design and manufacture of usable consumer products… · design and manufacture of usable consumer...
TRANSCRIPT
1
DESIGN AND MANUFACTURE OF USABLE CONSUMER PRODUCTS:PART I - REVIEW OF THE LITERATURE
Majorkumar Govindaraju and Anil Mital
Industrial Engineering
University of Cincinnati
Cincinnati, OH 45221-0116
ABSTRACT
Survival of a company in these times of
increased global competition depends upon
developing high quality products at
affordable cost. It calls for a strategic
approach to developing usable and needed
products by integrating product planning, its
design, and manufacturing. A hard to use
product, even one with many functions, will
fall by the way side. Usability of a product is
generally determined by how easily and
completely it meets the users’ needs. The
criteria for usability have, however, been
gradually changing. Recent trends, such as
increased customer demand to satisfy
personal needs, are forcing the
manufacturers to design a variety of usable
products customized to individual needs.
Also, as a result of an increased
environmental awareness, customers are
seeking products that are environment
friendly, energy efficient, and recyclable.
Thus, the attributes of a product that make it
usable are changing to encompass its entire
life cycle. These changes in usability need to
be reflected in the design of a product and
the selection of processes to achieve its
manufacture. This article, part I of a two-
part paper, defines product usability in the
context of the global market and reviews
tools and guidelines available in the
published literature to produce usable
products.
1.- INTRODUCTIONProduct design is the process of creating
new and improved products for people to
use. Consumer products are products
designed for use by the general public
whereas commercial products are products
used to produce goods and services.
Consumer products are different from
commercial products in several respects as
far as the user is concerned: (a) the user is
generally untrained, (b) the user often works
unsupervised, and (c) he/she is part of a
2
diverse population (Cushman, 1991). The
process of designing and manufacturing
consumer products is greatly influenced by
the needs and demands of the customers.
In the early twentieth century,
consumer products were primarily designed
to provide functionality. Later, the form and
appearance began to be emphasized. Though
this resulted in nice looking products with
an array of features, such products were
often difficult to use (Ulrich, 1995). During
the 1980s, designers started emphasizing
user friendliness of consumer products.
Requirements such as product-user interface
design and safety were incorporated into the
design. Concern for the environment and
resource utilization in recent years has
stimulated new awareness among users to
seek products that pose minimal risk of
environmental pollution, consume less
energy, have very little toxic emissions
during use, and are recyclable when
disposed. For making products usable by
making them environmentally friendly,
designers need to emphasize energy
efficiency, recyclability, and disposability.
This calls for considering all life-cycle
phases of a product, i.e., design, production,
distribution, usage, maintenance, and
disposal/recycling, simultaneously in
determining its usability. Figure 1 shows the
various phases in the life cycle of a product.
Figure 1: Life Cycle Analysis of a Product
Recently, designers are emphasizingcustomizing the products to meet thedemands from the users to satisfy theirindividual tastes and preferences.
The following may be regarded as
the criteria for designing and manufacturing
usable consumer products:
1. Functionality
2. Ease of operation
3. Aesthetics
4. Reliability
5. Maintainability/Serviceability
6. Environment friendliness
7. Recyclability/Disposability
8. Safety and
9. Customizability
The needs and wants of customers listed
above are linked to the product design and
3
manufacture. To fulfill these needs and
wants, consumer products need to be
designed to incorporate those features that
meet the user requirements and then
manufactured by appropriate selection of
materials, processes, and tools (Figure 2).
Figure2: Usability Criteria and Design /Manufacturing Factors
The purpose of this paper (part I of a two-
part paper) is to review published literature
pertaining to design tools, methodologies,
and guidelines that are available to design
and manufacture usable consumer products.
How the usability criteria may be linked to
manufacturing attributes is shown in Part II.
2.- Criteria for designing and
manufacturing usable consumer
products:
2a. FUNCTIONALITY
The design activity is usually preceded by
obtaining information about the needs and
wants of the users through market research
(McClelland, 1990). Figure 3 shows a
structured approach to obtaining information
pertaining to user needs in the design
process for developing usable consumer
products (Mital, 1992). Conceptual design
deals with the activities that happen early in
the product development (Dika, 1988). It
involves creation of synthesized solutions in
the form of products that satisfy users’
perceived needs through the mapping
between the functional requirements in the
functional domain and the design parameters
in the physical domain, through proper
selection of design parameters that satisfy
the functional requirements. This mapping is
not unique and the outcome depends on the
creative process of individual designer.
Many techniques have been advanced to
enhance the creative process, including: (1)
trigger-word technique, (2) checklist
technique, (3) morphological technique, (4)
attribute-seeking technique, (5) Gordon
technique, and (6) brainstorming technique
(Suh, 1990).
4
Figure 3: Design flow for Product Usability
In the trigger word technique, the
verb word in the problem definition
statement is analyzed recursively to create
different set of connotations and ideas to
solve the problem. The checklist method
consist of a series of standard set of
question; each question can have more
related questions. The checklist serves to
focus at various ways of looking at the
problem and to stimulate the imagination to
explore less obvious concepts surrounding
the problem. The morphological chart
technique involves analyzing the problem to
determine the independent parameters that
are involved. Each of these parameters is
then considered separately for possible
alterative methods. All methods are
tabulated in a matrix which can be cross
correlated to produce possible solutions to
the problem. In the attribute-seeking
technique, all essential characteristics (i.e.,
attributes), that comprise a possible solution
to the problem, are singled out and analyzed
individually using either trigger-word or
checklist approach. The Gordon technique
deals with the basic underlying concepts
involved in the situation, instead of
considering the obvious aspects of the given
problem. This approach compels the
designer to take a much broader view by
analyzing the reasons why the problems
exist in the first place. For example, when
designing home-disposal appliance, one may
seek to eliminate the cause of trash rather
than dealing with the disposal of trash.
Brainstorming is a group-ideation technique
usually consisting of 6 to 8 individuals who
are conversant with the field. A moderator
defines the situation and provides
interpretation of the problem. The success of
this technique depends on the compounding
effect of each person in the group
responding to the ideas expressed by others.
5
Umeda et al. (1997) proposed
Function-Behavior-State (FBS) modeling
and a conceptual design-support tool called
FBS Modeler based on it. The FBS modeler
has knowledge bases for function
prototypes, physical features, and physical
phenomena. With these knowledge bases,
the FBS Modeler supports conceptual design
as follows:
1. The designer selects required
functions from the function prototype’s
knowledge base.
2. Aided by decomposition knowledge
of function prototypes, a designer
decomposes the required function and
sub-functions.
3. The designer chooses physical
features that can embody each
subfunction. After instantiating physical
features, the designer might discover that
some features cannot occur. In such a
case, a subsystem, Qualitative Process
Abduction System (QPAS), reasons out
candidates for the missing physical
features to satisfy the physical
conditions.
4. Next, the designer connects the
instantiated physical features to
complete the functional hierarchy. This
process constructs the behavioral-level
network structure.
