2002 a hybrid systematic and conventional approach for the design and development of a product a...
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Systematic approach to design breaks down the design process into
a sequence of transparent activities1 and each of these activities are
further assisted by design tools which are generally called design
methods. One such systematic approach is Design Function Deployment,
DFD2,3. The underlying structure of DFD is given in Figure 1 where level
1 represents the design model consisting of six stages and level 2 consists
of the design methods.
In a computer implementation level 0 represents the initialisation where
the chosen design methods from level 2 are incorporated with the stages
in level 1 to form the process chain of the design process. This process
chain creates the path followed in the designing of a product, unique and
1 Cross, N Engineering designmethods John Wiley and Sons,
Chichester, 2nd edition (1994)
2 Sivaloganathan, S, Evbu-omwan, N F O, Jebb A andWynn , H P Design function
deploymenta design system
for the future Design StudiesVol
16 No 4 (1995)
3 Sivaloganathan, S, Evbu-omwan, N F O and Jebb, A A
design system for concurrent
engineering Concurrent Engin-
eering Research and Appli-
cations Vol 3 No 4 (1995)
www.elsevier.com/locate/destud
0142-694X/00 $ - see front matter Design Studies 21 (2000) 5974
PII: S0142-694X(99)00004-6 59 2000 Elsevier Science Ltd All rights reserved Printed in Great Britain
A hybrid systematic and conventionalapproach for the design anddevelopment of a product: a case
studyS Sivaloganathan, T M M Shahin, M Cross and M Lawrence,
Engineering Design Group, Department of Manufacturing and
Engineering Systems, Brunel University, Uxbridge, Middlesex UB8
3PH, UK
This paper aims to study the effectiveness of systematic and conventional
approaches to design. A team of students who had been educated on the
systematic approach to design was engaged in the design of a new
producta disposable bicycle made out of paper. The students tried the
systematic approach wherever they could use it and adopted the
conventional approach whenever they encountered difficulties with
systematic design. When they adopted new philosophies or concepts not
proven by either systematic or conventional models, some rework was
needed. The work suggests that a hybrid approach is the most suitable
one when developing new products with limited data available. This
paper describes the different approaches and the approach undertaken
by the students. 2000 Elsevier Science Ltd. All rights reserved
Keywords: product design, systematic design, intuitive design, design
studies, case study
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appropriate in each case. The success of DFD depends on the design
methods that are used in conjunction with its design model shown from
left to right in level 1.
A conventional approach to design on the other hand defines the problem
as a Brief. It then collects as much relevant data to the problem and
solution as possible to develop adequate insight. Conceptual solutions are
then proposed and developed in an iterative fashion until they meet the
specifications. Models of subsystems are then built to prove the designs.
The Engineering Design Group at Brunel University and the Centre for
Design Research at Stanford University put a group of students to work
on the design and development of a cardboard bicycle in order that they
might build the prototype within 15 days. This was carried out as part of
the Stanford postgraduate module Design Project Experience. The stu-
dents had formal education in systematic design (advocated by DFD) and
in design methods. This paper describes the way the product was designed
and developed and identifies the strengths and weaknesses of both system-
atic and conventional approaches to design. It identifies a hybrid approach
as a suitable way for new product development. Section 1 describes the
problem, Section 2 describes the way it should have been handled using
a systematic approach as per DFD, Section 3 describes the way it would
have been handled in a conventional way, Section 4 describes how the
team actually designed and built the product, and Section 5 discusses the
advantages and disadvantages of the three approaches. Finally conclusions
are drawn in Section 6.
60 Design Studies Vol 21 No 1 January 2000
Figure 1 Structure of Design Function Deployment
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4 Akiyama K Function analy-sissystematic improvement of
quality and performance Pro-
ductivity Press, Ohio, USA
(1991)
1 The problemA successful entrepreneur turned cyclist has hypothesised that there is a
market for disposable bicycles. The requirement is to construct a prototype
of a disposable bicycle made out of paper that can be shipped in oversized
shipping cartons. It can involve the words some assembly required to
minimise the shipping volume. The use of non-paper materials is permittedbut at a significant cost, so they should be considered as a precious resource
and used wisely. The bicycle should withstand the travel of four laps
around a predefined course. A design constraint uses a standard inter-
national shipping formula from UPS, FedEx, etc. Determine the dimen-
sional weight in pounds by dividing the cubic size, in inches, of the ship-
ment by 166: dimensional weight = L W H/166. Increase fractions of
a pound to the next full pound. Bicycle cartons with a dimensional weight
of greater than 166 lb or an actual weight of greater than 166 lb will be
returned to the design team for modification. Each team will be assigned
a client team and the clients requirements should also be taken into con-sideration.
