17th
International QFD Symposium, ISQFD 2011 - Stuttgart
1
© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
Why we need matrices in QFD
Monika Thiess
Gaggenau Industrie S.A.S.
Lipsheim/Strassbourg
Gerd Streckfuß
Institut für Qualitätsmanagement
Dr. F.Weigang und Partner (IQM)
Dr.Walter Jahn (†)
SPQ
Leipzig
ABSTRACT
In this paper, we describe the need of using special matrices in QFD to achieve sustainability. These matrices inside of the
House of Quality (HoQ) were always criticized regarding the time consuming effort and the minimum of benefit in regard of
the results. But in the last decade, there is a revival of the QFD matrices. This paper will present the specific reasons for this
future trend and the prerequisites to handle the matrices inside QFD and discuss the results of several, selected projects.
KEYWORDS
QFD, House of Quality, Special Matrices, Optimization Direction, Conflicts and Contradictions, QFD and TRIZ, Mahalanobis-
Distance
1. INTRODUCTION When QFD was born, the House of Quality (HoQ), as a tool was an important integral part of using QFD. The HoQ was
derived from the “fish-bone” diagram, which was one of the most important “new 7 tools” to identify all potential factors
causing one effect. 1
Sometimes, the meaning of QFD was identical to the HoQ and reverse.
The negative impacts in using the House of Quality were discussed ever since it was published in the QFD Literature (Mazur
et.al). 2
Main items refer to:
The enormous time needed to handle large matrices
Wrong input in regard to Customer Requirements gives wrong output:
Garbage in = expensive garbage out
The results as outcome of the calculations with the relationship-figures were nontransparent, sometimes obscure.
The results did not get any acceptance in the R&D Departments. Engineering was more interested in getting valid
Customer Requirements (if there was already a customer orientation) and no technical solutions “produced by QFD”.
But talking to practiced customers, who are using QFD since more than a decade and our own experience, there is now a
revival in using Matrices and in the calculation of the results. New needs and requirements in a global development world are
reasons for this approach.
2. The Impact of using matrices.
2.1 Time consuming? Using QFD for a product with 5 Customer Requirements (CR) and 5 Technical Requirements (CTQ) gives a feasible Matrix
5 x 5 = 25. But there is no need to use QFD for this simple product.
17th
International QFD Symposium, ISQFD 2011 - Stuttgart
2
© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
E.g. in areas of high-end home appliances or medical healthcare equipments, these products have several hundred of
requirements and technical features. It is, of course, impossible to handle these large matrices. It was the impact of the Kano-
Chart, which allows an effective filter, to reduce the number of requirements, and in connection the number of CTQ’s. The
filter is very simple and easy to use:
Only these Requirements are listed for QFD:
They are: They are not:
1. New and 1. Already implemented
2. Important for Customers and 2. Basic requirements
3. Difficult for R&D 3. R&D says: “Easy…”
In most cases, it reduces the number of items between 30 to 80.
This gives still large matrices and would likely kill the QFD session. The solution is in separating the global group into “sub-
groups” of 3 people, each of the subgroup is handling a part of the matrix. Only the outcome will be discussed at the end
within the total group. (“Reading the Matrix, Sanity check”). E.g. given 50 CR and 25 CTQ’s and the total group of 15 People,
gives 250 relationship numbers for one subgroup.
The main reasons for extensive discussions in this timeframe are caused by the unanswered meanings and understandings
regarding customer requirements, which was skipped at the beginning of the QFD. And remember: It takes us 3 to 5 years to
develop these products, we should be able to find 2 – 4 days in this period….
2.2 The “positive” and “negative” relationships
In the past, we asked only, if there is any
relationship between a specific customer
Requirement and a Technical Feature. If yes, we
tried to rate, how much, with values 9, 3, 1.
The value of this information for the R&D was
too simply, because it was not a new expert
knowledge.
Adding the figures or calculating the product of a
matrix by a scalar was an misleading result.
The new approach (which was not a total new
one) was the appearance of TQM (Total Quality
Management) with the request, to add the
Improvement Direction (or: Optimization
direction)
Figure 1: Simplified relations
17th
International QFD Symposium, ISQFD 2011 - Stuttgart
3
© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
Figure 2: Relations with optimization direction
There are now three questions to evaluate the relationship values:
1. Are there any relationship between a specific customer Requirement and a Technical Feature?
2. If yes, how much (1,3,9)?
3. If we improve the technical requirement because of customer request:
a. Will it be a benefit for the customer (positive)?
b. Or will it be a conflict in the view of the customer (negative)?
Remark: The summary of the technical Feature (e.g. scalar product, Tensor) must be separated in a positive and negative
result. To combine both together (e.g. positive = 50, negative = -50, Result = 0) is useless and misleading.
2.3 The correlation-Matrix (“Roof of the House of Quality”)
Technical features are always more or less strong correlated among one another. The analysis gives two interesting results:
1. This one Technical feature has influence to all other Technical Features; measured by the correlation matrix.
2. All technical Features together have influence to this one Technical Feature; measured by the multiple correlation
coefficients
It is obvious, the optimization direction has an important influence within the correlation matrix.
Considering the optimization direction together in the relation-matrix and the correlation-matrix, it gives a total new picture
and is difficult to evaluate. But it answers the question: what happens, if we improve a product in the view of the customers’
requests.
17th
International QFD Symposium, ISQFD 2011 - Stuttgart
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© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
Figure 3: House of Quality with optimization direction
2.4 The House of Quality with optimization direction To solve the negative influences is not an easy task:
To leave just one strong negative relation, this could become a “killing item”, which prevents the customer to buy or
to recommend the whole product.