5. Then, a qualitative reasoning
subsystem simulates behavior. As a
result of the simulation, the system
might discover inconsistencies between
the FBS model constructed by the
designer and the result obtained. The
system will then indicate phenomena
that will not occur even though the
designer specifies it in the initial FBS
module.
The main deficiency of the FBS method is
that it does not explicitly deal with the
geometry and kinematics of the product
which are essential concepts in mechanical
design. The approach by Chakrabarti (1996)
relates functions to the relative motions of
parts, unlike most approaches where
functions are related to the components.
These tools help designers develop the
physical design of a product given the
functional requirements specified by the
user. Any such conceptual design needs to
be further evaluated to determine whether it
is easy to use by consumers.
6
2b. EASE OF OPERATION
A product is considered user friendly if the
functions allocated to humans are within the
limitations of their abilities and constraints,
and the product-user interface is physically
comfortable and mentally not stressful
(Haubner, 1990, Nielsen, 1993a). The
system should be easy to learn, easy to
remember and relatively error free (Nielsen,
1992; Nielsen, 1993b).
Lee et al. (1997) have devised a
formal and systematic approach for
integrating the user needs and demands in
product design through a process called
High Touch. Once the customer needs are
obtained by appropriate tools such as focus
group methodology (Caplan, 1990), High
Touch process can be used for consumer’s
implicit needs and potential demands on a
product into design details. It includes
hierarchical structure of design variables,
relationship matrix among design variables,
and systematic evaluation of potential
product functions. The High Touch process
consists of a series of ergonomic analysis of
the product. A group of expert ergonomists
systematically evaluates the product through
focused group interviews, task analysis, and
field test from the consumer’s viewpoint.
Based on the results, ergonomic analyses
including design variables, such as human
characteristics, product functions, and
human-product interface variables, are
performed using a checking procedure. By
systematically analyzing the evaluation
results, many High Touch solutions such as
new product ideas, new product functions,
and design improvement are generated.
As the user-product interaction is
becoming less physical and more cognitive,
it is essential to understand the cognition of
the product semantics, i.e., the symbolic
interaction between users and products. Lin
et al.(1996), using multidimensional scaling
(MDS), present an approach that can be used
to study product semantics in product
design. MDS is a process whereby a matrix
of distance, either psychological or physical,
among a set of objects can be translated into
a representation of those objects in space.
The results from MDS analysis provide
designers with an idea of how to concentrate
their efforts in using product semantics for
consumer product design.
The consumer electronic products
are becoming more graphical user interface
intensive in recent years (Shneiderman,
1998) that is made possible by incorporation
of growing size of embedded software
(Tervonen, 1996). Product quality in such
7
products is greatly influenced by the
software quality (Kitchenham, 1996). Zero-
defect software can be obtained only by
emphasizing quality during all the phases of
software development cycle involving
requirement analysis, protype-software
development, architecture and component
design, realization, and testing (Rooijmans,
1996). The consumer product can be finally
tested for its ease of use by usability testing
procedures
such as thinking aloud method where users
work on a prototype (Jorgensen, 1990).
2c. AESTHETICS
A customer’s perception of a product’s
value is, in part, based upon its aesthetic
appeal (Logan, 1994). An attractive product
may create an aesthetic appeal and a sense
of high fashion, image, and pride of
ownership (Akita, 1991). The design of
products should induce a positive sensual
feeling (Hofmeester, 1996).
Kansei Engineering is a technology
that translates consumers’ feelings and
image for a product into design elements
(Nagamachi, 1995). Kansei Engineering
(KE) technology is classified into three
types: KE Type I, II, and III. KE Type I
deals with design elements of new products.
The customers’ feeling about a product are
broken down into a tree structure to get the
details about the design of the product.
Type II utilizes current computer
technologies, such as expert systems, neural
network models (Ishihara, 1995), and
genetic algorithms (Tsuchiya, 1996), and is
called computer assisted Kansei Engineering
System (KES). The KES architecture
basically has four databases: Kansei
Database, image database, knowledge base,
and design and color database. A consumer
inputs his image words concerning the
desired product in KES. The KES receives
these words firstly through Kansei word
database and tries to recognize them. The
inference engine in this stage works by
matching the rule-base and the image
database. Then, the inference engine
determines the design details and the KES
controller displays the part and color details
of the product on the screen. Type III is the
mathematical logic model (Nagamachi,
1995).
The Hybrid KES, a new framework
of KES, supports both the consumers and
designers. It consists of Forward Kansei
Engineering and Backward Kansei
Engineering. In the Forward KES, the
designer obtains the desired design through
8
an input of the Kansei words and outputs the
product design details. In the Backward
KES, the designer draws a rough sketch on
the computer screen and the computer
system recognizes the pattern of the design
input by the designer and shows the
estimated level of Kansei about the design
(Matsubara, 1997).
Functionality and user-friendliness,
designed into the product as indicated
above, implies that the product is able to
perform the desired functions without
posing excessive demands on the user at any
given time; the ability of the product to
function satisfactorily over a period of time
is indicated by its reliability.
2d. RELIABILITY
Reliability of a product is the probability
that it will perform satisfactorily for a
specified period of time under a stated set of
conditions (Anderson, 1991). Mean time to
failure (MTTF) is used as a measure of
reliability. MTTF is the average or mean
lifetime for a population of products.
Failures per billion operating hours (FITS),
a reciprocal of MTTF, is also used as a
measure of reliability.
Thayer (Thayer, 1986) describes a
three step process to improve the reliability
of a product during the concept design,
design verification and production
verification phases. First step is an
estimation of the reliability of each
subsystem of the existing design. The
product is depicted in the form of a chart
showing the structural hierarchy of
subassemblies. The subassemblies are
further divided into field replaceable units
(FRUs) identified by a certain numbering
scheme. Failure data are collected by part
number during the field diagnosis along with
an estimate of operating time to failure. The
failure analysis during the first step
identifies those low reliability subsystems
that should be designed out of the next
generation. During the second step involving
design verification a prototype is tested to
evaluate the design concepts. Engineering
changes are made to replace weak parts and
subassemblies and any reliability
improvement is verified through reliability
growth tests. Duane plots are a plot of the
log of cumulative test time vs the log of
either mean time between failure or the
failure rate. They are very effective in
predicting the ultimate reliability of the
product at the completion of the engineering
design phase. The design is found
satisfactory if the engineering changes are
effective in improving the reliability by
9
increasing the time between successive
failures to an acceptable level. The third step
is to release the finalized design to
production and test the reliability of units
built with the production tooling and labor.
The reliability testing is performed by
Weibull plotting of failure data. The Weibull
plots are usefull in predicting the mean time
between failure of the final product and in
identification of failures due to
manufacturing errors, wearout, or chance.
Reliability improvement is usually
achieved through continuous improvement
in materials, product design, manufacturing
processes and use environment (Alonso,
1990, Comizolli, 1990). Reliability growth
test management is a critical component of
the product assurance function (Bieda,
1992). Computer application such as
knowledge based decision support system
(DSS) are often used to assist in
quantification and monitoring of reliability
growth during the product development
phase (Nasser, 1989). The following choices
are available to a design engineer to
optimize reliability:
6. Simplify the design as much as
possible. The design with the least
complexity and fewer parts will
generally exhibit higher reliability
during operation. The reliability of the
individual components comprising the
product should be improved. Use
standard parts and materials with
verified reliability ratings (Priest, 1988).
