SUSTAINABILITY ANALYSIS AND CONNECTIVE ......by Raghunathan Srinivasan, M.S. Washington State...
87
SUSTAINABILITY ANALYSIS AND CONNECTIVE COMPLEXITY METHOD FOR SELECTIVE DISASSEMBLY TIME PREDICTION By RAGHUNATHAN SRINIVASAN A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN MECHANICAL ENGINEERING WASHINGTON STATE UNIVERSITY School of Mechanical and Materials Engineering DECEMBER 2011
Transcript of SUSTAINABILITY ANALYSIS AND CONNECTIVE ......by Raghunathan Srinivasan, M.S. Washington State...
SUSTAINABILITY ANALYSIS AND CONNECTIVE
COMPLEXITY METHOD FOR SELECTIVE
DISASSEMBLY TIME PREDICTION
By
RAGHUNATHAN SRINIVASAN
A thesis submitted in partial fulfillment of
the requirements for the degree of
MASTER OF SCIENCE IN MECHANICAL ENGINEERING
WASHINGTON STATE UNIVERSITY
School of Mechanical and Materials Engineering
DECEMBER 2011
ii
To the Faculty of Washington State University:
The members of the Committee appointed to examine the thesis of
RAGHUNATHAN SRINIVASAN, find it satisfactory and recommend that it be
accepted.
______________________________
Gaurav Ameta, Ph.D., Chair
______________________________
Jitesh H. Panchal, Ph.D.
______________________________
Uma Jayaram, Ph.D.
iii
ACKNOWLEDGEMENTS
This work would not have been possible without the constant support and guidance of
my mentor, Prof. Gaurav Ameta. I thank him profusely for providing me with the best
environment to work. I am grateful to him for giving me the freedom to explore and the
excellent opportunities to learn and grow as a researcher.
I would like to thank my committee members, Dr. Jitesh H. Panchal and Dr. Uma
Jayaram for sparing their valuable time to interact with me and for sharing their inputs
and feedback. I am grateful to them for accommodating my requests and deadlines.
I would like to thank all the members of the Sustainable Product Lifecycle Design
Lab and Collective Systems Lab at Washington State University. Thanks to He Huang,
Martin Baker and Bryant Hawthrone – it was an enriching and learning experience
working with you.
I would like to specially thank the faculty and staff of the School of Mechanical and
Materials Engineering for funding my education through a Teaching Assistantship. I also
thank them for all their support and effort to make my academic life a pleasant and
memorable one.
I would like to thank my brother Raghavendiran Srinivasan who is the constant
source of encouragement for all the work I do.
Thanks to all my friends for supporting me all through these years.
Last but not the least; I would like to thank my parents Jayalakshmi and Srinivasan
who are the key to success in every stage of my life.
iv
SUSTAINABILITY ANALYSIS AND CONNECTIVE COMPLEXITY
METHOD FOR SELECTIVE DISASSEMBLY
TIME PREDICTION
Abstract
by Raghunathan Srinivasan, M.S.
Washington State University
December 2011
Chair: Gaurav Ameta
The two main objective of this thesis are: 1) to develop a disassembly and
selective disassembly time prediction methodology and, 2) to evaluate the use
of environmental impacts of components in the selective disassembly time
prediction method. Disassembly time is very critical as it impacts the planning
and costs at the end of life of a product. Thus, disassembly time has direct
effects on the decisions and activities related to recycle, reuse, remanufacture
and disposal of a product.
The disassembly time prediction method first utilizes the assumption that
disassembly is the inverse of assembly and second uses the assembly time
prediction method. The assembly time prediction method is based on the use
of complexity metrics derived from assembly graph and bipartite graph of a
product. The notion of selective disassembly implies disassembling a product
in order to retrieve only a certain number of parts and not disassembling the
other components. There could be many applications for selective disassembly
v
from disassembly for material recovery, parts reuse and remanufacturing to
reduction in environmental impacts associated to disposing a hazardous
component. The determination of selective disassembly time is based on
recovering most material for recycling. The assembly graph for a product is
re-organized to group together parts that are close and are of same material.
The modified assembly graph is then used to compute the selective
disassembly time. Although, the method developed targets material recovery
for recycling, it can be used for parts recovery for reuse, remanufacturing or
other such purposes.
One of the widely used methodologies to assess the environmental impacts of
a product is called Life Cycle Assessment (LCA). LCA is applied to selective
components of the case studies (i.e. standard toaster and the eco-friendly
toaster) using SIMAPRO 7 to calculate the environmental impacts. The
environmental impacts of the selected components can be further utilized for
decision making and planning regarding selective disassembly.
vi
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ......................................................................................................................... iii
Abstract ........................................................................................................................................................ iv
LIST OF TABLES ..................................................................................................................................... viii
LIST OF FIGURES ..................................................................................................................................... ix
Chapter 1 - Introduction ................................................................................................................................ 1
1.1 Background ................................................................................................................................... 1
1.2 Product Life Cycle ........................................................................................................................ 1
1.3 Design phase ................................................................................................................................. 3
1.4 Raw material phase ....................................................................................................................... 3
1.5 Life Cycle Assessment .................................................................................................................. 5
1.6 Disassembly .................................................................................................................................. 6
1.7 Problem Statement ........................................................................................................................ 8
1.8 Outline........................................................................................................................................... 9
Chapter 2 - Literature review ...................................................................................................................... 10
2.1 Disassembly Modeling ...................................................................................................................... 11
2.2 Assembly and Disassembly time estimation ..................................................................................... 12
2.3 Life Cycle Assessment ...................................................................................................................... 13
Chapter 3 – Life Cycle Assessment of the toasters based on selective components for recycling ............. 14
3.1 Background ....................................................................................................................................... 14
3.2 Disassembly and Selective disassembly ........................................................................................... 14
3.3 Components investigated .................................................................................................................. 15
3.4 Life Cycle of a Toaster ..................................................................................................................... 17
3.5 Use Phase Energy Calculation .......................................................................................................... 18
3.6 Impact Assessment Methodology ..................................................................................................... 20
3.6.1 Using SIMAPRO ........................................................................................................................... 21
Chapter 4 – Assembly Time calculation using Connective Complexity Matrices method ........................ 26
4.1 Complexity design ............................................................................................................................ 26
4.2 Complexity Metrics .......................................................................................................................... 26
4.3 Methodology ..................................................................................................................................... 27
vii
4.3.1 Assembly Graph ......................................................................................................................... 27
4.3.2 Shortest Path Length .................................................................................................................. 29
4.3.3 Path Length density .................................................................................................................... 30
4.3.4 Disassembly time ....................................................................................................................... 30
4.3.5 Selective Disassembly time prediction ...................................................................................... 31
Chapter 5 – Case studies ............................................................................................................................. 34
5.1 Case Study 1: Standard Toaster ........................................................................................................ 34
5.1.1 Standard Toaster – Components ................................................................................................ 34
5.1.2 Bipartite Graph for a Standard toaster ....................................................................................... 36
5.1.3 Assembly graph and disassembly time calculation before material-wise separation ................ 40
The total disassembly time for the standard toaster is estimated as 197 seconds. .................................. 44
5.1.4 Assembly graph and disassembly time calculation after material-wise separation ................... 44
5.2 Case study 2 – Eco-Friendly toaster ................................................................................................. 49
5.2.1 Eco-friendly Toaster - Components ........................................................................................... 49
5.2.2 Bipartite Graph of an eco-friendly toaster ................................................................................. 52
5.2.3 Assembly graph before material-wise separation ...................................................................... 57
5.2.4 Assembly graph and disassembly time calculation of an eco-friendly toaster after material-wise
separation ............................................................................................................................................ 61
5.9 Results ............................................................................................................................................... 67
Chapter 6 – Conclusion and Future Work .................................................................................................. 68
6.1 Contributions..................................................................................................................................... 68
6.2 Limitations ........................................................................................................................................ 69
6.3 Future Work ...................................................................................................................................... 69
References ................................................................................................................................................... 71
viii
LIST OF TABLES
Table 1 Weight of the Components .............................................................................................. 16
Table 2. Use Phase energy in KWh .............................................................................................. 20
Table 3 Disassembly time calculation before material separation ................................................ 31
Table 4 Disassembly time calculation after material separation .................................................. 33
Table 5 (a) Disassembly time calculation of a standard toaster before material separation ......... 41
Table 5 (b) Disassembly time calculation of a standard toaster before material separation ......... 42
Table 5 (c) Disassembly time calculation of a standard toaster before material separation ......... 43
Table 6 (a) Disassembly time calculation of a standard toaster after material separation ............ 46
Table 6 (b) Disassembly time calculation of a standard toaster after material separation ........... 47
Table 6 (c) Disassembly time calculation of a standard toaster after material separation ............ 48
Table 7 (a) Disassembly time calculation of an eco-toaster before material-wise separation ...... 58
Table 7 (b) Disassembly time calculation of an eco-toaster before material-wise separation ...... 59
Table 7 (c) Disassembly time calculation of an eco-toaster before material-wise separation ...... 60
Table 8 (a) Disassembly time calculation of an eco-toaster after material-wise separation ......... 64
Table 8 (b) Disassembly time calculation of an eco-toaster after material-wise separation ........ 65
Table 8 (c) Disassembly time calculation of an eco-toaster after material-wise separation ......... 66
Table 9 Disassembly time results ................................................................................................. 67
ix
LIST OF FIGURES
Figure 1 A typical product life cycle showing stages of assembly and disassembly……..2
Figure 2 Components investigated - standard toaster……………………………………16
Figure 3 Components investigated – eco-friendly toaster……………………………….16
Figure 4 Life Cycle of a Toaster…………………………………………………………17
Figure 5 Experimental Setup…………………………………………………………….19
Figure 6 Network diagram of LCA of Standard toaster using Simapro 7……………….22
Figure 7 Network diagram of LCA of eco-friendly toaster using Simapro 7……………23
Figure 8 Weighting for Standard toaster…………………………………………………24
Figure 9 Weighting for eco-friendly toaster……………………………………………..24
Figure 10 Environmental impacts of standard and eco-toasters…………………………25
Figure 11 Assembly graph before material-wise separation…………………………….27
Figure 12 Bipartite graph………………………………………………………………...29
Figure 13 Assembly graph after material-wise separation………………………………32
Figure 14 Outer Casing, Inner Casing, Heating Element, Wire Mesh…………………..34
Figure 15(a) Bipartite graph of a standard toaster……………………………………….37
Figure 15(b) Bipartite graph of a standard toaster.............................................................38
x
Figure 15(c) Bipartite graph of a standard toaster……………………………………….39
Figure 16 Assembly graph of a std. toaster before material-wise separation……………40
Figure 17 Assembly graph of a std. toaster after material-wise separation……………..45
Figure 18 Outer Casing, Inner Casing, Heating Element, Wire Mesh of eco……………49
Figure 19a) Bipartite graph of an eco-friendly toaster…………………………………...53
Figure 19(b) Bipartite graph of an eco-friendly toaster………………………………….54
Figure 19(c) Bipartite graph of an eco-friendly toaster………………………………….55
Figure 19(d) Bipartite graph of an eco-friendly toaster………………………………….56
Figure 20 Assembly graph of an eco-toaster before material-wise separation…..………57
Figure 21 Assembly graph of an eco-toaster after material-wise separation…………….63
xi
DEDICATION
To my maternal grandparents, my mother Jayalakshmi, my father Srinivasan and my
brother Raghavendiran Srinivasan.
