Translating Customer
Requirements into Product
Design
By Dr Mohammed Arif – licensed under the Creative Commons
Attribution – Non-Commercial – Share Alike License
http://creativecommons.org/licenses/by-nc-sa/2.5/
Translating Customer Requirements into Product Design
Contents
Section[1] ................................................................................................................................................ 3
Concurrent Engineering – Introduction and History ............................................................................ 3
Background ......................................................................................................................................... 3
Concurrent Engineering (CE) – Definition ........................................................................................... 4
Different Aspects of CE.................................................................................................................... 5
Managerial and human aspect ........................................................................................................ 5
Technological aspects ..................................................................................................................... 5
Soft & Hard Factors of CE ............................................................................................................... 5
Implementation related issues in CE ............................................................................................... 6
Section[2] ................................................................................................................................................ 7
Quality Function Deployment (QFD): Definition and history ............................................................... 7
Section[3] ................................................................................................................................................ 9
Product Development in Off-Site Construction ................................................................................... 9
(DESIGN FOR MANUFACTURING) ................................................................................................... 9
Introduction: ......................................................................................................................................... 9
The Design for Manufacture (DFM) process: ...................................................................................... 9
DFM objectives: ................................................................................................................................. 10
Versions of the DFM: ......................................................................................................................... 10
DFM Methodology: ............................................................................................................................ 11
Basic principles of designing for economical production: .................................................................. 13
Product design principles for efficient manufacturing: ....................................................................... 14
CASE STUDY .................................................................................................................................... 17
REFERENCES .................................................................................................................................. 17
Translating Customer Requirements into Product Design
By
Dr.Mohammed Arif
School of the Built Environment
University of Salford
Section[1]
Concurrent Engineering – Introduction and History
Background
There is a growing awareness of the need for changes within the construction industry in its
current practices and processes of project development which include design, procurement,
construction, project delivery etc. This is mainly caused by the following:
1. The dramatically decreasing construction costs through standardisation of construction
processes (CIRIA Report,1999);
2. The increasing demand and sophistication of clients (de Graaf et al., 1996);
3. The rising requirements for project functionality through growing competition;
4. The rapid developments in communication and information technologies; and
5. The recommendations in UK Government-initiated reports such as the Latham Report
(1994) and the Egan Reports (1998, 2002).
Many construction companies are responding to this increasing importance of project
development processes by incorporating concurrent engineering practices to improve their
project development capability (de Graaf and Sol, 1994).
Not only the construction industry, but also other industries are increasingly challenged with
growing competition, reduced product life cycle, and changing market and customer
demands. To meet these demands, organisations within these industries are forced to develop
new products, which have to be cheaper, delivered faster and provide greater functionality.
The product development process in many organisations, however, presents many problems
with respect to the required product quality, time-to-market, and costs. To achieve a better
performance level, a new or better configuration of processes and technology, consisting of
people and means, is needed. Concurrent Engineering is considered to offer a solution to the
problems encountered. The practice of Concurrent Engineering is known to combine high
quality, low cost and a short time to market (de Graaf et al., 1996). Other possible effects of
implementation of CE could be a good product development practice, which includes
innovation and organisational learning (Bergman and Ohlund, 1995).
In the manufacturing sector, a great improvement in performance and productivity has been
achieved through the application of Concurrent Engineering (CE). This application refers to a
design process where all life cycle stages of a product are considered simultaneously, from
the conceptual stage through the detailed design stage to construction, operation, and eventual
disposal of a facility (Tummala, 1996). The CE approach to manufacturing aims to increase
product quality and reduce cost and development time, by integrating diverse specialities into
a unified development process. The CE approach to product development seeks continuous
process improvement. This includes increased organisational effectiveness and efficiency, the
elimination of non-value added activities that is waste, and continuous optimisation or
refinement of the entire system which includes design, manufacturing, production and
marketing for an improved productivity and quality (Love and Gunasekaran, 1997). The
popularity in CE use is, no doubt, a result of the associated benefits in adopting its principles.
These includes (de Graaf et al., 1996; Tummala, 1996; Kamara et al., 1997):
 A reduction in product development time and time to market;
 An overall cost saving;
 Products that match customers needs;
 Assured quality; and
 Low service cost throughout the life of the product.