7. Design products with redundant,
duplicate or backup systems to enable
them to continue operation should a
primary device fail. Use component
derating to improve the ratio of load to
capacity of the components. The
operation of a part at less severe stresses
than those for which it is rated is known
as derating (Alexander, 1992).
8. Give priority to improving weak
components than other parts. Design to
avoid fatigue failures such as corrosion
fatigue (Rao, 1992). Stress concentration
points are most prone to fatigue failures.
Designers should eliminate sharp
internal corners as they act as stress
concentrators. The prime cause of
reduced service life of electronic
products is overheating. Adequate means
such as ventilation or heat sinks must be
provided to prevent overheating.
9. Reduce the adverse effects of the
environment in which the product must
operate by: (a) providing insulation from
sources of heat, (b) providing seals
10
against moisture, (c) using shock
absorbing mounts, ribs, and stiffeners to
make the product rugged against shock,
and (d) providing shield against
electromagnetic and electrostatic
radiation (Bralla, 1996).
It is either technically difficult or
prohibitively expensive to produce fail proof
products. Every consumer is aware of the
fact that during the life span of the product,
repair or maintenance service will be
needed. However, when a product fails it
should fail safely and the down time should
be as short as possible. A product that can be
repaired or serviced easily and quickly has a
high maintainability. Serviceability and
maintainability can be considered as
equivalent terms.
2e. SERVICEABILITY /
MAINTAINABILITY
Maintainability / serviceability is the
element of product design concerned with
assuring the ability of the product to perform
satisfactorily throughout its intended useful
life span with minimum expenditure of
effort and money. Maintenance can either be
preventive maintenance (regular or routine
service required for preventing operating
failures) or breakdown maintenance (repair
service after some failure or decline of
function has occurred). Designing for good
serviceability means providing for ease of
both these kinds of maintenance (Blanchard,
1995).
There is a strong overlap between the
objective of achieving high product
serviceability and other desirable design
objectives such as reliability and ease of
assembly/disassembly. Easy serviceability
can often compensate for lower reliability. If
a component is prone to failure but can be
easily replaced or repaired, the
consequences of failure are less severe. The
availability of product for use depends both
on the reliability and serviceability. High
availability means that the product is ready
for full use a high percentage of the time
because failure of components is rare or
11
because replacement of failed components is
rapid or both (Smith, 1993).
Berzak (1991) has developed a
methodology to rate a product design for its
serviceability based on the calculation of the
total cost to service a product. The three
major independent contributors to the
service cost are cost per part, the failure
distribution and the labor associated with the
repair. The first two contributors are
interrelated. The failure distribution can be
reduced by raising the quality of the product
through selecting better materials, choosing
higher factor of safety in the design, or
applying more rigorous quality assurance
methods. However, all these measures will
increase the cost per part. The labor
associated with repair can be reduced by
easing the accessibility to those parts which
have to be serviced often, selection of
appropriate method of assembly and
sequence of assembly. Calculation of cost
and frequency associated with any given
service enables a designer to identify
problematic areas and to correct them before
the product is produced, rather than devising
methods of dealing with them after the
product is already in the market. A designer
has many options available to facilitate
effective and economical service.
10. Design the product so that
components prone to wear or failure are
easily visible and accessible for
inspection, testing, and easy replacement
(Mital, 1995). The covers, panels and
housings should be easy to be removed
and replaced. The product must be
designed so that the parts with high
reliability are assembled first and in a
lower, less accessible position and those
with less reliability are assembled last so
that they are closer to the cover and in an
accessible position when the cover is
removed. High-mortality components
should be located such that they can be
replaced without removing or changing
the settings of the other parts.The
product should be repairable by the user
rather than demanding attention of a
specialist. For easy field replacement
and repair the design should require
commonly available standard types of
tools (Bralla, 1996).
11. Use quick disconnect attachments
and snap fits to join the high-mortality
parts, or those that may need frequent
replacement or removal for service.
Funnel openings and tapered ends and
plug-in or slip fits facilitate easy
disassembly. Avoid press fits, adhesive
12
bonding, riveting, welding, brazing, or
soldering of such parts.
12. Consider the use of modules which
are easily replaced when necessary and
easily tested to verify their operability.
As a module is a self-contained unit
comprising a group of components and
subassemblies serving a particular
function, they all can be easily installed
or replaced as one unit at the same time
(Moss, 1985). Testing and other
maintenance is also facilitated especially
when it is advantageous to do this when
the module is removed from the basic
product. Modular design makes it easier
to isolate faults. If spare modules are
available, the defective one can be
removed and repaired while it is
replaced with a spare, thus putting the
product back in service much more
quickly. The use of modules, however, is
not always preferable. Modules are
effective when testing and replacement
are rapid and when the accompanying
parts in the module are not expensive
(Karmarkar, 1987).
13. Design the product for easy
testability. Some testability principles
are: (a) as much as possible, design the
product and its components so that these
tests can be made with standard
instruments, (b) incorporate built-in test
capability and, if possible, built-in self-
testing devices in the product, (c) make
the tests themselves easy and
standardized, capable of being
performed in the field, (d) provide
accessibility for test probes: for example,
make test points prominent and provide
access parts or tool holes, and (d) make
modules testable while still assembled to
the product (Anderson, 1991).
2f. ENVIRONMENTAL
FRIENDLYNESS The accelerated flow of
waste and emission due to explosion in
industrial activities spurred by rising
demand for consumer products is causing an
increase in the pollution of the eco-system.
The consumers are demanding ‘green’
products as a result of a new environmental
awareness and the responsibility of the
manufacturers is gradually expanding over
the entire product life cycle (Tipnis, 1993).
A design that has minimal or no harmful
effects during manufacture, use and disposal
is considered environment friendly (Kaila,
1996). Life cycle assessments (LCA) tools
have been developed to analyze and
compare the environmental impact of
13
various product designs (Hoffman, 1997).
LCAs review a product by summing up the
influence of all the processes during the life
of a product on various envrionmental
impact classes such as ozone depletion,
global warming, smog, acidification,
eutrophication, heavy metals, pesticides and
carcinogenics. The disadvantage with life
cycle analysis is that in order to evaluate the
environmentally responsible product rating
every LCA tool needs substantial database
for process information of all stages of the
life cycle and for various impact classes
with weighting factors for all materials,
emissions and other reaction products during
the product design stage itself (Nissen,
1997).
Some simplified procedures use
mass and energy used in a product or
processes as indicators instead of looking at
the often diffuse environmental impact
properties of a design. This is based on the
assumption that an ecologically undesirable
product will consume large material and
energy resources during its manufacture and
usage, and will need additional resources to
suppress the side effects during product
disposal.
