Reprinted from the Proceedings of the 10th Annual
Quality Function Deployment Symposium, 1998
By Dr. Noel León-Rovira and Ing. Humberto Aguayo, MSC
Instituto Tecnológico y de Estudios Superiores de Monterrey,
Ave. Eugenio Garza Sada # 2501, Col. Tecnológico,
CP 6409, Monterrey, NL, Mexico.
(email: nleon@campus.mty.itesm.mx)
Abstract:
An integrated model of the Conceptual Design Process is presented, which is based on
QFD, Functional Analysis and TRIZ. It is analyzed how to use TRIZ, starting from the
QFD-Diagrams and continuing through Functional Analysis during the conceptual design stage
of new products. The information obtained during the Functional Analysis is used to
identify the product structure which reveals the technical parameters needed for the QFD
process. Two cases are presented and analyzed on how the "roof" of the
"House of Quality" may be used as an interface to the Technical Contradictions
Matrix in TRIZ, as contradictory parameters are identified and the design conflicts may be
solved based on the Technical Contradictions Matrix.
1. Introduction
This paper is the first of a series of papers about the research work that is being
undertaken at the Center for Integrated Manufacturing Systems of the Monterrey Institute
of Technology in Monterrey, Mexico, looking for the integration of different design tools
and methodologies.
This work is based on the experience gained of several real product design projects
that have been undertaken since 1995 on a contractual basis together with industrial
enterprises in Mexico which are looking for the improvement of their products to compete
in the international market.
Some of these product design projects have been undertaken by student teams of the
master degree program on Manufacturing Engineering, as part of an effort to change the way
design is taught, providing hands-on experience in classes involving students in
full-scale product development resulting in functional or virtual prototypes. In these
paper two cases are discretionary presented to illustrate the approaches applied.
The main scope of our research work is to search for synergy between existing design
methods and tools while evaluating the results of the design process through measuring the
competitive advantage gained by the enterprises for which the projects are being
developed.
This first paper is aimed at the integration of QFD, Functional Analysis and TRIZ,
because the integration of these tools may improve the performance of the early stages of
the design process, which, as most specialists agree, determine more than 75 % the cost of
the designed products [1]
Today companies are attempting to understand quality better, and to predict product
performance, but the lack of integration of these tools increases cycle time. This was
stated at the workshop held at Gold Canyon, Arizona, from May 22 - 25, 1995 and supported
by the National Science Foundation, with the purpose to determine research priorities in
engineering design by examining industry and education needs,
One of the conclusions of this workshop is that greater demand for product efficiency,
reliability, quality, compactness, variety and customization combined with cycle time
reduction of 60 to 90% are needed to stay competitive in the future.
The workshop participants also concluded that research areas that will have the
greatest impact on engineering design over the next 10 years are: Collaborative Design
tools and techniques, Prescriptive models/methods, System Integration
Infrastructure/Tools, and Design Information Support Systems. [2]
One further conclusion was that there is a need for more generalists in product design
who can understand the big picture, not just some specialized problems. However, currently
much integration is being done by engineers lacking a real understanding of the
integration problem and at the same time, the knowledge burden on the designer keeps
increasing as more materials and more options become available.
Work in prescriptive models has been taking place largely in Europe especially in
Germany [3,4, 5]. However, such systematic prescriptive methods are not based on any
theoretical foundations, and in fact, some doubt that there is sufficient evidence that
prescriptive methods produce better results. Work on experimental validation is just
beginning in Germany.
U.S. and Latin American industry (and even academia) is relatively unaware of the
German systematic methods, but Taguchi methods and other techniques such as Quality
Function Deployment have been imported from Japan and used in practice.
2. QFD and Functional Analysis
QFD is a very important tool to improve market share by reducing the gap between the
customer's desires and the product's performance. The fundamental principle of QFD is to
drive the design of a product or service by gathering all relevant information about the
customers’ wishes through surveys, interviews, tests, benchmarks, etc. [6]. That
means that the primary function of QFD is to identify the most important issues and
parameters of the products and to link priorities and target values back to the customer.
As long as it is known how to satisfy the wishes (WHATs) from the customers through the
properties, parameters and attributes of the products (HOWs ) this primary function may be
fulfilled.
But QFD is not a problem-solving tool, although it is very useful in identifying what
has to be solved or improved in order to increase market share.