To change the optimization direction only moves the conflict from one relation to the other(s)
To compromise is always a way out to prevent new solutions.
To skip the Customer Requirement, which “causes” the conflict, means, we just “skip” the customer. Nevertheless, it
is one of the most misappropriated solutions. (Motto: The customer is always the central point in our business, that
the reason, why he always stands in our way….)
In all the QFD Sessions, we run in the last years, there was none one without negative relations in the matrix. Changing
Parameters have always a positive and negative impact. This is also valid for changing parameters in the direction of
improvement.
In the meantime, R&D (not the Marketing or Sales teams) is looking more than ever to find these conflicts from the very first as
to look after the positive numbers. But these dependencies could only be detected, analyzed and justified by using a matrix. A
single, linear deployment of just one Customer Requirement will not ensure the faultfinding’s.
17th
International QFD Symposium, ISQFD 2011 - Stuttgart
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© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
2.5 Detecting “Killing Items” We all know the exemplary cases, where single faults cause extreme cost and reputation. E.g. the product recalls in the
automotive industry. In practice, there are few negative relations, especially if only enhancements of a product are requested.
But it needs the QFD-House of Quality to detect these single ”killing items”, showcased in the picture below.
Case 1: It is apparently a negative relationship; the increase of speed of the shutter will cause an increasing noise. In practice,
very often these basic contradictions are overseen. But to know these contradictions at the beginning of the product
development is essential, because in most cases technical solutions could be found at this stage.
Case 2: More difficult are hidden contradictions. The Customer requires the turn down of the shutter, not only if a bright
sunshine is detected, also if a high temperature is measured. But in this case, also a fire inside of a house will close the shutter
and prevent the fire fighters to enter the rooms. This single feature - “killing item” -would definitely produce a recall or stop the
sales.
Also in products, which are well known in all aspects of development, simple changes causes contradictions, even though the
quantity is in general not high. Also Teams, adept very well in QFD, need the QFD Matrices to detect them. It is the human
behavior, that you will get after the detection of killing items comments like: “….if anybody has asked me before…”
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6 K1 K2 A B C D E F G H I J K + + +/- + + - - + + - - + + + + - - - + - + - + + + + + + - + - - + + + - # 40
7 G undbedürf nissProj.: symp11 167 139 133 115 115 110 86 75 73 71 70 65 63 62 59 59 56 55 55 54 53 53 50 42 39 38 32 30 22 16 11 6 3 3 0 0
8 S icherheitKunde: Benutzer 100,00 8 7 6 6 6 5 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 1 1 1 1 0 0 0 0 0
9 K KommunikationGruppe: -129 104 52 54 87 58 50 59 41 43 53 40 50 47 67 29 34 26 26 33 3 29 40 37 41 30 17 22 21 10 5 10 11 1 2 0 17 0 0 0 ENDE
10 P restigeModerator: 0 5 3 3 4 3 2 3 2 2 3 2 2 2 3 1 2 1 1 2 0 1 2 2 2 1 1 1 1 0 0 0 1 0 0 0 1 0 0 0
11 SW elbsverwirklichungDatum: nur heute schwacher Erfüllungsgrad 104 52 54 87 58 50 59 41 43 53 40 50 47 78 118 34 26 26 33 32 29 40 37 41 30 17 22 21 10 5 10 11 1 2 0 17 0 0 0
12 R eklamationVersion 1 0 0 0 0 0 0 0 0 0 0 0 0 0 -11 -89 0 0 0 0 -29 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
13
14
15 Mittelwerte: 2 6,9 # # # # 1,7 1,1 13,9 2,9 3
16 Nr. Customer needs M.C.GewHeuM.BM.RM.S Pla 303,5 62 100 einzelne 9, d.h. nur dieses Q-Merkmal als Einfluss-Faktor.Schwache Reihen=keine Q-Merkmale?schache, siguläre Spaltn=schwache Q-Merkmale aus Kundensicht (Kosten!)
171
tro tz Stromaus fa l l funk tions tüc htig
1 10 1 4 1 5 5,0 1,5 75,0 15,4 106 1 9 3 9 3 3 1 28
18 2 bei Däm m erung früher / s päter abs enk en / ö ffnen
1 8 1 3 2 5 5,0 1,5 60,0 12,3 119 2 3 9 3 1 16
19 3 bei hoher Innentem peratur Abs enk ung des Rol l ladens
1 8 1 1 1 5 5,0 1,2 48,0 9,9 131 3 3 3 9 -9 6
20 4 k le ine Abm aße
2 8 2 1 1 7 3,5 1,0 28,0 5,8 141 4 9 1 9 9 3 9 9 3 3 55
21 5 m ehrere Program m ierungs m ögl ic hk ei ten
2 5 1 3 3 3 3,0 1,2 18,0 3,7 146 5 9 3 9 -3 9 27