1
Chapter 1 - Introduction
1.1 Background
In a country with a population of about 300 million and counting, on an
average, each person generates about five pounds of waste every day. In the
year 2008 alone, the U.S. produced 254 million tons of solid waste of which
more than a third was recycled or recovered [1]. Most of the solid waste ends
up in landfills and the rest gets recycled through community recycling
programs or through natural cycles. Also, the manufacturers should retake the
product at its end-of-life (EOL). The manufacturers should try to figure out
which EOL option can be more beneficial to the company and the
environment. One way of doing the take back of products is by implementing
strict legislative measures by the government.
1.2 Product Life Cycle
Every product has its own life cycle. May it be a screw or an airplane,
each product passes through five major phases known as the product life
cycle. They are the design phase, raw material phase, the manufacturing
phase, the use phase and the end-of-life phase. Figure 1 represents a typical
product life cycle showing stages of assembly and disassembly.
2
Figure 1 A typical product life cycle showing stages of assembly and disassembly.
Design
Phase
Recycle Raw Material
Phase
Remanufacture Manufacturing
and
Assembly
Phase
Reuse Use Phase
Disassembly
End-of-life
Phase
Disposal
3
1.3 Design phase
The design and planning phase is where each and every component of a
product is designed based on the data provided by the manufacturer and based
on the customers‟ requirements. There are many constraints like cost,
tolerance, etc. involved while designing a product. The design team also
collects feedback and suggestions from the manufacturing team regarding the
possibility of manufacturing a product based on the design plan developed by
the design team. Based on these feedbacks the design team modifies the
design or creates a new design that can be manufactured more efficiently
according to the requirements. So, this design phase play a key role in the
product life cycle.
1.4 Raw material phase
The raw material phase includes the gathering of the required raw
materials from various suppliers and these raw materials are stored in storage
houses in the manufacturing plant before processing. Some of these raw
materials include hazardous materials or chemicals. These materials are safely
transported to the storage houses. Once all the raw materials are in place, the
manufacturing phase can begin.
1.4.1 Manufacturing and assembly phase
These raw materials are transported to the shop floor of the manufacturing
plant where these raw materials undergo various manufacturing processes to
obtain each component of the product. Also these components are assembled
4
to form sub-assemblies and these sub-assemblies are combined to form the
final assembly. Each manufacturing plant has its own predefined way of
manufacturing and assembling a product which are based on constraints like
time to assemble, ease of manufacturing and assembling, etc. When the final
product is assembled it is then shipped to the quality control department where
the products are inspected for any defects, after which these products are sent
to the packaging department where these products are packaged and shipped
to the consumer market.
1.4.2 Use phase
The use phase includes the duration in which the consumer utilizes a
product either for a household or business. These might also include the use of
electrical or mechanical energy to use the product. The manufacturer also
specifies a warranty for each product. The product is supposed to reach its
end-of-life at the end of warranty provided by the manufacturer. Most
products tend to last long than the warranty provided by the manufacturer. But
products do tend to die before its warranty. Once the product stops
functioning the way it is supposed the function then it is said to have reached
its end-of-life.
1.4.3 End-of-life phase
Once the products‟ end-of-life is reached, the end-of-life (EOL) decisions
have to be made. The possible EOL options include recycle, reuse,
remanufacture and disposal. The product can be disassembled to recover
5
components or materials and this product or its components can be recycled or
reused or remanufactured and the rest of the components can be disposed as
landfill. These EOL decisions have to be wisely chosen in such a way that it‟s
beneficial to the environment, manufacturer and the society.
1.5 Life Cycle Assessment
One of the widely used methodologies to assess the environmental impacts
of a product is called Life Cycle Assessment (LCA). LCA is a cradle to grave
approach for assessing the environmental impacts of a product. The cradle to
grave approach includes raw material phase, manufacturing and assembly
phase, use phase and end-of-life phase.
The United States Environmental Protection Agency defines a Life Cycle
Assessment (LCA) as „an objective process used to evaluate the
environmental burdens associated with a product, process or activity by
identifying and quantifying energy and materials used and wastes released to
the environment, and to evaluate and implement opportunities to affect
environmental improvements‟ [1]. Life Cycle Assessment (LCA) can also be
defined as a collection and estimation of the inputs, outputs and the possible
environmental impacts of a product system throughout its life cycle [2]. Life
Cycle Assessment (LCA) attempts to quantify the environmental impacts over
the entire life-cycle of a product from its raw material extraction,
manufacturing and assembly, and use phase to ultimate disposal [3].
6
1.6 Disassembly
In a product recovery environment, there are several situations where a
product may be disassembled for economic and regulatory reasons.
The main aim of a manufacturing system is to develop methods for
manufacturing new products from the conceptual design to final deliverance,
and ultimately to the end-of-life and disposal such that the environmental
standards and requirements are satisfied. On the other hand, the amount of
waste sent to landfills can be minimized by recovering parts or materials from
old or outdated products by means of disassembly, remanufacturing and
recycling, termed as product recovery. The objective of recycling is to recover
as much material as possible from the retired products by performing the
necessary disassembly, sorting, and physical and/or chemical separation.
However, in the case of remanufacturing, the product‟s identity is preserved
and also performs the required disassembly, sorting, refurbishing and
assembly operations to bring the product to a desired level of quality. While
the material and product recovery is feasible by allowing selective separation
of desired parts and materials by disassembling the product [4].
Typical objectives of disassembly may include;
recovery of valuable parts or subassemblies,
parts or components that can be reused in the production of a new
product,
7
retrieval of parts or subassemblies of discontinued products to suit
a sudden demand for these parts,
removal of hazardous subassemblies or parts,
increasing the purity of the remainder of the product for the
purpose of chemical reclamation,
decreasing the amount of waste being sent to landfills, and
achieving environmentally friendly manufacturing standards like
successfully implementing the required ratio of using recycled
parts to using new parts.
Although, disassembly highly facilitates to the success of product
recovery, it is an expensive process. Therefore, the disassembly has to be
performed in a cost-effective manner. Already many researchers have focused
on minimizing the resources invested in the disassembly process. To keep the
profitability and environmental features of the product recovery process at a
desired level some researchers have focused on the disassembly leveling
problem which targets the disassembly level to which the product of interest is
disassembled [5-7]. While other researchers focus on the generation of
efficient disassembly sequencing plans (DSP).
A disassembly sequencing plan is a sequence of disassembly operations
that aide in feasibly disassembly of a product and terminates in a state where
all of the parts/components are disconnected from one another. This can either
be a partial disassembly or a complete disassembly. An efficient DSP can
minimize the cost of disassembly process. Various researches have been done
8
in the area of disassembly sequence planning using graph theory, heuristics
and Petri nets [9 - 17].
