ESL-IE-02-04-34
Product Design for Energy: An Inverted Pyramid Approach
Ralph W. Plummer
B. Gopalakrishnan
Nasr M. Alkadi
Professor
Associate Professor
PhD Student, C.E.M
Department of Industrial and Management Systems Engineering
West Virginia University
Morgantown, WV 26506
bgopalak@mall.wvu.edu
from the outset, to consider all elements of the
product life cycle from conception through disposal,
including quality, cost, schedule, and user
requirements [17]. Jt merges the efforts of product
designers and manufacturing engineers to improve
manufacturing
processes
and
products with
concurrence, constraints, coordination, and consensus
as the primary ingredients [5,13,15,16]. Figure I
shows the flow of information in concurrent
engineering. During the preliminary and detail design
phases of a product, insignificant costs are actually
incurred while a significant amount of costs may be
committed. The committed costs usually pertain to
costs such as those associated with manufacturing,
assembly, testing, and disposal. The design of the
product conveys upon it several attributes in terms of
material, shape, and function. To enable the
realization of these attributes, product life cycle
phases such as manufacturing and assembly must be
involved.
ABSTRACT
The product design function is important
within the spectrum of the product life cycle.
Manufacturing processes are likely to consume much
energy, as evidenced in aluminium and steel
industries. The product design parameters such as the
material characteristics, geometry and system level
variables playa major role in the level of this energy
consumption. The sensitivity of the energy
consumption to these parameters and variables is
likely to reveal the satisfactory conditions within the
design spectrum leading to significant reductions in
manufacturing energy consumption. In the overall
process of concurrent engineering, applicable herein,
the information flow is often gradual, ranging from
broad issues relating to energy usage with minimal
user input to specific issues. This approach, termed as
the "inverted pyramid" approach, and outlined in this
paper is beneficial in providing energy related
information to product designers and manufacturing
process specialists at an early stage in the product life
cycle.
INTRODUCTION
Product design and manufacture has been an
important activity for decades and is continuing to be
so in organizations that cater to a variety of
marketplaces and which aim to be profitable so as to
survive in a globally competitive business climate.
As the desires of the consumer vary with time,
industries are being forced to redesign their products
and manufacture them so as to bring them to the
market in a short time. Some product life cycles can
be so short that it is becoming increasingly important
to reduce the product development time. Many
organizations are resorting to concurrent or
simultaneous engineering for enabling shorter
product and system development times. Concurrent
engineering can be defined as the systematic
evaluation of preliminary and detail designs to
activities that take place further down the product life
cycle [8]. It is the systematic approach to the
integrated concurrent design of products and their
related processes, including manufacture and support,
this approach being intended to cause developers,
Figure I.
The Flow of Information in Concurrent
Engineering
In the concurrent engineering environment,
design for manufacturability and other "ilities" have
been analysed and several models have been
developed to assist in evaluating evolving product
designs [9]. The focus almost always has been on
cost and time associated with elements such as
manufacturing processes and methods and assembly
methodologies. Energy is usually not considered as a
component of this cost. This can be understood easily
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ESL-IE-02-04-34
from the fact that the cost referred to herein is a
function of product development time, "ease" of
manufacture, and product quality. These three items
have been important elements as criteria in the
concurrent engineering process. Energy may not
have an important role to play in any of these criteria.
It is important that energy be a player in the
concurrent engineering scenario. In the light of
increasing energy costs, manufacturing processes
must be evaluated on the basis of energy in order to
derive meaningful conclusions regarding process
feasibility.
energy consumption during the design of a heat
exchanger network. It was found that from the
process design, demand for utilities could be
estimated. Then, the utility system is designed based
on the process design and the energy-integrated
process design can be introduced at this stage to seek
the design that requires minimum energy, and the
corresponding levels at which the utility should enter
the process can also be detennined [14]. Diana 1.,
Bauer has developed an integrated model of the
grinding process. The model evaluated the energy
utilization and waste mass flux for different surface
and process specifications [3]. Epstein, 1., Gary and
Ambs, Lawrence, have developed a technique for
estimating the energy end-use utilizing an interactive
computer model. The developed model served as a
tool for industrial managers to gain an understanding
of the relative magnitudes of energy consumption in
different use categories and assists in prioritising the
energy saving measures [6]. In conclusion, it can be
said that the concepts related to "Design for Energy"
have not been thoroughly explored in the literature.