2 Designing with the systematic approachThe systematic design within the taxonomy of DFD starts with establishing
the stakeholders and their prioritised requirements. In the case of the dis-
posable bicycle the stakeholders include the shipping companies, end users,
the entrepreneur (to decide on price etc.) and any others who have some
connection with it. Once these requirements and their relative importance
ratings are established the specifications of the product are drawn. Specifi-
cations essentially describe the functions that the product should performin order to satisfy the requirements. Specifications also include the restric-
tions that have to be imposed on the product, which are called the con-
straints. Since the product under consideration is a variant of an existing
product (a bicycle), a list of functions performed by the product can be
easily established by performing a function analysis4 of a normal bicycle
and then adapting it to a disposable bicycle. Once the specifications are
drawn the development of the solution can be started. Here the function
family tree established in function analysis is analysed critically to identify
the essential subsystems and the unnecessary subsystems for the disposable
bicycle. Using these, subsystems can be proposed for the paper bicycle.
A morphological analysis at this stage may reveal useful new conceptual
solutions. These conceptual solutions are then developed as embodiments
by specifying the constituent parts. These parts have to then be tested for
strength and other properties that are necessary for their functioning indi-
vidually and as part of an assembly. Often these tests are done with com-
puter models, which may be verified with a prototype. Since the material
used is to be mainly paper, little material selection is needed. However,
A hybrid systematic and conventional approach for the design of a product 61
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material for non-paper components must be selected and tested at this
stage. Subsequently, manufacturing methods also have to be established.
Thus, the design process for the paper bicycle under the systematic
approach under DFD should be as illustrated in Figure 2.
3 Designing under the conventional approachThe conventional approach often practised by designers, starts with theinterpretation of the design brief. In order to understand the design brief
a technical interpretation of it is written. Often at this stage, enough infor-
mation is collected and a better insight is derived. Then conceptual sol-
utions are proposed and often conceptual models are built. Inferences are
then made about the individual concepts by experimenting with conceptual
models. A set of assessment criteria is then developed to evaluate the vari-
ous concepts. Using these criteria, one solution is selected for further devel-
opment. At this stage a prototype is built and more tests are carried out.
Some of these tests may include building and experimenting with computermodels and relating the results with the results obtained from the prototype.
An evaluation is also carried out at this stage to identify unresolved issues.
62 Design Studies Vol 21 No 1 January 2000
Figure 2 Design process
under the systematic
approach
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The next stage in this process is to resolve the issues and improve the
prototype. At the end there will be a working prototype representing the
final design. The design process for the paper bicycle in the Conventional
approach can be described in the form of a flow chart as shown in Figure 3.
4 Design process as carried out by the studentsThe students started with individual brainstorming sessions. The results of
these sessions were not that impressive. They also used spider diagrams
to develop ideas unsuccessfully. Establishing a function tree for the new
design seemed to be a good idea. They triedagain unsuccessfully. At
this stage a parts analysis of an existing BMX bicycle appeared a suitable
option for the starting point of the project. This parts analysis, a design
A hybrid systematic and conventional approach for the design of a product 63
Figure 3 Design process in
a conventional approach
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method, often used under systematic design to analyse and improve exist-
ing designs, was used to develop the parts tree shown in Figure 4.
Once the parts tree of the BMX was complete, the essential subsystems
needed for the disposable bicycle were proposed using the parts tree as a
basis. This marked the starting point of the design process. A morphologi-
cal analysis was then carried out to consider the alternative subsystems for
the proposed bicycle. Figure 5 shows the morphological chart.
From the morphological analysis, a harmonious and conforming solution
was selected and the components were designed separately. The compo-
nents thus designed were as follows:
(1) Frame with seat and seat bar.
(2) Wheels.
(3) Steering system.
(4) Propulsion.
64 Design Studies Vol 21 No 1 January 2000
Figure 4 Partial parts tree of a BMX bicycle
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4.1 Frame with seat and seat post designThe bicycle frame with seat and seat post provides for a number of func-
tions. It gives a rigid platform to support the rider and also houses thedrive mechanism. The frame provides the reactions against the axle, the
total of which is equal to the weight of the rider plus the pedalling force.
The frame also supports the force produced as a result of the front forks
during a steering manoeuvre. The calculations of the dimensions for the
members of the frame proved to be difficult without a finite element analy-
sis, for which structural properties of various materials were required.
Hence, a trial and error method with physical members was used for decid-
ing the right dimensions for the members.