The design deficiencies identified
during the environmental assessment
procedure should be removed by (1)
eliminating environmentally unfriendly
materials from the product and
manufacturing process, (2) if elimination is
not possible, reducing the quantity of such
materials, (3) designing the product so that
components can be reused with or without
refurbishing, and (4) designing the product
so that such materials can be recycled
(Glantschig, 1990). Some of the options that
a designer has in enhancing environmental
friendliness are:
14. Use of toxic materials in the
product or in the production
processes should be avoided.
Eliminate use of substances such
as CFCs or HCFCs . Reduce
manufacturing residues such as
mold scrap, cutting scrap and
minimize the use of solvents, oils
and acids during the
manufacturing process. Minimize
equipment cleanouts that generate
liquid or solid residues (Billatos,
1997).
15. Avoid product materials which
are restricted in supply. Avoid
product materials which have
disposal problem. Use recycled
materials rather than virgin
14
materials if possible (Ashley,
1993). Minimize the amount of
periodic disposal of solid
materials such as cartridges,
containers and batteries. Design
to utilize recycled consumables
from outside suppliers. Design
products to minimize liquid
replenishment such as coolants
and lubricants. Design products to
minimize gaseous emissions such
as carbon dioxide or tetraethyl
lead (Bralla, 1996).
16. Design products to consume less
energy. Also, choose the form of
energy alternative which has the
least harmful effect on the
environment. Design should
include features such as sleep
mode which conserves energy
during the time when the product
is not in use(Shiovitz, 1997).
17. Designs requiring spray-painted
finishes should be avoided
(Lankey, 1997). The need for
environmentally damaging
solvents can be avoided by using
powder coating, roll-coating or
dip-painting for surface finishing
of metals. Plastic parts which are
molded in color eliminates the
need for painting.
2g. RECYCLABILITY /
DISPOSABLITY Thousands of consumer
goods come to the end of their useful life
every day and joins the waste stream. It is
estimated that more than 10 million vehicles
reach the end of their useful lives every year
and an estimated 150 million discarded
personal computers will have been landfilled
by the year 2005 (Chen, 1993). To deal with
such a situation it is imperative that the
products are designed for recyclability.
Product recycling reduces adverse impact on
the environment by reducing the volume of
materials deposited in the landfills, and
conserves scarce natural resources (Tipnis,
1994, Pnueli, 1997). The steps involved in a
recycling program are (1) collection of
worn-out products, (2) disassembly of the
product and sorting of incompatible
materials, (3) cleaning, shredding, and
grinding of materials as necessary, and
separation of high value materials such as
steel for reclaiming, (4) conversion into
quality-consistent, usable material, and (5)
discarding the fluff to the waste stream or
landfill.
The considerations for design for
recyclabilty often overlap with the
15
considerations for design for disassembly
(Zussman, 1994). Srinivasan has developed
a disassembly tool to support product design
for recyclability (Srinivasan, 1997). It
identifies the abstract design modules that
need to be developed to build a geometric
virtual disassembly tool. The modules are
software programs executed as part of four
step design process involving (1) product
analysis, (2) disassemblability analysis, (3)
optimal disassembly sequence generation,
and (4) design rating. The product analysis
step involves selection of components that
need to be disassembled and the appropriate
de-manufacturing application. The
information regarding the components to be
disassembled is obtained from the (1)
knowledge-base which consists of material,
environment and application domain
database, and (2) the user requirements. The
disassemblability analysis step consists of
determining the disassemblability
components and analyzing all possible
disassembly methods and the selection of an
appropriate disassembly that best fits the
user requirements. The third step consists of
generating an optimal disassembly sequence
and disassembly directions for the
components to be disassembled. The final
step involves disassembly evaluation,
disassembly rating and design
recommendations. A typical rating index
depends on the number of components
disassembled, ease of disassembly,
complexity of path, and time taken for
disassembly. The design recommendations
focuses on enhancing the product design by
minimizing the disassembly cost and time
involved in the overall product cycle.
Chen (1993) presents a cost benefit
analysis as another tool for assessing the
economics of designing for recyclability.
The cost of recycling includes cost of
disassembly, shredding, material recovery
and dumping. The total benefit from
recycling includes revenue from used parts,
revenue from used parts and recovered
material, and benefit of emission reduction
from energy saving. The guidelines that help
in reducing the cost and increase the revenue
due to recycling are:
18. The product and its components
should be designed such that they can be
reused. The major components should be
designed to be remanufactured or
refurbished rather than reclaimed only
for its materials.
19. Minimize the number of parts it
contains as fewer parts make sorting of
materials easy for recycling. Avoid the
16
use of separate fasteners, if possible.
Snap-fit connections between parts are
preferable because they do not introduce
a dissimilar material and often easier to
disassemble with simple tools. The
number of screw head types and sizes
used in fasteners in one product should
be minimized so that changing of the
tools used to loosen and remove
fasteners is reduced during recycling
(Bralla, 1996). Use of fewer number of
fasteners reduces the disassembly time.
Modular design simplifies disassembly.
20. Minimize the amount of material in
the product. The less the amount of
material involved, the simpler the
eventual disposal problem when the
product has reached the end of its useful
life. Less material also means that,
eventually, the product will need less
landfill space. By designing for near-net-
shape manufacturing processes that
minimize material scrap, designers can
achieve benefits comparable to
designing smaller and lighter parts.
21. Reduce the number of different
materials in a product. Use of dissimilar
materials that can not be separated or are
difficult to separate from the basic
materials should be avoided (Berko-
Boateng, 1993). As thermoplastic
materials can be recycled by melting,
they are preferred to thermosetting
materials. For joining plastics solvent,
friction, or ultrasonic welding is
preferable to adhesive bonding and for
metals welded joints are preferable to
brazed or soldered joints (Dewhurst,
1993). If adhesive bonding can not be
avoided, an adhesive material that is
compatible need to be used when the
components are recycled. For labels
water-soluble adhesives facilitate
separation during recycling.
2h. SAFETY
The increasing number of injuries filed each
year in courts due to personal injuries while
using consumer products indicates that
safety may be the most basic consideration
in product design from human as well as
cost standpoint (Heideklang, 1990; Ryan,
1983). ‘Safety’ implies absence of hazards
or the minimal exposure to them during
entire life cycle of the product (Bass, 1984).
Schoone-Harmsen (1990) developed an
iterative three step method to detect and
solve safety problem during product design.
It consists of (1) analysis of the problem, (2)
identification of critical factors, and (3)
17
synthesis. The analysis step is used to
evaluate the product on their safety, by
gaining insight into possible accidents
connected with either the product, the
actions of the user, or environmental
conditions. The second step consists of
identifying the factors that are critical
among those found in the analysis. If a
critical factor is related to the product, the
hazard can be removed by changing the
corresponding characteristics of the product.
If actions or posture of the user or
environmental conditions cause the hazards,
the designer should change the product
features connected with such critical factors.
