EUROGRAPHICS Workshop on Sketch-Based Interfaces and Modeling (2004)
John F. Hughes and Joaquim A. Jorge (Editors)
Sketching in early conceptual phases of product design:
guidelines and tools
Josef Ponn, Udo Lindemann, Holger Diehl, Franz Müller
Institute of Product Development
Technische Universitaet Muenchen
Boltzmannstr. 15,
85748 Garching, Germany
ABSTRACT
The early phases of product development play a significant role for the success of a product and the prevention of
time and money consuming changes in late phases. This paper describes a new methodological approach for the
genereration of principle solutions in the form of sketches in early phases of product development. A guideline has
been developed for a target-oriented and efficient progression from working principles to principle solutions. In
particular, the linkage between physical effects and form parameters (geometry, materials etc.) has been investi-
gated. A computer system including physical effects as features which can be used for the generation of digital
principle sketches is described as a vision. Such a system offers the potential of facilitating routine work and sup-
porting the engineer in defining solution concepts at early stages of product design.
Categories: Inferring shape from sketches, sketching diagrams.
Also, a vision of a sketching system is pictured which
1. Introduction
supports the processes in the form design phase.
In early phases of design, concepts are created by defining
2. Motivation of research
functions to be realized, searching for adequate working
principles and deriving principle solutions. In this phase
Before describing the new approach to the creation of
sketching plays an important role since the level of infor-
principle solutions, the motivation of the research activity
mation is still relatively low, the created product represen-
shall be explained. First, the importance of early phases of
tations are fuzzy and not as exact as the CAD models
product development is stressed. This is followed by the
which are created later in order to allow for manufacture of
consideration of how design methodology supports a sys-
the product. A lot of expensive and time consuming
tematic proceeding in this phase. Also, the reference to the
changes in late phases of a project can be avoided by put-
topic of the workhop, sketching, is pointed out.
ting more effort into systematic, methodological proceed-
ing during the early phases.
2.1 Importance of early stages of product development
Within the scope of this paper a new approach to design in
early phases of product development is introduced which
Errors, unwise decisions and unsystematic proceeding in
focusses on a systematic derivation of principle solutions
early stages of the product development process lead to
from working principles. The main idea is to link physical
expensive changes in late phases. This is a fact stated by
effects to corresponding form parameters.
many experts in industry. Important aspects with respect to
this problem are:
A working principle reflects the physical effects needed
for the fulfilment of a given function. A principle solution
" The information level in early phases is still low.
represents the concretization of the working principle
Therefore the best solution to a problem is not obvi-
within a working structure [PB*96]. The principle solution
ous at once in most cases. Here, a thorough clarifica-
comprises aspects like the overall shape, material or ar-
tion and documentation of requirements, systems en-
rangement of product elements. Corresponding product
gineering and functional analysis can help cope with
representations are sketches, schematic drawings etc. as
this fact.
opposed to detailed CAD drawings which include all in-
" Often the first solution that comes in mind is chosen,
formation needed for production (such as exact geometry,
worked out and elaborated. After spending a consider-
tolerances etc.). Common expressions used in literature for
able amount of time and money, it becomes clear that
the same context are: form design, layout design, draft
there are flaws in the concept or important require-
design or scheme design.
© The Eurographics Association 2004.
28 J. Ponn, U. Lindemann, H. Diehl & F. Müller / Sketching in early conceptual phases of product design: guidelines and tools
ments have been neglected. Again, a careful clarific- 3.1 Processes and product representations in early
tion of the task is vital, as well as the explicite consid- phases of design
eration of possible alternative solutions.
In design methodology various procedural models have
" Existing knowledge from previous projects is often
been devised for a systematic navigation through the de-
not considered or used, the wheel is reinvented, so to
sign process. The four main phases according to Pahl and
speak. Helpful in this context are solution catalogues,
Beitz [PB*96] are the clarification of the task, the concep-
(containing physical effects, machine elements etc.)
tual design, the embodiment design and the detail design.
for a targeted search for existing solutions. Graphical
When referring to the  early phases , the focus shall be
representations of the solutions contained within these
placed on the conceptual design stage within this context.
catalogues (drawings, sketches, schematic figures) are
A more detailed process model is given by VDI 2221
an essential part of the information and helpful for a
[PB*96] (see figure 1).
fast retrieval.