1.7 Problem Statement
Disassembling the whole product at EOL is influenced by time constraints,
cost constraints and also based on the condition of the product after usage. So,
in order to achieve an effective disassembly the manufacturer must figure out
whether the complete disassembly of the product is needed for a product or
not. If the cost and time to disassemble the whole product and recovering the
material tends to end up in not making a profit then the complete disassembly
principle is of no use to the manufacturer. However, the manufacturer can still
apply the selective disassembly principle by which they can selectively
disassemble few components or sub-assemblies thereby minimizing the
manpower and time incurred for total disassembly, and also more material
might be recovered from these selected components that can be reused or
remanufactured while the rest of the product can be disposed. In this method
of applying this selective disassembly principle based on size and weight the
manufacturer can profit in material recovery and at the same time the junk
being disposed as landfill can be reduced in huge amounts every day.
This research proposes a method to calculate the assembly time based on
complexity matrices to two toasters and a possible generalized methodology
for applying to other possible products based on connectivity between the
parts or components of a product. Also, LCA was performed on selective
9
components of the two toasters where the selection of components was based
on weight and size.
1.8 Outline
Chapter 2 includes the literature review. Chapter 3 provides the LCA of
the Toasters based on selective components for recycling. Chapter 4 explains
the methodology for selective disassembly of a product. Chapter 5 presents
the application of this methodology to a case study of comparing two toasters
(standard and an eco-friendly toaster). Chapter 6 gives the conclusion and
future work of this research.
10
Chapter 2 - Literature review
Some of the better alternatives for reducing the environmental problems
resulting from the huge amounts of waste currently arriving at landfills are to
recycle the products and components of these products. Further, the success of
these alternatives varies based on the product esp. due to the difficulty in
obtaining efficiency and also repairing or refurbishing [18].
When reuse, remanufacturing or repair are not competitive, in most cases
the product is shredded in order to recover some value from material recycling
or disassembling the product in order to carry out re-use or recycling of
individual components. Although shredding is less time-consuming,
disassembly seems to be much more interesting from the environmental
perspective. Disassembly allows the separation of high recovery value or
hazardous components and also the reuse or remanufacturing of individual
components, thus avoiding waste generation [19].
Disassembly plays a key role when trying to select a product at the end of
life (EOL). On one hand, it is essential to ensure the required purity of
recycled materials by separating components made up of different materials so
that they can be accepted by secondary manufacturers [20]. On the other, it is
needed to release components and subassemblies susceptible to repair, re-use
or remanufacturing [21].
Major research efforts in EOL practices focus on the field of disassembly
because the approaches within this field of work basically differ with respect
11
to the kind of problem they address [22]. Also, it depends on the way of
modeling the problem, and the techniques used for solving the problem.
2.1 Disassembly Modeling
Regarding the modeling methods, three main approaches can be found in
the literature for describing the disassembly process:
1. And/or graphs [23],
2. State diagrams [25] and
3. Disassembly precedence graphs [26].
The AND/OR graph lessens the number of nodes in the depiction of all
possible plans and provides the basis for planning by tree search. The
AND/OR graph representation is useful in assembly planning where it covers
all possible partial arrangements of assembly operations with a reduced
number of nodes. The ongoing researches focus on the construction of the
AND/OR graph that will have the ability to find all connected stable
subassemblies and all physically feasible disassembly operations of a given
assembly.
In the case of state diagrams, the assembly sequences are represented as
paths through a network of assembly states which acts as nodes and the
assembly moves are shown by arcs.
A more vital improvement was the use of precedence diagrams for the
representation assembly and disassembly plans, where the search space of a
12
disassembly precedence graph is large, but that technique has limitations such
as it allows only a small amount of flexibility which is typically related to its
number of components.
2.2 Assembly and Disassembly time estimation
The main objective of design for assembly (DFA) is to create a design
solution that will make the assembly process of a product more simple and
feasible. In the 1960‟s, many companies succeeded in developing handbooks
for designers which helped in creating parts for manufacturing ease [27]. The
advantage of using these design manuals was to facilitate and assemble many
simple parts, focusing on making the method of manufacturing cheaper.
However, this was before performing analyses both theoretically and
experimentally on the assembly time of the parts based on the effects that part
features had on these parts [28].
From such studies, a DFA Methodology was developed by Boothroyd and
Dewhurst [29-31], which helps in comparing and rates the productability of
various designs [32]. Minimizing the assembly times and costs based on
minimizing the number of individual parts was addressed by the Boothroyd
and Dewhurst DFA method [30], also individual part design was optimized
for the ease of handling and joining [33]. But the Boothroyd method is tedious.
Many high end manufacturing companies have their own customized DFA
methods like Texas Instruments, Ford Motor Company, General Motors and
Motorola [28].
13
All these DFA processes discussed here are used towards the end of the
design process and they don‟t account for the effective disassembly planning
during the design stage which can beneficial towards the end-of-life of a
product.
However a methodology using the assembly graphs and bipartite graphs in
computing the selective disassembly time has not yet been developed.
2.3 Life Cycle Assessment
ISO 14044 describes LCA as a tool that helps in comprehending
effectively and addressing the environmental impacts associated with products
and services.
LCA can also be applied to evaluate the impact of the energy and
materials used and released into the environment. LCA can also be used to
identify and evaluate the possibilities for environmental improvement [34].
Identifying the environmental burdens during each phase of the whole
product life cycle can help in reducing the environmental impact, such as
global warming, and ozone problems which can be achieved using LCA [35].
The main advantage of using LCA in disassembly is because it
emphasizes that products must be produced, distributed, used and disposed of
or recycled without harming the environment in any phase [36].
14
Chapter 3 – Life Cycle Assessment of the toasters based on selective components for
recycling
3.1 Background
In a country with a population of about 300 million and counting, on an
average, each person generates about five pounds of waste every day. In the
year 2008 alone, the U.S. produced 254 million tons of solid waste of which
more than a third was recycled or recovered [37]. Most of the solid waste ends
up in landfills and the rest gets recycled through community recycling
programs or through natural cycles. Strict legislative measures should be
implemented by the government so that the manufacturers should retake the
product at its end-of-life and try to figure out which EOL option can be more
beneficial to the company and the environment and thereby implementing it.
3.2 Disassembly and Selective disassembly
Disassembling the whole product at EOL is influenced by time constraints,
cost constraints and also based on the condition of the product after usage. So,
in order to achieve an effective disassembly the manufacturer must figure out
whether the complete disassembly of the product is needed for a product or
not. If the cost and time to disassemble the whole product and recovering the
material tends to end up in not making a profit then the complete disassembly
principle is of no use to the company. However, the company can still apply
the selective disassembly principle by which they can selectively disassemble
few components or assemblies thereby they don‟t spend their manpower in
15
total disassembly, and also they might recover more material from these
selected components that can be reused or remanufactured while the rest of
the product can be disposed. In this method of applying this selective
disassembly principle based on size and weight the manufacturer can profit in
material recovery and at the same time the junk being disposed as landfill can
be reduced in huge amounts every day.
So, in this chapter, the possibility of applying the selective disassembly
principle to the two toasters is investigated. Here this selective disassembly is
implemented to components that are large and heavy and those which provide
the possibility for more material recovery at EOL.
3.3 Components investigated
The major components of the standard and eco-friendly toasters that are
investigated include the outer casing, inner casing, heating elements and wire
mesh. These components are shown in the figure below and their
corresponding weights are tabulated.
16
Figure 2 a) Outer Casing, b) Inner Casing, c) Heating Element, d) Wire mesh
Figure 3 a) Outer Casing, b) Inner Casing, c) Heating Element, d) Wire mesh
Table 1 Weight of the Components
Components Number of
Components
Standard Toaster
(grams)
Eco-Toaster
(grams)
Outer Casing 1 513.20 726.35
Inner Casing 1 478.51 490.50
Wire mesh 4 32.27 11.83
Heating plate 3 25.43 38.97
Total 9 1049.41 1267.65
17
3.4 Life Cycle of a Toaster
Figure 4 Life Cycle of a Toaster
Figure 4 presents a simplified schematic of the life cycle of a toaster. It
includes the design phase, raw material phase, manufacturing and assembly
phase, use phase and End-of-life. In the design phase the complete design
specifications of each component is specified by the design team which also
includes the tolerance specifications. In the next stage, i.e., the raw material
phase, where these raw materials are brought in from a storage plant and they
undergo various manufacturing processes like forging, casting, etc. to form
each component which is assembled based on the design specifications in the
manufacturing and assembly phase. Hazardous wastes and industrial wastes
maybe generated during this manufacturing and assembly phase. Most of
these hazardous and industrial wastes are usually drained in the neighboring
18
lakes or rivers which might cause severe damage to the marine habitat in that
area. Next phase is the use phase, where the consumer‟s utilization of this
product in his/her day to day routine which also causes air emissions. The
final phase is the End-of-life phase, where the end-of-life (EOL) decisions
such as recycle, reuse, remanufacture or disposal are made according to the
cost and environmental constraints.