The frame consists of four components shown in Table 1 and Figure 6.The main tube was essentially a tube with two holes cut for the forks and
the seat post. A slot was cut at the rear to house the rear wheel and drive
system. Reinforcement was added to the rear by gluing a section of tube
inside the main tube. The same technique was used to reinforce the seat
post where it housed the drive crank. Gluing a 6-in. diameter tube section
into the tube perpendicular to the main tube reinforced the front of the main
A hybrid systematic and conventional approach for the design of a product 65
Figure 5 Morphological
analysis of concepts
Table 1 Main frame
Component Made from Length (in.) Diameter (in.) Wall thickness
(mm)
1 Main tube Tube 47 8 62 Seat post Tube 27.3 4.5 53 Seat Laminated N/A N/A N/A
corrugated card4 Bearing surface Tube and 3 6 5
corrugated card
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tube. This, along with the fork-bearing surface, eliminated deformation of
the main tube. The seat post was glued in place and secured with a smaller
cardboard tube through both main tube and seat-post.
4.2 WheelsThe wheels provide a number of functions within the bicycle. Firstly, they
must be sufficiently robust to support the total force exerted on them by
the axles. They must rotate in order to allow motion and propulsion. They
therefore must be circular and have a high friction surface around the per-
iphery to provide traction. They must also provide a cambered surface to
allow the bike to tilt during cornering. The wheels were fabricated from
10 layers of corrugated cardboard laminated with a 72 lay-up. The layers
were secured using wood glue. The layers were angled to give the
maximum possible strength from the grain of the card. A diagram of
this configuration is shown in Figure 7.
66 Design Studies Vol 21 No 1 January 2000
Figure 6 Main frame ass-
embly with the drive system
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The wheel diameters were chosen to fit the tyre diameters available from
the local cycle shop. The wheel rims were made from strips of hard board,
which were glued around the perimeter. Three strips each having a different
width were used. This gave the wheel the required camber as shown in
Figure 8. The tyres were then glued on top of the rim. Finally, cardboard
tube bushes were glued into the centre of the wheels. Trials with these
bushes showed heavy friction and PVC tubes were then used as the axles
and bushes.
4.3 Steering systemThe forks and handlebars provide the steering function. The direction con-
trol of the rider is transmitted to the steering column by rotation of the
handlebars, which in turn rotate the column within the main frame. The
forks were built from two sections of cardboard tube as shown in Figure 9.
A hybrid systematic and conventional approach for the design of a product 67
Figure 7 Cardboard lay-up
procedure for wheels
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The final fork assembly consists of a 6-in. diameter tube joined to a 4.5-
in. diameter tube joined by two smaller diameter tubes glued in place per-
pendicular to the main tube.
68 Design Studies Vol 21 No 1 January 2000
Figure 8 Part cross section
of wheel showing reinforc-
ing rims
Figure 9 Fork assembly
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The handlebars made from 2.5-in. diameter cardboard tube, simply fitted
into a hole in the top of the forks. Trials with the system revealed that the
friction at the interface between the fork and the main frame was too high.
Therefore, a circular piece of transparency film was placed between the
mating surfaces to reduce the friction.
4.4 Drive systemThe cogs for the drive system were cut from an MDF sheet of 18-mm
thickness. The rear cog was attached to the wheel using five lengths of
dowel as shown in Figure 10.
They were driven by a knotted rope drive to act like a chain. The knots
were placed at intervals of 50 mm from each other. In order to provide a
free wheel action the tooth profile had a sloping relieve side and sharp
engaging side. As trials with the drive showed slipping, groves to lower
the rope were cut in the teeth to alleviate this problem. The main drivecog was glued to the crankshaft using a keyway and an MDF key. The
cranks were also cut from MDF as shown in Figure 11.
4.5 Full assemblyThe final bike assembly with all the subsystems is presented in Figure 12
5 Advantages and disadvantages of the approachesEvaluating the effectiveness of the three approaches needed a set of criteria.
The following seven characteristics were seen as the requirements for
evaluation.
(1) Clear starting point. Clear starting point is an important aspect
because this avoids the waste of time at the early stages when the
A hybrid systematic and conventional approach for the design of a product 69
Figure 10 Rear drive cog
assembly
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insight of the problem and solution space is low. This permits the
development of insight while working on the project.
(2) Clear steps. Clear steps provide for the planning of the project. This
is particularly useful when the time allowed for the project is limited.
70 Design Studies Vol 21 No 1 January 2000
Figure 11 Crank and pedal assembly
Figure 12 Final bike assembly
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(3) Requirement of market data. This is the data on the shapes, forms,
sizes and prices of different materials available in the market. This
is very important because a design, which may be optimal in several
perspectives, may have to be tailor made and hence become very
expensive.
(4) Requirement of properties. This relates to the data on material proper-ties such as, Youngs Modulus, surface roughness and friction, etc.
The properties required may not be known at the beginning of a pro-
duct and this can aggravate the situation.
(5) Reliance on models and tests. Tests with physical models are carried
out for two reasons: (a) to ensure compliance with the laws of physics
and nature and (b) to estimate the performance characteristic, which
is difficult to do otherwise.
(6) Reliance on computer models. Because physical models are difficult
to make there is now an increasing tendency to use computer models.