Stages Results
Stages Results
(Documents )
" The verbal description of problems or solutions entails (Documents )
Task
Task
communication problems, especially in processes
where the information content is still low. There exist
Clarify and define
Clarify and define
1
1
the task
the task
different points of view and a different vocabulary
S pecification
S pecification
(provider vs. client, product designer vs. manufactur-
Determine functions
Determine functions
2
2
and their structure
and their structure
ing engineer, technician vs. sales staff) By working
Function structures
Function structures
with graphical representations, some of these prob- S earch for solution principles
S earch for solution principles
3
3
and their combinations
and their combinations
lems can be dealt with more easily!
P rinciple solutions
P rinciple solutions
Divide into realisable
Divide into realisable
4
4
To avoid undesired effects such as the ones mentioned
modules
modules
Module structures
Module structures
above special importance has to be placed on the early
Develop layout of
Develop layout of
5
5
stages of product development. Here, requirements have to
key modules
key modules
P reliminary layouts
P reliminary layouts
be clarified and solution concepts are created. In order to
Complete overall
Complete overall
6
6
create high quality solutions while keeping the effort (time,
layout
layout
Definitive layouts
Definitive layouts
cost) low, engineers should have methods, guidelines and
P repare production and
P repare production and
7
7
tools at hand supporting them in this stage of the design
operating instructions
operating instructions
Product Documents
Product Documents
process.
Further realisation
Further realisation
2.2 Importance of sketching in early phases
Figure 1: VDI 2221
First concepts are rarely modeled in CAD systems since
The process starts with clarification and definition of the
they imply the implementation of exact geometrical infor-
task and specification of requirements. Based upon these
mation. The images and ideas which arise in the mind of
requirements, functions and their structures are defined and
the engineer while working on a design task or problem are
modeled. Then, working principles can be determined
fuzzy and often undefined. Sketching plays an important
which are suitable for the realization of the defined func-
role in this stage. Design is creating product representa-
tions. Principle solutions are created, the shape of the prod-
tions: pencil sketches on paper, abstract schematic draw-
uct, in particular the geometry, is elaborated in more and
ings, concrete illustrations of details etc. Two aspects of
more detail until the product documentation is obtained,
interest that have to be considered are:
which allows further realization of the product (material
" How are sketches created? This aspect refers to the acquisition, manufacture etc.).
tools and systems supporting the engineer in the crea-
tion of sketches. Requirements
Requirements
A
A
" Why are sketches created? Which purpose serves the
1
1
sketch? What is represented in the sketch?
Functions
Functions
B
B
Question number one, dealing with sketching systems,
will be addressed in chapter 4.5. First of all, a closer look
2
2
Working principles
Working principles
C
C
is taken on the second question. In order to give an answer,
the underlying processes of design in early product devel-
3
opment stages have to be considered. 3
Principle solutions
Principle solutions
D
D
3. Methodological background
Figure 2: Simplified model containing different levels of
product representation and process steps
In literature, there exist various procedural models indicat-
In each step of the whole process product representations
ing how design processes can be executed with efficiency
are created. Figure 2 shows a simplified model of the dif-
and target orientation. In this chapter, the dimensions of the
ferent levels of product representations. With each level
design process are looked at from a methodological point
from the top to the bottom, the product is more and more
of view and the utility of sketching is considered.
concretized.
previous and following s tages
previous and following s tages
Iterate forwards and backwards between
Iterate forwards and backwards between
Abstraction
Abstraction
Concretization
Concretization
J. Ponn, U. Lindemann, H. Diehl & F. Müller / Sketching in early conceptual phases of product design: guidelines and tools 29
In this context the focus shall be placed on the following transforms the design problem into an abstract level allow-
process steps and corresponding product representations: ing for a more systematic search for solutions, and by that
enables the possible overcoming of barriers (like blockades
" from requirements to functions
of the mind, lack of creativity, solution fixations etc.).