During the synthesis step a structured list of
solution strategies to the detected safety
problems is developed. Correcting a critical
product feature is done through selection of
a different working principle, deactivation
during use before injury or damage occurs,
separation of the user from the source of
danger, and limitation of the possibility of
the user to modify the product. Correcting a
critical action associated with the user or the
environment is achieved by influencing the
actions of the user through the product,
selection of the user by anthropometric or
cognitive characteristics, and influencing the
selection of place of use through the
product. The effectiveness of the design
solutions can be found by performing the
analysis step again. If the improvement is
not sufficient or new hazards have been
identified the whole process can be repeated
till all the hazards are either eliminated or
are found acceptable, and all the safety
standards are complied with (Wilson, 1984).
Standard techniques such as fault
tree analysis, failure mode analysis and
sneak circuit analysis can be used to design
safety into a product (Hammer, 1980).
Safety concerns often overlap with
reliability and ease of use. The following
considerations are intended to aid the
designer in creating a safe product:
22. The products should be fail-safe. As
users can occasionally make mistakes in
the operation of a product the design
should allow for human error. When
such human errors happen, or when
there is failure of mechanism, it should
not result in an accident. Products
should be designed to be user-friendly
and to operate with the human
capabilities to minimize the possibility
of human errors that can cause accidents
(Chow, 1978).
23. Parts that require service should be
freely accessible, easily repairable and
18
replaceable without causing interference
with other assemblies and without
posing hazards to the user. To avoid
shearing or crushing points in which
hands or other parts of an operator’s
body might be caught or injured
adequate clearances should be provided
between moving parts and other
elements. Design should replace sharp
corners with liberal radii as sharp
external corners are hazards during
operation and maintenance of the
product.
24. The design of the product should be
robust enough to withstand adverse
environment in which it will be used and
provide safeguards against those
environmental factors such as corrosion,
vibration, pressure changes, radiation,
and fire which could create safety
hazards (Witherall, 1985). Reduce the
level of noise (Lyon, 1994) and vibration
(Fraser, 1993) to avoid their harmful
effects on users. Provide adequate
ventilation and lighting.
25. Make the product from high-impact
or resilient materials so that it does not
break, when dropped accidentally, into
small fragments with sharp edges or
sharp points that are potentially
swallowable by children. Use of
flammable materials including
packaging materials should be
minimized. Avoid the use of materials
that are a hazard when burned, recycled,
or discarded (Bralla, 1996).
2i. CUSTOMIZABILITY
So far, the aim of product design and
development has been to create a product
that satisfies the needs of the average
customer. No consideration has been given
to differences in individual tastes and
preferences. Often, customers are willing to
pay more if their individual needs are better
satisfied. Design for mass customization
(DFMC) is a new approach to producing an
increasing variety of customer’s
requirements without a corresponding
increase in the cost and lead-time (Tseng,
1996). Providing products and services
which best serve the customers’ needs while
maintaining mass production efficiency is a
new paradigm for industries. The
recognition of each customer as an
individual and the subsequent production of
products with tailor-made features is the
basis of this new approach. The core of
DFMC is to develop a mass customization
oriented product family architecture (PFA)
19
with a meta level design process integration
as a unified product creation and delivery
process model. The inherent repetition in
product marketing, design, and
manufacturing can be recognized through
the establishment of patterns. Once patterns
are identified and formulated into a product
family architecture, scale of economy can be
applied for efficiency. The formulation of
PFA enables the optimization of
reusability/commonality in both product
design and process selection from the
product family perspective. It also provides
a basis to facilitate the front-end
configuration in order to fulfill the
individual requirements of the customers
(Tseng, 1997).
While product customization enables
the design of products and processes to meet
individual customer needs, it is essential to
note that such needs change frequently,
forcing frequent modification in product
design. This calls for a dynamic
reconfiguration of manufacturing systems to
accommodate the swift changes in product
design. Development of Integrated
Manufacturing Systems (IMS) aimed at
multi-product, small-batch production, fast
and optimized design, speedy product
development, and just-in-time delivery made
possible by Strategic Information Systems
(SIS) has been in use as a strategy to achieve
this (Hitomi, 1991). Now, agile
manufacturing is an emerging concept in
industry that aims at achieving flexibility
and responsiveness to changing customer
needs. Agile manufacturing systems seek to
produce a large variety of products
efficiently and are recongfigurable to
accommodate changes in the product mix
and design changes (Kusiak, 1997).
3. DESIGN SUPPORT TOOLS /
METHODOLOGIESBesides the design approaches and
guidelines discussed so far, the following
design methodologies and tools are also
widely used: (1) Design for Producibility,
(2) Design for Assembly, (3) Robust Design,
(4) Group Technology, and (5) Quality
Function Deployment. Genetic algorithms
(Balakrishnan, 1996; Balakrishnan, 1995)
and Conjoint analysis (Kohli, 1987) methods
are mathematical tools associated with
product design.
3a. Design for Producibility: The design of
an individual component will have a strong
effect on the attributes of the product in
which it is used. Design for producibility
20
emphasizes that design of detailed parts
cannot be independent of the manufacturing
process (Burhanuddin, 1992). Design
principles and guidelines for a part that is
made with one process may not apply if
another process is used. For example, if a
part is to be die cast, the suitable materials,
the wall thickness, shape, complexity, size,
dimensional tolerances, and other
characteristics will be significantly different
from those applicable to a metal stamping or
a part made from metal powder. The
resultant part attributes, such as strength,
temperature resistance, and corrosion
resistance, may also be different. The
selection of part features and the processes
should occur simultaneously. There are
many guidelines for the design of individual
parts based on the manufacturing processes
used. Table 1 shows various processes and
the characteristics of parts made using them
and the variables that control the part quality
compiled from various manufacturing
handbooks (Bralla, 1986; Cubberly, 1989;
Dallas, 1976). The design principles given
below can however be applied to component
parts regardless of the process.
• Simplify the design of each part as
much as possible (Stoll, 1988). Use
simple shapes instead of complex
contours, undercuts, and elaborate
appendages. Parts of simple shape
have less opportunity to be defective.
Use the most liberal tolerance
possible, consistent with the quality
and functional requirements of the
part and with the capabilities of the
manufacturing processes involved.
Tolerances appropriate to the
primary operations eliminate the
need for costly secondary operations
to control dimensions and refine
surface finishes (Billatos, 1990).
• Select near-net-shape processes that
are capable of producing a part to or
near final dimensions with a limited
number of operations, particularly
minimum machining, such as
injection molding and powder
metallurgy. An injection molding
part can have all final dimensions,
identifying nomenclature, finish, and
color
provided in one operation. A powder metal
part can be complete with precision bearing
surfaces after only two or three high-
production operations. Standardize parts
21
features and minimize their number. Avoid
designs that require machining operations.
Often another process can be substituted for
one that primarily involves machining with
significant savings. For example, sheet
metal processes can be used to provide parts
with bearing surfaces, holes, reinforcing
ribs, etc. Extruding, precision casting, cold
rolling or the other near-net shape processes
may provide the precision needed for
elements and surfaces that otherwise would
require machining (Bralla, 1996). Use
materials formulated for easy manufacture.
For example, free-machining alloys for
machined parts, or high-ductility materials
for drawn part can be used.