These improvements in productivity, through the use of CE in manufacturing, provide a basis
for the adoption of its principles in other industries such as construction. Due to the
similarities between the construction and manufacturing industries, developments in
manufacturing processes that have led to improvements in the productivity can also be used
in the construction processes. These similarities include fulfilling the customers/clients
requirements, delivering assured product/project, minimum lead time, cost saving etc.
(Kamara et al., 1997). Furthermore, the changing environment within which the construction
industry operates, and the growing demand for more units of construction for fewer units of
expenditure, are similar to some of the challenges which led to the adoption of the concurrent
engineering in the manufacturing industry. And especially, for manufactured construction,
these concepts are extremely relevant because of similar processes adopted. It is therefore,
argued that, concurrent engineering can provide a suitable framework to improve the
construction process. However, while there are similarities, there are also marked differences
between manufacturing and construction which should be taken into consideration if CE is to
be effectively implemented in the construction industry and its processes (Kamara et al.,
1997).
While Concurrent Engineering (CE) is gaining acceptance, some implementation efforts have
not realised their full potential for reducing costs and improving time-to-market for product
development efforts. This is due in part to weak planning to support the implementation
(Componation and Byrd, 1996). One method that has been used successfully to improve
planning is to conduct a readiness assessment of an organisation prior to the introduction of
CE. Some studies have been conducted in manufacturing and software organisations using a
range of techniques. Similar studies have been conducted in the construction industry by
Khalfan et al (2005).
Concurrent Engineering (CE) – Definition
The UK Government initiated reports such as the Latham Report (1994) and the Egan
Reports (1998, 2002) have recommended the improvement of the construction industry’s
business performance. The need for greater co-ordination and integration within the industry
has led to the adoption of various concepts from other industries. One of these, which offers
major scope for effective co-ordination and integration within the industry, is Concurrent
Engineering (Kamara et al., 2000).
Concurrent Engineering, sometimes called simultaneous engineering, or parallel engineering
has been defined in several ways by different authors. The most popular one is that by
Winner et al. (1988), who state that concurrent engineering “…is a systematic approach to the
integrated, concurrent design of products and their related processes, including manufacture
and support. This approach is intended to cause the developers, from the outset, to consider
all elements of the product life cycle from conception through disposal, including quality,
cost, schedule, and user requirements.” Another definition is by Broughton (1990) who
defines simultaneous (concurrent) engineering as “…an attempt to optimise the design of the
product and manufacturing process to achieve reduced lead times and improved quality and
cost by the integration of design and manufacturing activities and by maximising parallelism
in working practices.”
Different Aspects of CE
There are eight basic elements of CE, which are divided into two aspects as follows
(Bergman and Ohlund, 1995; Chen, 1996, Componation and Byrd, 1996; de Graaf and Sol,
1994; Khalfan and Anumba, 2000c; Prasad, 1997):
Managerial and human aspect
Managerial and human aspect covers team development, leadership, and organisational
philosophy. It includes:
 The use of cross-functional, multidisciplinary teams to integrate the design of products
and their related processes;
 The adoption of a process-based organisational philosophy;
 Committed leadership and support for this philosophy; and
 Empowered teams to execute the philosophy.
Technological aspects
This includes use of technology for design and manufacturing, communication, coordination, and developing standards. It covers:
 The use of computer aided design, manufacturing and simulation methods to support
design integration through shared product and process models and databases;
 The use of various methods to optimise a product’s design and its manufacturing and
support process;
 The use of information sharing, communication and co-ordination systems; and
 The development and/or adoption of common protocols, standards, and terms within the
supply chain.
Soft & Hard Factors of CE
CE encompasses a number of business method, which comprises a series of interconnecting
practices relating to people, processes, computer-based support tools, and formal method (see
Figure 1). Broadly speaking, the model can be divided into those ‘soft’ or psychological
aspects of CE such as team working and team leadership, and those ‘hard’ factors or systems
of CE such as formalised methods, e.g. QFD, FMEA and computer-based support tools
(Dann et al., 1996).





