IDENT
OPP
GATHER
INFO
DEFINE
PROBLEM
GEN
CONCEPTS
SCREEN
CONCEPTS
IMPLEMENT
ME 4054W:
SENIOR DESIGN PROJECTS
Week 6 – Tuesday
Concept Screening
HANDOFF
Notes
• Mobile App Challenge
– Entrepreneurship / Design Challenge
– http://z.umn.edu/MobileAppChallenge
2
Class Agenda
• Methods of Concept Screening
• Concept Screening (Pugh) Matrix
• Concept Scoring (Decision) Matrix
3
Concept Selection
• While concept generation is easy (and fun),
concept selection is difficult (and fun)
*********************
• You never have enough
information
*******
• Use estimation, analysis, and
some prototyping
************
• Look for new concepts during
the process
***
• Weed out bad (vs picking “best”)
Controlled convergence
• Follow structured process
4
WAYS NOT TO DO SCREENING
•
•
•
•
•
Gut feel
Boss says, “Do it this way”
Single customer decides
One team member is strong champion
Influence of experienced designer
5
BETTER WAYS TO SCREEN CONCEPTS
• Multi-voting
– Each team member votes for several concepts. The
concept with the most votes is selected.
• Pros and cons
– The team lists the strengths and weaknesses of each
concepts. The group then selects the best concept
based on group opinion.
6
PREFERED Concept Selection Process
• Start with a Product Design Specification
• Examine ALL concepts at the same time
• Prototype and test
– Prototypes of each concept are built and tested and the
selection is made based upon the test data
• Decision matrices
– Unweighted
– Weighted
#1
#2
Criteria 1
++
+
0
--
--
Criteria 2
0
0
0
-
--
Criteria 3
-
0
0
0
0
Criteria 4
++
-
0
-
-
7
#3
#4
#5
Benefits of a Structured Method
for Concept Selection
• A customer-focused product
• A competitive design
• Better product-process coordination
• Reduced time to product introduction
• Effective group decision making
• Documentation of the decision process
8
2 Stages of Concept Selection
1. Concept screening
•
Reduce the many product concept ideas
generated to a relative few that will get
additional refinement and analysis
2. Concept scoring
•
Use objective methods to select to your
consensus final concept selection
9
Concept Screening
1. Prepare the selection/screening matrix
–
Selection criteria must relate to key customer needs
2. Rate the concepts
–
e.g., + = “better than”, 0 = “same as”, - = “worse than”
3. Rank the concepts
–
As objectively as possible using the concept rating
10
Concept Screening
4.
Combine and improve the concepts
–
–
Is there a generally good concept that is downgraded by
one feature?
Can two concepts be combined to preserve the “better
than” features while simultaneously removing any “worse
than” features?
5. Select one or more concepts for further
refinement and analysis
6. Reflect on the results and process
–
Are all team members “comfortable” with the decisions? If
not, what needs to be resolved?
11
Concept Screening Matrix Example
Exhibit 7-5
“Product Design and Development”
By Ulrich and Eppinger
12
Concept Scoring
1. Prepare the selection matrix
–
–
An optimized version of the concept screening matrix
Determine % weighting for each selection criteria
2. Rate the concepts
Page 135
“Product Design and Development”
By Ulrich and Eppinger
13
Concept Scoring
3. Rank the concepts
Page 136
“Product Design and Development”
By Ulrich and Eppinger
14
Concept Scoring
4. Combine and improve the concepts
5. Select one or more concepts for further
refinement and analysis
•
•
Sensitivity analysis
Build and test prototypes
6. Reflect on the results and process
•
Down-select to the consensus final concept selection
15
Concept Scoring Example
Sensitivity analysis on criteria
weighting may provide insight
Exhibit 7-7
“Product Design and Development
By Ulrich and Eppinger
16
Project Example:
Heated Veneer Press, Spring 2000
• Specifications taken from the product design specification
• If a specification does not differentiate one implementation
over another, remove it from the selection chart
• Limit specifications to 10 or less of the most important
• New specifications may arise associated with
manufacturability, etc. Add them to your PDS!