But before the correlation between WHATs and HOWs in the QFD-matrix may be established,
the functional structure of the products has to be decomposed on to its basic components.
In each case each one of the identified relevant WHATs should be supported by at least one
of the basic components of the functional structure of the already existing products.
To achieve this, the functional tree structure, as described by Clausing [7] and Pahl
and Beitz [4] (Fig. 1), is a very useful tool. The primary or global useful function of a
system is decomposed in sub-functions at different hierarchical levels. In this case the
term function is defined as the input/output relation in one technical system that has to
fulfill a task. Sub-functions are therefore also input/output relationships that fulfill
sub-tasks in the technical system. Functions are then described in terms of actions
fulfilled on objects, where the actions are described by verbs and the objects by
parameters or substantives: i.e. "to increase torque" "to transfer
load" "to decrease rotational speed" "to cut metal" etc.
Fig. 1 Functional tree structure
As stated earlier, the functional tree should be developed so far, that each
sub-function might be stated as an action on a functional parameter. Furthermore at least
one parameter should be determined that is related to each and every one of the WHATs
identified in the first stage of the QFD process. This is a non-trivial task and requires
experienced designers that are able to identify those correlations.
While applying QFD techniques we concluded that it is a mistake to try to establish the
functional parameters or HOWs of the new products as part of the QFD process, without
first establishing the relationships between WHATs and HOWs of the already existing
products.
As QFD is not a problem solving tool huge difficulties arise when trying to
simultaneously define the relationships between the wishes from the customers and the
functional structure and parameters of the new products being designed.
In appendix 1 a resumed QFD matrix is shown about the Railroad Brake Beam from ACERTEK1. The wishes of the customers were stated through market
research of the enterprise. Later our design team identified the relationships of the
wishes captured from marketing personnel with the structure and design parameters of the
brake beams that have been marketed during the last years. The parameters were stated
through functional analysis.
Therefore one conclusion of our research work is that the first stage of applying the
QFD methodology is to identify the relationships between customer satisfaction and prior
existing product structure, before attempting to synthesize a new product
structure through the QFD matrix.
In the mentioned product design projects, QFD approach has proved to be extremely
useful in understanding the strengths and weaknesses of prior existing products from the
viewpoint of the customer satisfaction. This understanding is indispensable for further
product development in a competitive environment. However, attempts to use the QFD’s
House of Quality as a problem solving tool in other product design projects have caused
increased development time and costs, without real gain in customer satisfaction and
product quality.
Based on this, we changed our approach and now recommend that QFD process and the
construction of the House of Quality (HOQ) should begin before a new product
design process is started.
This approach allowed us to gain a better understanding of the market and customer
needs and of its relationships to the existing product structure and parameters. Later,
this better understanding could be applied when new product design processes were started.
As one of the features of the HOQ diagram shows the directions in which product parameters
has to change, or which parameters should remain unchanged for a better customer
satisfaction, the new product design process may then focus on how to achieve this changes
to gain bigger market shares.
3. TRIZ
On the other side TRIZ has proved to be a very strong tool in helping to solve
difficult technical problems that requires inventive thinking; that means problems where
one or more technical contradictions are involved and which do not have known ways or
means of solution
Altshuller began his work on TRIZ in 1946. He studied the experience of inventive
creativity from a fundamental point of view and brought out the characteristics features
of good solutions and what distinguished them from bad solutions: "the solution of
inventive problems turned to be good if it overcame the technical contradiction contained
in the problem presented and bad if the technical contradiction was not revealed and
eliminated" [8]. From Altshuller’s point of view a technical contradiction
exists if when using certain methods to improve one part, function, sub-function or
parameter of a technical system it is inadmissible for an other part, sub-function or
parameter to deteriorate in the process [9].
Of course, not every one of the wishes of the customers involves an inventive problem.
Most of the work on identifying how to satisfy the needs from the customers has to be
solved based on the existing expertise of the designers. That means that designers have to
have enough knowledge and experience about the behavior and structure of their products in
order to be able to establish the links among WHATs and HOWs in the QFD correlation
matrix.
From the TRIZ point of view that means that the biggest part of the problems that arise
has solutions from levels 1 or 2.
TRIZ is not originally a tool that belongs to the classical product design
methodologies and its place in the product design process has yet to be better identified
in order to increase its efficiency. Some work has been already undertaken in this
direction by Savransky [10], who tries to find the links between TRIZ and other
methodologies of the classical German school.
