Tutorial_engineering Design 2011

ENGINEERING DESIGN

TMS 306

2 cr.

Mechanical Engineering DepartmentAndalas University

2010

Adjar Pratoto

Quotes

• If you fail to plan, you plan to fail. (Varanasi, 2006)

• The mere formulation of a problem is far more often essential than its solution, which may be merely a matter of mathematical or experimental skill. (Albert Einstein)

• If you don’t know where you’re going, you’ll probably end up somewhere else. (Yogi Berra)

Learning Objectives

differentiate the analytical approach and the design approach describe different design process models explain design phases communicate effectively work in team

After completing the course, the students should be able to:

References:

1. Cross, N., Engineering Design Methods, 2nd Ed., John Wiley & Sons, Chichester, 1994

2. Eggert, R.J., Engineering Design, Pearson Prentice Hall, Upper Saddle River, N.J., 2005

3. Dieter, G.E., Engineering Design, 3rd Ed., McGraw-Hill Intl. Ed., Singapore, 2000

Engineering Undertaking

Define need or opportunity

Specify criteria for success

Determine probability of success Market analysis

Product or system design and cost estimate

Feasibility study

Implement – construct or manufacture

Research and development

Low probability - drop

High probability

Not feasible - dropFeasibleRefine and revise

New idea

Stoecker, 1980

Product Realization Process

Customer need

Realized product

Sales/marketingIndustrial design

Engineering designProduct design

Manufacturing (Production)

Distribution

Service Disposal

Product development

Product Realization Process

Ref.: 2

• A customer need for a new or improved product can originate from almost anywhere in the firm, but the majority ideas usually originate from the sales or marketing group

• Industrial design activities focus on how the new or revised product idea is compatible with the customer’s anatomical limitations and/or aesthetic trends in the marketplace

• Engineering design activities result in recommended manufacturing specifications that satisfy the customer’s functional performance requirements and manufacturing constraints

• Production design activities involve the design, fabrication, and installation of production equipment, such as jigs, fixtures, quality control instrumentation, and material handling equipment. In some cases, it might involve the construction of a new factory.

Ref.: 2

• Manufacturing activities relate to fabrication, assembly, and testing. They also include training, scheduling, and supervising production employees. Significant coordination between engineering design, production planning, and manufacturing is necessary during ramp-up as bugs in the product design and manufacturing processes are worked out.

• Distribution activities involve shipping the product in wholesale-sized lots to distribution centers located around the country or world.

• Service activities for consumer products usually relate to repair or replacement at the factory. However, large appliance manufacturers will train repair persons for home service.

• Disposal activities involve the removal, elimination, and/or recycling of hazardous chemicals or scarce materials

Ref.: 2

Establish function

Determine formDesign

Manufacture

Use

Retire

Fabricate

Assemble

Distribute

Set up

Operate

Maintain

Repair

Take down

Disassemble

Recycle

Dispose

The four stages in the life of a product

Ref.: 2To satisfy the consumer…We must consider all the phases in the life of a product

What is engineering design?

• A goal directed problem solving activity (Archer)

• Decision making in the face of uncertainty with high penalties for error (Asimow)

• The use of scientific principles, technical information and imagination in the definition of a mechanical structure, machine or system to perform pre-specified functions with maximum economy and efficiency (Fielden)

• To device, subject to certain problem solving constraints, a component, system or process to accomplish a specified task optimally, subject to certain solution constraints (Dixon)

What is engineering design?

• Establishes and defines solutions to and pertinent structures for problems not solved before, or new solutions to problems which have previously been solved in a different way (Blumrich)

• Process of devising a system, component, or process to meet desired needs (ABET, Inc.)

• Engineering design integrates mathematics, basic sciences, engineering sciences and complementary studies in developing elements, systems and processes to meet specific needs. It is a creative, iterative and often open-ended process subject to various constraints (CAB, Canada)

• Iterative re-evaluation – re-assessment and re-development of work plans, specification and constraints

• Ongoing communication with key stakeholders or their representatives

• Co-operative approaches (team work)

In the course of performing design work, evidence of the following should be present:

The Four C’s of Design

Creativity • Requires creation of something that has not existed before or

not existed in the designer’s mind before

Complexity • Requires decisions on many variables and parameters

Choice • Requires making choices between many possible solutions at

all levels, from basic concepts to smallest detail of shape

Compromise • Requires balancing multiple and sometimes conflicting

requirements

Ref.: 3

Existing knowledge

Scientific curiosity

Hypothesis

Logical analysis

Proof

State of the art

Identification of need

Conceptualization

Feasibility analysis

Production

Com

mu

nic

atio

n

Acc

ept

ance

Scientific Method Design Method

Scientific method vs Design method

Types of design

• Original design• Variant design• Adaptive design• Selection design• Redesign• Artistic design• Tinkering

Ref.: 2

Variant design seeks to modify the performance of an existing product by varying some of its design variable values or product parameters, such as size, or specific material, or manufacturing processes.