3b. Design for Assembly: In this approach,
the overall assembly is analyzed primarily to
determine if components can be eliminated
or combined leading to a simplified product
assembly. Service and recycling are
facilitated when a product is simplified. A
product which is easy to assemble is
normally easier to disassemble when
maintenance, repair, or disassembly or
recycling take place (Eversheim, 1991).
Simpler assemblies can often be brought to
market sooner because of fewer parts to
design, procure, inspect, and stock with less
probability that a delay will occur. Products
with fewer parts will also have higher
reliability (Boothroyd, 1992; Boothroyd,
1994).
Processes such as injection molding
and die-casting permit very complex parts
that result when separate parts are combined
into one. By selecting flexible material and
making wall sections thin hinges and springs
can be incorporated in plastic parts. Integral
snap-fit elements, tabs, crimped sections or
catches, press fits and rivets can be used to
replace threaded fasteners (Joines, 1995).
With some manufacturing processes, it is
possible to incorporate elements such as
guides and bearings in the basic part by
selection of appropriate materials and
processes. Due to their natural lubricity
many plastic materials can be used in
applications involving bearing surfaces
when the velocity and pressure involved are
low. For more demanding bearing surfaces
powder metal part with sufficient precision
and porosity can be used as it can retain the
lubricating oil within itself (Bralla, 1996).
As modularity improves
serviceability and reliability, the design
should include modular subassemblies while
avoiding too many levels of subassembly at
the same time (Karmarkar, 1986). Adopt
layered and top-down assembly whereby
each successive part in the product can be
added to the assembly from above rather
than from the side or bottom. Design parts
22
such that they are self-aligning and that they
can not be inserted incorrectly. Design very
small or highly irregular parts that are
manually assembled for easy handling by
adding a grasping element to the parts.
3c. Robust Design: Robustness of a design
refers to the design that ensures that the
product will never fail to perform its
intended function during its useful life.
Robust design methodology, popularly
known as Taguchi Technique, provides a
way to develop specifications for robust
design by using the design of experiments
theory. The procedure attempts to find out
the settings of product design parameters
that make the product’s performance
insensitive to environmental variables,
product deterioration and manufacturing
irregularities. It is often more costly to
control causes of manufacturing variations
than to make a product or process
insensitive (or robust) to these variations
(Juran, 1974).
23
Taguchi separates off-line quality
planning and improvement activities into
three stages: system design, parameter
design, and tolerance design. System design
is the application of scientific and
engineering knowledge to produce a
functional prototype. This prototype model
defines the basic product/process design
characteristics (parameters) and their initial
settings. The goal of parameter design is the
identification of settings that minimize
variation in the performance characteristic
and adjust its mean to an ideal value.
Tolerance design is a method for
scientifically assigning tolerances so that
total product manufacturing and lifetime
costs are minimized (Nevins, 1989).
3d. Group Technology: Group Technology
procedure attempts to classify the system
into subsystems and subdivides them into
part families based on design attributes and
manufacturing similarities (Chang, 1991).
Group technology can be used for product
design and manufacturing system design.
For product design, components that have
similar shape are grouped into design
families and a new design can be created by
simply modifying an existing component
design from the same family. Using a coding
method, each part is given a numerical or
alphabetical code based on its geometrical
shape, complexity, dimension, accuracy and
raw material. By using this concept,
24
composite components can be identified.
Composite components are parts that
embody all the design features of a design
family or design subfamily (Farris, 1990).
For manufacturing purposes, parts with
similar processing requirements comprise a
production family. Since similar processes
are required for all family members, a
machine cell can be built to manufacture the
family. As a result the production planning
and control is made much easier and the
cycle time to manufacture a product is
greatly reduced even while maintaining
product variability. Thus, planning using
group technology method can be used in
production environment for manufacturing
goods for mass customization. (Shetty,
1993).
3e. Quality Function Deployment (QFD):
This is a methodology of translating the
requirements of the customers into product
and process design (Akao, 1990). The QFD
technique, using the house of quality, is used
to translate customer views systematically
into key engineering characteristics,
planning requirements, and, finally, into
production operations (Bergquist, 1996). It
is achieved through its four key documents
which are the product planning matrix, the
product deployment matrix, component
deployment matrix, and the operating
instruction sheet. The purpose of the product
planning matrix is to translate customer
requirements into important design features.
The individual customer needs are ranked
for importance and the cumulative effect on
each of the design features is obtained. A
product deployment matrix is then made for
each of the product features down to the
subsystem and component level. The
product deployment matrix shows to what
extent the relationship between component
and product characteristics are critical and
affordable. If a component is critical, then it
is further deployed and monitored in the
design, production planning, and control.
The component deployment matrix expands
the list of components or the exact
parameters required to design a complete
component. The operating instruction sheet
is the final key document that basically
defines the operator requirements as
determined by the actual process
requirements, the process checkpoints, and
the quality control points (Day, 1993). Thus
QFD tries to achieve quality products by
using the philosopy of concurrrent
engineering (Parsei, 1993) which integrates
product design, process design, and process
control (Maduri, 1993).
SUMMARY AND CONCLUSION
25
The various desirable usability objectives
and their realization through appropriate
product design and manufacture have been
reviewed in this article. The paper lists
various usability criteria and briefly reviews
the design and manufacturing issues for each
one of the them individually. As one may
note, in many cases, the design guidelines
serve and enhance more than one design
objective. For example simplifying the
design to incorporate a smaller number of
parts and using modular design improves
reliability as well as serviceability. Designs
that enhance safety often reduce the need for
physical exertion for the users, making such
designs easy to operate. Products which are
biodegradable are both recyclable and
environment friendly.
However, the design
recommendations are not always mutual and
are often seen to conflict with one another.
Using liberal tolerances reduces production
costs and eliminates expensive and time
consuming secondary operations. Tool
maintenance and quality inspection can be
reduced and higher speeds and feeds can be
employed. But liberal tolerances can lead to
more variations in components causing
variations in product performance, quality,
and reliability. Paints that enhance external
appearance often contain harmful heavy
metal elements and solvents which pose risk
to the environment. Hence the product and
process design recommendations should be
examined together for their effect on
enhancing or optimizing various usability
objectives. Such an examination calls for a
unified approach aimed at simultaneous
evaluation of various design options and
integrating the various phases of product
design, i.e., planning, concept design, and
process design. In Part II of this paper
(Govindaraju, 1998) we illustrate how QFD
matrices can be used for implementing an
holistic approach to product design.
REFERENCES
1. Akao, Y., 1990. Quality FunctionDeployment: Integrating CustomerRequirements into Product Design.Productivity Press, Cambridge, MA.
2. Akita, M., 1991. Design andergonomics. Ergonomics, 34(6): 815-824.
3. Alexander, S. M., 1992. ReliabilityTheory, in Industrial EngineeringHandbook, by Hodson (ed.). McGraw-Hill,New York, NY.
4. Alonso, R. Continuous improvementin reliability. pp. 109-114.
5. Anderson, D. M., 1991. Design forManufacturability. CIM Press, Lafayette,CA.
6. Ashley, S., 1993. Designing for the
26
environment. Mechanical Engineering,March.
