2103314 Mechanical System Design II

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2103-314Mechanical System Design II

• By Asst. Prof. Dr. Kaukeart Boonchukosol

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The Product Design Process
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Design Process the basic module
General Information
Specific Information
Design Operation
Outcome
Evaluation
Go to The Next Step
No
Yes
Feedback loop
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Exploring the alternating system
Formulating the mathematical model
Example of Design Operation
Specifying specific parts
Selecting a material
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Some kind of Information

• Manufacturers catalogue
• Handbook data
• National standard
• Technical paper
• Experience

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Problem Solving Methodology

• Definition of the problem
• Gathering of information
• Generation of alternative solutions
• Evaluation of alternatives
• Communication of the result

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Definition of the Problem
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Gathering Information

• What do I need to find out?
• Where can I find it and how can I get it?
• How credible and accurate is the information?
• How should the information be interpreted for my
  specific need?
• When do I have enough information?
• What decision result from the information?

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Detailed Description of Design Process
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Morphology of Design

• Phase I Conceptual Design
• Phase II Embodiment Design
• Phase III Detail Design
• Phase IV Planning for Manufacture
• Phase V Planning for Distribution
• Phase VI Planning for Use
• Phase VII Planning for Retirement of the Product

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Phase I Conceptual Design

• Identification of customer needs
• Problem definition
• Gathering information
• Conceptualization
• Concept selection
• Refinement of the PDS
• Design review

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Phase II Embodiment Design

• Product architecture
• Configuration design of parts and components
• Parametric design of parts and components

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Conceptual Design
Embodiment Design
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Phase IV Planning for Manufacture

• Designing specialized tools and fixtures
• Specifying the production plant that will be used
• Planning the work schedules and inventory control
• Planning the quality assurance system
• Establishing the standard time and labor costs
  for each operation
• Establishing the system of information flow
  necessary to control the manufacturing operation

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Need Identification
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Types of Design Project

• Variation of an existing product
• Improvement of an existing product
• Development of a new product for a low-volume
  production run
• Development of a new product for mass production
• One-of-a-kind design

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How to Gathering Information from Customer

• Interview with customer
• Focus group
• Customer surveys
• Customer complaints

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Levels of Customer Requirements

• Expecters the basic attribute that one would
  expect to see in the product
• Spokens the specific features that the customers
  say they want in the product
• Unspokens the product attributes the customer
  does not generally talk about, but are
  nevertheless are important to him or her
• Exciters or delighters the features that make
  the product unique and distinguish it from the
  competition

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Quality Function Deployment

• QFD is a planning and problem-solving tool that
  is finding growing acceptance for translating
  customer requirements into the engineering
  characteristics of a product.
• Group decision-making activity
• Graphical representation using a diagram called
  House of Quality

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Quality House
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From customer requirement to production planning
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Concept Generation and Evaluation
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Concept Generation
Evaluation
Problem decomposition
Absolute criteria
Explore fore ideas
Go-no-go screening
Relative criteria Pugh concept selection Decision
matrix Analytical hierarchy process
External to team
Internal to team Brain-storming
Explore systematically Morphological chart
Best concept
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Creativity

• Develop a creative attitude
• Unlock your imagination
• Be persistent
• Develop an open mind
• Suspend your judgment
• Set problem boundary

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Vertical and lateral thinking
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Invention

• Invention is something novel and useful, being
  the result of creative thought.
• Classified into 7 categories
• The simple or multiple combination
• Labor-saving concept
• Direct solution to a problem
• Adaptation of an old principle to an old problem
  to achieve a new result
• Application of a new principle to an old problem
• Application of a new principle to a new use
• Serendipity

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Psychological View of Problem Solving

• Four-stage model
• Preparation The element of the problem are
  examined and their relations are studied.
• Incubation You sleep on the problem.
• Inspiration A solution or a path toward the
  solution suddenly emerges.
• Verification The inspired solution is checked
  against the desired result.

