quality function deployment1

7/31/2019 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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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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Comparison of plastic coating P1 (low viscosity) & P2 (high

viscosity) & its impact on smoothness index

Smoothnessindex

viscosity

P1 P2


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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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.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

quality function deployment1

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