" from functions to working principles
3.2.2 Working principles, physical effects
" from working principles to principle solutions
Of course the process does not stop here. The design has
Once the functions a product has to fulfil are clear, it has
to be elaborated in detail with the help of CAD systems
to be investigated how they can be realized in principle.
etc. Yet, these processes will not be addressed in this con-
This is equivalent to a search for solutions on an abstract
text.
level. In most cases a function can be realized in many
synthesis
synthesis
different ways, each of which has advantages and disad-
Search for solution principles
Search for solution principles
vantages. A solution might fulfil one requirement perfectly
on an abstract level
on an abstract level
Functions
Functions
Working principles
Working principles
(e. g. performance, stability) but might stand in complete
problem solution
problem solution
contradiction to another one (e. g. cost, weight).
model principles
model principles
abstraction
abstraction
concretization
concretization The working principle can be described by the means of
functional analysis,
functional analysis,
definition of form
definition of form
technical (physical, biological etc.) effects or as rather
system analysis
system analysis
(shape, material etc.)
(shape, material etc.)
abstract principles such as described by Altshuller
principle
principle
[ALT*96]. Making use of Altshuller principles is also a
problem
problem
solutions
solutions
method in order to resolve contradictions. This paper fo-
barrier
barrier
Requirements
Requirements
Principle solutions
Principle solutions
cusses on physical working principles.
Sketches!!
Sketches!!
Catalogues of physical effects can be consulted when
Figure 3: From problem to principle solution
searching for appropriate working principles. They are
Figure 3 illustrates the relations between the steps shown
traditionally found in the form of paper catalogues. How-
in figure 2 from a different perspective. A further explana-
ever, the operability can be enhanced to a considerable
tion will be given in the next chapter.
degree in the form of digital databases. Figure 4 gives an
example how physical effects can be represented.
3.2 Levels of concretization from problem to solution
Name Illustration Formula
Name Illustration Formula
A list of requirements represents the specification of a
given problem indicating how the solution has to look like.
Einseitig
Einseitig
Einseitig
Einseitig
F, v
F, v
F, v
F, v
The generation of a corresponding solution is not always a
M = F Å" r
M = F Å" r
lever
trivial case. Here, a systematic proceeding including a lever
M, É
M, É
M, É
M, É
v = É Å" r
v = É Å" r
functional analysis and search for solution principles can
r
r
r
r
help overcome this barrier.
F1 s2
F1 s2
F1 s2
F1 s2
3.2.1 Functions
s1
s1
s1 s1
s1 s1
F2 = F1
F2 = F1
s2
s2
wedge
wedge
In order not to concentrate one s focus on a particular so- F2
F2
F2
F2
Ä…
Ä…
Ä…
Ä…
F2 = tanÄ… Å" F1
F2 = tanÄ… Å" F1
lution and risking the neglect of a better one, the problem
has to be analyzed on an abstract level. Function models
offer considerable help to get a clear picture of the design
Figure 4: Effect catalogue (excerpt)
task and to be free from fixation on existing solutions.
There exist various methods of function modeling, each
3.2.3 Principle solutions, form design
focussing on certain aspects, and therefore each appropri-
ate in certain situations. Functions can be structured in
Promising working principles are given form in the next
hierarchical function trees allowing to handle the complex-
step. The solution has to be concretized. Here, sketching
ity of a product by splitting up the overall function into
plays an important role. For the elaboration of a working
sub-functions. If a product is undergoing many different
principle there is an enormous number of design decisions
operations while changing its status with each step, flow
to be made considering overall shape, detailed geometry,
oriented function models are helpful. A relations oriented
materials etc. Various aspects have to be taken into consid-
function model is able to point out not only the desired
eration that have an influence on the design such as ergo-
functions in a product but also the harmful functions.
nomics, manufacturing procedures, assembly etc.
The derivation of function models bases on the specifica-
Tools for this purpose are checklists with form parame-
tion of requirements. It is essential to consider some basic
ters. An excerpt of such a checklist is displayed in figure 5
rules while defining and formulating functions (such as a
and figure 6. They can be worked through systematically in
solution neutral specification). A function model can be
order not to forget important aspects in the conceptual and
extremely formalized. Ehrlenspiel [EHR*03] for example
embodiment phase. They are an invaluable help in the
only allows five different types of functions. But it does
variation of the design in order to improve flaws or weak
not necessarily have to be like that. A functional analysis
spots and therefore optimize the design.