7. Balakrishnan, P.V.S., and Jacob,V.S., 1995. Triangulation in decisionsupport systems: algorithms for productdesign. Decision Support Systems, 14: 313-327.
8. Balakrishnan, P.V.S., and Jacob,V.S., 1996. Genetic algorithm for productdesign. Management Science, 42(8): 1105-1117.
9. Bass, S., Weis, P, Bass, L., andNoble, T.C., 1984. Human factors affectingsafety in product design. ASQC QualityCongress Transactions, pp. 397-401.
10. Bergquist, K., and Abeysekara, J.,1996. Quality Function Deployment (QFD) -A means for developing usable products.International Journal of IndustrialErgonomics, 18: 269-275.
11. Berko-Boateng, V., Azar, J., de Jong,D., and Yander, G.A., 1993. Asset recyclemanagement-A total approach to productdesign for the environment. IEEEInternational Symposium on Electronics andthe Environment. IEEEService Center,Piscataway, NJ., pp. 19-31.
12. Berzak, N., 1991. Serviceability bydesign. Proceedings of 23rd InternationalSAMPE Technical Conference. SAMPE,Covina, CA, USA. v 23. pp. 1060-1071.
13. Bieda, J. Reliability growth testmanagement in the automotive componentindustry. pp. 387-393.
14. Billatos, S. B. Guidelines for productdesign, process selection andmanufacturability. pp. 129-136.
15. Billatos, S. M., and Basaly, N. A.,1997. Green Technology and Design forEnvironment. Taylor and Francis,Washington, DC.
16. Blanchard, B. S., Verma, D., andPeterson, E. L., 1995. Maintainability: AKey to Effective Serviceability andMaintenance Management. John Wiley &Sons, Inc., New York, NY.
17. Boothroyd, G., and Alting, L., 1992.Design for assembly and disassembly.Annals of CIRP, 41(2): 625-636.
18. Boothroyd, G., 1994. Product designfor manufacture and assembly. Computer-Aided Design, 26(7): 505-520.
19. Bralla, J. G., 1986. Handbook ofProduct Design for Manufacturing: APractical Guide to Low-Cost Production.McGraw-Hill Book Company, New York,NY.
20. Bralla, J.G., 1996. Design forExcellence. McGraw-Hill, Inc., New York,NY.
21. Burhanuddin, S., and Randhawa,S.,1992. A framework for integratingmanufacturing process design and analysis.Computers and Industrial Engineering, 23(1-4): 27-30.
27
22. Caplan, S., 1990. Using focus groupmethodology for ergonomic design.Ergonomics, 33(5): 527-533.
23. Chakrabarti, A., and Bigh, T.P.,1996. An approach to functional synthesis ofsolutions in mechanical conceptual design,Part III: Spatial configuration. Research inEngineering Design, 8(2): 116-124.24. Chang, T., Wysk, R.A., and Wang,H., 1991. Computer-Aided Manufacturing.Prentice Hall, Englewood Cliffs, NJ.
25. Chen, R.W., Navin-Chandra, D., andPrinz, F.B., 1993. Product design forrecyclability: a cost benefit analysis modeland its application. IEEE, pp. 178-183.
26. Chow, W., 1978. Cost Reduction inProduct Design. Van Nostrand Reinhold,New York, NY.
27. Comizzoli, R.B., Landwehr, J.M.,and Sinclair, J.D., 1990. Robust materialsand processes: key to reliability. AT&TTechnical Journal, Nov/Dec: 113-128.
28. Cubberly, W. H., and Bakerjian, R.,1989. Tool and Manufacturing EngineersHandbook, Desk Edition. Society forManufacturing Engineers, Dearborn, MI.
29. Cushman, W. H., and Rosenberg, D.J., 1991. Human Factors in Product Design.Elsevier Science Publishers, Amsterdam,The Netherlands.
30. Dallas, D. B., 1976. Tool andManufacturing Engineers Handbook.McGraw-Hill Book Company, New York,
NY.
31. Day, R. G., 1993. Quality FunctionDeployment: Linking a Company with itsCustomers. ASQC Quality Press,Milwaukee, WI.
32. Dewhurst, P., 1993. Disassembly byDesign. Assembly, April.
33. Dika, R. J., and Begley, R. L.Concept development through teamwork -working for quality, cost, weight andinvestment. pp. 277-288.
34. Eversheim, W., Baumann, M., 1991.Assembly-oriented design process.Computers in Industry, 17: 287-300.
35. Farris, J., and Knight, W.A., 1992.Design for Manufacture: expert processingsequence selection for early product design.
36. Fraser, J. W., and Gureghian, R. S.,1993. Controlling shock and vibration inelectronic products. MechanicalEngineering, Dec: 82-84.
37. Glantschig, W. J. Design forEnviornment (DFE): A SystematicApproach to Green Design in a ConcurrentEngineering Environment. AT&T BellLaboratories, Princeton, NJ.
38. Govindaraju, M., and Mital, A.,1998. Design and manufacture of usableconsumer products: Part II - Developing theusability-manufacturing linkages.
28
39. Hammer, W., 1980. Product SafetyManagement and Engineering. PrenticeHall, Englewood Cliffs, NJ.
40. Haubner, P. J., 1990. Ergonomics inindustrial product design. Ergonomics,33(4): 477-485.
41. Heideklang, H. R., 1990. Safeproduct design in law, management andengineering. Marcel Dekker, New York,NY.
42. Hitomi, K., 1991. Strategicintegrated manufacturing systems: theconcept and structures. International Journalof Production Economics, 25: 5-12.
43. Hoffman III, W.F., and Locascio, A.,1997. Design for environment developmentat motorola. IEEE, pp. 210-214.
44. Hofmeester, G.H., Kemp, J.A.M.,and Blankendaal, A.C.M., 1996. Sensualityin product design: a structured approach.CHI, Apr: 13-18.
45. Ishihara, S., Ishihara, K.,Nagamachi, M., and Matsubara, Y., 1995.An automatic builder for a KanseiEngineering expert system using self-organizing neural networks. InternationalJournal of Industrial Engineering, 15: 13-24.
46. Joines, S., and Ayoub, M.A., 1995.Design for assembly: an ergonomicapproach. Industrial Engineering, Jan: 42-46
47. Jorgensen, A. H., 1990. Thinking-aloud in user interface design: a method
promoting cognitive ergonomics.Ergonomics, 33(4): 501-507.
48. Juran, J. M., Gryna, F. M., andBingham, R. S., Jr., 1974. Quality ControlHandbook. McGraw-Hill Book Company,New York, NY.
49. Kaila, S., and Hyvarinen, E., 1996.Integrating design for environment into theproduct design of switching platforms.IEEE, pp. 213-217.
50. Karmarkar, U.S., and Kubat, P.,1987. Modular product design and productsupport. European Journal of OperationalResearch, 29: 74-82.
51. Kitchenham, B., and Pfleeger, S. L.,1996. Software quality: the elusive target.IEEE Sofware, Jan: 12-21.
52. Kohli, R., and Krishnamurthi, R.,1987. A heuristic approach to productdesign. Management Science, 33(12): 1523-1533.
53. Kusiak, A, and He, D.W., 1997.Design for agile assembly: an operationalperspective. International Journal ofProduction Research, 35(1): 157-178.