3.5 Use Phase Energy Calculation
Three different situations were analyzed in this study. First, the standard
toaster was experimented with two sets of bread (two slices in each set). Then,
the eco-friendly toaster was experimented with its lid in open condition with
similar sets of bread. Finally, the eco-friendly toaster was tested with its lid in
closed condition with similar sets of breads. The time taken to toast was noted
in all these three cases at the maximum and minimum positions of the knob
and the time taken to toast was tabulated. Using this data from time taken to
toast and the wattage readings the energy consumption of each toaster is found
by using the formula,
…………………………………………..(1)
Where,
E is the Energy Consumed,
T is the time to toast, and
W is the wattage value specified by the manufacturer.
19
Figure 5 Experimental Setup
The wattage values specified by the manufacturer are 950 W and 900 W
respectively for the standard and the eco-friendly toaster.
All experiments were conducted using the electricity mix available in
Washington State. The experimental setup is shown in Figure 5. The
electricity mix is supplied to the toaster for the experiment from an electricity
outlet available in the lab.
To compare and calculate the energy efficient toaster, the recorded values
were tabulated as shown in Table 2. Based on the preliminary study of use
phase impacts, 6 trial readings were recorded and the average of the six values
is tabulated as in Table 1. From Table 1, it can be concluded that the Eco-
Closed lid is more eco-friendly with less energy usage compared to Eco-Open
lid and Standard toaster. The standard toaster is more eco-friendly with less
Stop Watch
20
energy used than Eco-Open lid. Also, In the case of a standard toaster, there is
comparatively more heat loss than the eco-friendly toaster. This is due to the
absence of lids in the standard toaster. These lids in the eco-friendly toaster
help to minimize heat dissipation.
It is important to note that the maximum and minimum level of toasting, in
both the toasters, is assumed to be same.
Table 2. Use Phase energy in KWh
3.6 Impact Assessment Methodology
Environmental impacts have gained high importance in manufacturing
sectors due to legislative pressures to protect the environment and to upgrade
their products in an environmentally conscious way [38]. Therefore,
identifying factors that have a major influence on the environmental impact of
the product is very important. Eco-indicators should be used as problem
Type/Model Position Time to toast (s) Energy in KWh
Oster Minimum 71 67,450
Oster Maximum 192 182,400
Eco-Open lid Minimum 91 81,900
Eco-Open lid Maximum 190 171,000
Eco-closed lid Minimum 72 64,800
Eco-closed lid Maximum 156 140,400
21
pointers to indicate the order of magnitude of impact effects and to enlighten
critical issues.
3.6.1 Using SIMAPRO
This study is focused on the eco-indicator 99 method to compare various
features of eco-friendly and standard toasters. Figure 8, 9 and 10, shows the
environmental impacts of the standard and the eco-friendly toaster. This is
calculated by applying eco-indicator method using SimaPro 7. These single
core graphs clearly show that the standard toaster has higher environmental
impacts than the eco-friendly toaster. One of the main environmental impact
factors is the use of fossil fuels.
22
Figure 6 Network diagram of LCA of Standard toaster using Simapro 7
23
Figure 7 Network diagram of LCA of eco-friendly toaster using Simapro 7
24
Figure 8 Weighting for Standard toaster
Figure 9 Weighting for eco-friendly toaster
25
Figure 10 Environmental impacts of standard and eco-toasters
Figures 8 and 9 show how the two toasters affect the environment based
on the carcinogenic effects produced, the fossil fuels generated, and the
acidification rate. It also describes how it affects the ozone layer. Further,
from Figure 10, we refer that the overall impacts reach 900 pt in the case of a
standard toaster, while the overall impact is 500 pt in the case of an eco-
friendly toaster. This result is of greater significance, since it describes how
effective is the impact of standard and eco-friendly toasters on the
environment and also why eco-friendly toasters are better than standard
toasters.
0
50
100
150
200
250
300
350
1 2 3 4 5 6 7
Std
Eco
1. Carcinogens 2.Resp. inorganics 3.Climate change 4.Radiation 5.Ecotoxicity 6.Minerals 7.Fossil fuels
26
Chapter 4 – Assembly Time calculation using Connective Complexity
Matrices method
4.1 Complexity design
A design could be very complicated to create, but if it was quick to
develop, economical to make, and flawless in performance then there would
be no need to worry about its complexity. However, this also depends on the
processes involved in making the product [43]. The complexity of a design
increases the costs involved in manufacturing and makes it more prone to
failure [44]. However, at the same time exceedingly simple designs can be
completely spiked by a minor failure. As each component of a product might
have multiple connections between the other components or subassemblies,
the methodology described below is helpful in addressing the product which
has components with multiple connections between them.
4.2 Complexity Metrics
Most previous approaches to engineering design complexity have focused
on addressing a single representation within a constrained set of conventional
linking properties. One approach, proposed by [43], is capable of addressing
multiple representations by translation through bi-partite graphs. However,
this approach does not address the effects of directionality on the system.
Therefore, there exists a need for complexity metrics which can address
multiple aspects of complexity within a mixed graph environment.
27
4.3 Methodology
In this methodology, the product under study has 15 components/parts
namely part B, part C, part D, part E, part F, part G, part H, part I, part J and
part K, part L, part M, part N, part O, part P which are assembled to form the
whole product A as shown in the assembly graph below.
4.3.1 Assembly Graph
Figure 11 Assembly graph before material-wise separation
28
This assembly graph is used in calculating the number of relationships
between each component with the other components which helps in
calculating the disassembly time.
The bipartite graph here is used for individual representation of the
instances that connect the products with one another and they are separately
shown based on each manufacturing and assembly instance by the graph
which has the products/components on one side and their connecting instances
on the other side.
29
Figure 12 Bipartite graph
4.3.2 Shortest Path Length
Path length measurements are based on the number of relationships which
must be passed through to travel from one element to another [40,41]. For
example, to travel through the system A>B>C from A to C is a path length of
30
2. Here, we focus on the measurement of the shortest available path between
any two elements in the system.
Total Path length denoted by TPL, is the sum of all the shortest path
lengths in the system.
Average Path length (APL) is determined by dividing the total path length
by the product of total number of components in the system and the total
number of components in the system minus the empty identity.
………………………………...……..…..(2)
Where n is the total number of components in the system.
4.3.3 Path Length density
Path length density, also known as PLD is derived from average path
length by dividing the APL by the number of relationships in the system.
…………………………………................(3)
Where N is the total number of relationships in the system.
4.3.4 Disassembly time
The disassembly time is calculated using the formula,
PLD
d nAPLt 185.1= ……………………......................(4)
Where td, is the disassembly time.
31
This equation has been developed by [44] for predicting the assembly time.
The equation has been found to estimate assembly time within 16% of the
assembly time as computed through the Boothroyd and Dewhurst method.
Disassembly is usually considered as the inverse of assembly. By utilizing the
assumption that disassembly is the inverse of assembly, in this research we
have used the equation (4) for disassembly time prediction.
Table 3 Disassembly time calculation before material separation
PA PB PC PD PE PF PG PH PI PJ PK PL PM PN PO PP
PA 0 1 2 2 1 1 1 1 2 2 2 2 3 3 3 2 28
PB 1 0 1 1 2 2 2 2 3 3 3 3 4 4 4 3 38
PC 2 1 0 1 3 3 3 3 4 4 4 4 5 5 5 4 51
PD 2 1 1 0 3 3 3 3 4 4 4 4 5 5 5 4 51
PE 1 2 3 3 0 1 1 1 2 2 2 1 2 2 3 2 28
PF 1 2 3 3 1 0 1 1 1 1 2 2 2 2 2 2 26
PG 1 2 3 3 1 1 0 1 2 2 1 2 3 3 2 2 29
PH 1 2 3 3 1 1 1 0 2 2 1 2 3 3 2 1 28
PI 2 3 4 4 2 1 2 2 0 1 3 2 1 2 2 3 34
PJ 2 3 4 4 2 1 2 2 1 0 2 2 2 1 1 2 31
PK 2 3 4 4 2 2 1 1 2 2 0 3 2 2 1 1 32
PL 2 3 4 4 1 2 2 2 2 2 3 0 1 1 2 3 34
PM 3 4 5 5 2 2 3 3 1 2 2 1 0 2 1 2 38
PN 3 4 5 5 2 2 3 3 2 1 2 1 2 0 1 2 38
PO 3 4 5 5 3 2 2 2 2 1 1 2 1 1 0 1 35
PP 2 3 4 4 2 2 2 1 3 2 1 3 2 2 1 0 34
28 38 51 51 28 26 29 28 33 31 33 34 38 38 35 34
4.3.5 Selective Disassembly time prediction
After identification of materials, a new assembly graph is drawn to
calculate the Path Length, Path Length Density and the Disassembly time
based on material-wise separation.
32
Figure 13 Assembly graph after material-wise separation
Here the focus is on material T5 which needs to be recovered. The
disassembly is performed based on recovering more amount of material T5
which is the needed material that can be recycled, reused or remanufactured.
This helps in reducing the manufacturing time and cost of this material T5
which is required for manufacturing a new product which uses the same
material/component. Materials T2 and T3 are unwanted or materials that have
to be disposed in a landfill and the components that contain these materials
need not be disassembled which will minimize the disassembly time further
and help in recovery of more material T5.
