Chapter 6: Product Specifications
Product Design and Development
Fifth Edition
by Karl T. Ulrich and Steven D. Eppinger
Product Development Process
Planning
Concept
System-LevelDetail
DevelopmentDesign
Design
Testing and Production
Refinement Ramp-Up
Remember that we are looking at an overall Product Development Process.
We are going into more detail on Concept Development. We did a lecture,
quiz and homework assignment on customer needs. Now we are ready to
go to the next step in Concept Development.
Concept Development Process
Identify
Customer
Needs
Establish
Target
Specifications
Generate
Product
Concepts
Select
Product
Concept(s)
Test
Product
Concept(s)
Set
Final
Specifications
Plan
Downstream
Development
Perform Economic Analysis
Benchmark Competitive Products
Build and Test Models and Prototypes
Target Specs
Final Specs
Based on customer needs
and benchmarking
Based on selected concept,
feasibility, models, testing,
and trade-offs
Development
Plan
Product Design Specifications
• Basic control and reference document for the design and
manufacture
• Specific, measurable, testable criteria
• “Unambiguous, Understandable, Correct, Concise, Traceable,
Traced, Design Independent, Verifiable, Unique, Complete,
Consistent, Comparable, Modifiable, Attainable”
• Functional decomposition
• Performance targets
• Constraints (Demands, Musts)
• Goals (Wishes, Wants)
• Features
The Blind Men and the Elephant
A Hindu fable by John Godfrey Saxe
from Elephants Ancient and Modern by
FC Sillar and RM Meyler.
It was six men of Indostan
To learning much inclined,
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind.
The First approached the Elephant,
And happening to fall
Against his broad and sturdy side,
At once began to bawl:
`God bless me! but the Elephant
Is very like a wall!'
The Second, feeling of the tusk,
Cried, `Ho! what have we here
So very round and smooth and sharp?
To me 'tis mighty clear
This wonder of an Elephant
Is very like a spear!'
The Third approached the animal,
And happening to take
The squirming trunk within his hands,
Thus boldly up and spake:
`I see,' quoth he, `the Elephant
Is very like a snake.'
The Fourth reached out his eager hand,
And felt about the knee.
`What most this wondrous beast is like
Is mighty plain,' quoth he;
`'Tis clear enough the Elephant
Is very like a tree!'
The Fifth who chanced to touch the ear,
Said: `E'en the blindest man
Can tell what this resembles most:
Deny the fact who can,
This marvel of an Elephant
Is very like a fan!'
The Sixth no sooner had begun
About the beast to grope,
Than, seizing on the swinging tail
That fell within his scope,
`I see,' quoth he, `the Elephant
Is very like a rope!'
And so these men of Indostan
Disputed loud and long,
Each in his own opinion
Exceeding stiff and strong,
Though each was partly in the right,
And all were in the wrong!
So, oft in theologic wars,
The disputants, I ween,
Rail on in utter ignorance
Of what each other mean,
And prate about an Elephant
Not one of them has seen!
Writing a good PDS is very difficult
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Customer
Regulatory Bodies
Laws of Physics
Functional Analysis
Company Constraints
Social, Political, and Legal Requirements
The Product Specs Process
• Set Target Specifications
– Based on customer needs and benchmarks
– Develop metrics for each need
– Set ideal and acceptable values
• Refine Specifications
– Based on selected concept and feasibility testing
– Technical modeling
– Trade-offs are critical
• Reflect on the Results and the Process
– Critical for ongoing improvement
Product Specifications Example:
Mountain Bike Suspension Fork
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
NEED
Imp
reduces vibration to the hands.
3
allows easy traversal of slow, difficult terrain.
2
enables high speed descents on bumpy trails. 5
allows sensitivity adjustment.
3
preserves the steering characteristics of the bike.4
remains rigid during hard cornering.
4
is lightweight.
4
provides stiff mounting points for the brakes.
2
fits a wide variety of bikes, wheels, and tires.
5
is easy to install.
1
works with fenders.
1
instills pride.
5
is affordable for an amateur enthusiast.
5
is not contaminated by water.
5
is not contaminated by grunge.
5
can be easily accessed for maintenance.
3
allows easy replacement of worn parts.
1
can be maintained with readily available tools.
3
lasts a long time.
5
is safe in a crash.
5
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Maniray 2
#
1
2
3
4
5
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19
20
ST Tritrack
Start with the Customer Needs
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What are some customer needs for the
catapult-like device?
Size matters not.