54. Lankey, R., McLean, H., and Sterdis,A., 1997. A case study in environmentallyconscious design: wearable computers.IEEE, pp. 204-209.
55. Lee, M.W., Yun, M.H., Jung, E.S.,and Frievalds, A., 1997. High Touch:
29
Ergonomics in a conceptual design process-Case studies of a remote controller andpersonal telephones. International Journal ofIndustrial Ergonomics, 19: 239-248.
56. Lin, R., Lin, C.Y., and Wong, J.,1996. An application of multidimensionalscaling in product sementics. InternationalJournal of Industrial Engineering, 18: 193-204.
57. Logan, R. J., Augaitis, S., and Renk,T., 1994. Design of simplified televisionremote controls: a case for behavioural andemotional usability. Proceedings of theHuman Factors and Ergonomics Society 38th
Annual Meeting: 365-369.
58. Lyon, R. H., 1994. Engineering forsound quality. NOISE-CON 94: 3-8.
59. Maduri, O., 1993. Design Planningof an Off-Highway Truck - A QFDApproach, in Quality Through EngineeringDesign, by Kuo, W., and Pierson, M. M.(ed.). Elsevier Science Publishers,Amsterdam, The Netherlands.
60. Matsubara, Y., and Nagamachi, M.,1997. Hybrid Kansai Engineering Systemand design support. International Journal ofIndustrial Engineering, 19: 81-92.
61. McClelland, I., 1990. Marketingergonomics to industrial designers.Ergonomics, 33(4): 391-398.62. Mital, A., and Anand, S., 1992.Concurrent design of products andergonomic considerations. Journal of Designand Manufacturing, 2: 167-183.
63. Mital, A., 1995. Is the backgroundknowledge of ergonomists important ifergonomics is to succeed within asimultaneous engineering (SE)environment? International Journal ofIndustrial Ergonomics, 16: 441-450.
64. Moss, M. A., 1985. Designing forMinimal Maitenance Expense. MarcelDekkar, New York, NY.
65. Nagamachi, M., 1995. KansaiEngineering: A new ergonomic consumer-oriented technology for productdevelopment. International Journal ofIndustrial Ergonomics, 15: 3-11.
66. Nasser, S. M., and Souder, W. E.,1989. An interactive knowledge-basedsystem for forecasting new productreliability. Computers and Engineering,17(1-4): 323-326.
67. Nevins, J.L., and Whitney, D.W.,1989. Concurrent Design of Products andProcesses. McGraw-Hill, New York, NY.
68. Nielsen, J., 1992. The usabilityengineering life cycle. Computer, Mar: 12-22.
69. Nielsen, J., 1993. Iterative user-interface design. Computer, Nov: 32-41.
70. Nielsen, J., 1993. UsabilityEngineering. Academic Press, Inc., SanDiego, CA.
30
71. Nissen, N.F., Griese, H.,Middendorf, A., Pottor, M.H., and Reichl,H., 1997. Environmental assessments ofelectronics: a new model to bridge the gapbetween full life cycle evaluations andproduct design. IEEE, pp. 182-187.
72. Parsei, H. R., and Sullivan, W. G.,1993. Concurrent Engineering:Contemporary Issues and Modern DesignTools. Chapman & Hall, London, SE1 8HN,UK.
73. Pnueli, Y., and Zussman, E., 1996.Evaluating the end-of-life value of a productand improving it by redesign. InternationalJournal of Production Research, 35(4): 921-942.
74. Priest, J.W., 1988. EngineeringDesign for Producibility and Reliability.Marcel Dekker, Inc., New York, NY.
75. Rao, S. S., 1992. Reliability-BasedDesign. McGraw-Hill, Inc., New York, NY.
76. Rooijmans, J., and Aerts, H., 1996.Software quality in consumer electronicsproducts. IEEE Software, Jan: 55-64.
77. Ryan, J. P., 1983. Human factorsdesign criteria for safe use of consumerproducts. Proceedings of the Human FactorsSociety- 27th Annual Meeting, pp. 811-815.
78. Schoone-Harmesen, M., 1990. Adesign method for product safety.Ergonomics, 33(4): 431-437.
79. Shetty, D., 1993. Production orienteddesign: an integrated approach in design formanufacturing. Design forManufacturability, 52: 123-128.
80. Shiovitz, A., Craig, E., 1997. Usingdata to determine design for environmentproduct goals. IEEE, pp. 105-108.
81. Shneiderman, B., 1998. Designingthe User Interface: Strategies for EffectiveHuman-Computer Interaction. Addison-Wesley, Reading, MA.
82. Smith, D.J., 1993. Reliability,Maintainability and Risk. Practical Methodsfor Engineers. Butterworth-Heinemann Ltd.,Oxford OX2 8DP, U.K..
83. Srinivasan, H., Shyamsundar, N.,and Gadh, R., 1997. A virtual disassemblytool to support environmentally consciousproduct design. IEEE, pp. 7-12.
84. Stoll, H. W., 1988. Design forManufacture. Manufacturing Engineering,Jan: 67-73.
85. Suh, N.P., 1990. The Principles ofDesign. Oxford University Press, New York.
86. Tervonen, I., 1996. Support forquality-based design and inspection. IEEEsoftware, Jan: 44-54.
87. Thayer, S.B., 1986. Three steps toimprove product reliability. ASQC QualityCongress Transactions. pp. 301-306.
31
88. Tipnis, V.A., 1993. Evolving issuesin product design life cycle design. Annalsof the CIRP, 42(1): 169-173.
89. Tipnis, V.A., 1994. Challenges inproduct strategy, product planning andtechnology development for product lifecycle design. Annals of the CIRP, 43(1):157-162.
90. Tseng, M.M., 1996. Design for masscustomization. Annals of the CIRP, 45(1):153-156.
91. Tseng, M. M., 1997. Masscustomization - opportunities and challengesfor high value added products and services.International Conference in IndustrialEngineering and Practice. pp. 19-27.
92. Tsuchiya, T., Maeda, T., Matsubara,Y., and Nagamachi, M., 1996. A fuzzy ruleinduction method using genetic algorithm.International Journal of IndustrialErgonomics, 18: 135-145.
93. Ulrich, K.T., and Eppinger, S.D.,1995. Product Design and Development.McGraw-Hill, Inc., New York, NY.
94. Umeda, Y., and Tomiyama, T., 1997.Functional reasoning in design. IEEEExpert, Mar-Apr: 42-48.
95. Wilson, J.R., 1984. Standards forproduct safety design: A framework for theirproduction. Applied Ergonomics, 15(3):203-210.
96. Witherall, C. E., 1985. How to
Avoid Product Liability Lawsuits andDamages. Noyes Publications, Park Ridge,NJ.
97. Zussman, E., Kriwet, A., and Seliger,G., 1994. Disassembly-oriented assessmentmethodology to support design forrecycling. Annals of the CIRP, 43(1): 9-14.