33
Table 4 Disassembly time calculation after material separation
PA PB PC PD PE PF PG PH PI PJ PK PL PM PN PO PP
PA 0 1 0 0 1 1 0 1 2 0 0 4 3 5 0 0 18
PB 1 0 0 0 2 2 0 2 3 0 0 5 4 6 0 0 25
PC 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PD 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PE 1 2 0 0 0 1 0 1 2 0 0 4 3 5 0 0 19
PF 1 2 0 0 1 0 0 1 1 0 0 3 2 4 0 0 15
PG 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PH 1 2 0 0 1 1 0 0 2 0 0 4 3 5 0 0 19
PI 2 3 0 0 2 1 0 2 0 0 0 2 1 3 0 0 16
PJ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PK 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PL 4 5 0 0 4 3 0 4 2 0 0 0 1 1 0 0 24
PM 3 4 0 0 3 2 0 3 1 0 0 1 0 2 0 0 19
PN 5 6 0 0 5 4 0 5 3 0 0 1 2 0 0 0 31
PO 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PP 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
18 25 0 0 19 15 0 19 16 0 0 24 19 31 0 0
Based on the above described methodology the material T5 is recovered to
a more extent in this case compared to the previous disassembly methodology
and at the same time the disassembly time is also minimized because of not
wasting time with disassembling the unwanted components.
This same methodology is applied to the case study of two toasters in the
next chapter.
34
Chapter 5 – Case studies
This chapter will present case studies demonstrating the selective
disassembly methodology. The case studies selected are two toasters. The first
one is a standard oster toaster model number #6325. The second one is
EcoToaster model number #TE-249.
5.1 Case Study 1: Standard Toaster
This section will describe the main components of the standard toaster,
creation of bi-partite graph, assembly graph, total disassembly time estimation
and selective disassembly time computation for the standard toaster.
5.1.1 Standard Toaster – Components
There are 32 components in the standard toaster as listed below and some
of the components are shown in the figure 14.
Figure 14 Outer Casing, Inner Casing, Heating Element, Wire Mesh
1) Casing A
2) Handle 1
3) Screw 1
4) Screw 2
35
5) Heating Element 1
6) Heating Element 2
7) Heating Element 3
8) Slide
9) Inner Casing base plate
10) Back Plate
11) Front Plate
12) Side Plate 1
13) Side plate 2
14) Bread Support Plate
15) Rod 1
16) Rod 2
17) Part-E
18) Slides & Hotches
19) Small spring 1
20) Small spring 2
21) Large spring
36
22) K plate
23) L plate
24) J plate
25) Handle 2
26) Bottom B
27) Slider C
28) Slider base D
29) Light
30) Switch
31) Knob
32) Electronic component
5.1.2 Bipartite Graph for a Standard toaster
The 32 components and their assembly are then used to create assembly
and bipartite graphs. The bipartite graph is used in calculating the number of
relationships (i.e, connection instances) between each component with the
other components. The bipartite graph is shown in Figure 15 and represents
the components of a standard toaster on one side and their connecting
instances on the other side. Different types of assembly instances in the
37
standard toaster are bolting, press fit, sliding, welding, snap fit and series
connection.
Figure 15(a) Bipartite graph of a standard toaster
38
Figure 15(b) Bipartite graph of a standard toaster
39
Figure 15(c) Bipartite graph of a standard toaster
40
5.1.3 Assembly graph and disassembly time calculation before material-wise
separation
Now the assembly graph is drawn (Figure 16) which helps in calculating
the shortest path between one component with the rest of the components. The
shortest path is used in the calculation of the Total Path Length, Average Path
Length, Path Length Density and Disassembly time as described in Chapter 4.
Figure 16 Assembly graph of a standard toaster before material-wise separation
41
Then, the total disassembly time is estimated by creating a matrix (Table 5)
and computing TPL, APL and PLD, as described in Chapter 4.
Table 5 (a) Disassembly time calculation of a standard toaster before material separation
CA H1 S1 S2 H.1 H.2 H.3 Se IC BP FP SP1
CA 0 1 1 1 2 2 2 3 3 4 4 4 H1 1 0 1 1 3 3 3 4 4 2 2 3 S1 1 1 0 1 3 3 3 4 4 3 3 4 S2 1 1 1 0 3 3 3 4 4 3 3 4 H.1 2 2 2 2 0 1 1 1 1 2 2 3 H.2 2 2 2 2 1 0 1 1 1 2 2 3 H.3 2 2 2 2 1 1 0 1 1 2 2 3 Se 3 2 3 3 1 1 1 0 1 2 2 3
IC 3 1 3 3 1 1 1 1 0 1 1 2
BP 4 2 3 3 2 2 2 2 1 0 1 1
FP 4 2 3 3 2 2 2 2 1 1 0 1
SP1 4 3 4 4 3 3 3 3 2 1 1 0
SP2 4 3 4 4 3 3 3 3 2 1 1 1
BSP 4 3 4 4 3 3 3 3 2 1 1 2
R1 3 2 3 3 2 2 2 2 1 2 1 2
R2 3 2 3 3 2 2 2 2 1 2 1 2
P-E 1 1 1 1 1 1 1 2 2 3 3 4
S&H 2 2 2 2 1 1 1 2 2 3 3 4
S.Sp1 4 3 3 3 3 3 3 3 2 2 1 2
S.Sp2 4 3 3 3 3 3 3 3 2 3 2 3
L.Sp 4 3 3 3 3 3 3 3 2 2 1 2
KP 4 3 3 3 3 3 3 3 2 3 2 3
LP 5 4 4 4 4 4 4 4 3 4 3 4
JP 5 4 4 4 4 4 4 4 3 4 3 4
H2 5 4 4 4 4 4 4 4 3 4 3 4
BoB 1 1 1 1 2 2 2 3 3 4 4 5
SC 2 2 2 2 3 3 3 4 3 4 4 5
SBD 2 2 2 2 3 3 3 4 2 3 3 4
Light 1 1 1 1 2 2 2 3 2 3 3 4
Switch 1 1 1 1 2 2 2 3 2 3 3 4
Knob 1 1 1 1 2 2 2 3 2 3 3 4
E.C 2 2 2 2 2 2 2 2 1 2 2 3
85 66 76 76 74 74 74 86 65 79 70 97
42
Table 5 (b) Disassembly time calculation of a standard toaster before material separation
SP2 BSP R1 R2 PE S&H SS 1 SS 2 LS KP LP JP
CA 4 4 3 3 1 2 4 4 4 4 5 5
H1 3 3 2 2 1 2 3 3 3 3 4 4
S1 4 4 3 3 1 2 3 3 3 3 4 4
S2 4 4 3 3 1 2 3 3 3 3 4 4
H.1 3 3 2 2 1 1 3 3 3 3 4 4
H.2 3 3 2 2 1 1 3 3 3 3 4 4
H.3 3 3 2 2 1 1 3 3 3 3 4 4 Se 3 3 2 2 2 2 3 3 3 3 4 4
IC 2 2 1 1 2 2 2 2 2 2 3 3
BP 1 1 2 2 3 3 2 3 2 3 4 4
FP 1 1 1 1 3 3 1 2 1 2 3 3
SP1 1 2 2 2 4 4 2 3 2 3 4 4
SP2 0 2 2 2 4 4 2 3 2 3 4 4
BSP 2 0 2 2 4 4 2 3 2 3 4 4
R1 2 2 0 1 3 3 1 1 2 1 2 2
R2 2 2 1 0 3 3 1 1 2 1 2 2
P-E 4 4 3 3 0 1 4 4 4 4 5 5
S&H 4 4 3 3 1 0 4 4 4 4 5 5
S.Sp1 2 2 1 1 4 4 0 1 2 1 2 2
S.Sp2 3 3 1 1 4 4 1 0 2 1 2 1
L.Sp 2 2 2 2 4 4 2 2 0 1 1 1
KP 3 3 1 1 4 4 1 1 1 0 1 1
LP 4 4 2 2 5 5 2 2 1 1 0 1
JP 4 4 2 2 5 5 2 1 1 1 1 0
H2 4 4 2 2 5 5 2 2 1 1 1 1
BoB 5 5 4 4 1 2 5 5 5 5 6 6 SC 5 5 4 4 2 3 5 5 5 5 6 6 SBD 4 4 3 3 2 3 4 4 4 4 5 5 Light 4 4 3 3 1 2 4 4 4 4 5 5 Switch 4 4 3 3 1 2 4 4 4 4 5 5 Knob 4 4 3 3 1 2 4 4 4 4 5 5
E.C 3 3 2 2 2 3 3 3 3 3 4 4
97 98 69 69 77 88 85 89 85 86 113 112
43
Table 5 (c) Disassembly time calculation of a standard toaster before material separation
H2 BoB SC SBD Light Switch Knob E.C CA 5 1 2 2 1 1 1 2 85 H1 4 1 2 2 1 1 1 2 74 S1 4 1 2 2 1 1 1 2 81 S2 4 1 2 2 1 1 1 2 81 H.1 4 2 3 3 2 2 2 2 71 H.2 4 2 3 3 2 2 2 2 71 H.3 4 2 3 3 2 2 2 2 71 Se 4 3 4 4 3 3 3 2 82 IC 3 3 3 2 2 2 2 1 60 BP 4 4 4 3 3 3 3 2 79 FP 3 4 4 3 3 3 3 2 70 SP1 4 5 5 4 4 4 4 3 97 SP2 4 5 5 4 4 4 4 3 97 BSP 4 5 5 4 4 4 4 3 98 R1 2 4 4 3 3 3 3 2 69 R2 2 4 4 3 3 3 3 2 69 P-E 5 1 2 2 1 1 1 2 77
S&H 5 2 3 3 2 2 2 3 88
S.Sp1 2 5 5 4 4 4 4 3 85
S.Sp2 2 5 5 4 4 4 4 3 89
L.Sp 1 5 5 4 4 4 4 3 85
KP 1 5 5 4 4 4 4 3 86
LP 1 6 6 5 5 5 5 4 113
JP 1 6 6 5 5 5 5 4 112 H2 0 6 6 5 5 5 5 4 113
BoB 6 0 1 1 1 1 1 2 95 SC 6 1 0 1 2 2 2 2 108
SBD 5 1 1 0 2 2 2 1 92 Light 5 1 2 2 0 1 1 1 81
Switch 5 1 2 2 1 0 1 1 81 Knob 5 1 2 2 1 1 0 1 81 E.C 4 2 2 1 1 1 1 0 71
113 95 108 92 81 81 81 71 2712 Total Path Length (TPL) = ∑ Mij 2712
Average Path Length APL = TPL/ n(n-1) 2.733871 Path Length Density = APL/ No. of Relationships (51) 0.049707
Disassembly Time (ta) = APL * n^(1.185 + [PLD]) 197.3317
44
The total disassembly time for the standard toaster is estimated as 197
seconds.