Need #s
Metric #
Establish Metrics and Units
1
1,3
2
2,6
3
1,3
4
1,3
5
4
6
5
7
5
8
6
9
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10
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11
9
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17
12
18
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19
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20
15
21 16,17
22 17,18
23
19
24
19
25
20
26
20
Metric
Attenuation from dropout to handlebar at 10hz
Spring pre-load
Maximum value from the Monster
Minimum descent time on test track
Damping coefficient adjustment range
Maximum travel (26in wheel)
Rake offset
Lateral stiffness at the tip
Total mass
Lateral stiffness at brake pivots
Headset sizes
Steertube length
Wheel sizes
Maximum tire width
Time to assemble to frame
Fender compatibility
Instills pride
Unit manufacturing cost
Time in spray chamber w/o water entry
Cycles in mud chamber w/o contamination
Time to disassemble/assemble for maintenance
Special tools required for maintenance
UV test duration to degrade rubber parts
Monster cycles to failure
Japan Industrial Standards test
Bending strength (frontal loading)
Imp
Units
3
dB
3
N
5
g
5
s
3 N-s/m
3
mm
3
mm
3 kN/m
4
kg
2 kN/m
5
in
5
mm
5
list
5
in
1
s
1
list
5
subj
5
US$
5
s
5 k-cycles
3
s
3
list
5 hours
5 cycles
5 binary
5
MN
Metrics Exercise:
Ball Point Pen
Customer Need:
The pen writes smoothly.
Additional Areas to Consider
• Physical requirements
• Functional requirements
• Service environment (comprehensive: insect and bird
damage)
• Kinematics – type of motion, direction, velocity,
acceleration
• Forces - direction, magnitude, frequency, resonance,
stiffness
• Materials – properties of final product, flow of
materials, design for manufacturing
Design Specification Checklist
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Performance At what speed must it operate? How often will it be used (continuous or discontinuous use)?
How long must it last?
Environment (during manufacture, storage and use) All aspects of the product’s likely environment should
be considered: for example temperature, humidity, risk of corrosion, vibration.
Target product cost This is strongly affected by the intended market.
Competition What is the nature and extent of existing or likely competition? Does our specification differ
from the competition? If so, why?
Quantity and manufacture Should it be made in bulk, in batches, or as individual items made to order?
Does it have to be a particular shape? Can we make all the parts or must we buy some in?
Materials Are special materials needed? Do we have experience of working with the likely candidate
materials?
Quality and consistency What levels of quality and consistency does the market expect for this product?
Does every product have to be tested?
Standards Does the product need to conform to any local, international or customer standards? Is the
product safe?
Patents Are there any patents we may either infringe or register?
Packaging and shipping How will the product be packaged? How will the product be distributed?
Aesthetics and ergonomics Is the product easy and fun to use? Is it attractive to the right customer?
Market constraints Does a market already exist or must it be created? What is the likely product lifetime?
How long do we have to get the product to market? What are the customers’ likes and dislikes?
Company constraints Does the product fit in with company image? Are we constrained in material or
process choice? Are there any political considerations?
http://labspace.open.ac.uk/mod/resource/view.php?id=194654
More Things to Think About
• Production – Factory limitations, outsourcing,
tolerancing (You may wait on actual tolerances until
later – just think about the big picture.)
• Assembly
• Transport
• Costs
• Schedule
• Life-cycle issues
• Human factors
Social, Political, Legal
• Safety and environmental regulations
• STANDARDS
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–
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–
–
–
www.ul.com
www.outdoorindustry.com
www.cpsc.gov
www.astm.org
www.nfpa.org
http://www.nssn.org/
• Safety and product liability
• Patents and intellectual property
•
Bending strength (frontal loading)
•
Japan Industrial Standards test
Special tools required for maintenance
Time to disassemble/assemble for maintenance
Cycles in mud chamber w/o contamination
Time in spray chamber w/o water entry
•
Unit manufacturing cost
•
Instills pride
•
Fender compatibility
•
Monster cycles to failure
•
UV test duration to degrade rubber parts
•
Time to assemble to frame
•
Maximum tire width
•
Wheel sizes
•
Steertube length
•
Headset sizes
•
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Lateral stiffness at brake pivots
•
8
Total mass
•
7
Lateral stiffness at the tip
•
6
Rake offset
•
5
Maximum travel (26in wheel)
Spring pre-load
Need
1
reduces vibration to the hands. •
2
allows easy traversal of slow, difficult terrain.
3
enables high speed descents on bumpy trails. •
4
allows sensitivity adjustment.
5 preserves the steering characteristics of the bike.
6
remains rigid during hard cornering.
7
is lightweight.
8
provides stiff mounting points for the brakes.
9
fits a wide variety of bikes, wheels, and tires.
10
is easy to install.
11
works with fenders.
12
instills pride.
13
is affordable for an amateur enthusiast.