Note, however, that the fundamental working principle or concept is usually maintained.

Original design : conceiving and embodying an original, innovative concept for a given task. It develops a new component, assembly, or process that had not existed before.

Selection design : matching the desired functional requirements of a component with the actual performance of standard components listed in vendors’ catalogs.

Adaptive design is when we adapt a known solution to accomplish a new task.

Redesign. Much of our working career will be devoted to the improvement of existing products. To obtain the improvements we usually modify parts, or subassemblies, or combinations thereof, by changing their shapes, sizes, configurations, materials, and manufacturing processes. Since design is determining “form”, whenever we improve an aspect of form, we are essentially redesigning

Artistic design It deals with an object’s appearance (clothing, furniture, etc.). It is not considered as engineering design.

Tinkering. Development of products (pots, pans, cutlery, sofas, etc.) using new material or try different fabrication method without regard to the underlying sciences. It is not considered as engineering design.

Detail Design

Parametric Design

ConfigurationDesign

Detail Design

Parametric Design

Detail Design

Formulation

Concept Design

Detail Design

Parametric Design

ConfigurationDesign

variant design

selection design

originaldesign

partdesign

Design projects commonly fall into one of five types:

• 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

Ref.: 3

Design Phases

• Anybody can design products!

• The design engineer has specific skills:

- He can use analytical tools

Structured Design Methodologies Get Results!

• Notable design cycle time reductions:• Xerox (design cycle)

• 70s 3 yr.• 1990 < 2 yr.• 1995 30 wk.

• Caterpillar• 1980 50 mo.• 1993 20 mo.

Steps in the Engineering Design Process

Design Phases

Formulation

Detail

Parametric

Configuration

Concept

Embodiment Design

Preliminary Design

Need

Analysis of problem

Problem statement

Conceptual design

Selected schemes

Embodiment of schemes

Detailing

Working, drawing, etc

FRENCH’S MODEL

Ugr

ade

and

impr

ove

Clarity the task Elaborate the specification

Identify essential problems Establish function structures Search for solution principles Combine and firm up into concept variants Evaluate against technical and economic criteria

Develop preliminary layouts and form designs Select best preliminary layouts Refine and evaluate against technical and economic criteria

Optimize and complete form designs Check for errors and cost effectiveness Prepare the preliminary parts list and production documents

Finalize details Complete detail drawings and production documents Check all documents

Task

Specification

Concept

Preliminary layout

Definitive layout

Documentation

Solution

Det

ail d

esig

n

Em

bod

imen

t d

esig

n

Con

cep

tual

des

ign

C

lari

fica

tion

of

th

e ta

sk

Op

tim

izat

ion

of t

he

layo

ut

and

form

s

Op

tim

izat

ion

of t

he

pri

nci

ple

PAHL and BEITZ MODEL

s ite vis itQ F D /H o QE ng. C ha ra c te ris tic sC o ns tra intsS a isfa c tio n c urve sS e le c t s tra te gyD e ve lo p p la nD e sign re vie w m e e ting

P ro b le m F o rm ula tio n

G e ne ra te a lte rna tive c o nc e p tsA na lyze a lte rna tive sE va lua te a lte rna tiveR e fineD e s ign re vie w m e e ting

C o nc e p t D e sign

D e ve lo p a rc hite c tureG e ne ra te c o nfigura tio ns

D F AD F M

A na lyze

E va lua teR e fineD e s in re vie w m e e ting

C o nfigura tio n D e s ign

P a ra m e tric p ro b le m fo rm ula tio nG e ne ra te a lte rna tive s

F M E AF a ult tre e sF ishb o ne d ia gra m s

A na lyze a lte rna tive s

E va lua te a lte rna tive sO p tim iza tio nM ulti- a ttrib ute o p t.D e s ign re vie w m e e ting

P a ra m e tric D e sign

D e ta il d ra w ingsA sse m b ly d ra w ingsIllus tra tio nsP ro je c t R e p o rtP ro to typ e te s t re p o rtsO ra l p re se nta tio nsD e s ign re vie w m e e ting

D e ta il D e sign

W id ge tD e s ign

Work breakdown structure

Customer needs

FormulationCustomer requirementsImportance weightsEng. Charact.Eng. Design Spec.

