• Robot
• Amusement park ride

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ABET Definition of Design

• Engineering design is the process of devising a
  system, component, or process to meet desired
  needs.
• It is a decision-making process (often
  iterative), in which the basic sciences,
  mathematics, and engineering sciences are applied
  to convert resources optimally to meet a stated
  objective.
• Among the fundamental elements of the design
  process are the establishment of objectives and
  criteria, synthesis, analysis, construction,
  testing, and evaluation.

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ABET Definition of Design

• The engineering design component of a curriculum
  must include most of the following features
• development of student creativity,
• use of open-ended problems,
• development and use of modern design theory and
  methodology,
• formulation of design problem statements and
  specifications,
• consideration of alternative solutions,

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ABET Definition of Design

• feasibility considerations,
• production processes,
• concurrent engineering design,
• and detailed system descriptions.
• Further, it is essential to include a variety of
  realistic constraints such as economic factors,
  safety, reliability, aesthetics, ethics, and
  social impact.

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10-step Design Process.

• 1.Identification of a need
• 2.Problem definition
• 3.Search
• 4.Constraints
• 5.Criteria

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10-step Design Process

• 6. Alternative solutions
• 7. Analysis
• 8. Decision
• 9. Specification
• 10.Communication

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Design Process

• Design is a structured problem-solving activity
• Process is a phenomenon identified through
  step-by-step changes that lead toward a required
  result
• Cyclic and iterative process

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1.Identify the need
10. communication
2. Define problem
9. Specification
3. search
Iterative Design Process
8. Decision
4. Constraints
7. Analysis
6. Alternative solutions
5. criteria
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Design Process cont

• All projects have time and budget constraints
• Example a new car must come to the market in a
  limited time frame even though engineers like to
  do more
• Design phases
• Definition of a problem (step 1 identify need and
  step 2 define problem)

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Design Process cont

• Design Phases
• Conceptual design phase
• Information is gathered (step 3 search)
• Constraints are established (step 4 constraints)
• Multitude of possible solutions are generated
  (step 6 alternatives)
• Preliminary design phase
• Development of criteria (step 5 criteria)
• Analysis of potential solutions (step 7 analysis)
• Select best solution (step 8 decision)

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Design Process cont

• Design Phases
• Detailed design phase
• Selection of stock parts, the design of all other
  components, and the optimization of the solution
  (step 9 specification)
• Optimization considering cost, materials,
  performance, manufacturability and feasibility
• Example moving product from East Coast to the
  West Coast airplanes, trucks and airplanes? New
  factory?

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Design Process cont

• Design Phases
• Prototype design phase
• Extensive tests before mass production
• Final Design (Mass production)
• Communicated (step 10) to manufacturing for
  production

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Design and the Customer

• The result of the execution of the design process
  is a new product, process or system
• Identification of need starts from customers
  suggestions or requests
• Final design must satisfy customer requirements
  or exceed expectation

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Design and the Customer

• If customer requirements are not clear, engineers
  must consult with customers
• Customers must be informed of the design status
  at all times
• Both design team and customers may have to modify
  their requirements in order to meet time, cost,
  performance and manufacturing constraints

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Kano Model

• Relationship between degree of achievement and
  customer satisfaction
• Basic customer requirements are simply expected
  by the customer and assumed to be available
• Exciting customer requirements are generally
  suggested by the design team usually outside of
  customer knowledge or vision

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Customer Satisfaction
Performance Related
Exciting
Degree of Achievement
Basic
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Example of Kano Model

• New electric powered barbeque grill
• Design team starts from existing successful
  design?basic
• Customer may specify performance-related items
  such as ease of cleaning, ease of setting the
  controls cooking time, cooking effectiveness
• New concept, such as programmable cooking cycle,
  can give unexpected bonus to customer, make it
  selling point and create excitement.

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The Nature of Engineering Design

• Is engineering design an art?
• It is an cognitive process that requires a broad
  knowledge base, intelligent use of information,
  and logical thinking
• Design team consists of engineers, marketing
  personnel, economists, management, customers, etc

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Cognitive Process

• Benjamin Bloom (1950s) Blooms taxonomy
• Knowledge the ability to recall information,
  facts, or theories
• Example what was the date of the Challenger
  space shuttle accident?
• Comprehension ability to make sense
  (understand)the material
• Explain the cause of the Challenger accident

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Cognitive Process

• Application ability to use knowledge and
  comprehension in a new situation and to
  generalize the knowledge
• What would have you done to prevent the Challenge
  accident?
• Analysis ability to break learned material into
  its component parts so that the overall structure
  may be understood

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Cognitive Process

• Analysis cont
• It includes part identification, relationships of
  the parts each other and to the whole, and
  recognize of the organizational principles
  involved
• Example what lessons did we learn about the
  space program from the Challenger accident?