30 J. Ponn, U. Lindemann, H. Diehl & F. Müller / Sketching in early conceptual phases of product design: guidelines and tools
Categorie Nr Form design parameter
Categorie Nr Form design parameter
Type 1
Type 1
Area and volume body 01 Shape
Area and volume body 01 Shape
Type 2
Type 2
02 Position
02 Position
03 Number
03 Number
04 Size, extent
04 Size, extent
Relations of 05 Type of bond, linkage
Relations of 05 Type of bond, linkage
Area and volume body 06 Type of contact
Area and volume body 06 Type of contact
07 Type of coupling
07 Type of coupling
Type 3
Type 3
08 Structure of bond, linkage
08 Structure of bond, linkage
09 Order, sequence
09 Order, sequence
10 Compactness of structure
10 Compactness of structure
Material properties 11 Type of material
Material properties 11 Type of material
Figure 5: Checklist form design parameters (excerpt)
Mobility Rigid Jointed Elastic
Mobility Rigid Jointed Elastic
F
F
F
F
F F
F F
F F
F F
Figure 7: Nutcracker types
Detachability Detachable Non-detachable
Detachability Detachable Non-detachable
The first steps of the design task are the clarification of the
requirements and a functional analysis, which will not be
Type of bond Material fit Force fit Form fit
Type of bond Material fit Force fit Form fit
described within the scope of the paper. The two functions
F
F
F
F
(Type of fit) (e. g. adhesive bond) (e. g. friction bond)
(Type of fit) (e. g. adhesive bond) (e. g. friction bond)
that will be looked at more closely are  apply splitting
F
F
F
F
F
F
F
F
force on the nutshell and  separate nutshell from kernel
(after splitting) .
Figure 6: Detail checklist type of bond (excerpt)
4.2 From functions to working principles
On each level of concretization (functions, working prin-
ciples, principle solutions) there exist various methods and
The step of deriving working principles from functions
tools for the generation and variation of corresponding
can be formalized and therefore automated to a certain
product respresentations. Examples such as effect cata-
degree. A function can be described as an operation turning
logues and checklists have been presented in this chapter.
physical input parameters into physical output parameters.
A new approach for the progression from abstract levels to
Once input and output are defined, corresponding physical
more concrete ones is described in the following.
effects can be found by the help of a computer program.
The automated generation of working principles does not
4. Generation of principle solutions from functions
guarantee the obtainment of the best solution. However, in
and working principles: examples, guidelines, tools
situations where the lack of new ideas is predominant, an
extremely formalized proceeding might help trigger the
Methods and tools to support the design process can help
engineer s imagination. There can be no complete automa-
automate former manual operations, facilitate routine tasks
tion of the design process, since it still needs human crea-
or allow for a targeted and efficient navigation through the
tivity and intuition in steps of analysis and synthesis.
process. In order to illustrate the presented ideas more
clearly they will be demonstrated on an exemplary product,
Muscular T ransmit and
Muscular T ransmit and
S plitting force on
S plitting force on
B
B
a nutcracker force amplify force
force amplify force
the nutshell
the nutshell
F1 F2
F1 F2
4.1 Exemplary product: nutcracker
Input parameter Operation Output parameter
Input parameter Operation Output parameter
Consider the task of designing an innovative nutcracker.
Out
Out
F s p &
There already exists an abundant number of alternative F s p &
In
In
product solutions. Three types of nutcrackers available on
2
2 F &
2 F &
the market are shown in figure 7. Each of these nutcrackers
s &
s &
works in a different kind of way.
p &
p &
& & & & &
& & & & &
However, many of these designs still contain flaws or po-
tential for optimization. Requirements to consider are for Lever
Lever
Wedge Chain-block &
Wedge Chain-block &
Einseitig
Einseitig
Einseitig
Einseitig
F, v F1 s2
F, v F1 s2
F, v F1 s2
F, v F1 s2
example: compact format, no damaging of the kernel, low
s1
s1
s1
s1
cost, simple working principle, portability etc.
M, É
M, É
M, É
M, É
F2
F2
F2
F2
Ä…
Ä…
Ä…
Ä…
In the three shown examples the kernel might be damaged
r
r
r
r
C
C
while trying to open the shell. Also, there is no contain-
ment for kernel and shell. Once the nut is broken into parts,
Figure 8: From functions to working principles
these might be distributed all over the place.