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Creativity Methods
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Mental Block

• Perceptual blocks
• Stereotyping
• Information overload
• Limiting the problem unnecessarily
• Cultural blocks
• Environmental blocks

• Emotional blocks
• Fear of risk taking
• Unease with chaos
• Adopting a judgmental attitude
• Unable or unwilling to incubate
• Intellectual blocks

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Brainstorming

• Four fundamental brainstorming principles
• Criticism is not allowed.
• Ideas brought forth should be picked up by other
  people present.
• Participants should divulge all ideas entering
  their minds without any constraint.
• A key objective is to provide as many ideas as
  possible within a relatively short time.

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Stimulation of ideas

• Combination What new ideas can arise from
  combining proposes and functions?
• Substitution What else? Who else? What other
  place? What other time?
• Modification What to add? What to subtract?
  Change color, material, motion, shape?
• Elimination Is it necessary?
• Reverse What would happen if we move it
  backward? Turn it upside down? Inside out?
• Other use Is there a new way to use it?

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Creative Idea Evaluation
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Theory of Inventive Problem Solving (TRIZ)

• TRIZ is Russian acronym
• Developed by Genrich Altshuller and his coworkers
  in Russia, since 1946
• About 1.5 million patents were studied, and
  discovered that only a few dozen inventive
  principles were used for solving the problems

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Five levels of problem solutions

• Level 1 Routine design solutions arrived at
  methods well known in the specialty area. 30
• Level 2 Minor correction to an existing system
  by methods know in the industry. 45
• Level 3 Fundamental improvement to an existing
  system which resolve contradictions within the
  industry. 20
• Level 4 Solution based on application of new
  scientific principle to perform the primary
  function of the design. 4
• Level 5 Pioneering inventions based on rare
  scientific discovery. 1

TRIZ is aimed at improving design concept at
levels 3 and 4
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Engineering Parameters used

• Weight of moving object
• Weight of nonmoving object
• Length of moving object
• Length of nonmoving object
• Area of moving object
• Area of nonmoving object
• Volume of moving object
• Volume of nonmoving object
• Speed
• Force

• Tension, Pressure
• Shape
• Stability of object
• Strength
• Durability of moving object
• Durability of nonmoving object
• Temperature
• Brightness
• Energy spent by moving object
• Energy spent by nonmoving object

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Engineering Parameters used

• Power
• Waste of energy
• Waste of substance
• Loss of information
• Waste of time
• Amount of substance
• Reliability
• Accuracy of measurement
• Accuracy of manufacturing
• Harmful factors acting on object

• Harmful side effects
• Manufacturability
• Convenience of use
• Repairability
• Adaptability
• Complexity of device
• Complexity of control
• Level of automation
• Producibility

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The Inventive Principles

• Segmentation
• Extraction
• Local quality
• Asymmetry
• Combining
• Universality
• Nesting
• Counterweight

• Prior counteraction
• Prior action
• Cushion in advance
• Equipotentiality
• Inversion
• Spheroidality
• Dynamicity
• Partial or overdone action

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The Inventive Principles

• Moving to a new dimension
• Mechanical vibration
• Periodic action
• Continuity of useful action
• Rushing through
• Convert harm into benefit

• Feedback
• Mediator
• Self-service
• Copying
• An inexpensive short-lived object instead of an
  expensive durable one
• Replacement of a mechanical system

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The Inventive Principles

• Use of a pneumatic or hydraulic construction
• Flexible film or thin membranes
• Use of porous material
• Change the color
• Homogeneity
• Rejecting and regenerating part

• Transformation of physical and chemical states of
  an object
• Phase transition
• Thermal expansion
• Use strong oxidizers
• Inert environment
• Composite materials

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Example

• A metal pipe was used to pneumatically transport
  plastic pellets. A change in the process required
  that metal powder now be used with the pipe
  instead of plastic. The harder metal powder
  causes erosion of the inside of the pipe at the
  elbow where the metal particles turn 90o.
  Conventional solutions to this problem might
  include reinforcing the inside of the elbow with
  an abrasion-resistant hard-facing alloy,
  providing for an elbow that could be easily
  replaced after it has corroded, or redesigning
  the shape of the elbow. However, all of these
  solutions require significantly extra costs, so a
  more creative solution was sought.

