VALUE ENGINEERING AND DESIGN
Ed McMahon
The University of Tennessee at Chattanooga
College of Engineering and Computer Science
Chattanooga, TN 37403, 423-425-4771
BIBLIOGRAPHY
Ed McMahon, PhD, P.E. is a professor in the College of Engineering
and Computer Science at the University of Tennessee at Chattanooga,
specializing in design and product development. He is Director of
Industrial and Electrical Engineering, Engineering Management, and
Engineering Technology Management. He holds a B.S. from Rutgers
University and a M.E. and Ph.D. from New York University in
Chemical Engineering. He is a registered Professional Engineer in
Tennessee.
In 2002 he received a grant from the Lawrence D. Miles Value
Foundation to establish Value Methodology training at the graduate and
undergraduate level. With this support he became an AVS.
He has nineteen years of industrial experience in industrial process and
product development in the detergent, paper, and packaging industries.
He currently teaches design methodology at the undergraduate level and
product development and value management in the graduate
Engineering Management program. His research interests are in the
areas of teamwork in design, computer-based design, engineering
economy, value management, product and process development,
entrepreneurship in engineering, and the effective management of
technology.
ABSTRACT
An engineering design process has been developed based on: (a) design as a transition from a
functional description to a physical description, (b) concepts from Value Engineering, and (c) an
emphasis on the customer.
The design process begins with the identification of a customer function; what the device does, and
the target cost. The customer requirements are derived from the customer functions. These
customer requirements will be used to validate the design. A FAST diagram is developed based on
the customer function and the technical functions. The technical requirements are derived from the
technical functions. A function-based House-of-Quality is built to determine the relationship
between the customer requirements and the technical requirements. Target costs can be apportioned
to customer functions and allocated to technical functions to establish function/cost guidelines.
Functional synthesis is used to generate ideas for the functions. The function cost for implementing
the function is compared with the allocated function cost. The design is connected with new
technologies by defining the technologies in functional terms.
This function-based methodology deviates in seemingly small ways from traditional design
methodology but the continuous thread of functions enhances the design process.
INTRODUCTION
In many prescriptive methods of design, such as Pahl and Beitz [3] and VDI 2221 [4], the first
phase of the design process is the problem clarification/needs analysis. The main emphasis is on
understanding the problem and developing design requirements. The conceptual design includes
functional analysis, concept generation, and selecting a concept. In function-based design, the
design process starts with functions. The initial input is the customer's definition of what the device
does. From the designers point of view this defines the task function. It is then up to the designer
to formulate the problem in terms of the technical functions and the requirements of the system.
The approach is similar to a scenario outlined by Cross [1] where establishing functions precedes
setting requirements.
The method is focused on the customer and combines techniques associated with traditional design
methodology, value engineering, target costing, and quality function deployment.
BACKGROUND
Design Model
Design can be considered as a transformation from a functional description to a physical
description. The model suggests starting with the customer inputs to the design process, generation
of a functional description, transforming the functional description to a physical description at the
conceptual, layout, and finally the detail design level.
Customer
Technical
Inputs
Requirements
Input
INFORMATION PROCESSING ACTIVITY
Functional
Description
Physical
Description
TRANSFORMATION
Output
Best at
Each Stage
Detail
Manufacturing
Design
Instructions
Figure1: Design as a Transformation Process
Emphasis on Customer
Function-based design is also based on a model of the importance of the customer in the design
process. The customer is both a supplier of information and the evaluator of the results. The
concept of users as suppliers of information and also as consumers is consistent with a lifecycle
model of design where the customer defines the needs and ultimately evaluates and uses the results.
The customer input on what they want the design to do and the desired level of performance is used
directly in the Functional Analysis and Systems Technique and in identifying customer
requirements.
Value Engineering
Value Engineering is a structured problem solving technique which was originally aimed at
reducing cost. The modern versions of the technique include performance and an emphasis on the
customer. "The single objective of modern value analysis is to deliver to the user/customer the
required functions at minimum cost." [2].
The primary component of the technique applied in function based design is the Functional
Analysis and Systems Technique (FAST). This technique is a means of organizing functions. The
emphasis of defining the functions of the design is what the design does rather than what it is. The
functions are organized into a FAST diagram. The customer-based FAST diagram is used with
some modification. The diagram used is a customer-based FAST diagram that is based on the
process not the device. For example, the function of a hair dryer is to dry hair. The FAST diagram
for the task function, Dry Hair, looks at the process for drying hair not just what the product, a hair
dryer, does.
Functions are organized into a task function, which is the one that fulfills the overall need of the
user, the basic functions, which are essential for the task function, supporting functions, which are
essential for acceptance of the design, and subfunctions which add more detail to the functions by
answering the question "How?". Some of the supporting functions and subfunctions are identified
as technical functions.
Target Costing
Target costing is a structured approach to determine the lifecycle cost at which a proposed product
with a specific functionality and quality must be produced to generate the desired level of
profitability over its life cycle when it is sold at the anticipated selling price. [5] The principles of
target costing are:
• Know what the project will cost before it is designed
• Design team must meet cost goals
• Goals based on customer needs and company profitability
• Cost drives the design
• Product must work at a defined cost
The process involves setting cost targets for the major functions related to the subassemblies. This
is the responsibility of the design engineer.