Cross-functional teams
Team Leadership
Team Development
Reward and Recognition
Structures
Co-location
Process





Project Management
Formal NPD procedures
Customer/Supplier integration
Formal Team Briefings
Organisation Redesign
Tools




Computer Networks
CAD
CAE
Simulation
Formal
Methods




QFD
Design of Experiment
DFM
FMEA
People
‘Soft’ factors
of CE
Concurrent
Engineering (CE)
‘Hard’ factors
of CE
Figure 1: Characterisation of Concurrent Engineering (Dann et al., 1996)
Implementation related issues in CE
In order to compete and cut down the lead-time for introducing new products, many of the
large automotive industries in the western world are adopting this integrated approach to
product development. The theory of simultaneous engineering is simple, the implementation
however has proved to be a difficult task. Attempts to implement simultaneous engineering
can result in restructuring and reorganisation of a company. The major issue involved with
implementation can be summarised as follows (Sya, 1997):
a)
b)
c)
d)
e)
Senior management commitment;
People management;
Product costing;
Monitoring, feedback and control; and
Financial Justification.
Implementing Concurrent Engineering, however, is not straightforward, but requires welldesigned improvement cycles. In Figure 2 the four successive stages in an improvement cycle
are depicted. These stages are awareness, readiness, deployment and improvement. In the
awareness stage, the potential benefits of Concurrent engineering are becoming known. In the
readiness stage, the company is measured with respect to certain performance criteria. These
measurements lead to decisions concerning adaptation to the organisation, the technology and
the process, composing the product development process. In the deployment stage, specific
improvement plans are made and implemented. In the improvement stage, the progress is
measured and the improvement cycle is closed by re-entering the readiness stage for further
improvement (de Graaf et al., 1996).
Improvement
Deployment
Readiness
Awareness
Figure 2: The improvement cycle (de Graaf et al., 1996)
Chen (1996) has described two basic issues, which are very important for the success of
implementation of CE: organisational management and human issues. Organisational
management and human issues can be further sub-divided into other issues at three levels:
individual level, team level, and organisation level (see Figure 3). A brief description on each
of these levels is presented below (Brooks and Foster, 1997; Chen, 1996; de Graaf et al.,
1996; Deasley and Lettice, 1997; Johansson et al., 1999; Thamhain, 1994; Tummala et al.,
1996):
Section[2]
Quality Function Deployment (QFD): Definition and history
Quality Function Deployment (QFD) is a process where a multi-functional team translate
Voice of the Customer to Voice of the developer. This translation is accomplished by
developing customer needs into product characteristics and, subsequently, developing process
specifications from product characteristics.
Profitable revenue growth is a pursuit shared by all commercial enterprises even by the
higher education establishments. Organisations holding high share of the markets they
operate are generally better suited to see higher revenue growths as they exercise some
influence over the market or market segment. High customer satisfaction and customer
loyalty helps organisations to establish/strengthen the position of market leadership and more
importantly in their pursuit of higher revenue growth. And, customer is satisfied if they get
what they want (if not all, even the few important ones, ‘must-be’s). Customers possibly buy
the same product/service if they have experience of previous satisfaction.
Therefore, meeting the customer needs is essential to any business. Meeting customer needs
should therefore be fundamental to all measures of quality. There are two broad aspects of
quality: negative and positive. You can assess whether customer needs were met after the
product/service is developed or before. Most of the efforts on quality have focussed on
negative quality perceptions of existing products (e.g. correcting deficiencies) through use of
Statistical Process Control (SPC).
Japan took a different approach in the form of Company-Wide Quality Control (CWQC)
which is largely acknowledged as one of the key foundations of Japanese manufacturing
success. Development of CWQC is attributed to Ishikawa, Demming and Juran. CQQC’s
approach to quality is articulated by Ishikawa (1985):
To practice quality control is to develop design, produce and service a quality product which
is most economical, most useful and always satisfactory to the consumer.
This understanding of ensuring customer demand for quality being addressed during the
product development process (against ensuring quality after the product development) is
expressed in the findings of MIT Commission on Industrial Productivity in 1986. The
commission emphasised the need for all segments of organizations to work toward greater
functional integration. This can be accomplished through multi-functional teams which can
work with greater speed in product development and better respond to changing markets
(Dertouzous, Lester, Solow; MIT Commission on Industrial Productivity, 1989).
This lays the foundation of concurrent engineering, where marketing, manufacturing,
engineering, procurement and supply, finance and other disciplines necessary to develop a
new product simultaneously design product and processes to manufacture that product from
its concept stage.