5.1.4 Assembly graph and disassembly time calculation after material-wise
separation
For estimating the selective disassembly time, material recovery for
recycling is considered in this case study. In order to compute the selective
disassembly time for material recovery, material is assigned to each of the
parts of the standard toaster. This material assignment is then labeled in the
assembly graph as shown in Figure 25. The labels T1 through T5 are used as
material labels in Figure 25 and represent the following materials.
T1 – Steel/Stainless steel,
T2 – Plastic,
T3 – Black Plastic,
T4 – Nichrome,
T5 – Aluminium wire and copper connections.
The material in focus, for this case study, is T1-steel/stainless steel, which
needs to be recovered. The selective disassembly is performed based on
recovering more amount of steel (T1) that can be recycled, reused or
remanufactured for the new toaster. This helps in reducing the
remanufacturing time and cost associated with T1 Material T2-Black Plastic is
an unwanted material in this case which has to be disposed in a landfill and
45
the components that contain these materials need not be disassembled which
will minimize the disassembly time further and help in recovery of more T1-
material.
Figure 17 Assembly graph of a standard toaster after material-wise separation
46
After identification of materials, a new assembly graph is drawn to
calculate the Path Length, Path Length Density and the Disassembly time
based on material-wise separation, as discussed in Chapter 4. The
computations are also demonstrated in Table 6.
Table 6 (a) Disassembly time calculation of a standard toaster after material separation
CA H1 S1 S2 H.1 H.2 H.3 Se IC BP FP SP 1
CA 0 1 1 1 2 2 2 3 3 6 5 6
H1 1 0 1 1 3 3 3 4 4 4 3 4
S1 1 1 0 1 3 3 3 4 4 4 3 4
S2 1 1 1 0 3 3 3 4 4 4 3 4
H.1 2 2 2 2 0 1 1 1 1 4 3 4
H.2 2 2 2 2 1 0 1 1 1 4 3 4
H.3 2 2 2 2 1 1 0 1 1 4 3 4 Se 3 2 3 3 1 1 1 0 1 4 3 4
IC 3 1 3 3 1 1 1 1 0 3 2 3
BP 6 4 4 4 4 4 4 4 3 0 1 1
FP 5 3 3 3 3 3 3 3 2 1 0 1
SP1 6 4 4 4 4 4 4 4 3 1 1 0
SP2 6 4 4 4 4 4 4 4 3 1 1 1
BSP 6 4 4 4 4 4 4 4 3 1 1 2
R1 3 2 3 3 2 2 2 2 1 2 1 2
R2 3 2 3 3 2 2 2 2 1 2 1 2
P-E 1 1 1 1 1 1 1 2 2 5 4 5
S&H 2 2 2 2 1 1 1 2 2 5 4 5
S.Sp1 4 3 3 3 3 3 3 3 2 2 1 2
S.Sp2 4 3 3 3 3 3 3 3 2 3 2 3
L.Sp 4 3 3 3 3 3 3 3 2 2 1 2
KP 4 3 3 3 3 3 3 3 2 4 2 3
LP 5 4 4 4 4 4 4 4 3 5 3 4
JP 5 4 4 4 4 4 4 4 3 5 3 4
H2 5 4 4 4 4 4 4 4 3 5 3 4
BoB 1 1 1 1 2 2 2 3 3 4 4 5
SC 2 2 2 2 3 3 3 4 3 4 4 5
SBD 2 2 2 2 3 3 3 4 2 3 3 4
Light 0 0 0 0 0 0 0 0 0 0 0 0
47
Switch 0 0 0 0 0 0 0 0 0 0 0 0
Knob 0 0 0 0 0 0 0 0 0 0 0 0
E.C 2 2 2 2 2 2 2 2 1 2 2 3
91 69 74 74 74 74 74 83 65 94 70 95
Table 6 (b) Disassembly time calculation of a standard toaster after material separation
BP FP SP 1 SP 2 BSP R 1 R 2 P-E S&H SS1 SS2 LS KP
CA 6 5 6 6 6 3 3 1 2 4 4 4 4
H1 4 3 4 4 4 2 2 1 2 3 3 3 3
S1 4 3 4 4 4 3 3 1 2 3 3 3 3
S2 4 3 4 4 4 3 3 1 2 3 3 3 3
H.1 4 3 4 4 4 2 2 1 1 3 3 3 3
H.2 4 3 4 4 4 2 2 1 1 3 3 3 3
H.3 4 3 4 4 4 2 2 1 1 3 3 3 3 Se 4 3 4 4 4 2 2 2 2 3 3 3 3
IC 3 2 3 3 3 1 1 2 2 2 2 2 2
BP 0 1 1 1 1 2 2 5 5 2 3 2 4
FP 1 0 1 1 1 1 1 4 4 1 2 1 2
SP1 1 1 0 1 2 2 2 5 5 2 3 2 3
SP2 1 1 1 0 2 2 2 5 5 2 3 2 3
BSP 1 1 2 2 0 2 2 5 5 2 3 2 3
R1 2 1 2 2 2 0 1 3 3 1 1 2 1
R2 2 1 2 2 2 1 0 3 3 1 1 2 1
P-E 5 4 5 5 5 3 3 0 1 4 4 4 4
S&H 5 4 5 5 5 3 3 1 0 4 4 4 4
S.Sp1 2 1 2 2 2 1 1 4 4 0 1 2 1
S.Sp2 3 2 3 3 3 1 1 4 4 1 0 2 1
L.Sp 2 1 2 2 2 2 2 4 4 2 2 0 1
KP 4 2 3 3 3 1 1 4 4 1 1 1 0
LP 5 3 4 4 4 2 2 5 5 2 2 1 1
JP 5 3 4 4 4 2 2 5 5 2 1 1 1
H2 5 3 4 4 4 2 2 5 5 2 2 1 1
BoB 4 4 5 5 5 4 4 1 2 5 5 5 5
SC 4 4 5 5 5 4 4 2 3 5 5 5 5
SBD 3 3 4 4 4 3 3 2 3 4 4 4 4
Light 0 0 0 0 0 0 0 0 0 0 0 0 0
Switch 0 0 0 0 0 0 0 0 0 0 0 0 0
48
Knob 0 0 0 0 0 0 0 0 0 0 0 0 0
E.C 2 2 3 3 3 2 2 2 3 3 3 3 3
94 70 95 95 96 60 60 80 88 73 77 73 75
Table 6 (c) Disassembly time calculation of a standard toaster after material separation
LP JP H2 BoB S C SBD Light Switch Knob E.C CA 5 5 5 1 2 2 0 0 0 2 91 H1 4 4 4 1 2 2 0 0 0 2 77 S1 4 4 4 1 2 2 0 0 0 2 79 S2 4 4 4 1 2 2 0 0 0 2 79 H.1 4 4 4 2 3 3 0 0 0 2 71 H.2 4 4 4 2 3 3 0 0 0 2 71 H.3 4 4 4 2 3 3 0 0 0 2 71 Se 4 4 4 3 4 4 0 0 0 2 79 IC 3 3 3 3 3 2 0 0 0 1 60 BP 5 5 5 4 4 3 0 0 0 2 94 FP 3 3 3 4 4 3 0 0 0 2 70 SP1 4 4 4 5 5 4 0 0 0 3 95 SP2 4 4 4 5 5 4 0 0 0 3 95 BSP 4 4 4 5 5 4 0 0 0 3 96 R1 2 2 2 4 4 3 0 0 0 2 60 R2 2 2 2 4 4 3 0 0 0 2 60 P-E 5 5 5 1 2 2 0 0 0 2 80
S&H 5 5 5 2 3 3 0 0 0 3 88 S.Sp1 2 2 2 5 5 4 0 0 0 3 73 S.Sp2 2 1 2 5 5 4 0 0 0 3 77 L.Sp 1 1 1 5 5 4 0 0 0 3 73 KP 1 1 1 5 5 4 0 0 0 3 75 LP 0 1 1 6 6 5 0 0 0 4 99 JP 1 0 1 6 6 5 0 0 0 4 98 H2 1 1 0 6 6 5 0 0 0 4 99
BoB 6 6 6 0 1 1 0 0 0 2 92 SC 6 6 6 1 0 1 0 0 0 2 102
SBD 5 5 5 1 1 0 0 0 0 1 86 Light 0 0 0 0 0 0 0 0 0 0 0
Switch 0 0 0 0 0 0 0 0 0 0 0 Knob 0 0 0 0 0 0 0 0 0 0 0 E.C 4 4 4 2 2 1 0 0 0 0 68
99 98 99 92 102 86 0 0 0 68 2358
Total Path Length (TPL) = ∑ Mij 2358
49
Average Path Length APL = TPL/ n(n-1) 2.377016
Path Length Density = APL/ No. of Relationships (51) 0.043218
Disassembly Time (ta) = APL * n^(1.185 + [PLD]) 167.7587
The selective disassembly time computed for recovery of T1 material is
167 seconds.
