21Oct13_QFD

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Quality Function Deployment (QFD)Quality Function Deployment (QFD)

Course on

“Systems Engineering”

for

CASDE, Aero. Dept., IIT Bombay

ostgra uate tu ents o

21st October, 2013

Defence Institute of Advanced Technology, Pune

8/13/2019 21Oct13_QFD


What is QFD?

Quality Function Deployment (QFD) is a planning tool

that has been adopted by many companies for satisfying

the customer requirements.

The term ‘deployment’ refers to the fact that the method

determines the important set of requirements that should


.

QFD also helps in identifying those technical

characteristics that help in meeting the identified

requirements.

In effect, QFD helps the system designer to prioritize the

various requirements to improve customer satisfaction.

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Concept of PrioritizationConcept of Prioritization

Following table demonstrates the prioritization task.


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Background of QFD

Quality Function Deployment (QFD) was developed in

Japan in the early 1970s, with its first large-scale

application in the Kobe shipyard of Mitsubishi Heavy

Industries.

It was rapidly adopted by the Japanese industry and by

mid-1980s, man US auto, defence and electronic


component industries were using QFD.

A recent survey of 150 US companies showed that 71% of

these have adopted QFD since 1990. Further, these

companies reported that 83% believed that using QFDhad increased the customer satisfaction. 76% felt that

QFD facilitated the rational design.

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QFD Elements and Structure

QFD is largely a graphical process that aids a design

team in systematically identifying all the elements that go

into the product development process.

It is a well structured methodology that forces the design

team to answer questions that might be glossed over and

brin s in the re uired amount of ri our into the overall


design process.

QFD also forces the design team to learn what it does not

know about the problem and also creates a high level of

‘buy-in’ and group understanding of the problem.

QFD can be used throughout the design process as well

as multiple levels of the design.

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Complete QFD process is schematically shown below.

QFD ProcessQFD Process


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We see that QFD elements are represented in the form of

‘houses’, which is a graphical representation of various

matrices (or tables) that capture the prioritization process.

The ‘house’ gets inputs from the customer requirements,

called attributes, which are then weighted based on their

QFD House of Quality (HOQ)QFD House of Quality (HOQ)


QFD method also forces the customer to rank the

requirements and help the design team to trade-off one

design approach against another.

It can be seen that through QFD, the ‘customer voice’ is

included at all stages of the system design.

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House of Quality (HOQ) Concept House of Quality (HOQ) Concept

QFD process involves constructing, one or more matrices,

first of which is often called ‘HOQ’, as shown below.


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Starting on the left side of the structure is theidentification of the customer needs and the ranking of

those needs in terms of their relative importance and

priority. (Whats)The top part of the HOQ identifies designer’s technical

response relative to attributes that must be incorporated

House OF Quality (HOQ) Description House OF Quality (HOQ) Description


into the design, in order to respond to the needs. (Hows)The centre part of the HOQ conveys the strength or the

impact of the proposed technical response on the

identified requirement.Lastly, the bottom part allows a comparison between

possible alternatives, while right side is used for planning.

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Another representation of HOQ is as shown below.

House of Quality (HOQ) Alternate Form House of Quality (HOQ) Alternate Form


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It is clear that all ‘rooms’ of the HOQ, arrangedhorizontally, pertain to the customer requirements, while

the ‘rooms’ arranged vertically pertain to the engineering

characteristics.

The HOQ shown previously uses eight ‘room’ format, in

‘ ’

Alternative HOQ Description Alternative HOQ Description


requirements to engineering characteristics.

‘Rooms’ 5, 7 and 8 perform the ranking and technical

assessment, leading to the target values that flow to the

next level of the design process.

HOQ is the most important document of the design.

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In general, not all design exercises need the constructionof all eight ‘rooms’ of the HOQ and basic translation of

CRs into ECs can be done using ‘rooms’ 1, 2 ,4 and 5.

Room – 1: Customer Requirements are listed by rows in

room 1, along with a column listing importance rating for

Process to Construct HOQ Process to Construct HOQ


Room – 2: Engineering Characteristics are listed by

columns in room 2, which can generally consist of

weight, force, velocity, power consumption and reliability.

Preferred symbols, ‘↑’ (higher to be better) or ‘↓’ (lower

to be better) are used for improvement direction.

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Room – 4: Relationship Matrix is at the centre of an HOQand is created by intersection of rows of CRs with

columns of ECs. Further, each cell in the matrix is marked

with a symbol to indicate strength of causal association. Itis computed by taking each EC and moving down the

column cells asking whether or not the EC will, fulfill CR.



Room – 5: Importance Ranking of ECs is carried out to

determine which ECs are of critical importance to satisfy

the CRs listed in ‘room’ 1. Those ECs with the highest

ratings are given special consideration. In general,absolute importance, relative importance and rank order

of ECs are used as additional discriminators.

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Given below is the schematic of the basic HOQ process.



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HOQ Construction Example HOQ Construction Example

A group of students is conducting a survey to improvethe design and usefulness of the standard CD storage

case. Following questionnaire is prepared for the survey.


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HOQ Construction Example HOQ Construction Example

Above survey results in the following responses, whichrepresent customer requirements (CRs) in this case.


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HOQ of the CD Case HOQ of the CD Case

Streamlined HOQ configuration of CD case example.


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Correlation Matrix of the CD caseCorrelation Matrix of the CD case

Given below is the applicable correlation matrix.


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HOQ HOQ With Competitor AssessmentWith Competitor Assessment

Data available from HOQ is augmented by adding resultsof any benchmarking activity carried out.


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There are a few features that, if present in HOQ, provideadditional information.

1. An empty row signals that no EC exists to meet the CR.

2. An empty column indicates an irrelevant EC.

3. A row without “strong relationship” highlights a CR

Important Features of HOQ Important Features of HOQ


t at w e cu t to ac eve.4. An EC column with too many relationships signals

that it is really a cost, reliability or safety item that must

always be considered, irrespective of its ranking.5. An HOQ displaying diagonal matrix signals that ECs

may not yet be expressed in proper terms.

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Overall QFD ApplicationOverall QFD Application

Overall application of QFD in SE is as shown below.


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Following aspects are a result of building the HOQ.

1. HOQ helps to identify ECs that are most important in

fulfilling the important CRs.

2. The highest ranking ECS are usually the constraints or

the design variables, whose values can be used as decision

Interpreting Results of HOQ Interpreting Results of HOQ


.

3. If a high ranking EC is the design variable that can

take many values (e.g. weight, power output etc.), it is a

good EC to use as metric to compare conceptual designs.

4. Lowest ranking ECs are not critical to the design and

can be used as the freedom features to trade-off.

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SummarySummary

Quality Function Deployment (QFD) is an extremelyimportant aid for prioritizing the customer requirements

and includin the customer’s voice into the desi n.


QFD also provides information about the importantengineering characteristics that should be on the

dashboard during the design process.

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