A new terms denoted as Inventive Engineering as a further Step from Design Engineering
has been coined in a Web publication from Arciszewski and Zlotin [11], denoting the need
to introduce innovative concepts in new product design to remain competitive.
Terninko [9] has also identified several links between TRIZ and QFD in his analysis of
the connection of these tools.
Although not yet a comprehensive approach for the integration has been established and
further work is being undertaken, several opportunities of synergy and need of improvement
have been recognized between QFD/Functional Analysis and TRIZ
3.1. The Ideal Final Result Concept
At the kernel of TRIZ lies the Concept of Ideal Final Result, which states that the
ideal solution of a technical contradiction should be that which enables to increase the
usefulness of the product without introducing new harmful effects, maximizing the
ideality. Ideality may be expressed as:
Ideality = Benefits / ( Costs + Harm)
The Ideal Final Result describes the solution to a technical problem, independent of
the mechanism or constraints of the original problem. It is the upper limits of the
"ideality" equation, and can be visualized as "ideal": The ideal
system delivers benefit without harms (no undesired side effects.)
By removing the mental constraints of existing solutions, it gets people to think
"out of the box" and encouraging breakthrough thinking by enabling designers to
define the roadblocks they had been facing. [12]
At our design projects, the first step after having a complete description of customer
needs and wishes, has been to formulate the IFR of the product being developed. A written
formulation of the IFR proved to be helpful in breaking the psychological inertia.
However, attempts to formulate the IFR as a target of the design process lead to
inhibition of designers in maximizing ideality. One thinking aid that has been helpful was
to start from the functional tree, eliminating all harmful effects and the functions that
are used to correct or eliminate harmful side effects.
3.2. The Contradiction Matrix
As stated earlier in this section the elimination of technical or physical
contradictions is the basic evaluation criteria for good innovative design solutions.
One of the first tools developed by Altshuller was the Contradiction Matrix, where
inventive principles screened from the patent analysis were classified based on the
technical contradiction that were solved.
As at the roof of the HOQ are identified the contradictory relationships among the
design parameters, it seems straightforward to use these identified contradictory
parameters to find a link to Altshuller’s Technical Contradiction Matrix.
In Fig. 2 a simplified representation of the link between the QFD-diagram and the
contradictions matrix is shown.
Fig. 2 Simplified representation of the link between QFD-diagram and TRIZ's contradiction
matrix
As during the last semester 8 student teams worked on the same number of design
projects, a systematic analysis was undertaken in each case: those parameters between
which contradictory relationships had been identified in the QFD diagram, were then
compared with the 39 general parameters from the Contradictions Matrix. The intention was
to find a match among the contradictory parameters from the HOQ and the 39 Altshuller's
parameter and to identify inventive principles that could be applied to solve the
technical contradictions that had been stated.
It was concluded that Altshuller’s Contradiction Matrix is useful in finding
inventive principles to solve technical contradictions. Several useful ideas were derived
from the use of the contradiction matrix, during the conceptual design stage of the
nopal-cactus dethorning machine. The inventive principles segmentation, previous action,
mediator, use of hydraulic and pneumatic construction have been used to increase the
Ideality of the solutions applied in this project.
However, in other cases the usefulness was only to a limited extent because several of
the parameters that had been identified in QFD diagrams could not be matched with any of
the 39 general parameters defined in the Matrix. For example such parameters as the degree
at which items has to be previously ordered or aligned before processing them and
inventive principles to solve technical contradictions related to this parameter are not
included.
In other cases, solution principles that were used to solve design problems are not
included in the matrix, as for example increasing the inertial moment of structural
sections to solve the technical contradiction between strength and weight.
Other authors [13, 14] have recognized the need to enhance the Contradiction Matrix
with new parameters and inventive principles that improve the success rate in using this
tool.
In our group, further work is being developed in this direction. As in each product
design project a thoroughly patent search has to be completed, students are being
encouraged to identify if the found patents solve any technical contradiction. When this
is the case, the parameters and inventive principles applied in those patents should be
identified and compared with those of Altshuller’s Matrix. In a later paper the
achieved results will be published.