5.2 Case study 2 – Eco-Friendly toaster
This section will describe the main components of the Eco-friendly toaster,
creation of bi-partite graph, assembly graph, total disassembly time estimation
and selective disassembly time computation for the Eco-friendly toaster.
5.2.1 Eco-friendly Toaster - Components
An eco-friendly toaster in this study is a TRUeco toaster model#TE-249. The
components of this eco-friendly toaster are listed below and a few components are
shown in the figure below:
Figure 18 Outer Casing, Inner Casing, Heating Element, Wire Mesh
1) Casing A
2) Handle 1
3) Screw 1
50
4) Screw 2
5) Heating Element 1
6) Heating Element 2
7) Heating Element 3
8) Slide
9) Inner Casing base plate
10) Back Plate
11) Front Plate
12) Side Plate 1
13) Side plate 2
14) Bread Support Plate
15) Rod 1
16) Rod 2
17) Part-E
18) Slides & Hotches
19) Small spring 1
20) Small spring 2
51
21) Large spring
22) K plate
23) L plate
24) J plate
25) Handle 2
26) Bottom B
27) Slider C
28) Slider base D
29) Light
30) Switch
31) Knob
32) Electronic component
33) Outer Lid 1
34) Outer Lid 2
35) Switch/Handle 3
36) Spring 1
37) Spring 2
52
38) Spring 3
39) Spring 4
There are 39 components listed above and these components of the
standard toaster are represented by assembly and bipartite graphs.
5.2.2 Bipartite Graph of an eco-friendly toaster
The bipartite graph is used in calculating the number of relationships (i.e,
connection instances) between each component with the other components.
The types of assembly instances (Figure 26) for the eco-friendly toaster are
bolting, press fit, sliding, welding, snap fit and series.
53
Figure 19(a) Bipartite graph of an eco-friendly toaster
54
Figure 19(b) Bipartite graph of an eco-friendly toaster
55
Figure 19(c) Bipartite graph of an eco-friendly toaster before material-wise separation
56
Figure 19(d) Bipartite graph of an eco-friendly toaster before material-wise separation
57
5.2.3 Assembly graph before material-wise separation
Then, the assembly graph for the eco-friendly toaster is created as shown
in Figure 20. Following the methodology as described in Chapter 4, the total
disassembly time is computed through the matrix represented in Table 7.
Figure 20 Assembly graph of an eco-friendly toaster before material-wise separation
58
Table 7 (a) Disassembly time calculation of an eco-toaster before material-wise separation
CA H1 S1 S2 H.1 H.2 H.3 Se IC BP FP SP 1 SP 2 BSP
CA 0 1 1 1 2 2 2 3 3 4 4 4 4 4
H1 1 0 1 1 3 3 3 4 4 2 2 3 3 3
S1 1 1 0 1 3 3 3 4 4 3 3 4 4 4
S2 1 1 1 0 3 3 3 4 4 3 3 4 4 4
H.1 2 2 2 2 0 1 1 1 1 2 2 3 3 3
H.2 2 2 2 2 1 0 1 1 1 2 2 3 3 3
H.3 2 2 2 2 1 1 0 1 1 2 2 3 3 3
Se 3 2 3 3 1 1 1 0 1 2 2 3 3 3
IC 3 1 3 3 1 1 1 1 0 1 1 2 2 2
BP 4 2 3 3 2 2 2 2 1 0 1 1 1 1
FP 4 2 3 3 2 2 2 2 1 1 0 1 1 1
SP1 4 3 4 4 3 3 3 3 2 1 1 0 1 2
SP2 4 3 4 4 3 3 3 3 2 1 1 1 0 2
BSP 4 3 4 4 3 3 3 3 2 1 1 2 2 0
R1 3 2 3 3 2 2 2 2 1 2 1 2 2 2
R2 3 2 3 3 2 2 2 2 1 2 1 2 2 2
P-E 1 1 1 1 1 1 1 2 2 3 3 4 4 4
S&H 2 2 2 2 1 1 1 2 2 3 3 4 4 4
S.Sp1 4 3 3 3 3 3 3 3 2 2 1 2 2 2
S.Sp2 4 3 3 3 3 3 3 3 2 3 2 3 3 3
L.Sp 4 3 3 3 3 3 3 3 2 2 1 2 2 2
KP 4 3 3 3 3 3 3 3 2 3 2 3 3 3
LP 5 4 4 4 4 4 4 4 3 4 3 4 4 4
JP 5 4 4 4 4 4 4 4 3 4 3 4 4 4
H2 5 4 4 4 4 4 4 4 3 4 3 4 4 4
BoB 1 1 1 1 2 2 2 3 3 4 4 5 5 5
SC 2 2 2 2 3 3 3 4 3 4 4 5 5 5
SBD 2 2 2 2 3 3 3 4 2 3 3 4 4 4
Light 1 1 1 1 2 2 2 3 2 3 3 4 4 4
Switch 1 1 1 1 2 2 2 3 2 3 3 4 4 4
Knob 1 1 1 1 2 2 2 3 2 3 3 4 4 4
E.C 2 2 2 2 2 2 2 2 1 2 2 3 3 3
OL1 1 2 2 2 3 3 3 4 3 4 4 5 5 5
OL2 1 2 2 2 3 3 3 4 3 4 4 5 5 5
59
S/H 3 2 3 3 3 4 4 4 5 4 5 5 6 6 6 Sp 1 2 3 3 3 4 4 4 5 4 5 5 6 6 6
Sp 2 2 3 3 3 4 4 4 5 4 5 5 6 6 6
Sp 3 2 3 3 3 4 4 4 5 4 5 5 6 6 6
Sp 4 2 3 3 3 4 4 4 5 4 5 5 6 6 6
97 85 95 95 100 100 100 119 91 112 103 137 137 138
Table 7 (b) Disassembly time calculation of an eco-toaster before material-wise separation
R 1 R 2 P-E S & H SS1 SS2 LS KP LP JP H2 BoB SC
CA 3 3 1 2 4 4 4 4 5 5 5 1 2
H1 2 2 1 2 3 3 3 3 4 4 4 1 2
S1 3 3 1 2 3 3 3 3 4 4 4 1 2
S2 3 3 1 2 3 3 3 3 4 4 4 1 2
H.1 2 2 1 1 3 3 3 3 4 4 4 2 3
H.2 2 2 1 1 3 3 3 3 4 4 4 2 3
H.3 2 2 1 1 3 3 3 3 4 4 4 2 3
Se 2 2 2 2 3 3 3 3 4 4 4 3 4
IC 1 1 2 2 2 2 2 2 3 3 3 3 3
BP 2 2 3 3 2 3 2 3 4 4 4 4 4
FP 1 1 3 3 1 2 1 2 3 3 3 4 4
SP1 2 2 4 4 2 3 2 3 4 4 4 5 5
SP2 2 2 4 4 2 3 2 3 4 4 4 5 5
BSP 2 2 4 4 2 3 2 3 4 4 4 5 5
R1 0 1 3 3 1 1 2 1 2 2 2 4 4
R2 1 0 3 3 1 1 2 1 2 2 2 4 4
P-E 3 3 0 1 4 4 4 4 5 5 5 1 2
S&H 3 3 1 0 4 4 4 4 5 5 5 2 3
S.Sp1 1 1 4 4 0 1 2 1 2 2 2 5 5
S.Sp2 1 1 4 4 1 0 2 1 2 1 2 5 5
L.Sp 2 2 4 4 2 2 0 1 1 1 1 5 5
KP 1 1 4 4 1 1 1 0 1 1 1 5 5
LP 2 2 5 5 2 2 1 1 0 1 1 6 6
JP 2 2 5 5 2 1 1 1 1 0 1 6 6
H2 2 2 5 5 2 2 1 1 1 1 0 6 6
BoB 4 4 1 2 5 5 5 5 6 6 6 0 1
SC 4 4 2 3 5 5 5 5 6 6 6 1 0
60
SBD 3 3 2 3 4 4 4 4 5 5 5 1 1
Light 3 3 1 2 4 4 4 4 5 5 5 1 2
Switch 3 3 1 2 4 4 4 4 5 5 5 1 2
Knob 3 3 1 2 4 4 4 4 5 5 5 1 2
E.C 2 2 2 3 3 3 3 3 4 4 4 2 2
OL 1 4 4 2 3 5 5 5 5 6 6 6 2 3
OL 2 4 4 2 3 5 5 5 5 6 6 6 2 3