22 6 s ol l gewic hts unabhängig, bes tändig und g le ic hm äßig funk tion ieren
3 8 2 3 3 4 2,0 1,0 16,0 3,3 150 6 9 1 9 1 3 3 26
23 7 in k urz er Zei t Öffnen, Sc hl ießen
4 6 2 3 4 5 2,5 1,0 15,0 3,1 153 7 1 1 9 3 -9 3 8
24 8 z uv erläs s iger Betrieb
4 10 4 4 4 5 1,3 1,0 12,5 2,6 156 8 1 3 3 1 9 17
25 9 Zuv erläs s iger Kundendiens t
1 10 5 3 4 5 1,0 1,2 12,0 2,5 158 9 3 3
26 10 einfac he Ins ta l la tion
1 9 4 2 1 5 1,3 1,0 11,3 2,3 161 10 1 9 1 3 3 1 18
27 11 geringer Strom v erbrauc h
2 9 4 3 1 4 1,0 1,2 10,8 2,2 163 11 9 9 3 3 3 9 1 37
28 12 m ehrere Geräte m i t e inem Bediente i l
1 7 5 1 1 5 1,0 1,5 10,5 2,2 165 12 3 1 1 3 1 9
29 13 Gerät s o l l le is e s e in be i Betrieb
2 10 4 1 1 4 1,0 1,0 10,0 2,1 167 13 1 3 1 9 3 17
30 14 bei s tark er Sonneneins trah lung abs enk ung des Rol l ladens
1 8 4 5 3 5 1,3 1,0 10,0 2,1 169 14 3 9 3 9 24
31 15 s elbs terk lärend
3 8 4 2 3 5 1,3 1,0 10,0 2,1 171 15 1 9 9 19
32 16 einfac he Program m ierung
3 10 5 1 2 5 1,0 1,0 10,0 2,1 173 16 9 3 1 9 22
33 17 geeignet für a l le gängigen Gurtbre i ten
5 10 4 5 5 4 1,0 1,0 10,0 2,1 175 17 9 3 3 15
34 18 Wartungs arm
5 10 5 5 5 5 1,0 1,0 10,0 2,1 177 18 3 1 9 9 9 1 32
35 19 Bi l l ig in der Ans c haffung
4 8 5 1 2 5 1,0 1,2 9,6 2,0 179 19 3 9 3 15
36 20 öffnen / s c h l ießen durc h Handz ug s o l l noc h m ögl ic h s e in
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37 21 Aus s perrs ic herung
1 6 3 5 1 4 1,3 1,2 9,6 2,0 183 21 9 9 18
38 22 orts unabhängige Bedienung, Steuerung
1 6 4 1 1 4 1,0 1,5 9,0 1,9 185 22 3 1 3 9 16
39 23 einfac he Bedienung
4 9 5 4 4 5 1,0 1,0 9,0 1,9 187 23 3 3 1 9 1 17
40 24 v ers tändl ic her Aufbau
2 9 4 2 2 4 1,0 1,0 9,0 1,9 189 24 1 1 2
41 25 Kinders ic her
1 8 4 4 1 3 0,8 1,5 9,0 1,9 190 25 3 3 9 9 3 1 28
42 26 einac heTec hnik
3 6 3 2 3 4 1,3 1,0 8,0 1,6 192 26 1 1 1 1 3 7
43 27 Gerät s o l l unabhängig v on der Gurtlänge funk tion ieren
1 8 5 1 1 3 0,6 1,5 7,2 1,5 193 27 9 9 3 21
44 28 Eink lem m s c hutz
2 8 4 4 1 3 0,8 1,2 7,2 1,5 195 28 3 9 9 21
45 29 s ol l große Gewic hte bewegen k önnen
3 6 4 3 3 4 1,0 1,0 6,0 1,2 196 29 9 1 3 9 -1 9 3 33
46 30s c höne Form 1 4 4 3 3 4 1,0 1,2 4,8 1,0 197 30 3 1 9 1 9 23
47 31 unauffä l l iges Aus s ehen
1 2 2 2 3 4 2,0 1,0 4,0 0,8 198 31 3 9 3 15
48 32 große Speic herk apaz i tä t
1 1 1 4 2 2 2,0 1,2 2,4 0,5 199 32 9 3 3 3 9 27
49 33 le ic ht z u re in igen
4 2 5 2 3 5 1,0 1,0 2,0 0,4 199 33 3 1 1 3 3 9 9 3 1 33
50 34 s ol l optis c h in d ie Wohnung pas s en
1 1 3 3 3 5 1,7 1,2 2,0 0,4 199 34 1 1 9 3 14
51 35Längere Betriebs z ei ten m ögl ic h 2 1 3 1 3 3 1,0 1,0 1,0 0,2 200 35 1 9 3 13
- 9
- 9
Fire control access (Case 2)
Low noise required (Case 1)
Actin
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Figure 4: Single “killing items” (shutter)
17th
International QFD Symposium, ISQFD 2011 - Stuttgart
6
© 2011 QFD Institut Deutschland e.V. © Thiess, Streckfuß, Jahn
Figure 5: “Only” six contradictions in a product improvement, but likely killing the product.
To find out the various relationships between Customer Requirements and Features respectively Functions and the correlations
between the Features (Quality Features, CTQ’s) are important on new, innovated products. In an extreme situation, the result of
a QFD could lead to a stop of these developments. The following charts are demonstrating the various QFD results of an new
inventive product development, which was after the QFD sessions reappraised as too difficult to continue without making
major changes.
2.5.1 Results of a relationship matrix
Positive and negative weight Quality Features
-100
-50
0
50
100
150
200
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Cu
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K2 A B C D E F G H I J K 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Project: New Optim.direction: - + - + + + + + + + + + + + + + + + + + + + + + + + - + +Company: F fix (Target) Cost:
Team: 1829 -7 27 28 50 -27 113 95 84 92 127 179 63 39 130 72,8 -22 0 8,8 177 114 91 168 49 106 3,86845 40,205 26,8 0,1426 0
100 0 1 2 3 -1 6 5 5 5 7 10 3 2 7 4 -1 0 0 10 6 5 9 3 6 0 2 1 0 0Facilitator: G.Streckfuss/IQM 21 20 17 27 6 43 49 44 32 48 61 41 24 63 46 4 0 15 69 58 43 64 25 39 25 27 33 34 0
Date: -20 -7 -7 -4 -16 -4 -4 -6 -3 -1 0 -5 -6 -1 -11 -13 0 -3 -6 0 0 0 0 -1 -23 -20 -12 -37 0
Version: 4.0 (GS) Technical Difficulties (10-1)
Spezification: HOW MUCH
5,9 2,5 1,9 2,5 2,3 3,3 1,4 1,1 9,0 2,6
V K M WF Pot. Nr.