17
PDS (Abbreviated):
Veneer Press
Need #'s
Metric
Importance
Units
Marginal Value
Ideal Value
5
Surface flatness
5
mm/m
< 2.0
< 1.0
10
Cost
3
US $
< 800
400
4
Laminating
pressure
5
kPa
50-60
50-100
12
Pressure
variation over
panel surface
4
kPa
< 40
< 20
9
Duration of
pressure
application
3
hours
0-2
0-24
8
Set-up time
2
min
< 30
< 10
7
Loading time
3
minutes
< 10
<1
18
Concept Screening Matrix:
Veneer Press
Criteria
Roller
Clamp
Dead Weight
Vacuum
Surface flatness
-
0
0
-
Pressure variation
over panel
surface
-
0
0
0
Duration of
pressure
application
-
0
0
0
Loading time
-
+
0
-
Set-up time
+
+
0
-
Cost
+
0
0
-
Net score
-2
+2
0
-4
Rank
3
1
2
4
19
Concept Scoring Matrix:
Veneer Press
Weighting
Factor
Roller
Clamp
Dead Weight
Vacuum
Surface
flatness
25
2
5
5
2
Pressure
variation over
panel surface
20
2
5
5
4
Duration of
pressure
application
20
1
5
5
5
Loading time
15
3
5
4
3
Set-up time
10
5
4
4
3
Cost
10
5
3
4
2
Total score
100
255
470
465
325
4
1
2
3
Criteria
Rank
20
Concept Selection Exercise
• Review Evolving PDS
• Identify Specs to Include on Concept Selection
Charts
• If Time: Construct a Concept Screening Matrix
– Fill in w/ Top Concepts
(5 minutes)
21
AFTER SCREENING
• Do results make sense?
• Do you have client (advisor) buy-in ?
• Do you have to generate more concepts?
– Or combine elements from several concepts?
• Document the process
– ME4054: for Design Show and report
BOTTOM LINE: Have a structured
process for concept screening.
Document and defend your choices.
22
Commons Pitfalls in Concept Selection
•
•
•
•
•
•
•
•
•
Not doing it
Running with the first idea
Forgetting the customer
Selection chart criteria don't correspond to PDS
Letting an "experienced" designer make the choices
Going by gut feel
Letting a manager decide
Not buying into the process as a team
Ignoring cost
23
Congratulations!
IDENTIFY
OPPORTUNI
TY
GATHER
INFORMATIO
N
DEFINE
PROBLEM
GENERATE
CONCEPTS
SCREEN
CONCEPTS
IMPLEMENT
• You are now ready to implement a design solution
that addresses the customer’s needs (PDS).
• Implementation includes, but is not limited to:
–
–
–
–
–
Design and analysis
Fabrication of prototype(s)
Testing
Optimization
Documenting the design and design process
24
HANDOFF
25
Unweighted (Pugh) method
Cordless nailer
Battery
Pneumatic
Corded Electric
Int. Combustion
Setup
+
S
+
+
Operating
+
S
S
+
Weight
-
S
-
-
Manufacturing Cost
-
S
-
-
Time to Market
-
S
-
-
# of Pluses
2
0
1
2
# of Minuses
3
0
3
3
Keep?
Y
N
N
Y
Ease of Use
26
Weighted selection matrix
Cordless nailer
Wght
Ease of Use
Battery
Pneumatic
Corded Electric
Int. Combustion
40
Setup
20
5
1
2
4
Operating
20
4
2
2
3
Weight
30
2
4
3
2
Manufacturing Cost
20
3
4
3
2
Time to Market
20
3
4
3
3
360
340
290
300
1
2
4
3
Total Score
Rank
27
Lab kit: Hall-effect sensors are cheap, compact
and non-contact
Design Criteria
Cost
Accuracy
Size
Reads Position
Friction
Net Score
Servopot Hall Effect IR Encoder
0
+
+
0
0
0
0
+
+
0
0
0
+
+
0
3
2
Current setup uses a Potentiometer and two gears
$11.19
+
2*$4.31 = $19.81 Hall effect sensor
~$1 each
Source: Honeywell
International, Inc.
Source: Vishay
Intertechnology, Inc.
28
Rubber band is a good solution but non-ideality
leads to consideration of others
Tension
non- rotary
Rubber
spring wrapped spring Elastomer
s
Torsion
Selection Criteria
Band w/wrapping spring
linearity
0
+
+
0
ease of
installation
0
0
0
0
size
0
0
0
price
0
range of motion
0
0
longevity
0
+
+
+
+
Net Score
0
0
-3
0
-2
Tension spring w/wrapping
29
Rotary Springs
Source: Xiamen Shuangyuan Springs Co., Ltd
Air vane damping shows potential improvement
over Newton friction
Selection
Rotary
Criteria Friction Damper(oil) Fan
linearity
0
+ +
ease of
installation
0
0
size
0
Small B
0
- +
Net Score
0
-2
1
Deforming an
Elastomer
0
-3
Rotary Damper
Source: McMaster-Carr Online Catalog
30
Fan / Air Vane