It is therefore important to know which model uses this techniquemore.
(7) Knowledge capturing. This is one of the most important aspects of
the design process because the information captured not tells us which
considerations were used but also which considerations were not used
in the various decisions made. This will enable an explanation of the
performance to be made and thus provide ways of improving the
product at later stages in time.
5.1 Systematic approach
The Systematic approach to handle this problem is given in section 3. Ifthe approach is considered according to the above criteria the following
observations can be made:
(1) Clear starting point. The starting point under the systematic approach
is to establish the list of stakeholders and their requirements. These
are collected to establish the specifications of the product together
with their constraints.
(2) Clear steps. In the systematic approach this means the process chain
with computer modelling and analysis.
(3) Requirement of market data. This becomes a standard requirement in
the systematic approach because the computer models and their analy-
sis needs them. Without this data, it is not possible to perform any
analysis. In the case of the paper bicycle the lack of data on paper
and different available forms almost inhibited the use of systematic
methods.
(4) Requirement of properties. This relates to the data on material proper-
ties such as, Youngs Modulus, surface roughness and friction, etc.
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These form the other component of data required for analysis. The
lack of this group of information on materials for the paper bicycle
was another reason preventing the systematic approach for design.
(5) Reliance on models and tests. In systematic design most of the tests
are carried out with computer models and the final confirmation tests
are only carried out with physical models.(6) Reliance on computer models. Most of the tests are carried out with
computer models.
(7) Knowledge capturing. Knowledge capturing is much easier with sys-
tematic design because each stage in the design process has a speci-
fied output.
5.2 Conventional approachThe conventional approach to handle this problem is given in section 3. If
the approach is considered according to the above criteria the following
observations can be made:
(1) Clear starting point. The starting point in the conventional approach
is the need statement or brief. It does not have a clear format and
hence understanding the need statement takes quite a lot of time
and effort.
(2) Clear steps. There are no clearly defined steps. The designer is
expected to plan his work.
(3) Requirement of market data. Even though this data is important the
method relies on working around what is available in the market andhence does not create serious problems.
(4) Requirement of properties. Here again the data is important. But the
absence of it is not crucial because estimates can be made from exper-
imentation.
(5) Reliance on models and tests. The conventional design approach
relies heavily on building models and testing them.
(6) Reliance on computer models. Computer models form part of the
testing programme.
(7) Knowledge capturing. Special effort has to be taken to capture
design knowledge.
5.3 Approach by the studentsThe students started with a systematic approach and deviated from it wher-
ever they found it difficult and the conventional approach proved easy. If
the approach is considered according to the above criteria the following
observations can be made:
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(1) Clear starting point. The students approach used the parts tree analy-
sis as the starting point for the design. This is somewhat similar to
the function structure advocated by the systematic approach.
(2) Clear steps. The students tried to follow the steps defined by DFD
but found it difficult. The reason being the lack of availability of
market data and the properties of the materials.(3) Requirement of market data. The students tried to collect data, but
managed to procure only the available materials within the two-
week period.
(4) Requirement of properties. The students could find a limited infor-
mation only during the two-week programme.
(5) Reliance on models and tests. The students relied heavily on testing
the physical model and wherever this was insufficient they had prob-
lems.
(6) Reliance on computer models. Very limited computer modelling was
done because of the lack of required data.(7) Knowledge capturing. Special effort had to be taken to capture
design knowledge.
5.4 DiscussionComparison of the three approaches shows that the systematic approach is
easy and comfortable when the problem is clearly defined and the required
data and information are available. This facilitates computer modelling and
analysis and thus eliminates the necessity for extensive physical modelling.
However, the approach becomes difficult with limited data. The conven-
tional approach on the other hand permits the use of limited data and usesphysical modelling and experimentation as the principal tools for
developing the design. In the absence of a lot of information this method
seems to be more efficient. The students used a hybrid systematic and
conventional approach. For instance establishing the parts tree is a system-
atic approach. Using the structured layering and other methods in the fabri-
cation of wheels were systematic methods that worked. When details were
not known, as in the design of the main frame, they brought the materials,
built the models and tested to prove the design. Wherever they did no
testing and had limited knowledge, they encountered failures. Therefore,
it is safe to conclude that the systematic approach is easy only when enough
data is known and the conventional approach is easy when limited data is
known. A hybrid approach is the most suitable when developing a new
product. This permits the benefits offered by both approaches.
6 ConclusionsThe design process adopted by a team of students trained in the systematic
approach to design was engaged into the design of a new product. Their
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approach followed the easy methods in both systematic and conventional
design methods. Analysis revealed that with a lack of the required data,
the systematic design approach had limited success whilst the conventional
approach was effective in these circumstances. It is therefore safe to con-
clude that a hybrid systematic and conventional approach is the easy way
for the development of new products.
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