Customer Requirements and
Needs (CR)Gew Heu M.A M.B. Test Pla 54 42,2 350,7 100 Nr
1,9 3,2 2,1 12,7 3,3 No Environment 7 3 3 1,0 1,0 7,0 2,0 2 1
5 3 1 15 3 1
My appliance is not wasting energy, I save energy 8 4 2 4 5 5 1,3 1,2 12,0 3,4 5 2 9 9 -1 -3 -1 -1 -3 9 -1 -3 -3 -1 3 1 -9 -3 -9
2 3 1 6 2 2
I own a "green cooler" / "green freezer", I protect the environment , I save energy, I can
easily sell the product, I set myself apart from the "others", I am interesting, I save money, I
got a good feeling, my appliance matches to the kitchen5 3 2 3 2 3 1,0 1,0 5,0 1,4 7 3 9 9 -1 -1 1 1 3 1 -3 -3 3 1 3 3 1 -1 -1
4 4 1 16 1 3I may use the waste heat of my appliance, I save time, I save energy, I protect the
environment, I am able to concentrate on more important things, nothing is constraining me,
I'm a gourmet4 2 2 2 1 2 1,0 1,2 4,8 1,4 8 4 1 1 1 9
0 4 Comfort 7 3 3 0,0 1,0 0,0 0,0 8 5
1 3 3 9 4 5 My appliance is silent, I am not negatively experiencing my appliance 7 3 2 3 5 4 1,3 1,0 9,3 2,7 11 6 9 -1 -1 -3 -3 -3 -1 1 -1 -1 -1
1 4 3 12 2 6My appliance sounds valuable while opening or shutting, I like my kitchen, It's fun, my
kitchen is reliable , in my kitchen everything works the same way, I can easily sell this
product6 3 2 4 1 4 1,3 1,0 8,0 2,3 13 7 1 9 1
1 4 4 16 4 7My appliance seems to be quite valuable while using, I got a good feeling, I am not
negatively experiencing my kitchen, everything is running smoothly , there are no stops in
the workflow, I got optimal ergonomics6 2 2 3 1 3 1,5 1,2 10,8 3,1 16 8 3 3 1 3 3 3 3 9 9 9 9 9 3 1 3 3 1
3 3 2 18 2 8
My appliance is abacterial, my live is convenient, I save time, cleaning activities will be
decreased , I feel good in my kitchen 1 3 3 1 5 3 1,0 1,2 1,2 0,3 17 9 3 3 9 3 -9 9
3 4 1 12 4 9
Easy to clean (Selfcleaning) 7 3 3 2 5 4 1,3 1,0 9,3 2,7 19 10 1 -1 -3 -3 -1 3 9 3 9 3 -3 -9 9 -3
1 4 4 16 10 My appliance seems to be very valuable, everything is running smoothly 6 2 3 3 1 3 1,5 1,2 10,8 3,1 22 11 3 3 1 3 3 3 3 9 9 9 9 9 9 3 3
2 5 4 40 4 11
I would like to have a "multimedia" kitchen, I don' t need to search things, everything is
running smoothly, nothing is constraining me, I may design my kitchen according to my
needs, I set myself apart from the "others", I may live in my kitchen , I may do different things
in my kitchen
5 1 1 1 1 3 3,0 1,5 22,5 6,4 29 12 -1 -1 -1 1 1 1 1 3 3 3 3 3 9
2 4 3 24 1 12I know what I need to buy, I love to be a perfect host, I save time, I am not negatively
experiencing my kitchen, I am always prepared , everything is running smoothly, I protect the
environment5 1 1 1 1 3 3,0 1,2 18,0 5,1 34 13 1 9 3 1 3 9 3 3
3 3 1 9 3 13My appliance has got enough space, space in the appliance is optimally used , my
appliance fits my requirements, I may store as much as I want, I am always prepared 7 4 2 4 5 4 1,0 1,0 7,0 2,0 36 14 -1 -1 -1 9 9 1 1 3 3 -1 -1
0 14 Cooling 6 3 3 1,0 1,0 6,0 1,7 38 15
1 1 1 1 2 15In my fridge there are various cool drinks all the time, I don' t need to search goods, I am
prepared, I save time, there are no stops in the workflow, I am a perfect host , I protect the
environment6 3 2 3 3 3 1,0 1,0 6,0 1,7 39 16 -1 1 1 3 -1 1 9 9 9 1 1 1 3 1
2 3 1 6 4 16I've got enough ice cubes any time, I am a perfect host , my love to visit me, I am always
prepared, I save time, I don't have negative experiences in my kitchen 5 2 2 2 1 3 1,5 1,0 7,5 2,1 41 17 -3 -3 -1 -1 -1 1 3 9 1 9 1
1 1 1 1 4 17It's not smelly when I open my appliance, I don' t have to expect something negative, I need
less cleaning my appliance, I cannot smell my appliance 6 2 2 2 1 3 1,5 1,0 9,0 2,6 44 18 9 -1 3 3 1 1 9
2 4 1 8 4 18I am able to store my bread for long times whithout freezing, I don't have to expect
something negative, I may optimize my shopping , nothing is constraining me, I protect the
environment7 2 1 2 1 3 1,5 1,0 10,5 3,0 47 19 -1 -1 -1 3 1 3 -3
2 3 1 6 2 19
My stored glass bottles are always cool, I am well prepared, I don't have negative
experiences, I love to be a perfect host , my friends love to visit me, I may concentrate on
more important tasks5 2 3 2 1 3 1,5 1,0 7,5 2,1 49 20 -9 -1 -1 -1 1 1 -3 3 9 3 3
4 1 1 4 3 20I may optimally cool my goods, I may optimally store my goods, I save time, I don't need to
search my goods , I'm well organized 6 4 3 4 5 4 1,0 1,0 6,0 1,7 51 21 -3 -1 -1 -1 -1 3 -1 9 9 9 9 1 9
2 3 1 6 1 21my drinks could be stored longer after opening, I am not experiencing my appliance
negatively, I may optimize my shopping 5 1 1 1 1 2 2,0 1,0 10,0 2,9 54 22 1 -1 9
0 22 Ergonomics 6 3 3 1,0 1,0 6,0 1,7 55 23