Traditionally, sequential product development process involved (Hinckley, 1993):
1. Senior management outlining a concept for new product
2. Concepts being refined by product planners and stylist
3. Specifications developed and tested by product engineering
4. Manufacturing and purchasing manufacturing the product.
Sequential model of product development process is handicapped by communication
problems, long product development time and, frequent and costly product changes.
Concurrent engineering aims to overcome these handicaps of traditional product
development process including costly product changes in particular but it needed a structure
and medium to address communication problems during product development.
Quality Function Deployment (QFD) provides that structure and medium to facilitate
communication where the multi-functional product development team deploys requirements
from the Voice of the Customer to the following:
1. Critical product control characteristics
2. Component characteristics
3. Process control characteristics
4. Operation instructions
This could be better understood in the context of using QFD in manufacturing (Crowe and
Cheng, 1996). Crowe proposed four stages: functional strategies, manufacturing priorities,
action plans and detail tasks. In the first stage all functional level strategies are realized and
they become the whats for the next stage (i.e. component characteristics). In the second stage,
all parallel functional level strategies are their potential customers. For example, marketing
requirements can be an input to the QFD matrix and the output would be a set of
manufacturing priorities to fulfil the requirements. In the third stage, broad manufacturing
priorities are translated into detailed action plans for implementation (i.e. process control
characteristics). The last stage is identifying specific tasks (i.e. operation instructions) to
realize the plans.
Section[3]
Product Development in Off-Site Construction
(DESIGN FOR MANUFACTURING)
Introduction:
Design for manufacture (DFM) represents a new awareness of the importance of design as
the first manufacturing step. It recognises that a company cannot meet quality and cost
objectives with isolated design and manufacturing engineering operations. To be competitive
in today’s marketplace requires a single engineering effort from concept to production. The
essence of the DFM approach is therefore the integration of product design and process
planning into one common activity, Kuo, et.al, (2001).
The DFM approach embodies certain underlying imperatives that help maintain
communication between all components of the manufacturing system and permit flexibility to
adapt and to modify the design during each stage of the product’s realisation. Chief among
these is the team approach or simultaneous engineering, in which all relevant components of
the manufacturing system including outside suppliers are made active participants in the
design effort from the start. The team approach helps ensure that total product knowledge is
as complete as possible at the time each design decision is made. Other imperatives include a
general attitude that resists making irreversible design decisions before they absolutely must
be made and a commitment to continuous optimisation of product and process.
The Design for Manufacture (DFM) process:
The DFM process begins with a proposed product concept, a proposed process concept, and a
set of design goals. All three of these inputs would be generated by a thorough product plan
developed using the team approach. Design goals would include both manufacturing and
product goals.
Each of the activities within the DFM process addresses a particular aspect of the design.
Optimisation of the product/process concept is concerned with integrating the proposed
product and process plan to ensure inherent ease of manufacture. The simplification activity
focuses on component design for ease of assembly and handling. This activity can often be
rapidly effective because the integrated product and process requirements and constraints
help identify problem areas. The third activity ensures conformance of the design to
processing needs. For example, if an assembly is to be built on a particular flexible assembly
(FAS), it is important that the assembly be designed in such a way that it can be assembled
using the programmable gripper engines, flexible fixtures, and assembly operations available
within the FAS. Finally, functional optimisation considers appropriateness of material
selection and parameter specification that maximise the design objectives.
By reversing the process, this DFM approach helps ensure that all of the design constraints,
including assembly, material transformation processes, and material handling requirements
are included as part of the functional optimisation of the design. In this way, the DFM
process enables the designer or design team to consider all aspects of the product’s design
and manufacture in the early stages of the design cycle, so that design iteration and
accompanying engineering changes can be made easily and cost effectively. Finally, by
integrating the product and process design, it is possible to include manufacturing
recommendations and a process plan as part of the engineering release package.
This has great advantages because it leads to few, or no, manufacturing surprises. Also, both
manufacturing and engineering share equally in ownership of and ultimate commitment to
design.
DFM objectives:
The objectives of the design for manufacture approach are to:
1- Identify product concepts that are inherently easy to manufacture.
2- Focus on component design for ease of manufacture and assembly.
3- Integrate manufacturing process design and product design to ensure the best matching
of needs and requirements.