14
is not contaminated by water.
15
is not contaminated by grunge.
16
can be easily accessed for maintenance.
17
allows easy replacement of worn parts.
18
can be maintained with readily available tools.
19
lasts a long time.
20
is safe in a crash.
4
Damping coefficient adjustment range
3
Minimum descent time on test track
2
Maximum value from the Monster
1
Attenuation from dropout to handlebar at 10hz
Metric
Link Metrics to Needs
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Gunhill Head Shox
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Tonka Pro
Rox Tahx Ti 21
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Rox Tahx Quadra
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
The suspension
NEED
Imp
reduces vibration to the hands.
3
allows easy traversal of slow, difficult terrain.
2
enables high speed descents on bumpy trails. 5
allows sensitivity adjustment.
3
preserves the steering characteristics of the bike.4
remains rigid during hard cornering.
4
is lightweight.
4
provides stiff mounting points for the brakes.
2
fits a wide variety of bikes, wheels, and tires.
5
is easy to install.
1
works with fenders.
1
instills pride.
5
is affordable for an amateur enthusiast.
5
is not contaminated by water.
5
is not contaminated by grunge.
5
can be easily accessed for maintenance.
3
allows easy replacement of worn parts.
1
can be maintained with readily available tools.
3
lasts a long time.
5
is safe in a crash.
5
Maniray 2
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
ST Tritrack
Benchmark on Customer Needs
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Benchmarking
Product Design by Otto and Wood, 2001
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Look at your customer needs and your metrics
Form a List of Related or Competitive Products
Conduct an Information Search
Establish Best-in -Class Competitors
Develop Specifications
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Less than
Greater than
Range
Discrete values
Exactly X
Sources of Product Information
•
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Library
Thomas Register
Market Share Reporter
National Bureau of
Standards
• Census of Manufactures
• Moody’s Industry Review
• Consumer Reports
Magazine
• Trade Magazines
• Patents
• Market Research Databases
– DIALOG, Predicasts, American
Demigraphics
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Web
Vendors
Technical Specialists
Experts/Friends in Industry
NAICS (North American Industry
Classification System) Codes
Here are some ideas that you might like. Please feel
free to generate your own!
• http://www.statease.com/golftoy.html
• http://www.statease.com/pubs/hockey.pdf
FOLD DOWN
CUT
FOLD UP FIRST
DOE 1
BODY 1
WIDTH
BODY 2
WIDTH
FOLD UP
FOLD UP END
WING 1
LENGTH
WING 2
LENGTH
CUT
BODY 1
LENGTH
BODY 2
LENGTH
CUT
CUT
HELICOPTER 1
HELICOPTER 2
CUT
DOE 1
Crunch
Perceptual Mapping Exercise
KitKat
Peanut
M&Ms
Opportunity?
Almond
Joy
Plain M&Ms
Chocolate
11
12
9 Headset sizes
9 Steertube length
13
9
14
9
15
10
16
11
17
12
18
13
19
14
20
15
21 16,17
Wheel sizes
Maximum tire width
Time to assemble to frame
Fender compatibility
Instills pride
Unit manufacturing cost
Time in spray chamber w/o water entry
Cycles in mud chamber w/o contamination
Time to disassemble/assemble for maintenance
22 17,18 Special tools required for maintenance
23
19 UV test duration to degrade rubber parts
24
19 Monster cycles to failure
25
20 Japan Industrial Standards test
26
20 Bending strength (frontal loading)
5
in
8
15
10
15
9
550
760
500
710
480
3.6
3.2
3.7
3.3
3.7
13 11.3 12.6 11.2 13.2
0
0
0
200
0
28
48
43
46
33
41.5
39
38
38 43.2
59
110
85
85
65
1.409 1.385 1.409 1.364 1.222
295
550
425
425
325
1.000
1.000
1.000 1.125 1.000 1.125 1.000
1.125 1.250 1.125 1.250 1.125
5
mm
150
180
210
230
255
5
5
1
1
5
5
5
5
3
list
in
s
list
subj
US$
s
k-cycles
s
26in
1.5
35
Zefal
1
65
1300
15
160
3
5
5
5
5
140
165
190
215
150
170
190
210
26in 26in
1.75
1.5
35
45
none none
4
3
105
85
2900 >3600
19
15
245
215
list
hex
hex
hex
hours
400+