1 4 4 16 5 23I am able to easily pull out my interior elements, I like my kitchen, I am not experiencing my
appliance negatively, everything is running smoothly , there are no stops in the workflow, I
got optimal ergonomics6 4 2 4 3 4 1,0 1,2 7,2 2,1 57 24 -1 -1 9 -1 -1 3 9 -3 -1
2 4 5 40 4 24I may individually adapt my appliance, I am well prepared, I may optimize my shopping, my
goods are optimally stored, my fridge is variable 6 2 2 2 3 2 1,0 1,5 9,0 2,6 60 25 1 -1 3 9 9 1 3 9 1 1 -3
1 3 1 3 3 25It's easy to open bottles without any help, I don' t need to search things, my kitchen is tidy,
everything is running smoothly, I am not experiencing my appliance negatively, my
appliance supports me in daily live5 1 1 1 1 2 2,0 1,0 10,0 2,9 63 26 1 3 -3
2 3 1 6 4 26I may enlarge my compartments on if required, I am always prepared, my kitchen is tidy, I
may optimize my shopping, I am optimally using my appliance's space , I may buy what and
as much as I want6 2 2 2 5 3 1,5 1,0 9,0 2,6 65 27 1 1 3 9 9 1 -3
1 5 4 20 4 27I'm able to open my appliance's doors with little effort, it has optimal ergonomics , I like it
very comfortable , my appliance supports my daily life 7 2 2 2 3 4 2,0 1,2 16,8 4,8 70 28 -1 3 9 -1
1 4 4 16 5 28I'm able to close my appliance's doors with little effort, it has optimal ergonomics , I like it
very comfortable , my appliance supports my daily life 7 2 2 3 3 4 2,0 1,2 16,8 4,8 75 29 -1 9 9 -1
0 29 Light 5 3 3 1,0 1,0 5,0 1,4 76 30
1 4 3 12 5 30My fridge is enjoyably illuminated, I may show what's inside my fridge, I like my goods
looking nice, I love to open my fridge , I feel good in my kitchen 7 2 2 3 5 4 2,0 1,2 16,8 4,8 81 31 -1 1 9 9 9 9
1 4 4 16 1 31my fridge/freezer is a "Highlight" in the kitchen, my kitchen is transparent, the appliance
matches to my kitchen , I feel good in my kitchen, my kitchen astonishes my guests 5 3 1 4 1 4 1,3 1,2 8,0 2,3 84 32 1 1 1 3 1 9 9 9 3 3 3 1 9 3 9 3 3 3 3 1 9
0 32 Sales/Service 7 3 3 1,0 1,0 7,0 2,0 86 33
1 1 1 1 5 33
It's all BSH appliances , It fits to the other family 4 2 2 1 1 2 1,0 1,0 4,0 1,1 87 34 1 1 1 -1 1 3 3 3 9 3 3 3 3
4 3 1 12 3 34
I may easily mount the panel, Quick and easy installation , my installation team will be
happier, I can easily replace old products, it is simplifying my working life 7 3 2 3 1 4 1,3 1,0 9,3 2,7 89 35 -3 3 -9
4 3 1 12 4 35
All necessary fixing parts are already pre-mounted, I save time, I can save installation costs,
quick and easy installation , my installation team will be happier, I can easily sell this product,
I can easily replace old products, 7 2 1 2 1 4 2,0 1,0 14,0 4,0 93 36 -1 -1 -3 -3
1 1 2 2 4 36Door panel may be safely mounted, my appliance fits me, I have a nice kitchen , I feel good
in my kitchen, my installation team will be happier, I can easily sell this product 7 4 3 4 1 4 1,0 1,0 7,0 2,0 95 37
1 3 1 3 2 37The doors (thickness=25mm) may be openend without problems, my appliance fits me, I
like my kitchen, my installation team will be happier , I can easily sell this product 6 2 2 2 1 3 1,5 1,0 9,0 2,6 98 38 1 -3
1 3 1 3 5 38 Heavy front panel (30 kg) could be adapted 5 2 1 2 1 3 1,5 1,0 7,5 2,1 100 39 -3
0 39 40
41
42
Su
m:
Weight
Rel. weight (%)
Positive weight
Negativ e weight
Considerable number of negative relationships, also on important customer requirements.
negative
positive
Positive and negative weight: Quality-features from customer view
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Figures 6: Results of the relationship matrix (new innovative product)
2.5.2 Results of the correlation matrix (“roof”)
Figure 7: Results of the “roof” of the House of Quality (new innovative product):
negative
The change (Optimization) of one Quality Feature influences all other Quality
Features
-30
-20
-10
0
10
20
30
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
positive
e.g. Many Quality features with less customer importance but extreme technical difficulties. This causes a cost problem. Customer pays for "importance", not for technical difficulties.
negative
It is an advantage, that the most important Quality Features
(customer view) have many positive correlations to the other
Quality Features, except “increasing speed”
(except one (the increasing speed))
There are many conflicts between the Quality Features. It shows
the need of additional, inventive solutions. negative
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2.6 QFD Matrices in concept selections
2.7 QFD and TRIZ
QFD was originally not qualified to generate inventive solutions; the focus was on the deployment of customer requirements.