RELEVANT LITERATURE
Drexel University, under a contract with the
U.S. Department of Energy, initiated a program to
develop a detailed database of industrial energy
utilization. This database consists of typical process
configurations and energy and material balances for
108 industrial processes representing 60 four-digit
Standard Industrial Classification (SIC) industries.
The outcome of this study was the development of
energy and mass balances On a per unit basis (e.g. per
pound product, per pound input) for each of the unit
operations that comprise the 108 industrial processes
[4]. Luis G., and Hyman, B. have developed a
general approach for combining end-uses and process
steps into calibrated energy consumption models of
manufacturing processes using the Manufacturing
Energy Consumption Survey (MECS). The main
objective was to build complete, fully documented,
end-use models for pulp, paper, and paperboard mills
that are consistent with the 1991 MECS data and to
depict the energy flows between inputs and end-uses
in a manner that clarifies the energy-use patterns
underlying the data [7]. Anders Martensson has
investigated the impact of information technology on
energy efficiency using steel-reheating furnace as an
example to pursue this implication. The model
evaluated the effect of process changes during the 12­
year period. Changes in furnace efficiency were
detected and attempts were made to correlate these
changes with known measures. It was found that
energy use was lower than expected, with differences
up to 17%. The deviations were found to be
statistically significant on a 95% level [12]. Tracy
Reed has developed a general method for estimating
the physical energy-intensity of manufacturing a
product. The approach was demonstrated for the
electric intensity of pulp, paper, and paperboard.
They found that relative physical electric intensity of
products could be quite different from the relative
economic electric intensities for the industries that
produce those products [10]. A. E. Saeed has studied
the effect of process integration on the reduction of
ENERGY SENSITIVE DESIGN ATTRIBUTES
The product design parameters that are most
sensitive to energy requirements are the material
properties and product geometry. Production volume
also influences energy considerations. Material
hardness and microstructure often have a large
impact on the type of manufacturing processes that
can be successfully applied. Machining in general
less energy intensive than casting or forming, as it is
mainly electrical energy that is being expended in
motor operations. Casting processes require metal
melting, an energy intensive process using either gas
or electrically fired furnaces. The forming processes
also require considerable electrical energy for the
large sized motors that operate the die movements.
Some materials such as aluminium and cast iron lend
themselves to casting more easily than machining on
account of their properties. Greater the hardness of
the material more difficult it may be to machine.
The product geometry may be critical in
terms of machining time. More intricate the product
geometry, more will be the complexity of the
machining process and the tool movements, thus
leading to increased energy requirements in terms of
increased machining time. Casting a product
possessing complex geometrical features may result
in postoperative machining, thus leading to increased
overall energy consumption. The same principle
applies to formed products.
Low production volumes can be targeted by
machining operations in batches while large
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ESL-IE-02-04-34
THE OPERAnON OF THE DES
production volumes often necessitate the use of
casting or forming processes. The production rate
required thus has a significant effect on the chosen
manufacturing
process
strategy.
Operations
management personnel focus much on the production
volumes required to meet customer demand
fluctuations and are interested in having the
manufacturing process infrastructure be flexible
enough to support the mission and objectives of the
organization. Hence, whether it is casting, machining,
or forming processes, energy requirements are
definitely related to the properties of the material, the
product's geometry, and required production
volumes.
The nature of the operation of the DES is
important. From analysing the systems diagram
shown on figure 2, it is apparent that there may not
be a consistent and complete amount of information
emanating from the preliminary and the detail design
functions as well as from the manu facturing function.
This is because these functions are still evolving in
terms of their accomplishment of their functionality
at the early stages in the product development cycle.