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Solution

• What is the main function of our elbow?
• To change the direction of flow of metal particle
• What we want to improve?
• Increase the delivered particles speed
  (parameter 9)
• Reduce the energy required (parameter 19)

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Solution
Improving speed
Improving energy
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Solution

• By counting the frequency of inventive principles
  suggested, the Principle 28 is the most cited (4
  times).
• The others Principles cited are 13(3), 15(3), and
  38(3).
• Then Principle 28 shall be firstly considered.

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Solution

• The full description of Principle 28 is
• 28 Replacement of a mechanical system
• Replace a mechanical system by an optical,
  acoustical, or odor system.
• Use an electrical, magnetic, or electromagnetic
  field for interaction with the object.
• Replace fields. Example (1) stationary field
  change to rotating field (2) fixed fields become
  fields that change in time (3) random fields
  change to structural one.
• Use a field in conjunction with ferromagnetic
  particles.
• Then possible solution may be placing a magnet at
  the elbow to attract and hold a thin layer of
  powder that will serve to absorb the energy of
  particles navigating the 90o bend, thereby
  preventing erosion of the inside wall of the
  elbow.

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Algorithm of Inventive Problem Solving
Formulate initial physical contradiction
Original problem statement
Formulate technical contradiction
Analysis of conflict domain resource
Formulate ideal solution
Formulate main contradiction
Method of elimination of Physical contradiction
NO SOLUTION
Reformulation of problem statement
Knowledge base of effects
SOLUTION
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Conceptual Decomposition

• It is common tactic to decompose the problem into
  smaller parts.
• Connections of elements in terms of structure and
  function within the blocks shall be stronger than
  those between the blocks.
• There are two main approaches
• Decomposition in the physical domain
• Functional decomposition

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Decomposition in the Physical Domain

• Decompose the product into subassemblies and
  components that are essential for the all
  functioning of the product.
• Need to understand the interactions and
  connections that each of these subassemblies and
  elements has with each other. The connection can
  be physical, energy, or force connection.

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Functional Decomposition

• Function is in the nature of a physical behavior
  or action
• Function tells us that what the product must do.
• The process of functional decomposition describes
  the design problem in term of a flow of energy,
  material, and information.

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Functionality of some common device
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Subfunctions required to open and close CD case
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Generating Design Concept
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Morphological Chart

• Proposed by Zwicky
• Steps to follow
• Arrange the functions and subfunctions in logical
  order
• List for each subfunction how
• Combine concepts

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Example CD case
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Example CD case
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Example CD case
The combinations of these concepts generate many
possible solutions for the design. There are
162,000 combinations in this design.
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Assume that 5 concepts are drawn from the
previous chart. Concept 1 Conventional square
box (1), with the incline plane lock (2) and a
slide-out matchbox (3) for a hinge. The CD is
secured with a conventional rosetta (1) while
the leaflet is secured with tab (1). Concept 2 A
streamline curved box to fit the hand (3), with a
friction lock (2) and a conventional hinge (3).
The CD is secured in padded elastomer cradle (3)
and the CD case are designed to stack flat
(2). Concept 3 The box is grooved to the shape
of the finger (2), with a magnetic lock (3) and
conventional hinges (1). A new lift/lock secures
the CD (2). The leaflet fits in a slot in the top
of the case (2). Concept 4 A standard square box
(1) with magnetic lock (3) and conventional
hinges (1). The CD is secured with a padded
cradle (3), while the leaflet is secured with
Velcro straps (3). Concept 5 A curved box (3)
with inclined plane lock (2), with a slide-out
matchbox (3). The CD is held by a rosetta (1) and
the leaflet fits into a slot (2). The cases are
designed to stack (2).
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Axiomatic Design

• Developed by Professor Nam Suh and his colleagues
  at MIT
• Focus around 2 design axioms
• Axiom 1 The independent axiom
• Maintain the independence of functional
  requirements (FRs).
• Axiom 2 The information axiom
• Minimize the information content.