J. Ponn, U. Lindemann, H. Diehl & F. Müller / Sketching in early conceptual phases of product design: guidelines and tools 31
In the nutcracker example, the application of a splitting effect on a given problem, parameters such as shape, size
force can e. g. be realized by the amplification of a manual and the allocation of elements are defined. The amount of
force. Input parameter is muscular force F1, output parame- product information is increased.
ter the (increased) splitting force on the nutshell F2. Corre-
sponding physical effects which can be chosen for the re-
4.4 Linking physical effects and form parameters:
alization of this function are among others lever or wedge,
a guideline
such as realized in the nutcrackers of type 1 and type 3 (see
figure 7). Figure 8 displays the function  transmit and am- If the lever solution is chosen, parameters that have to be
plify force and corresponding effects as described in an
defined are for example: number of lever arms, length of
effect catalogue.
lever arm, diameter of bearing, type of bearing (sliding
contact bearing, rolling contact bearing). If the wedge solu-
tion is chosen, following parameters have to be defined:
4.3 From working principles to principle solutions
wedge angle (thread pitch), diameter of the drive screw,
However, the effects from the catalogue only show the length of drive screw etc.
general physical principle, which still has to be applied to
The example shows that, depending on the physical effect,
the nutcracker. This step represents the generation of a
different form parameters are addressed. Thus, once the
form solution and therefore a further concretization. Fig-
working principle is chosen, there are still a lot of decisions
ure 9 shows the effects lever and wedge and their applica-
to be made. And depending on these decisions, concrete
tion on the nutcracker. Up to now, this step is not yet opti-
solutions might look completely different even though the
mally supported by methodology or tools. There remain a
working principle is the same. This aspect is demonstrated
lot of questions to be asked while executing this step. A
in figure 10, where four different nutcrackers are shown
more systematical proceeding can be enhanced with the
which all base on the lever principle.
approach described within this paper.
lever wedge
lever wedge
C
C
Einseitig
Einseitig
Einseitig
Einseitig
F, v F1 s2
F, v F1 s2
F, v F1 s2
F, v F1 s2
s1
s1
s1
s1
M, É
M, É
M, É
M, É
lever
lever
F2
F2
F2
F2
Ä…
Ä…
Ä…
Ä…
3
3
3
r
r
r
r
D
D
Figure 10: Same principle, different solutions
To facilitate the process of defining principle solutions
basing on certain working principles a guideline has been
devised. This guideline enables the engineer to keep the
overview over the important parameters in this phase of the
design and allow a more systematic proceeding.
Figure 9: From working principles to principle solutions
" Define functions to be realized.
The application of a physical effect to a given problem
leads to a principle solution, which can be represented in
" Choose appropriate physical effects as working
sketch. These drawings show how the function of applying
principles for the given functions. In many cases not
a splitting force to the nutshell can be realized in principle.
a single effect is needed, but a chain of effects (in the
A multitude of other solutions is possible, not only includ-
nutcracker of type 3 the function  transmit and am-
ing mechanical, but also electronical, electromagnetic,
plify force is realized by combination of the effects
pneumatic, hydraulic, thermal etc. effects.
lever and wedge).
Physical effects can be described by equations containing
" Consider the major form parameters linked to the
the relations between parameters such as length, mass,
effect. This does not yet mean the exact geometric
forces, temperature etc. The equations base on equilibrium
specification, but the definition of the rough form di-
conditions such as conservation of energy etc. In many
mensions. Linked to the effect are those form parame-
cases geometrical parameters such als length, angle, area,
ters which are of relevance for the corresponding ef-
volume etc. are involved. The choice of physical effect
fect. A checklist for these linkages between physical
brings about a number of design decisions to be made in
effects and corresponding form parameters has been
the followig steps in order to concretize the solution. The
worked out (see figure 11).
step of progressing from working principles to principle
" Sketch principle solutions. The sketches represent
solutions typically involves the creation of sketches. Physi-
the application of the effect(s) to the given problem.