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Cognitive Process

• Analysis cont
• The highest level of convergent thinking, whereby
  the individual recalls and focuses on what is
  known and comprehended to solve a problem through
  application and analysis

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Cognitive Process

• Divergent thinking
• The individual process information and produces
  new insights and discoveries that were not part
  of the original information
• Synthesis ability to put parts together to form
  a new plan or idea
• Example propose an alternative to the Challenger
  O-Ring design that would perform the required
  function

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Cognitive Process

• Evaluation ability to judge the value of
  material based on specific criteria
• Usually the individual is responsible for
  formulating the criteria to be used in the
  evaluation
• Example assess the impact of the Challenger
  accident on the U.S. space program

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Blooms Taxonomy
Divergent Thought
complexity
Evaluation
Synthesis
Analysis
Convergent Thought
Application
Comprehension
Knowledge
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Design Steps 1. Identification of a Need

• Usually other than the engineer decides that a
  need exists
• Products have life cycle. New profitable products
  must be developed
• The consumers are ultimately the judges of
  whether there is truly a need any product that
  doesnt satisfy customers are doomed
• Citizens of a community decide to have roads,
  libraries, buildings, etc. Engineers can help
  decision makers by providing information

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Design Steps 1. Identification of a Need

• Example
• Dormitory rooms are crowded with beds, desks,
  shelving units, etc.
• There is a need to utilize better dormitory
  living space for college students
• Maybe lofts (elevated beds) that can be a
  combined system with desk, closet, dresser and
  shelves could be a solution

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2. Problem Definition cont

• A loft can be built with a few boards, nails, and
  a hammer
• How about stability? Efficiency of assembly?
  Efficient use of space? Regulation of the
  college and government?
• Brainstorming all possibilities that might
  satisfy the need

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2. Problem Definition cont

• Symptom vs. Cause
• Rainfall drain of a new development
• Storm sewer systems? It only transport the water
  problem to downstream for someone else to handle
• Holding ponds onsite treatment
• Real problem is not how to get rid of the
  rainfall as rapidly as possible, but how to
  control the water

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2. Problem Definition cont

• Solving the Wrong Problem
• In the 1970s, to reduce auto accident fatalities,
  using lap and shoulder belts were required
• The solution technique that was implemented was
  an interlock system that requires the belts be
  latched before the auto could be started
• Drivers attitude was the real problem it failed

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2. Problem Definition cont

• Broad definition of problem may show
• Purchase a prefabricated loft system
• Purchase parts and assemble after sketching a
  possible solution
• Rent two rooms and cut a connecting door, so on
• Obtain the most concise and complete problem
  definition
• State A (Undesirable situation) ?State B
  (Desirable situation )

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2. Problem Definition cont

• Crowded living conditions ?Uncrowded living
  conditions
• Too broad
• Existing dorm furnishings ? Existing furnishings
  with lofted beds
• Complete considerations needed time constraints
• Existing dorm beds ?Lofted beds

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Design Steps 3. Search

• Locating, applying, and transferring information
  lots of information is needed
• Open to many alternative solutions
• Gathering information may help for a better
  definition of the problem and a better solution

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3. Search cont

• Type of Information
• What has been written about it?
• Is something already on the market that may solve
  the problem? (already patented? Group
  technology?)
• What is wrong with the way it is being done?
• What is right the way it is being done?

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3. Search cont

• Type of Information
• Who manufactures the current solution?
• How much does it cost?
• Will people pay for a better one if it costs
  more?
• How much will they pay (or how bad is the
  problem)?

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3. Search Source of Information

• Existing solutions reverse engineering
• Internet search
• Library search
• Government documents
• Professional organizations
• Trade journals
• Vendor catalog
• From experts

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3. Search Example Project

• Loft bed state or other government state codes
• Assemble with simple tools
• Standard parts as possible
• Preferred wood construction
• No guard rail or ladder
• No need for handicap access

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3. Search Example Project cont

• Survey
• If students like loft bed and why
• If students like current bed and why
• How much students are willing to pay
• List of important factors such as durability,
  accessibility, stability, cost, appearance, easy
  of assembly, safety and maintenance

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Design Steps 4. Constraints

• There could be many solutions, but there are
  physical and practical limitations (constraints)
• Examples
• Market competition
• Too expensive
• Thin laptop or cell phone
• Legal restriction
• Boundary conditions

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4. Constraints Example Project

• Example
• Cost must not exceed 1500
• Must meet safety codes
• Must accommodate a unit bed size of 78 X 36
  inches
• Must be freestanding and cannot affect the
  existing structure of the room