3.3. SUH diagrams
SUH diagrams from the Innovation Workbench have been widely used, because they allow an
extensive analysis of the possible solutions in order to increase Ideality. SUH diagrams
have proved to be a useful tool if applied carefully without exaggerating its use.
The connection between SUH diagrams and Functional Analysis is straightforward. As
Functional Analysis allows to recognize the different useful functions and the derived
lateral harmful effects, it proved to be a very important step in building the SUH
diagrams to classify the decomposed functions in useful ones and those that are needed to
eliminate or reduce lateral harmful effects.
Attempts to develop SUH diagrams without determining first the functional structure was
not as useful and clear as those made after the functional tree structure was first
thoroughly identified, and the functions classified according to the described criteria.
In figure 3 the schematically relationship between the functional tree and the SUH
diagram is shown.
Fig. 3 Relationship between functional tree and the SUH diagram
Figure 4 shows one of the SUH diagrams developed during the design of the new optimal
brake beam.
Fig. 4 SUH diagram for the new optimal brake beam.
4. Conclusions
Synergies may be found among QFD/Functional Analysis and TRIZ, which allow improving
the structure of the design process and shortening cycle time reducing design iterations
by solving complex design projects where inventive thinking is needed. Successful results
were achieved in several complex design projects that were developed during the last 2
years.
Students and research assistants participating in these projects agree that the
combined and systematic use of these tools facilitated their tasks and helped them in
finding better solutions.
Common sense has also proven to be very useful in identifying the tasks where different
methods and inventive tools are more efficiently applied. For example using conventional
design tools as morphological matrix or simple design rules where no innovative or
inventive solutions are needed, has proven to be a more efficient way because less time
and effort is required. Innovative efforts may then be concentrated on the more relevant
parameters accordingly to the evaluation rates in the HOQ Diagrams. In those cases TRIZ
tools, specially SUH diagrams, and Contradictions Matrix have proven to be very useful.
The concept of Ideal Final Result has shown to be a universal and robust way to lead to
better solutions, as psychological inertia and creativity inhibitions are eliminated.
Opportunities have been also identified of improving some TRIZ tools. For example the
need was recognized to enhance and further complete the Contradiction Matrix adding new
parameters and inventive principles.
5. References:
- Pugh, Stuart.Total design : integrated methods for successful product engineering ,
Wokingham, England ; Addison-Wesley Pub. Co., c1991.
- Shah J. Shah et. al. Research opportunities in Engineering Design, NSF Strategic
Planning Workshop, Final Report April 1996, Arizona State University.
Http://ASUdesign.eas.edu/NSF
- Verein Deutscher Ingenieure: VDI Guidelines - Systematic approach to the design of
technical systems and products, VDI 2221, 1987.
- Pahl, G., Beitz, W.: Engineering Design: A systematic approach, Springer, 1988
- Leon, N. and Soucek R.: Beitrag zur Verallgemeinerung der Ordnungsebenen Theorie in der
Konstruktionslehre. Wiss. Zeitschrift der Technischen Universität Dresden 32 (1983) H.4
Pag.7 - 19.
- Terninko, J The QFD, TRIZ and Taguchi Connection: Customer-Driven Robust Innovation. The
Ninth Symposium on Quality Function Deployment, June 10, 1997
- Clausing, D.P., Total Quality Development: a step-by-step guide to world class
concurrent engineering, ASME Press, New York 1994
- Alshuller, HS, Creativity as an exact science : the theory of the solution of inventive
problems New York : Gordon and Breach, 1995
- Derrick,T. and Nordlund M., Synergies between American and European approaches to
design, Integrated Design and Process Technology, IDPT-Vol 1, Pag. 103- 109
- S.D. Savransky, http://www.trizexperts.net
- Arciszewski T, and Zlotin B: IDEATION/TRIZ: INNOVATION KEY TO COMPETITIVE ADVANTAGE AND
GROWTH. http://www.ideationtriz.com/report.html
- Ellen D., How to Help TRIZ Beginners Succeed, http://triz-journal.com
- Williams, T: Reversability of the 40 Principles of Problem Solving,
http://triz-journal.com, May Issue, No. 1
- Savransky, S.D A few words about the Altshuller's contradiction matrix ,
http://triz-journal.com, August 1997
FOOTNOTES
1
ACERTEK S.A. de C.V. is a Mexican entirprise that shares a big
part of the railroad brake beams market in North America