Meeting these objectives requires the integration of an immense amount of diverse and
complex information. This information includes not only considerations of product from,
function, and fabrication, but also the organisational and administrative procedures that
underline the design process and the human psychology and cognitive processes that make it
possible.
Versions of the DFM:
Many different versions of the DFM process have been proposed. Each version is likely to be
similar in the issues addresses and the concepts embodied. One proposed version of the DFM
process is shown in Figure (1), (Stoll, 1988). The four activities comprising this process are
arranged in a circular fashion to emphasise the iterative nature of the process. Traditionally,
many products have been designed by starting with functional optimisation of the product
design itself, followed by detail design of each part to be made by a particular process, then
simplification, and finally design of a process to manufacture and assemble the product. As
shown by the arrows, the progression of steps in the proposed DFM process is just the reverse
of the more traditional design approach.
Proposed product
concept Proposed
process plan
Design goals
Optimise
Product/Proce
ss
Concept
Engineering Release
Package:
- Part Drawings
- Part List
- Assembly Drawings
- Process Plan
Simplif
y
Produ
ct
Design
Imperatives:
- Team Approach
- Least Commitment
- Continuous
Optimisation
Of
Product
and
Process
Optimis
e
Product
Functio
n
Ensure
Product/Proces
s
Conformance
Figure (1) Typical DFM Process (Stoll, 1988)
DFM Methodology:
The development and use of design methodologies that help the design team achieve an
optimised design solution is an important part of the DFM approach (Boothroyd, et.al. 2002).
DFM is a relatively new way of looking at a very old problem. To appreciate the problem and
to understand where DFM is today and what needs to be done in the future, it is necessary to
look briefly at traditional practice and at some of the organisational issues which are involved
in the DFM approach. The importance of manufacturability in product design has been
recognised for years. For its importance, is illustrated by the well-known fact that up to 80%
or more of production decisions are directly determined by the product design (Ertas & Jones,
1993), which leaves very little freedom of choice for process planning.
The concept of design for manufacture is predicted on the recognition that:
iii-
Design is the first step in product manufacture.
Every design decision, if not carefully considered, can cost extra manufacturing
effort and productivity loss.
iii- The product design must be carefully matched to advanced flexible manufacturing,
assembly, quality control and material-handling technologies in order to fully realise
the productivity improvements promised by these technologies.
To maximise the quality of early design decisions and thereby minimise the amount of
engineering change, the DFM approach seeks to involve input from as many manufacturing
system activities as possible as early as possible. Ideally, convergence to ‘globally optimal’
product and process decisions should occur at the early, low-cost stages of the project. This
approach requires the simultaneous engineering model depicted in Figure (2).
In a study addressing integration of design and manufacturing during deployment of advance
manufacturing technology, Corbett et al., (1991) identified five mechanisms which illustrate
trends in administrative innovation:
12345-
Design-manufacturing team;
Common CAD systems for design and tooling;
Common reporting position for computerisation;
Philosophical shift to DFM;
Development and promotion of the engineering generalist.
Market
analysis
Product
Design
Sales and
distribution
Production
System
design
Manufacturin
g
Figure (2) Simultaneous engineering model (Corbett, J. 1991)
Basic principles of designing for economical production:
The following principles, applicable to virtually all manufacturing processes, will aid
designers in specifying components and products that can be manufactured at minimum cost;
1- Simplicity:
Other factors being equal, the product with the fewest parts, the least intricate shape, the
fewest precision adjustments, and the shortest manufacturing sequences will be the least
costly to produce. Additionally, it usually will be the most reliable and the easiest to
service.
2- Standard materials and components:
Use of widely available materials and off-the-shelf parts enables the benefits of mass
production to be realised by even low-unit-quantity products. Use of such standard
components also simplifies inventory management, eases purchasing, avoids tooling and
equipment investments, and speeds the manufacturing cycle.
3- Standardised design of the product itself:
When several similar products are to be produced, specify the same materials, parts, and
subassemblies for each as much as possible. This procedure will provide economies of
scale for component production, simplify process control and operator training, and
reduce the investment required for tooling and equipment.
4- Liberal tolerances:
Although the extra cost of producing too tight tolerances has been well documented, this
fact is often not appreciated well enough by product designers. The higher costs of tight
tolerances stem from factors such as;
(a) extra operations such as grinding, honing, or lapping after primary machining
operations,
(b) higher tooling costs from the greater precision needed initially when the tools are
made and the more frequent and more careful maintenance needed as they wear,
(c) longer operating cycles,
(d) higher scrap and rework costs,
(e) the need for more skilled and highly trained workers,
(f) higher materials costs, and
(g) more sizable investments for precision equipment.