250 400+
cycles 500k+ 500k+ 500k+
binary
pass pass pass
MN
55
89
75
Gunhill Head Shox
Units
dB
N
g
s
N-s/m
mm
mm
kN/m
kg
kN/m
Tonka Pro
Imp
3
3
5
5
3
3
3
3
4
2
Rox Tahx Ti 21
Metric
Attenuation from dropout to handlebar at 10hz
Spring pre-load
Maximum value from the Monster
Minimum descent time on test track
Damping coefficient adjustment range
Maximum travel (26in wheel)
Rake offset
Lateral stiffness at the tip
Total mass
Lateral stiffness at brake pivots
Rox Tahx Quadra
1,3
2,6
1,3
1,3
4
5
5
6
7
8
Maniray 2
Need #s
1
2
3
4
5
6
7
8
9
10
ST Tritrack
Metric #
Benchmark on Metrics
13
680
3.4
11
0
38
39
130
1.1
650
NA
150
170
150
190
190
210
210
230
220
NA
26in
700C 26in
26in
1.75
1.5
1.5
45
35
85
none none
all
5
3
5
115
80
100
>3600 2300 >3600
25
18
35
245
200
425
hex,
long
pin
hex
hex wrnch
400+ 400+
250
480k 500k+ 330k
pass pass pass
75
62
102
1
2
3
4
5
6
7
8
9
10
11 Headset sizes
12 Steertube length
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Wheel sizes
Maximum tire width
Time to assemble to frame
Fender compatibility
Instills pride
Unit manufacturing cost
Time in spray chamber w/o water entry
Cycles in mud chamber w/o contamination
Time to disassemble/assemble for maintenance
Special tools required for maintenance
UV test duration to degrade rubber parts
Monster cycles to failure
Japan Industrial Standards test
Bending strength (frontal loading)
Units
dB
N
g
s
N-s/m
mm
mm
kN/m
kg
kN/m
in
mm
list
in
s
list
subj
US$
s
k-cycles
s
list
hours
cycles
binary
MN
Ideal Value
Metric
Attenuation from dropout to handlebar at 10hz
Spring pre-load
Maximum value from the Monster
Minimum descent time on test track
Damping coefficient adjustment range
Maximum travel (26in wheel)
Rake offset
Lateral stiffness at the tip
Total mass
Lateral stiffness at brake pivots
Marginal Value
Assign Marginal and Ideal Values
>10
>15
480 - 800 650 - 700
<3.5
<3.2
<13.0
<11.0
0
>200
33 - 50
45
37 - 45
38
>65
>130
<1.4
<1.1
>325
>650
1.000
1.000
1.125
1.125
1.250
150
150
170
170
190
190
210
210
230
26in
26in
700c
>1.5
>1.75
<60
<35
none
all
>3
>5
<85
<65
>2300
>3600
>15
>35
<300
<160
hex
hex
>250
>450
>300k
>500k
pass
pass
>70
>100
Now What? Can you get there from here?
•
•
•
•
Make a functional model of the product
Make a technical model of the product
Make a cost model of the product
Refine the specifications, making trade-offs
where necessary.
• Flow down the specifications as appropriate
• Reflect on the results and the process.
Estimated Manufacturing Cost
($)
Specification Trade-offs
Trade-off Curves
for Three Concepts
Score on Monster (Gs)
Set Final Specifications
1
2
3
4
5
6
7
8
9
10
METRIC
Attenuation from dropout to handlebar at 10hz
Spring pre-load
Maximum value from the Monster
Minimum descent time on test track
Damping coefficient adjustment range
Maximum travel (26in wheel)
Rake offset
Lateral stiffness at the tip
Total mass
Lateral stiffness at brake pivots
11 Headset sizes
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Steertube length
Wheel sizes
Maximum tire width
Time to assemble to frame
Fender compatibility
Instills pride
Unit manufacturing cost
Time in spray chamber w/o water entry
Cycles in mud chamber w/o contamination
Time to disassemble/assemble for maintenance
Special tools required for maintenance
UV test duration to degrade rubber parts
Monster cycles to failure
Japan Industrial Standards test
Bending strength (frontal loading)
Units
dB
N
g
s
N-s/m
mm
mm
kN/m
kg
kN/m
in
mm
li st
in
s
li st
su bj
US$
s
k-cycl es
s
li st
ho urs
cycles
bi nary
MN
Value
>1 2
65 0
<3 .4
<1 1.5
>1 00
43
38
>7 5
<1 .4
>4 25
1.000
1.125
15 0
17 0
19 0
21 0
23 0
26 in
>1 .75
<4 5
Ze fal
>4
<8 0
>3 600
>2 5
<2 00
he x
>4 50
>5 00k
pa ss
>1 00
Quality Function Deployment
(House of Quality)
technical
correlations
relative
importance
customer
needs
engineering
metrics
relationships between
customer needs and
engineering metrics
target and final specs
benchmarking
on needs
Perceptual Mapping Quiz
Crunch
Name:______________________ CM:______
Name:______________________
Chocolate