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Design Steps 5. Criteria

• Criteria are desirable characteristics of the
  solution which are established from experience,
  research, market studies, and customer
  preferences
• Criteria are used to judge alternative solutions
  on a qualitative basis, unless quantitative
  evaluation by mathematical model is available

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5. Criteria cont

• Weighting factor for criteria
• Typical design criteria
• Cost
• Reliability
• Weight (either heavy or light)
• Ease of operation and maintenance
• Appearance
• Compatibility

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5. Criteria cont

• Typical design criteria
• Safety features
• Noise level
• Effectiveness
• Durability
• Feasibility
• Acceptance

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5. Criteria Example Project
Stability 15
Easy of assembly 35
Cost 25
Functionality 25
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Design Steps 6. Alternative Solutions

• It is just like selecting the best person among
  the candidates for a new management position. A
  list of candidates must be made for interview and
  review processes
• Likewise we need a list of possible answers to
  our problem before selecting the best one

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6. Alternative Solutions cont

• The word invention strikes fear into the minds
  of many people
• We learned that if we were like the other kids,
  no one laughed at us
• If not already done well, few people are willing
  to try new
• Fear that people laugh at us
• Fear of failure (new experiments fails a lot)

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6. Alternative Solutions cont

• There are techniques that can be used to assist
  us in developing a list of possible solutions
• Checkoff lists
• The list suggest possible ways that an existing
  solution to your problem might changed and used
• Use modify and rearrange to guide or focus on the
  efforts to obtain a new solution

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6. Alternative Solutions cont

• Checkoff lists (cont)
• Modify?
• Use laminates instead of solid wood
• Use glue instead of bolts and screws
• Rearrange?
• Bed on the floor, desk and shelves above
• Ladder on side of bed instead of end
• Ask yourself Why is the solution like it is?
  Will change make it better or worse?

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6. Alternative Solutions cont

• Brainstorming
• The leader states the problem clearly and ideas
  about its solution are invited
• About 3-15 people, usually 4-8 works well
• Free expression is essential no discouraging
  word, no evaluation during brainstorming about
  the idea
• The leader sets the tone and tempo of the session
  and provides a stimulus when things begin to drag

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6. Alternative Solutions cont

• Brainstorming (cont)
• The members of the group should be equals no
  reason to impress or support any other member
• Recorders are necessary

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Design Steps 7. Analysis

• In order to find the best solution in light of
  available knowledge and criteria, we must analyze
  the alternative solutions to determine
  performance capability
• Use of mathematical and engineering principles
• The goal is to obtain quantitative information
  for the decision step in the design process
• The time required to produce an analysis is
  critical

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7. Analysis cont

• Many laws of nature conservation of mass,
  momentum, energy, etc
• Mathematical model
• Graphics
• Cardboard cutouts
• Subscale model or pilot plants
• Balance between accuracy and time money

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Design Steps 8. Decision

• There may be no perfect one solution
• Trade-offs many alternatives to satisfy criteria
• Decision is very hard part
• You need information in order to evaluate each
  alternative against each of the criteria

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8. Decision cont

• Analysis can provide basis for decision
• If time and money permits, experiment or
  prototype can help
• Poor research, a less than adequate list of
  alternatives, or inept analysis would prevent
  good decision
• Decision making is an art and a science

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8. Decision cont

• There has been a lot of efforts to make decision
  process as a science
• Probability
• Statistics
• Optimization (pay-off function)
• Utility theory

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Design Steps 9. Specification

• After designing, it must be clearly defined to
  others in detail specifically
• Drawings, database, bill of materials
• A sufficient number of databases describing the
  size and shape of each part
• Layouts to delineate clearance and operational
  characteristics
• Assembly and subassemblies to clarify the
  relationship of parts

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9. Specification cont

• Database cont
• Written notes, standards, specifications, and so
  on, concerning quality and tolerances
• A complete bill of materials
• Local or national codes and standard must be
  satisfied
• Utilize written, spoken, and graphical language
  in order to develop and interplete specifications

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Design Steps 10. Communication

• Great emphasis nowadays
• Selling your design and idea
• If if your design is superb, you have to convince
  other people

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10. Communication cont

• Written report
• Appropriate cover page
• Abstract
• Table of contents
• Body
• Conclusion and recommendation
• appendixes

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10. Communication cont

• Oral Presentation
• Be prepared
• rehearse
• use adequate audio/visual equipment
• Stand in such a way so that you do not detract
  from what you are saying or showing
• Look at your audience and maintain eye contact

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10. Communication cont

• Project your voice by consciously speaking to the
  back row
• Speak clearly

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Team Project

• A home caregiver of a severe stroke patient has a
  trouble to bathe the patient. Towel bath is not
  sufficient for a long period of time.
• As more people in America becomes heavy and the
  most of caregivers are women, it could be a
  problem
• Design a device that a slim women can bathe a
  heavy patient at home.

