Quality Function Deployment1
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Transcript of Quality Function Deployment1
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Quality Function Deployment
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QFD
It is philosophy and a set of planning and
communication tools that focus on customer
requirements in coordinating the design,
manufacturing, & marketing of goods orservices
Developed by the Japanese in 1970
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Benefits of QFD
Better communication & team work among allconcerned with design of a product
Determines the causes of customerdissatisfaction
Comparative analysis of product quality by topmanagers
Simulates the effects of a new design idea /
concept Develops the product to satisfaction of the
customers; listens to the voice of the customer
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QFD- the House of Quality
QFD focuses on turning the customer
requirements into technical requirements that
characterize a design and provide the blue
print for manufacturing or delivering a service.
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Building a house of Quality-Steps
1. Identify the voice of the customer & technical
features of the design
2. The technical features must be expressed in the
language of the designer & engineer to form thebasis for subsequent design & manufacture
3. The roof of the House of Quality shows the inter
relationship between any pair of technicalfeatures to examine them collectively
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Building a house of Quality-Steps
4. Develop relationship matrix between the
customer requirements & technical features;
if a technical feature does not affect any
customer attribute; it may be redundant
5. Market evaluation & key selling point as
compared to existing competing products
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The House of Quality
.
Technical requirements
Relationship Matrix
Voice of
thecustomer
Inter-
relationship
Customer
Requirementpriorities
Competitive
evaluation
Technical requirement
priorities
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The House of Quality for a Pizza
price
size
amount-Cheese
Typeoftopping
amounto
ftopping
5
3
4
4
Customerimportance
5
3
4
4
4
3
3
3
4
4
3
5
Taste
Nutrition
Visual appeal
Good value
Our priority
Competitor-A
Competitor-B
Deployment
5 4 4 4 5
2 5 3 2 4
3 4 4 3 3
US A B
VERY STRONG RELATIONSHIP
STRONG RELATIONSHIP
WEAK RELATIONSHIP
Competitive evaluation
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The 4 houses of Quality Hierarchy
1. Customer requirements technical requirements
2. Technical requirements components
characteristics
3. Component characteristics process operations
4. Process operations Quality control plan
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Quality relationship matrix-screwdriver
Price
interchangeable
bits
Steelshaft
Rubbergrip
Ratchetcapability
Plastichandle
Easy to use
Does not rust
Durable
Comfortable
Versatile
Inexpensive
priority
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Quality relationship matrix exercise-screwdriver
Price
interchangeable
bits
Steelshaft
Rubbergrip
Ratchetcapability
Plastichandle
Easy to use
Does not rust
Durable
Comfortable
Versatile
Inexpensive
priority
Very strong relationship
Strong relationship
Weak relationship
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Taguchi method
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Taguchi concept of Quality
It combines engineering & statistical method
to reduce cost & improve quality. It optimizes
product design & manufacturing programme
Companies like ITT Corp. & AT&T have gained
substantially by using Taguchi methods to
improve the quality.
T hi f Q li
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Taguchi concept of Quality
Quality Loss function
More the deviation of the quality parameter
from the target value, poorer is the quality
function & higher the social cost.
Target value of product
attribute
Socialcost
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Taguchi method
Red process has more quality loss function
though both are confirming processes
Lowercontrollimit
Uppercontrollimit
Target value
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Quality loss function -example
Thin coating of plastic on a metal base; thequality parameter is the smoothness index ofcoating.
The process has the following choices
Plastic coating P1--- Having low viscosity
Plastic coating P2--- having high viscosity
Metal surface M1
Metal surface M2 Possible combinations areP1M1, P1M2, P2M1,
P2M2
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Quality loss function -example
The Taguchi method would prefer thatcombination that would give the least
variation in surface finish.
The experimental comparison of two of thecombinations are shown below
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Quality loss function -example
Comparison of plastic coating P1 (low viscosity) & P2 (high
viscosity) & its impact on smoothness index
Smoothnessindex
viscosity
P1 P2
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Quality loss function -example
Comparison of plastic coating P1 (low viscosity) & P2 (high
viscosity) & its impact on smoothness index
Smoothnessindex
viscosity
M1 M2
Metal quality
variation in M1&M2
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Quality loss function -example
.P2M1 is a better process as compared to P1M2
P2MI
P1M2
SURFACE FINISH
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Views on confirming process
Traditional view there is no loss
as long as parameters are within
the specified limits
Taguchi view- there is loss when
the parameter deviates from the
target value
0.48 0.50 0,52
loss loss
Target parameter
No loss
0.48 0.50 0,52
loss loss
No loss
US plant
Jap plant
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Quality loss function
L (x) = k (x-T) where L (x) = monetary value of loss due to variation from the
target value
X =actual value of parameter
T= target value of the parameter
K = constant to convert quality loss into $ value
T hi t f
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Taguchi concept of
Quality Loss function
.
T=Target value of product
attribute
K(x-T
)
X
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Quality loss function
Tolerance specification 0.500+ .O2, therefore
failure happens when actual dimensions are at
the extreme of the tolerance range i.e. 0.48 or
0.52 If x-T= 0.02, Then assume that cost of repair=$50
L(x) =$50 = k (.52 -.50) , therefore
k=50/.0004=125,000 If deviation from target is0.01, the quality
loss=125,000 x (0.01) =$12.5