cal effects are usually also represented by symbols or sche-
matic illustrations such as shown in figure 9. To apply the
32 J. Ponn, U. Lindemann, H. Diehl & F. Müller / Sketching in early conceptual phases of product design: guidelines and tools
The tool would be useful for similar contexts as the sys-
Effect Specific effect types
Effect Specific effect types
tem described by Kurtoglu and Stahovich [KS*02], i. e. the
F F
F F
lever
lever
treatment of mechanical, electrical etc. systems on a rather
abstract level. Their system enables the recognition and
interpretation of schematic sketches using geometrical as
r r
r r
well as physical reasoning. The difference is, that the sys-
tem focusses on sketch analysis rather than sketch creation,
F
F
Form parameters
Form parameters
which is not supported (freehand sketches). Davis also
Number of lever arms
Number of lever arms
describes systems developed at MIT enabling sketch inter-
r
r
" One / two / &
" One / two / &
pretation [DAV*02]. A combination of both functionalities
Size of lever arm r
Size of lever arm r
(sketch creation and interpretation) might be promising.
" rough dimension, not exact value F F
" rough dimension, not exact value F F
Type of bearing:
Type of bearing:
" Sliding contact / rolling contact / &
" Sliding contact / rolling contact / &
5. Summary and conclusions
Type of bond in the bearing (mobility)
Type of bond in the bearing (mobility)
r r
r r
" Rigid / jointed / elastic / &
" Rigid / jointed / elastic / &
This contribution describes a new way of methodological
Etc.
Etc.
&
&
support for the genereration of sketches in early phases of
Figure 11: physical effects and linked form parameters product development. The focus lies on a systematic deri-
vation of principle solutions from working principles. A
At the moment, a database is being implemented which
guideline has been developed for a target oriented and
allows for an automatic linkage between physical effects
efficient proceeding supporting the designer with the deci-
and form parameters.
sions to be made along the solution concretization process.
The functionality of a computer system basing on this
4.5 Vision: A sketching tool for principle solutions
guideline and including physical effects as features which
can be inserted into a digital sketch is described. Further
The presented guideline is the basis for a digital sketching
work includes the creation of a digital database with physi-
system where working principles (physical effects) can be
cal effects and form parameters, where the links are auto-
included. The functionality of the system, which is still a
matically generated, and the realization of the digital
vision, is conceived as follows (see figure 12):
sketching tool where the depicted vision is implemented.
" A menu bar shows categories of physical effects such
as mechanics, electromangetism, fluidics etc. (1).
References
" Each category contains physical effects depicted with
[PB*96] PAHL G., BEITZ W.: Engineering Design. A
symbols (2).
Systematic Approach. Second Edition
" Choosing an effect leads to a second menu where the
(1996), Springer London.
effect has to be specified more exactly (3).
[EHR*03] EHRLENSPIEL, K.: Integrierte Produktent-
" A master of a principle working solution is created in
wicklung, Second Edition 2003, Hanser Mu-
the sketching area, where major parameters can be ad-
nich Vienna
justed. The parameters do not necessarily have to be
[ALT*96] ALTSHULLER, G.: And suddenly the inven-
of geometrical type (e. g. material parameters as in the
tor appeared: TRIZ, the Theory of Inventive
effect friction) (4).
Problem Solving. Worchester, Massachu-
Thus, physical effects can be handled analog to form fea-
setts: Technical Innovation Center 1996
tures in CAD models such as drill holes, bolts and screws.
[KS*02] KURTOGLU T., STAHOVICH T.: Interpret-
The difference is that CAD features are on a more concrete
ing Schematic Sketches Using Physical Rea-
level, while physical effects still contain many degrees of
soning. 2002 AAAI Spring Symposium on
freedom.
Sketch Understanding.
[DAV*02] DAVIS R.: Position Statement and Over-
view: Sketch Recognition at MIT. 2002
2 3
2 3
2 3
AAAI Spring Symposium on Sketch Recog-
4
4
4
nition.
Author Contact Information
Dipl.-Ing. Josef Ponn
Institute of Product Development
& &
& &
Technische Universitaet Muenchen
Boltzmannstr. 15,
85748 Garching, Germany
1
1
1
Mechanics Electromagn. Fluidics Optics Thermo.
Mechanics Electromagn. Fluidics Optics Thermo.
Tel: [phone]
Fax: [phone]
Figure 12: Tool for creating principle solutions (vision)
Email: [e-mail]