TRIZ on the other hand concentrates on finding new ideas to solve contradictions.
Concept_1 Concept_2 Concept_3 Concept_4 Concept_5 Concept_6
QFD House
of Quality III
V6.0 XLM
Interpretation
Concepts
Cu
sto
me
r F
ee
lin
gs
Imp
ort
an
ce
10
-1
Cu
rre
nt
Sta
tus
1
- 5
V
5 -
1
E
5 -
1
Pla
nn
ed
Sta
tus
1 -
5
Imp
rove
me
nt
E/B
Sa
les P
oin
ts
1,
1.2
, 1
.5
Imp
ort
an
ce
We
igh
t
A*F
*G
Re
lati
ve
We
igh
t (%
)
Re
l. W
eig
htt
(%
) P
are
to
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
Typ
e o
f M
otio
ns
Patie
nt p
ositi
on
ing
Siz
e/S
hap
e/ F
orm
A B C D E F G H I JProj.: Table Optim.Direction
Cust: Cost $Weight QF 0 4084 370 238 353 215 292 288 328 225 290 -29 -20 1 241 250 142 292 403 205 0
Team: Rel. Weight(%): 84 8 5 7 4 6 6 7 5 6 -1 0 0 5 5 3 6 8 4 0
Moderator: G.Streckfuss (IQM) Positive Weight: 370 248 353 388 411 337 328 240 290 166 65 27 241 250 142 324 403 237 0
Date: Negative Weight: 0 -11 0 -173 -118 -49 0 -16 0 -195 -85 -26 0 0 0 -32 0 -32 0
Version 1 Technical Difficulties(10-1)Techn.Spezification:HOW MUCH
Average 6,0 2,3 3,3 2,5 3,8 2,4 1,0 17,5 7,7
Maslo
w
Customer Requirements (CR) W
eig
ht
today
Varian
Ele
kta
Pla
nned S
tatu
s 5
-1
Impro
v.
SP
227,4
100
Re
latio
ns
1 1 1 1,0
1,0
1,0
0,4 0 1
1 Relative Patient Positioning (Isocenter Management) 12 8 1 1 1 5 5,0 1,1 44,0 19,3 20 1 10 1 3 9 9 3 3 9 9
1 Machine can support high patient load for lifetime of machine 2 9 1 4 4 4,0 1,2 43,2 19,0 39 1 55 3 9 3 1 1 3 1
4 Have a interchangable pallet for CT, ... And treatment 48 8 1 4 1 4 4,0 1,1 35,2 15,5 541 18 9 9 9 -9 -3 -3 9 9 9 -9 -1 -1 3 3 3 9 9 9
2 Collision avoidance 8 6 1 1 1 4 4,0 1,1 26,4 11,6 66 1 67 3 9 9 9 -1 1 3
3 Integrated controls 3 6 1 4 1 4 4,0 1,0 24,0 10,6 76 1 39 9 9 -1 9 1 1 9 9 -1 3 3 -3 -3
4 The table top should be radiotranslucent 36 8 2 4 4 2,0 1,1 17,6 7,7 841 21 3 9 -3 -9 1 3 -3 -9 3 3 9 9
1 Easy and fast mounting accessories must be possible 4 7 3 3 4? 4 1,3 1,0 9,3 4,1 88 1 43 1 -1 9 1 9 1 -3 3 -3 3 9 9 1 9
2 No workers comp 2 8 3 3 1,0 1,0 8,0 3,5 92 1 50 1 -1 9 1 3 9 3 -1 9 9 1 3 3 3 3
2 No obstruction to Pt transfer devices eg. Stretcher 2 5 3 2 3 4 1,3 1,0 6,7 2,9 95 1 28 1 -1 9 9 9 9 3 3 -3 3 1 3 9 9
1 Surface easy to clean 1 6 4 4 4 4 1,0 1,0 6,0 2,6 97 1 22 9 -1 1 1 3 9
1 High flexibility to position the table 4 5 5 5 5 5 1,0 1,0 5,0 2,2 100 1 9 3 9 9 -1 9 9 9 3 9 3 9 9
1 Avoid destruction of the table due to earthquarks 1 1 4 4 4 4 1,0 1,0 1,0 0,4 100 1 56 9 1 9 1 3 1
Conclusion
Only 6, but
important
requirements
(red) are the
major
differentiators to
concepts
Significant
differences Frame
Co
nc
ep
t-F
ea
ture
s
Concepts:
frame
-300
-200
-100
0
100
200
300
400
500
Concept_1 Concept_2 Concept_3 Concept_4 Concept_5 Concept_6
Solutions for killing items (-9):
Try to convert (move) the "+9"
solutions from other concepts to
solve "-9" conflicts. This will
assure the most clever product in
regard to customer requirements.
Concepts after using solutions from other concepts
-100
0
100
200
300
400
500
600
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
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Only new, innovative solutions can solve these contradictions. This was one of the reasons, why TRIZ was successful adapted
in the QFD community. TRIZ asks for an “input” of conflicts and contradictions and promises to support the findings of
inventive solutions by using a systematic workflow. QFD Matrices deliver this input.
2.7.1 Analyzing TRIZ results
TRIZ has 3 Levels of contradictions (Altshuller) . 4:
Level 1: Administrative, e.g. between needs and solutions
Level 2: Conflicts (“technical contradiction”), inverse correlation between technical features.