5- Use of the most processible materials:
Use the most processible materials available as long as their functional characteristics and
cost are suitable. There are often significant differences in processibility (cycle time,
optimal cutting speed, flowability, etc.) between conventional material grades and those
developed for easy processibility. However, in the long run, the most economical material
is the one with the lowest combined cost of materials, processing, and warranty and
service changes over the designed life of the product.
6- Teamwork with manufacturing personnel:
The most producible designs are provided when the designer and manufacturing
personnel, particularly manufacturing engineers, work closely together as a team or
otherwise collaborate from the outset.
7- Avoidance of secondary operations:
Consider the cost of operations, and design in order to eliminate or simplify them
whenever possible. Such operations as deburring, inspection, plating and painting, heat
treating, material handling, and others may prove to be as expensive as the primary
manufacturing operation and should be considered as the design is developed. For
example, firm, non-ambiguous gauging points should be provided; shapes that require
special protective trays for handling should be avoided.
8- Design appropriate to the expected level of production:
The design should be suitable for a production method that is economical for the quantity
forecast. For example, a product should not be designed to utilise a thin-walled die
casting if anticipated production quantities are so low that the cost of the die cannot be
amortised. Conversely, it also may be incorrect to specify sand-mould aluminium casting
for a mass-produced part because this may fail to take advantage of the labour and
materials savings possible with die castings.
9- Utilising special process characteristics:
Wise designers will learn special capabilities of the manufacturing processes that are
applicable to their products and take advantage of them. For example, they will know that
injection-moulded plastic parts can have colour and surface texture incorporated in them
as they come from the mould, that some plastics can provide “living hinges” that powdermetal parts normally have a porous nature that allows lubrication retention and obviates
the need for separate bushing inserts, etc. utilising these special capabilities can eliminate
many operations and the need for separate, costly components.
10- Avoiding process restrictiveness:
On parts drawings, specify only the final characteristics needed; do not specify the
process to be used. Allow manufacturing engineers as much latitude as possible in
choosing a process that produces the needed dimensions, surface finish, or other
characteristics required.
Product design principles for efficient manufacturing:
The following DFM principles are discussed to illustrate their global nature and to provide
insight into how such principles can be used to aid the product-development team.
i) Minimise total number of parts:
Fewer parts mean less of everything that is needed to manufacture a product. This includes
engineering time, drawings and part numbers; production control records and inventory;
number of purchase orders, vendors, etc; number of bins, containers, stock locations, buffers,
etc; amount of material-handling equipment, containers, number of moves, etc; amount of
accounting details and calculations; service parts and catalogues; number of items to inspect
and type of inspections required; and amount and complexity of part production equipment,
and facilities, assembly and training. Put another way, a part that is eliminated costs nothing
to make, assemble, move, handle, orient, store, purchase, clean, inspect, rework, service. It
never jams or interferes with automation. It never fails, malfunctions, or needs adjustment. A
part is a good candidate for elimination if there is:
abcd-
No need for relative motion;
No need for subsequent adjustment between parts;
No need for service or repair ability;
No need for materials to be different.
However, part reduction should not exceed the point of diminishing return where further part
elimination adds cost and complexity because the remaining parts are too heavy, or too
complicated to make and assemble, or are too unmanageable in other ways.
Perhaps the best way to eliminate parts is to identify a design concept which requires few
parts. Integral design, or the combining of two or more parts into one, is another approach
(Fisher, 1993). Besides the advantages given above, integral design reduces the amount of
interfacing information required, and decreases weight and complexity. One-piece structures
have no fasteners or joints, and fewer points of stress concentration. Conversely, structural
continuity leads to high strength and light weight.
Plastic is a major key to integral design. Plastic is available for making springs, bearings, cam
and gears, fasteners, hinges and optical elements. Powder metallurgy (P/M) is a good
alternative if plastic parts do not have adequate strength, heat resistance or cannot be held to
the tolerance needed (Boothroyd, & Alting, 1992).