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Mapping process of Suhs concept
Functional Requirements
Design Parameters
FR1
DP1
FR2
DP2
FR3
DP3
DP4
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Hierarchy of FRs for a metal cutting lathe
Metal removal device
Power supply
Workpiece rotation source
Speed- changing device
Workpiece support and toolholder
Support structure
Tool positioner
Support structure
Positioner
Tool holder
Tool holder
Rotation stop
Longitudinal clamp
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Hierarchy of lathe design in physical domain
Lathe
Motor drive
Head stock
Gear box
Tailstock
Bed
Carriage
Frame
Feed screw
Spindle assembly
Bolt
Handle
Clamp
Tapered bore
Pin
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7 corollaries are derived from the 2 axioms
mentioned before
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Evaluation
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Comparison Based on Absolute Criteria

• Evaluation based on judgment of feasibility of
  the design. Concept should be into one of three
  categories
• It is not feasible? Next question is Why is it
  not feasible?
• It is conditional it might work if something
  else happen?
• Looks as if it will work, then it seems worth to
  work further.

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Comparison Based on Absolute Criteria

• Evaluation based on assessment of technology
  readiness. The technology used in the design must
  be mature enough not to need any additional
  research. Their indicators are
• Can the technology be manufactured with known
  processes?
• Are the critical parameters that control the
  function identified?
• Are the safe operating latitude and sensitivity
  of the parameters known?
• Have the failure modes been identified?
• Does hardware exist that demonstrates positive
  answers to the above four questions?

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Comparison Based on Absolute Criteria

• Evaluation based on go-no-go screening of the
  customer requirements.
• After a design concept has passed filters 1 and
  2, the emphasis shifts to establishing whether it
  meets the customer requirements framed in the QFD
• Each requirement must be transformed into a
  question to be addressed to each concept.
• The questions should be answerable as either yes
  (go), maybe (go), or no (no-go).
• The emphasis is not on a detail examination but
  on eliminating any design concepts that clearly
  not able to meet an important customer
  requirement.

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Pughs Concept Selection Method

• Choose the criteria by which the concepts will be
  evaluated
• Formulate the decision matrix
• Clarify the design concept
• Choose the datum concept
• Run the matrix
• Evaluate the rating
• Establish a new datum and rerun the matrix
• Plan further work
• Second working session

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Example of CD case
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Measurement Scales
Pairwise Comparison method
Assume 5 design objectives to be compared
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Weighted Decision Matrix
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Example of Steel Crane Hook A heavy steel crane
hook, for use in supporting ladles filled with
molten steel as they are transported through the
steel mill, is being designed. Three concepts
have been proposed (1) built-up from steel
plates, welded together (2) built-up from steel
plates, riveted together (3) a monolithic
cast-steel hook.
The design criteria investigated are (1) material
cost, (2) manufacturing cost, (3) time to produce
another if one fails. (4) durability, (5)
reliability, (6) reparability.
Crane hook O11.0
Oxyz here are weighted factors
Quality in service O120.4
Cost O110.6
Reliability O1220.3
Time to produce O1230.1
Durability O1210.6
Matl cost O1110.3
Mfg. Cost O1120.5
Reparability O1130.2
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Weighted Decision Matrix for a steel hook
Mag. Magnitude Exp. Experience Excell.
Excellent
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Analytical Hierarchy Process, AHP

• Multicriteria decision process introduced by
  Saaty
• Suited to hierarchically structural system
• Can work with both numerical and intangible and
  subjective factors
• Use pairwise comparison of the alternatives

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Example of crane hook design using AHP approach
Crane hook design
Material cost
Manufacturing cost
Reliability
Durability
Reparability
Time to produce
Built-up plates, welded steel
Built-up steel plates, riveted
Cast steel
Hierarchical structure of a crane hook design
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Saatys fundamental scale for pairwise comparison
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Square matrix to determine weighting factors
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Normalized values for square matrix
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Now construct the decision matrix using previous
values given.
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Final Decision Matrix for the Crane Hook Problem
Then riveted plate is the most appropriate
alternative for this design