Level 3: Contradictions (“physical contradiction”), contradictory optimization direction of one requirement.
Altshuller has proven the fact, that Conflicts (Level 2) are derived from Contradictions (Level 3). This implies, that the
inventive solution is embedded in contradictions.
Considering these arguments, it demonstrates the contrary way of the common way of engineering: We try to solve the
conflicts between technical features first (Level 2), and than, we discuss the impact on customer needs.
But it is the customer(!), who gives us the level 3 contradictions! It is the customer, who requires inventive ideas.
2.7.2 TRIZ tools in the QFD process
The method TRIZ includes numerous tools, which are very different in regard of effort, knowledge and cases of application. If
conflicts between technical features are relevant to customer requirements, than the first step is using the conflict Matrix with
Figure 8: Various links between
QFD and TRIZ 3 4
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the attached inventive principles (Altshuller, Matrix 2003). Also, this matrix is debatable among the TRIZ-Guru’s, it is our
experience that the matrix is able to deliver on the spot the first signs of new ideas, which are worth to follow up.
To solve the contradiction of one technical feature (Customer request low weight because of… and high weight because of…)
is not an easy task. TRIZ recommends using the 4 (or 6) principles in separation (in time, in space, in parts/whole, in
conditions). Practical experience realized in these cases also the need for additional TRIZ tools to address inventive solutions.
Common tools are here the Function Analysis, the Su-Field Analysis and the Anticipating Fault Determination)
3. The QFD-Q-Plan and the Mahalanobis-Distance To manage customer requirements (CR) in the QFD Process is still a never-ending story. Also QFD is in charge to deploy CR
in the various R&D and Engineering processes, it still requires, to ensure the quality of CR. Wrong input in QFD guarantees
well structured and expensive, but still wrong output.
Based on the Q-Plan structure, published in Akaos QFD book (1988/1992), QFD teams used these templates to analyze CR.
The row “importance” was availed oneself of an opportunity to discuss the meaning and understanding of CR than for rating
issues. The row “Current Status ” is one of the aching tasks, because it is often the result of: “We already fulfill these
requirements”.
Today, nearly all companies using regularly QFD modified and improved the Q-Plan to address their specific needs. They
added additional rows, common are “Value for the customer”, “Kano” and “Needs based on Maslow’s Theory”. These
different rows allow us, to discuss and rate the CR under different perspectives.
Figure 9: Extended QFD Q-Plan Matrix
This gives us a picture of a matrix (pattern), which could be analyzed. The focus is more on identifying the discrepancy
between the different values and not to calculate detailed numbers. Our first Goal is to understand and accept the customer
requirements.
Va
lue
Ka
no
Ma
slo
w
WF
=V
+K
+M
Po
ten
tia
l "Sanity Check" of the QFD
Q-Plan Matrix (extract)1
0 t
o 1
5 to
1
5 to
1
5 to
1
5 to
1
5 to
1
Imp
rove
me
nt
Sa
les F
acto
r
We
igh
t
rel. W
eig
ht
Pa
reto
avr. 2,3 3,7 2,3Remark: the text and the figures are slightly modified compared to the
original input 6,6 2,2 2,0 2,6 2,8 3,6 1,9 1,1 13,1 4,1
V K M WF P Customer Requirements and Needs Imp.Cur.M.A M.B. Test Pla 13,3 157,5 50
2 5 4 11 4 I like to have a "multimedia" environment 4 1 1 1 1 3 3,0 1,5 18,0 5,7 6
2 4 3 9 1 I know what I need to buy 5 1 4 5 5 3 3,0 1,2 18,0 5,7 11
1,0 5 4 10 4
To open and closing the cover with little effort, it has
optimal ergonomics8 2 2 2 3 4 2,0 1,2 19,2 6,1 17
1,0 4 3 8 5 The enviroment is enjoyably illuminated 9 2 2 3 5 4 2,0 1,0 18,0 5,7 23
4 2 1 7 4 All necessary fixing parts are already set-up 7 2 1 2 1 4 2,0 1,0 14,0 4,4 28
5 3 1 9 3 The environment is not wasting energy, I save energy 8 4 2 4 5 5 1,3 1,2 12,0 3,8 31
1,0 4 4 9 The environment seems to be very valuable 7 2 3 3 1 3 1,5 1,2 12,6 4,0 35
2 4 1 7 4 To store my food for long times whithout freezing 6 2 1 2 1 3 1,5 1,0 9,0 2,8 38
2 3 1 6 1 The drinks could be stored longer after opening 5 1 1 1 1 2 2,0 1,0 10,0 3,2 41
1,0 3 3 7 4 The enviroment is s ilent, the sound is pleasant 9 3 2 3 5 4 1,3 1,0 12,0 3,8 45
3 4 1 8 4 I want to see a selfcleaning enviroment 7 3 3 2 5 4 1,3 1,0 9,3 2,9 48
4 3 1 8 3 I may easily mount the cover 4 3 2 3 1 4 1,3 1,0 5,3 1,7 50
5 = high, 1= low
no customer value, means: Customer will not spend any money for it. Question: why is this importance high rated, if Value is low?
Question: why is importance low rated, if WF is high?
High value, but no excitement, no prestige issue? and there is challenge for improvement
Question: why is this importance low rated,
if competition is high rated?
Question: hight rated, also current status OK?
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3.1 The Mahalanobis Distance But the research of various examples demonstrated very clear, that the pattern in the QFD-Q-Plan are NOT independent, there
are correlations between these values. We used the Mahalanobis Metric to verify the differences.