Although switching to a different manufacturing process may lead to a more costly part,
experience with part integration has shown that a more costly part often turns out to be more
economical when assembly costs are considered (Precision Metal, 1975).
ii) Develop a modular design:
A module is a self-contained component with a standard interface to other components of a
system (Chow, 1978). Modular design offers the ability to standardize diversity because it
allows a product to be customized by using different combinations of standard components.
Modular design resists obsolescence and shortens the redesign cycle. A new generation
product can realize most of the old modules. Change is provided via a few, new, or improved
modules. Cost and ease of service and repair are enhanced because a defective module can be
quickly replaced by a good one. Most importantly, modular design simplifies final assembly
because there are fewer parts to downside, modular design can add cost and complexity
because of extra fittings and interconnections required. Therefore, modular design should not
be used unless its advantages are needed.
iii) Use standard components:
A stock item is always less expensive than a custom-made item. Standard components require
little or no lead time and are more reliable because characteristics and weaknesses are well
known. They can be ordered in any quantity at any time. They are usually easier to repair and
replacements are easier to find. Use of standardized components puts the burden on the
supplier and makes the supplier do more.
iv) Design parts to be multi-functional:
Combine function wherever possible. For example, design a part to act both as a spring and a
structural member, or to act both as an electrical conductor and a structural member. An
electronic chassis can be made to act as an electrical ground, a heat sink and a structural
member. Less obvious combinations of functions might involve guiding, aligning and/or selffixturing features to a part to aid in assembly, or providing a reflective surface or
recognizable feature to facilitate vision inspection. These latter examples illustrate inclusion
of functions which are only needed during manufacture. Such function combinations are
often the result of DFM awareness.
v) Design parts for multi-use:
Many parts can be designed for multi-use. For example, the same mounting plate can be
designed to mount a variety of components, (Stoll, 1986). One approach involves sorting all
parts (or a statistical sample) manufactured or purchased by the company into two groups
consisting of:
1. Parts which are unique to a particular product or model.
2. Parts which are generally needed in all products and/ or models
Each group is then divided into categories of similar parts (part families). Multi-use parts are
then created by standardizing similar parts. In standardizing, the designer should sequentially
seek to:
(1) Minimize the number of part categories;
(2) Minimize the number of variations within each category;
(3) Minimize the number of design features within each variation.
Once developed, the family of standard parts should be used wherever possible in existing
products and used exclusively in new product designs. Also, manufacturing processes and
tooling based on a composite part containing all design features found in a particular part
family should developed. Individual parts can then be obtained by skipping some steps and
features in the manufacturing process (Chow, 1978).
1- Design parts for ease of fabrication:
This principle requires that individual parts be designed using the least costly material that
just satisfies functional requirements (including style and appearance) and such that both
material waste and cycle time are minimized. This in turn requires that the most suitable
fabrication process available be used to make each part and that the part be properly designed
for the chosen process. Use of near-net shape processes is preferred whenever possible.
Likewise, secondary processing (finish machining, painting, etc.) should be avoided
whenever possible. Secondary processing can be avoided by specifying tolerances and
surface finish carefully and then selecting primary processes (precision casting, P/M, etc.)
which meet requirements. Also, material alternatives which avoid painting, plating, buffing,
etc., should be considered. This principle is based upon the recognition that higher material
and/or unit process cost can be accepted if it leads to lower overall production cost.
2- Minimize handling:
Position is the sum of location (x, y, z) and orientation (α, β, ɣ). Position costs money.
Therefore, parts should be designed to make position easy to achieve and the production
process should maintain position once it is achieved. Design in features which facilitate
product and component packing. Use standard outer package dimensions for machine feeding
and strong, design packaging adequately to protect and ensure quality at all stages of
handling, and design packing for easy handling. Consider material flows within the
production facility including product flow, workplace flow, supply flow, hardware flow, bulk
material flow, container flow and fixture flow. For each flow, consider how the product,
subassembly, component or part can be designed to simplify or eliminate the flow (Stoll,
1986).
CASE STUDY
You are the new Chief Design Officer (CDO) of a company engaged in manufactured
construction. Your company has had a reputation of producing NOT SO GOOD quality
products. Now that you are in-charge of product design you have taken upon yourself to
change the image of your company. You have decided that from now on, all the new products
being designed will have to be customer focussed and high quality.
Discuss how you will make your organisation customer centric, using the topics documented
in this package.
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