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Team Project

• A service club, like Lions Club, raises flag on
  the utility poles in downtown on national
  holidays.
• Because of busy traffic, flags are raised and
  lowered manually either by climbing poles or
  using special devices from the sidewalks.
• Design a device that can raise and lower the flag
  to and from the pole. Design better flag holders

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Design Process

• Design Process
• Unstructured problem
• Blank paper syndrome Dont know how to begin!
• structuring the unstructured problem?synthesis
  (putting together)?analysis?Iteration
• Identify the need
• e.g. we need a better lawn mower
• Background research
• Patented? GT?

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Design Process

• 3. Goal Statement
• Functional visualization
• Design a better lawn mower? Design a mean to
  shorten grass
• State problem generally, clearly, concisely
• 4. Performance Specification
• Define what the system must do. (Design
  specification? define how it must do it)
• Example of lawn mower
• self-contained power supply
• corrosion resistance
• cost less than 150
• Emit less than 80 db at 50 ft away
• to shorten ¼ acre of grass per hour, etc

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Design Process

• 5. Ideation and Invention
• Creative process
• Idea generation
• Brainstorming
• Use analogy (mechanical system?electrical system)
• Inversion
• Synonyms
• Move x from A to B ? push, pull, shove, throw,
  eject, jump, spill, ???

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Design Process Ideation

• Ideation, continued
• Large number of ideas?frustration?incubation?eurek
  a?iterate
• Fascination with a problem (motivation)?saturation
  with the facts, technical ideas, data, and the
  background of the problem? A period of
  reorganization

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Design process, Continued

• 6. Analysis
• 7. Selection
• Decision Matrix
• Weight factor
• 8. Detailed Design
• Cad, Iteration
• 9. Prototyping and testing
• 10. production

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Advice to Design Process

• KISS Keep it simple, stupid
• There are multiple solutions!!!!!!!
• No one has right answer
• Physical test is expensive? Do as much analysis
  on paper, computer as possible. Use Mathematical
  Model
• Human factors
• Ergonomics (Human factors engineering)
• Steps, car (clutch, brake distance, etc),
  utilities
• Uncomfortable to use, tiring, dangerous

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Design of Mechanical Systems

• If your only tool is a hammer, then every problem
  is a nail.
• Concurrent Engineering
• Failure
• Breaking
• Completely inoperable
• Unable to perform the intended function
• Unreliable or unsafe need service

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Design for Manufacture
Effect of manufacturing and assembly on design of
reciprocating power saw. (a) Original design,
with 41 parts and 6.37 min assembly time. (b)
modified design, with 29 parts and 2.58 min
assembly time. From Boothroyd (1992).
Text Reference Figure 1.2, page 14
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Safety Factor

• Ns?allowable/?design
• Nsgt1
• Safety factor
• Code, experience level, tested?, manned?
• NsN A,B,C N C, D
• A Quality of Materials, workmanship,
  maintenance, and inspection
• B Control over load applied to part
• C Accuracy of analysis, experimental data
• DDanger to personnel
• E Economic impact

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Example 1.1.A Wire Rope in Elevator to 20th
Floor 50 Overload Safety Factor?

• A (Quality of Materials, workmanship,
  maintenance, and inspection) should be very good
  life threatening
• B (Control over load applied to part) can be fair
  to poor because overload is permitted
• C (Accuracy of analysis, experimental data)
  should be good as highly regulated ASME code

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• D (Danger to personnel)very serious
• E (Economic impact) serious, possible lawsuit
• Ns1.61.5 2.4 but code gt7.6

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Puglsey Safety Factor Approach
Table 1.1 Safety Factor Characterisics A, B, and
C
Table 1.2 Safety Factor Characteristics D and E
Usage nsns,xns,y nssafety factor ns,x is
obtained from Table 1.1 ns,y from Table 1.2
Text Reference Tables 1.1 and 1.2, page 9
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Codes and Standards

• ANSI American National Standard Institute
• ASME American Society of Mechanical Engineers
• ASTM American society of testing and Materials
• AGMA American Gear Manufacturers Association
• AISI American Iron and Steel Construction
• AISC American Institute of Steel Construction
• ISO International standards Organization
• NFPA National Fire Protection Association

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Design for Safety

• Redundancy
• Active-e.g., two deadbolt locks on a door
• Passive-e.g.,one deadbolt lock plus a chain
• Fail-Safe
• If something goes wrong, it goes wrong to a safe
  way.
• Manifest Danger
• e.g.,Break system noise, leaking gas tank