In the concurrent engineering framework, the
interactions between product development phases are
often iterative and are usually subject to a constant
flow of constantly modified data. How should the
DES operate in such a scenario? The DES must be
able to:
l. Incorporate, acquire and process incomplete
information.
2. Provide meaningful feedback in light of
such information.
3. Incorporate, acquire and process information
as it evolves and becomes "complete".
SYSTEMS APPROACH
Consider the system as shown in Figure 2.
The preliminary and detail design functions generate
product attributes that are being evaluated by the
Design for Energy System (DES). The manufacturing
process attributes are also being evaluated by the
DES. The DES subjects the attributes to a rigorous
evaluation and provides feedback to the design
function on aspects that could be modified to cause a
reduction in manufacturing energy consumption. The
evaluations from the DES will be in terms of
providing the amount of energy required to make a
specific unit of the product. The specific unit could
be in terms of individual units, pounds, tons etc. The
system shown on figure I can be integrated into the
regular concurrent engineering framework, hence
providing an active energy based interface for
dialogue between the design function and otl1er down
the line functions in the spectrum of the product life
cycle.
As an example, consider someone who is
interested in knowing how much energy would be
needed to produce one pound of ice cream? This
person may be interested in erecting a factory to
produce the product and would be able to provide
minimal
information
about
the
production
infrastructure and requirements. Consider on the
other hand someone who already owns a machine
shop and is ready to introduce a new product into the
market. Such a person may have information that is
more detailed and complete and may be expecting
energy information that is much more accurate. The
third example relates to an evolving product design
function at which stage a reasonably accurate
estimate of energy requirements must be provided. In
all the three examples described, it is clear that the
design and manufacturing information is not at the
same level of "completeness". Thus the DES must
be able to deliver meaningful energy related advice in
the face of incomplete information and/or evolving
information.
PRELIM
DESIGN
Figure 2.
The Inverted Pyramid Approach
The DES must be able to provide a broad
range of information to the user using minimal input.
On the other hand, the DES must also be able to
provide focused detailed information to the user
using comprehensive input data. The completeness of
the data could vary and hence the level of
information supplied by the DES must also vary.
Consider the inverted pyramid shown in Figure 3. At
the top of the pyramid lies the broad range of
Design for Energy System Diagram
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Proceedings from the Twenty-fourth National Industrial Energy Technology Conference, Houston, TX, April 16-19, 2002
ESL-IE-02-04-34
infonnation which are good estimates as provided by
the DES while at the bottom of the inverted pyramid
lies focused information that is not estimates but
rather detailed and accurate. In between the top and
bottom of the inverted pyramid lie varying levels of
infonnation as supplied by the DES.
interface for providing any desired input and data is
necessary. When conclusions are being arrived at, the
user is presented with the workings of an
explanation-based subsystem that offers the
reasoning behind any conclusion that has been
reached. When the inference engine searches through
the knowledge base, intennediate conclusions are
often reached prior to the substantiation of the goals.
Thus, in this light a working memory, or a database is
necessary to hold the infonnation generated on an
intennediate basis.
Broad level of
energy
information
..-
A~
~,
Working
Memory
KnDWiedge
Base
A.
i
t
r
r
I
Focused and
detai led energy
information
Inference Engine
I
A~
~Ir
Figure 3.
...
The Inverted Pyramid Methodology
Contents Of The DES
In order for the DES to be able to supply
varying levels of infonnation to the user, its design
must be robust enough to incorporate and process
varying levels of input information. The basic design
attributes of the DES include quantitative algorithms
and expert systems for processing symbolic
infonnation. Expert systems are suited well for
processing incomplete information and are able to
adapt well to uncertainty in data. Algorithms and
associated databases on the other hand are well suited
for accurate numerical computation and are used to
model well known energy oriented information. An
expert system can be defined to be an intelligent
system composed of a knowledge base, an inference
engine, a working memory, a user interface, and an
explanation based subsystem, capable of solving
problems that are generally unstructured and difficult
enough for human beings to solve easily [1,2,11,18].