Concept DesignAbstract embodiment ofphysical principles

Material geometry

Configuration Design

Special-purpose parts.Standard parts

Parametric Design

Detail Design

Design variable valuesSizes, dimensionsMatl./Manufac. processes.Performance predictions.Overall satisfaction

Product specificationsProduction drawingsBills of materials.Manufact. specificationsPerformance tests

Problem Formulation

Need Identification - Clarifying objectives• When a client, sponsor or company manager first

approaches a designer with a product need, it is unlikely that the need will be expressed very clearly

• The starting point for a design is therefore very often an ill-defined problem

Customer requirements (Maslow, 1943):

• Physiological needs• Safety and security needs• Social needs• Psychological needs• Self-fulfillment needs

Ref.: 1, 3

Gathering Information from customers:

• Interviews with customers• Focus group discussion• Customer surveys (external and internal) • Customer complaints

Stage 1: Clarifying objectives

Constructing a survey instrument:

• Determine the survey purpose• Determine the type of data-collection method• Identify what specific information is needed• Design the questions• Arrange the order of questions• Pretest the survey• Administer the survey

Ref.: 3

Stage 1: Clarifying objectives

The Objectives Tree MethodPrepare a list of design objectives

Order the list into sets of higher-level and lower-level objectives

Draw a diagrammatic tree of objectives, showing hierarchical relationship and interconnections

The branches (or roots) in the tree represent relationship which suggest means of achieving objectives

Ref.: 1

Ref.: ECE 404 Scott Umbaugh

The Function Analysis Method• Express the overall function for the design in terms of the conversion

of inputs into outputs The overall , ‘black box’ function should be broad – widening the system

boundary.

• Break down the overall function into a set of essential sub-functions The sub-functions comprise all the tasks that have to be performed inside

the ‘black box’.

• Draw a block diagram showing the interactions between sub-functions The ‘black box’ is made ‘transparent’, so that the sub-functions and their

interconnections are clarified.

• Draw the system boundary The system boundary defines the functional limits for the product or device

to be designed.

• Search for appropriate components for performing the sub-functions and their interactions.

Many alternative components may be capable of performing the identified functions.

Establishing functions

Ref.: 1

Determining characteristics

Quality Function Deployment (QFD) – House of Quality

• QFD is a planning and problem-solving tool for translating customer requirements (CRs) into the engineering characteristics (ECs)

• “Listen to the voice of customer”

House of Quality

Customer

Requirement

“Whats”

House of quality

1. Identify the customers (internal and external): consumers, manufacturing, regulators, distribution, marketing, sales

2. List the customer needs (WHAT is to be done), they can be list as primary, secondary and tertiary

3. Determine the primary importance or priority of the customer needs (scale of 1-5 or 1-10) (use if possible pairwise comparison)

4. Translate customer needs into measurable engineering requirements (HOW to do it in term of measurements). Each customer need can correspond to multiple engineering requirements that can be expressed in quantifiable terms,

5. Determine relationship of engineering design requirements to customer needs

House of quality

6. Use customer to benchmark existing products and evaluate the perceived competition’s ability to meet the needs (1-not satisfied need, 5-fully satisfied need)

7. Rank the technical difficulty for each engineering requirement (1-5 or 1-10)

8. Define interrelationship between technical requirements,9. Set target values and ideal values for engineering

requirements,10.Define the most critical engineering requirements by

analyzing the conjunction between customer needs, benchmarking, interactions and importance

Design Requirements

Cu

sto

mer

R

equ

irem

ents

Design Requirements

Target

QFD 1Part

Requirements

Des

ign

R

equ

irem

ents

Part Requirements

Target

QFD 2Manufacturing Requirements

Par

t R

equ

irem

ents

Manufacturing Requirements

Target

QFD 3Production

Requirements

Man

ufa

ctu

rin

g

Req

uir

emen

ts

Production Requirements

Target

QFD 4

Generating alternatives


Alternative concepts

1 2 3

S

ubfunctions

Transmit Chain Belt Gearbox

Brake Disc Drum

Steer Handlebar Control Stick

Fly-by-wire


Feature Means

Support Wheels Track Air cushion Slides Pedipulators

Propulsion Driven wheels

Air thrust Moving cable

Linear induction

Power Electric Petrol Diesel Bottled gas Steam

Transmission Gears and shaft

Belts Chains hydraulic Flexible cable

Steering Turning wheels

Air thrust Rails

Stopping Brakes Reverse thrust

Ratchet

Lifting Hydraulic ram

Rack and pinion

Screw Chain or rope hoist

Operator Seated at front

Seated at rear

Standing Walking Remote control

Evaluating Alternatives

• Will the concept likely function?• Will the concept likely meet the customer’s minimum

performance requirements?• Will the concept likely survive the operating environment?• Will the concept likely satisfy other critically important

customer requirements?• Will the concept be manufacturable?• Will the concept likely satisfy the financial and/or marketing

requirements?