Function-Based Methodology
The first step is to define the customer functions and the task function, what the process or device
does from the customers’ point of view. The functions are expanded using the customer-based
Functional Analysis System Technique or FAST diagram [2]. In function-based design, many
requirements can be derived from the functions in the FAST diagram. These requirements are
related to the function. For example, consider the function "move device". The requirements
associated with this function include speed, distance, direction, and position. Customer
requirements are derived from the functions identified from the customers’ point of view. These
customer requirements are used to validate the design.
The technical functions are those functions that are required from a technical point of view to
achieve the customer functions. Technical requirements are derived from the technical functions
identified in the FAST diagram. Theses technical requirements are used to verify the design during
the design process. The outputs from the Problem Definition phase are the customer functions,
technical functions, a FAST diagram, customer requirements, and technical requirements. Based on
this effort a design objective and goals are defined.
In the Conceptual Design Phase the functions, already defined and organized in the Problem
Definition, are used to generate ideas using functional synthesis. The principal of functional
synthesis is to continue to ask the question "How?" for each of the functions and generate as many
ideas as possible. While the ideas are not solution principles yet, they serve the purpose of
stimulating creativity and when combined with other ideas will lead to solution principles. The
customer requirements, defined in the Problem Definition, are used to screen the solution principles
and decide on a conceptual design.
House of Quality
The House-of-Quality is one of the Quality Function Deployment tools. It provides a linkage
between the customer attributes, the performance the customer desires, and the design parameters or
engineering characteristics. The customer and technical functions, the customer and technical
requirements, and the target costs are captured in a modified House-of-Quality. Target costs could
also be allocated to the technical function cost similar to the method of allocating costs to functions
in a function vs. cost matrix [7].
EXAMPLE
An example will be used to illustrate the design methodology based on functions. The example is
based on a project conducted in a product development class. The focus of the project was to
produce an improved residential skylight. The target cost for the skylight was estimated to be $150
based on a selling price of approximately $250. The selling price was estimated based on existing
products on the market and an estimate of the product costs for these products.
Figure 2: Skylight with curb mounting
Problem Definition
The initial step is to identify the customer functions, what the customer wants the product or process
to do. These are the functions from the customers’ point-of-view. For the skylight, these were
light environment (task function), transmit light, resist elements, create atmosphere, enhance
appearance, and install skylight.
The second step is to derive the customer requirements based on the customer functions. These
customer requirements are used to validate the design from the customers’ point of view. These are
illustrated below.
Transmit light
Size of skylight
Brightness of light
Resist elements
No leaks
No UV
Clarity
Create atmosphere
Softness of light
Dispersion of light
Enhance appearance
Location of skylight
Finish of skylight
Install skylight
Ease of installation
Time to install
The next step is to identify the technical functions. These functions identify what the designer has
to do to support the customer functions or satisfy other requirements such as codes and regulations
or for manufacturability. Some of these functions are insulate heat, fit structure, ease installation,
and access environment. Another overall technical function is to select materials. As with the
customer requirements derived from the customer functions, technical requirements can be defined
for the technical functions.
Insulate heat
Degree of insulation
Type of insulation
Thickness of insulation
Fit structure
Location of skylight
Dimensions of structure
Select material
% Transmittance
Resistance to discoloration
Resistance to erosion
Light filtering properties
UV transmission
As indicated earlier the customer FAST diagram is viewed from the customer point of view and is
more of a process view than a product view. This is important in product development because
some of the major product improvements are based on looking at the process and having the
product perform the function instead of the user. For example, some skylights come with shades
that the user has to deploy when the light is too bright. A product could be designed that
automatically deployed shades or the product could be made of material that automatically changed
properties in bright sun like some sunglasses do.
It is necessary to verify the diagram by asking the questions "How?" and "Why?”. There should be
a clear flow in both directions. For example, prevent leaks. If the question "Why?" is asked the
answer is to ensure dependability. If the question "How?" is asked of prevent leaks the answers are
minimize joints and seal joints. The process ends when the answer to the “How?” question is no
longer solution neutral. The results of the exercise are shown in Figure 3. The diagram has been
simplified for clarity.
WHY?
HOW?
Generate Light
Transmit Light
Access Environment
Maintain Clarity
Assure Dependability
Prevent Leakage
Resist Weather
Ease Installation
Light Environment
Assure Convenience
Fit Structure
Enhance Appearance
Satisfy User
Create Atmosphere
Filter Light
Attract User
Insulate Heat
Soften Light
Figure 3: FAST Diagram for Function "Light Environment"
The functions and the customer and technical objectives are captured in the function-based Houseof-Quality.
The customer functions and customer requirements are on the right side where
customer attributes are usually listed. The customer requirements are weighted based on the
relative importance of the requirement to the customer. The technical function and technical
requirements are captured along the top of the diagram. A roof could also be added and other
features such as comparing the current product to competitors and a new product design on the right
side and setting target performance values for the technical requirements on the bottom. The
diagram is kept simple here for clarity. The latest development was to add the target cost to the
customer functions and also to try to estimate the target cost for the technical functions. The results
are shown in Figure 4.