Figure 4 shows the components of an expert system.
The knowledge base within an expert system contains
all the necessary infonnation represented in an
appropriate manner and amenable for the
employment of search procedures. The inference
engine uses search techniques to wade through the
knowledge base to arrive at conclusions. A user
Figure 4.
User
Components of an Expert System
Consider the DES architecture as shown in
Figure 5. The user is supplying information to the
DES that in tum is processed and provided back to
the user. The user will then be able to modifY the
infonnation and reinvoke the DES that can then fine­
tune the accuracy of the information provided earlier.
One of the important facets of the DES architecture is
the ability to perfonn sensitivity analysis. The user,
whether from the preliminary and/or the detail design
function or the manufacturing function, often has the
desire to know ''what if' some of the data is varied
within a range of values. Would the decision points
still stay the same? For example, if the hardness of
the material were varied from J 20 Bhn to 250 Bhn,
how would the energy cost per pound to manufacture
the product change? If the production volume were
varied from 500 pieces per hour to 2000 pieces hour,
how would the energy cost per unit manufactured
change? The answers to these questions are important
as the user must have the capability to exercise a
variety of design and manufacturing options in order
to successfully produce and market the products.
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ESL-IE-02-04-34
navigation procedures cannot happen without an
effective database interface. The database is crucial
for holding transient processed information that
translates from one system to another. It is also
required for being the repository for data so as to
enable the generality of the associated knowledge
based systems.
Inverted Pyramid
Figure 5.
Let us consider the type of information
processed and delivered by the DES. Say, the user is
a businessperson considering the development of a
manufacturing facility for producing product X. The
user, along with the manufacturing specialist invokes
the DES. It is required to manufacture 2,500 pieces of
X per month using the machining process. The DES
analyses this information at the highest level of the
pyramid and provides a response that the amount of
energy required to make each unit of X will be C
MMBtu. The user then changes the information on
the required production volume to vary from 2,500 to
5,500 per month and the DES responds with a graph
showing the change in energy requirements to
correspond to the change in production volume. The
manufacturing specialist then wishes to consider
heat-treating the product after machining and
provides relevant information in terms of temperature
gradients and time sensitive parameters. The DES
analyses this information and provides the necessary
energy requirements, functioning at a relatively lower
level of the pyramid. At this stage, the manufacturing
specialist may decide to enhance the information
provided such as in terms of specific nature of the
furnaces to be used, and detailed time temperature
variance. Armed with more detailed information, the
DES will be able to Refine its estimates arrived at
previously. The design specialist now enters the
dialogue and wishes to know if there would be any
cbanges to energy requirements if the material
changed from alloy A to alloy B. The design
specialist is able to provide all relevant details on
each alloy. The DES is now at a relatively middle
range in level and is able to cater to the request of the
designer. The DES will also be able to provide
feedback to the designer on possible "redesign"
options or identify key energy indices for the design
so as to reduce energy consumption.
Architecture of DES
RESULTS OBTAINED
The development of the DES is ongoing
within the architectural scope defined in this paper.
Preliminary research is being done to analyse the
effect of varying design parameters on manufacturing
energy consumption, especially in the machining and
heat treating areas. In the machining area the
experimental set-up has been determined to machine
a variety of material of varying geometry and
subsequent analysis of machine power consumption.
The key variables under consideration are the
material hardness, material removal rate, machining
conditions including cutting speed, feed, and depth of
cut to enable the required material removal rate, and
raw material stock geometry. In the heat treating
area, preliminary research with a reheating furnace of
a major steel manufacturer has revealed interesting
knowledge with respect to furnace energy
consumption as pertaining to variance in work
material properties and entry temperatures.
SYSTEM OPERAnON
How will the system operate when it has
been completed? The system will have user-friendly
features and incorporate the power of today's
software systems working within the confines of the
most suitable hardware system. The intent is to
enable energy based information to be provided to a
wide variety and spectrum of users, ranging from the
knowledgeable process engineer to the non-technical
operations management senior personnel. The DES
will have the client-server interface designed with
accuracy and user friendliness in mind. The user will
be able to navigate within varying levels of the
inverted pyramid and "zoom" in and expand on any
information provided at any level of the pyramid.