The screening criteria should focus on functionality and manufacturability:

The evaluation method:• Weighted-rating Method • Pugh’s Concept Selection Method

The weighted objectives method

• List the design objectives• Rank-order the list of objectives • Assign relative weightings to the objectives• Establish performance parameters or utility

scores for each of the objective• Calculate and compare the relative utility values

of the alternative designs


• List the design objectives• Rank-order the list of objectives • Assign relative weightings to the objectives• Establish performance parameters or utility scores for each of the

objective• Calculate and compare the relative utility values of the alternative

designs

The objectives: technical and economic factors, user requirements, safety requirements, and so on.

The objectives should be represented in such a way that could be assessed quantitatively




designs

The order of importance: B – C – D – A – E

For a pair of objectives, determine which is more important (A and B, A and C, and so forth); assign “1” for more important and “0” for less. Form a matrix.




designs

Assign a numerical value to each objective; use a scale of, say, 1 to

10 or 1 to 100 C. Alternatively, decide to share a certain number of

points – say 100.




designs

Pugh’s Concept Selection Method

Concept alternatives

Criteria Gears V-belts Chain

High efficiency + D +

High reliability + A +

Low maintenance + T S

Low cost - U -

Light weight - M -

+ 3 n.a. 2

- 2 n.a. 2

S 0 n.a. 1

Modified Pugh’s MethodImportance Concept alternatives

Criteria Weight (%) Gears V-belts Chain

High efficiency 30 + D +

High reliability 25 + A +

Low maintenance 20 + T S

Low cost 15 - U -

Light weight 10 - M -

100

+ 75 n.a. 55

- 22 n.a. 25

S 0 n.a. 20

Concept alternatives

Gears V-belts Chain

ImportanceRating

WeightedRating

WeightedRating

Weighted

Criteria Weight (%) Rating Rating Rating

High efficiency 30 4 1.20 2 0.60 3 0.90

High reliability 25 4 1.00 3 0.75 3 0.75

Low maintenance 20 4 0.80 3 0.60 2 0.40

Low cost 15 2 0.30 4 0.60 3 0.45

Light weight 10 2 0.20 4 0.40 3 0.30

100 3.50 2.95 2.80

Rating Value

Unsatisfactory 0

Just tolerable 1

Adequate 2

Good 3

Very good 4

Engineering Design – Selection

Fig. 1-2, Design of Machinery, by R. L. Norton, McGraw-Hill, 2001

• We have discussed phases in design

• However sometimes it helps to first

reverse engineer and then design

what is reverse engineering?

• Dissecting a product• Understanding how it functions• Learn basic principles• Designing/building a new product

with the knowledge from dissection

Initial Observation

• Let us explore how a vacuum cleaner works• First identify the vacuum cleaner: type, manufacturer, model#, and

performance specifications• Read the instruction manual• Plug the vacuum cleaner and run it • Listen to the sound • Feel how it runs • Record your observations

Dissection

• Wear safety glasses• Unplug the vacuum cleaner• Disassemble it as far as possible• Put all parts in a bin (with label of your group)• Note each part and their purpose (e.g. belt and pulley mechanism,

types of bearings/bushings, motor, etc.)• Are there any other alternatives of these components?

Reassemble

• Now reassemble your vacuum cleaner• Suggest any design changes to make reassemble easier• Once all parts are assembled, plug it in and run it (make sure you

have your safety glasses)• If it does not sound or feel like before or smoke comes out, unplug

immediately and run (try to fix the problem later !)

Drill DissectionWhat’s so interesting about a drill? It’s got lots of good stuff in it - electric

motors, gears, bearings, couplings, etc

It is a good example of an electro-mechanical power transmission system, and it is also an example of a machine tool (it drills holes)

FISHBONE DIAGRAM FOR MECHANICAL DISSECTION

(Example: Small Kitchen Scale)

Kitchen Scale

PLATFORM

TOP PLATE

RIVETSSTEM

SPRING MECHANISM

SPRING

THREADED PIN

NUT

FOUR-BAR MECHANISM & HOUSING(Example: Small Kitchen Scale)

LINK 3LINK 2

LINK 1

COVER

BOTTOM

READOUT

Fabricated cost

Purchased cost

Assembly cost

Total cost

Original product $3.27 $5.12 $0.30 $8.69 Redesigned product $2.7475 $4.1525 $0.10 $7.00 Save money $0.5225 $0.9675 $0.20 $1.69

original design new design

Pepper Grinder

Source: Huang, Chen, & Chen (2004)

Material Selection Chart

Ashby’s selection chart

Importance of manufacturability and communication

Second floor collapsed, 114 people died

No Job's Finished Until

the Paperwork is

Done

Tutorial_engineering Design 2011

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