0.4
Resist Elements
0.25
Create Atmosphere
0.1
Enhance Appearance
0.15
Install Skylight
0.1
Size of Skylight
$60 Brightness
No leakage
No UV
$38 Clarity
Softness
$15 Dispersion
Location
$23 Finish
Ease of installation
$15 Time to install
6
6
6
Connect
Skylight
# Tools required
Time to install
$9
Interference
Distance
Tolerences
Dimensions
6
9
Dimensions
Integrate
Skylight
$8
Cut Hole(roof)
$20
Location
# Joints
Impact resistance
Softness of light transmission
UV Transmission
Light Filtering prop.
Resistance to errosion
Resistance to Yellowing
% Transmittance
Target Function Cost
Relative Importance
Transmit Light
# or Pieces
Assemble
Skylight
$16
Select Materials
$98
9
6
6
6
9
3
9
9
9
6
9
9
3
3
6
9
9
6
6
6
6
6
6
9
9
9
3
3
9
9
3
3
Figure 3: Function-based House-of-Quality
Conceptual Design
Functions are generated in the conceptual design phase in traditional prescriptive methodologies. In
function-based design the functions have already been defined and organized. The functions are
used to generate ideas (Functional Synthesis), functions may be organized by a necessary sequence
(Function Structures or Functional Analysis), and functions may be used as a means of technology
transfer.
The idea of Functional Synthesis is to continue to ask the question how about each of the functions.
As many alternatives as possible should be generated for each of the functions. This is best done by
divorcing oneself from the problem at hand and thinking only of the function in as many contexts as
possible. This promotes lateral thinking.
FUNCTION
IDEAS
SOLUTION PRINCIPLE
For example, transmit light can be considered in a variety of applications and result in a list like:
Clear glass
Bronze tinted glass
Double glass
Acrylic
Heat mirror glass
Wire glass
Safety glass
Low Emissivity Glass
Polycarbonate
Stainless steel rings
Auxiliary light kit
Prismatic diffuser
Metalized Mylar
Impact glass
While these are not solution principles, they serve the purpose of stimulating creativity and when
combined with other ideas will lead to solution principles.
In the case of the skylight, even though the problem was aimed at transmitting, both the type of
material and the design of the frame must be considered to provide the light and to ease installation
and prevent leakage. The students in the class developed a design with about half of the target cost
and a product that was easy to produce and easy to install
Another use of functions in the Conceptual Design is to consider new technology for possible
linkage with the desired function. Normally technologies are defined as what they are and not what
they do. For example, we talk about vapor deposition as a scientific entity but seldom by what it
does, i.e. apply material, finish surface, or enhance aesthetics. Asking the question "Why?" for
technologies leads to a level of abstractness which is useful in design for integrating new
technologies. A skylight that darkened when exposed to bright light could be developed using new
technologies.
SUMMARY
Function-based design deviates in seemingly small ways from traditional design methodology but it
is significant in that it provides a more systematic framework for teaching design. It provides a set
of tools for identifying the customers’ needs and translating those needs into a design result. The
customer's needs are translated into design functions and requirements. Developing a FAST
diagram identifies technical functions that are necessary to implement to achieve the customer
functions. Technical requirements are derived from the technical functions. This information is
captured in a function-based house-of-quality. Functions are also used as a basis for alternative
generation and connection with new technologies.
Most of the function-based design techniques have been applied successfully in a course which
teaches design methodology to all engineering disciplines. The use of the function-based House-ofQuality was developed in a graduate product development course in 2004 and will be integrated into
the design course in the fall. The method is also applicable to the design of the manufacturing
process and this will be the next area of development.
ACKNOWLEDGEMENT
I would like to acknowledge the support of the Lawrence D. Miles Value Foundation. The support
has focused my interest in the use of value methodologies and the integration of these techniques
into design and product development courses as well as an undergraduate course in Value
Engineering and a graduate course in Value Management. I would especially like to thank Don
Parker and Jim Rains for their support.
BIBLIOGRAPHY
[1] Cross, N., Engineering Design Methods, J. Wiley &Sons, Chichester, U.K., 1989
[2] Fowler, Theodore C., Value Analysis in Design, Van Nostrand Reinhold, New York, 1990
[3] Pahl, G. and Beitz, W., Engineering Design, Springer Verlag, London, 1984.
[4] VDI 2221 Systematic Approach to Design of Technical Systems and products. VDI-EKV,
Beuth-Vertieb, 1986
[5] Cooper, R, and Slagmulder, R., Target Costing and Value Engineering, Productivity Press,
Portland, OR, 1997
[6] Shillito. M. Larry, and DeMarle, David J., Value – Its Measurement, Design and
Management, John Wiley & Sons, New York, 1992
[7] Sato, Y. and Kaufman, J, Value Analysis Tear-Down, Industrial Press, New York, 2005