The use of algorithmic and expert systems
programming will facilitate this aspect. The
At this stage, the maintenance specialist
enters the dialogue and wishes to know the specific
methods that can be used to reduce energy
consumption in machining processes that are
essentially motor oriented. The DES scopes the
possessed knowledge and is able to identify energy
conservation opportunities such as the use of cogged
belts, adjustable speed drives, and the use of energy
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ESL-IE-02-04-34
efficient motors. The maintenance specialist can driB
down to an even lower level of the pyramid and
obtain information on how exactly to implement such
energy conservation opportunities and what the
potential savings would be. Thus, the DES will be
able to adapt and modify its operational procedures to
cater to a varying audience interested in product and
system development.
Computer Model, Energy Engineering, Vol. 86, No.
2,1989.
[7] Giraldo, Luis, and Hyman, Barry, Energy End­
Use Models for Pulp, Paper, and Paperboard Mills,
Energy, Vol. 20, No. 10, pp 1005-1019, 1995.
[8] Gopalakrishnan, 8., Product Design and Process
Planning in Concurrent Engineering, International
Society for Productivity Enhancement, 1996.
[9] Huang, G.Q., Editor, Design for X, Concurrent
Engineering Imperatives, Chapman and Hall, 1996.
[10] Hyman, Barry, and Reed, Tracy, Energy
Intensity of Manufacturing Processes, Energy, Vol
20, No.7, pp 593-606, 1995.
[11] Kline, P., and Dolins, S., Designing Expert
Systems, John Wiley, New York, 1990.
[12] Martensson, A. The Impact ofInformation
Technology on Energy Efficiency: An Evaluation
Case Study of Steel-Reheating Furnaces, Energy,
Vol. 19, No.7, pp 717-728,1994.
[13] Nevins, J.L., Whitney, D.E., Concurrent Design
of Products and Processes, McGraw Hill, New York,
1989.
[14] Saeed, A.E., Blakemore, F.B., and Doulah,
M.S. Effect of Process Integration on the
Reduction of Fuel Consumption, Applied Energy,
Vol. 54, No.4, pp 287-300, 1996
[15] Stauffer, R.N., Simultaneous Engineering:
Beyond a Question of Mere Balance, Manufacturing
Engineering, Vol. 108, pp. 35-37, 1992.
[16] Stoll, H.W., Design for Manufacture,
Manufacturing Engineering, 1988.
[17] Winner, R.I., Pennel, J.P., Bertrand, H.E., and
Slusarczuk, M.M.G., The Role of Concurrent
Engineering in Weapons Systems Acquisition, Report
R-338, Institute for Defense Analysis, 1988.
[18] Yaghmai, N.S., and Maxin, J.A., "Expert
Systems: A Tutorial", Journal of American Society
ofInformation Science, Vol. 35, No.5, 1984.
CONCLUSION
There is definitely a need for the
development of a system such as the DES to function
in the concurrent engineering domain. The US
Department of Energy (USDOE) has identified
several industries including aluminium, steel, and
metal casting to be energy intensive enough to be
included in the Industries of the Future (IOF)
program, thus focusing on manufacturing energy
reductions at every stage. Systems such as the DES
will go a long way in enabling such visions to be a
reality as they place a capability in the hands of the
industrial practitioner that was not available
previously, namely the ability to evaluate the
sensitivity of energy with respect to key design and
manufacturing parameters. Performing the sensitivity
analysis of energy requirements with respect to
design and manufacturing parameters will enable
energy savings across major industrial sectors as they
facilitate the process within the scope of economic
competitiveness and business profitability, two
elements critical for survival in today's global
markets.
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[3] Bauer, 1., Diana, Thurwachter, S., and Sheng,
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End-Use Estimation Techniques With An Interactive
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Proceedings from the Twenty-fourth National Industrial Energy Technology Conference, Houston, TX, April 16-19, 2002