Figure 10: Different results using Linear Ratio, T-square and Mahalanobis
The chart above shows the different results, using QFD linear ratio, Statistic Hotellings (T-square) and the Mahalanobis
Distance. Mahalanobis and Hotelling are very close in regard to the results, but the QFD linear average values are considerable
different.
In statistics, Mahalanobis distance is a distance
measure introduced by P. C. Mahalanobis in
1936. It is based on correlations between
variables by which different patterns can be
identified and analyzed. It is a useful way of
determining similarity of an unknown sample set
to a known one. It differs from Euclidean
distance in that it takes into account the
correlations of the data set and is scale-
invariant. In other words, it is a multivariate
effect size….
Mahalanobis distance is widely used in cluster
analysis and classification techniques. It is
closely related to Hotelling's T-square
distribution used for multivariate statistical
testing and Fisher's Linear Discriminant
Analysis that is used for supervised
classification.
Source and more information’s in: Wikipedia.org
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The different results are caused by the fact, that the figures: “Value (V)”,
“Kano(K)”, “Maslow(M)” are NOT independent. The Correlation-Matrix shows,
that between “Kano” and “Maslow”, it exist a high rated positive correlation. But
“Value” has no correlation to “Kano” and even a negative correlation to
“Maslow”.
Pattern: Linear Ratio's to Mahalobis Distance
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Multiplication
Addition
Mahalanobis Distance
Figure 11: QFD-Q-Plan Pattern: Findings from the comparison
The addition of numbers is more close to the Mahalanobis distance compared to the multiplication.
The conclusion today is:
The patterns in the QFD-Q-Plan are not independent.
To multiply the numbers as a final result is critical.
But further research is required, to underline this predication and to understand the different results in practice.
4. Summary
1. Product development faces increasing demands on management and employees to fulfill different challenges:
Customers are today more critical in demanding fulfillment of their specific requirements.
Marketing must be positioned in a global world; product development is today a global task.
The number of CR’s and CTQ’s are growing because of the increasing complexity of products.
Very few faults and/or misunderstanding regarding customer needs could lead to unforeseeable major problems.
2. Product development is confronted with numerous multi-dependences.
It requires more multivariate methods, adapted to the needs of QFD.
Correlationmatrix V K M V 1.000 0.052 -0.208 K 0.052 1.000 0.467 M -0.208 0.467 1.000
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3. QFD has to address these challenges to remain sustainable:
We accept, it is the Customer who gives us the input in QFD as a human being and not as linear equation.
Therefore, it is more important to understand and accept the customer needs as to use intransparent math methods.
4. The House of Quality with the different tables, pattern and matrices is the link between understanding customer needs
and point out the various dependencies.
5. R&D is more looking to find conflicts and contradictions in the early stage of development. This saves time and
money.
In QFD, only the relationships and correlations in matrices are capable to do this.
6. Because of the increasing complexity of the today products, it is necessary to find ways to handle large matrices.
Matrices are images, illustrating the “Quality” of a product in the view of a customer. Therefore, we should more
read these images and as to calculate the figures.
7. Last, but not the least, Marketing and R&D are the customer of QFD. Therefore, QFD has to fulfill their requirements
(and not reverse) to guarantee its sustainable future.
5. REFERENCES [1] Akao, Yoyi (1992) QFD, Wie Japaner Kundenwünsche in Qualitätsprodukte umsetzen. Verlag Moderne Industrie.
[2] Mazur, Glenn (www.mazur.net), Modern Blitz QFD ® (no matrix).
[3] Saatweber, Jutta (2007), Kundenorientierung durch Quality Function Deployment, Symposium Publishing GmbH.
[4] Gundlach, Carsten, Nähler, Horst (Hrsg.) (2006) Innovationen mit TRIZ, Symposium Publishing GmbH
BIOGRAPHIES OF THE AUTHORS
Dipl.Ing. Monika Thiess
Monika Thiess is Senior Project Manager, responsible for global R&D projects at Gaggenau Industrie in Lipsheim near
Strasbourg/France. Since 1999, she is also responsible for the introduction of Quality methods in product development, process
optimization, standardization, R&D processes, also qualified as DGQ- and internal auditor. Since 2007, Monika Thiess is
certified as QFD Moderator and since 2009 Certified QFD Architect according to the QFD-Institute Germany e. V.
Gerd Streckfuß
Gerd Streckfuß is today Partner at the "Institut für Qualitätsmanagement, Dr.Weigang + Partner".. He had assignments at
Schlumberger Technologies, CAD/CAM Division as Technical Manager in Germany and Business Development Manager
Europe, responsible for the introduction of TQM in the European operations including QFD. He is also member at the QFD
Institute Deutschland e.V. and qualified as Certified QFD Architect conferred by the QFD-Institute Germany e. V.
Dr.rer. nat. Walter Jahn (†)
After his study of mathematics, Dr.Walter Jahn worked in the mathematical institute of the University Leipzig on the field’s
stochastic and mathematical statistics. His activity centers were aspects of multivariate statistical theory including their
application in the industry. He worked as an adviser for the industry.
Some of the books with applications are:
Jahn,W. und H. Vahle [1970]: Die Faktoranalyse und ihre Anwendungen Verlag „Die Wirtschaft“ Berlin
Jahn, W. u.a. [1972]: Analyse und statistische Prozessmodellierung für die Prozesssteuerung Verlag Technik Berlin
Jahn, W. und P. Langrock [1979]: Einführung in die Theorie der Markovschen Ketten und ihre Anwendungen, Teubner
Verlagsgesellschaft
Jahn, W. und L. Braun [2006]: Praxisleitfaden Qualität – Prozessoptimierung mit multivariater Statistik
in 150 Beispielen, Hanser Verlag München Wien.