S/H 3 5 5 3 4 6 6 6 6 7 7 7 3 4 Sp 1 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 2 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 3 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 4 5 5 3 4 6 6 6 6 7 7 7 3 4
102 102 96 114 125 129 125 126 160 159 160 114 134
Table 7 (c) Disassembly time calculation of an eco-toaster before material-wise separation
SBD Lt Swh Kb E.C OL1 OL2 S/H3 Sp1 Sp2 Sp3 Sp4
CA 2 1 1 1 2 1 1 2 2 2 2 2 97
H1 2 1 1 1 2 2 2 3 3 3 3 3 93
S1 2 1 1 1 2 2 2 3 3 3 3 3 100
S2 2 1 1 1 2 2 2 3 3 3 3 3 100
H.1 3 2 2 2 2 3 3 4 4 4 4 4 97
H.2 3 2 2 2 2 3 3 4 4 4 4 4 97
H.3 3 2 2 2 2 3 3 4 4 4 4 4 97
Se 4 3 3 3 2 4 4 5 5 5 5 5 115
IC 2 2 2 2 1 3 3 4 4 4 4 4 86
BP 3 3 3 3 2 4 4 5 5 5 5 5 112
FP 3 3 3 3 2 4 4 5 5 5 5 5 103
SP1 4 4 4 4 3 5 5 6 6 6 6 6 137
SP2 4 4 4 4 3 5 5 6 6 6 6 6 137
BSP 4 4 4 4 3 5 5 6 6 6 6 6 138
R1 3 3 3 3 2 4 4 5 5 5 5 5 102
R2 3 3 3 3 2 4 4 5 5 5 5 5 102
P-E 2 1 1 1 2 2 2 3 3 3 3 3 96
S&H 3 2 2 2 3 3 3 4 4 4 4 4 114
S.Sp1 4 4 4 4 3 5 5 6 6 6 6 6 125
S.Sp2 4 4 4 4 3 5 5 6 6 6 6 6 129
61
L.Sp 4 4 4 4 3 5 5 6 6 6 6 6 125
KP 4 4 4 4 3 5 5 6 6 6 6 6 126
LP 5 5 5 5 4 6 6 7 7 7 7 7 160
JP 5 5 5 5 4 6 6 7 7 7 7 7 159
H2 5 5 5 5 4 6 6 7 7 7 7 7 160
BoB 1 1 1 1 2 2 2 3 3 3 3 3 114
SC 1 2 2 2 2 3 3 4 4 4 4 4 134
SBD 0 2 2 2 1 3 3 4 4 4 4 4 118
Light 2 0 1 1 1 2 2 3 3 3 3 3 100
Switch 2 1 0 1 1 2 2 3 3 3 3 3 100
Knob 2 1 1 0 1 2 2 3 3 3 3 3 100
E.C 1 1 1 1 0 3 3 4 4 4 4 4 97
OL 1 3 2 2 2 3 0 1 1 1 1 1 1 120
OL 2 3 2 2 2 3 1 0 1 1 1 1 1 120
S/H 3 4 3 3 3 4 1 1 0 1 1 1 1 152 Sp 1 4 3 3 3 4 1 1 1 0 1 1 1 152
Sp 2 4 3 3 3 4 1 1 1 1 0 1 1 152
Sp 3 4 3 3 3 4 1 1 1 1 1 0 1 152
Sp 4 4 3 3 3 4 1 1 1 1 1 1 0 152
118 100 100 100 97 120 120 152 152 152 152 152 4670
Total Path Length (TPL) = ∑ Mij 4670
Average Path Length APL = TPL/ n(n-1) 3.321479
Path Length Density = APL/ No. of Relationships (51) 0.0511
Assembly Time (ta) = APL * n^(1.185 + [PLD]) 297.9213
The total disassembly time estimated for the eco-friendly toaster is 297 seconds.
5.2.4 Assembly graph and disassembly time calculation of an eco-friendly
toaster after material-wise separation
Materials T1 through T5 are assigned to the components of the eco-
friendly toaster. These labels represent the following materials.
T1 – Steel/Stainless steel,
T2 – Plastic,
62
T3 – Black Plastic,
T4 – Nichrome,
T5 – Aluminium wire and copper connections.
Here the material in focus is T1-steel/stainless steel, which needs to be
recovered. The selective disassembly is performed based on recovering more
amount of steel that is the needed for recycle, reuse or remanufacturing for a
new toaster. This helps in reducing the manufacturing time and cost of this
T1-material which is required for remanufacturing. Material T2-Black Plastic
is an unwanted material in this case which has to be disposed in a landfill and
the components that contain these materials need not be disassembled which
will minimize the disassembly time further and help in recovery of more T1-
material.
After identification of materials, a new assembly graph is drawn (Figure
21) to calculate the Path Length, Path Length Density and the Disassembly
time (Table 8) based on material-wise separation.
63
Figure 21 Assembly graph of an eco-friendly toaster after material-wise separation
64
Table 8 (a) Disassembly time calculation of an eco-toaster after material-wise separation
CA H1 S1 S2 H.1 H.2 H.3 Se IC BP FP SP 1 SP 2 BSP
CA 0 1 1 1 2 2 2 3 3 6 5 6 6 6
H1 1 0 1 1 3 3 3 4 4 4 3 4 4 4
S1 1 1 0 1 3 3 3 4 4 4 3 4 4 4
S2 1 1 1 0 3 3 3 4 4 4 3 4 4 4
H.1 2 2 2 2 0 1 1 1 1 4 3 4 4 4
H.2 2 2 2 2 1 0 1 1 1 4 3 4 4 4 H.3 2 2 2 2 1 1 0 1 1 4 3 4 4 4 Se 3 2 3 3 1 1 1 0 1 4 3 4 4 4
IC 3 1 3 3 1 1 1 1 0 3 2 3 3 3
BP 6 4 4 4 4 4 4 4 3 0 1 1 1 1 FP 5 3 3 3 3 3 3 3 2 1 0 1 1 1 SP1 6 4 4 4 4 4 4 4 3 1 1 0 1 2 SP2 6 4 4 4 4 4 4 4 3 1 1 1 0 2 BSP 6 4 4 4 4 4 4 4 3 1 1 2 2 0
R1 3 2 3 3 2 2 2 2 1 2 1 2 2 2
R2 3 2 3 3 2 2 2 2 1 2 1 2 2 2
P-E 1 1 1 1 1 1 1 2 2 5 4 5 5 5
S&H 2 2 2 2 1 1 1 2 2 5 4 5 5 5
S.Sp1 4 3 3 3 3 3 3 3 2 2 1 2 2 2 S.Sp2 4 3 3 3 3 3 3 3 2 3 2 3 3 3 L.Sp 4 3 3 3 3 3 3 3 2 2 1 2 2 2
KP 4 3 3 3 3 3 3 3 2 4 2 3 3 3
LP 5 4 4 4 4 4 4 4 3 5 3 4 4 4
JP 5 4 4 4 4 4 4 4 3 5 3 4 4 4
H2 5 4 4 4 4 4 4 4 3 5 3 4 4 4
BoB 1 1 1 1 2 2 2 3 3 4 4 5 5 5
SC 2 2 2 2 3 3 3 4 3 4 4 5 5 5
SBD 2 2 2 2 3 3 3 4 2 3 3 4 4 4
Light 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Switch 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Knob 0 0 0 0 0 0 0 0 0 0 0 0 0 0
E.C 2 2 2 2 2 2 2 2 1 2 2 3 3 3
OL 1 1 2 2 2 3 3 3 4 3 4 4 5 5 5
OL 2 1 2 2 2 3 3 3 4 3 4 4 5 5 5
S/H 3 2 3 3 3 4 4 4 5 4 5 5 6 6 6 Sp 1 2 3 3 3 4 4 4 5 4 5 5 6 6 6
Sp 2 2 3 3 3 4 4 4 5 4 5 5 6 6 6
Sp 3 2 3 3 3 4 4 4 5 4 5 5 6 6 6
65
Sp 4 2 3 3 3 4 4 4 5 4 5 5 6 6 6
103 88 93 93 100 100 100 116 91 127 103 135 135 136
Table 8 (b) Disassembly time calculation of an eco-toaster after material-wise separation
R 1 R 2 P-E S&H SS1 SS2 LS KP LP JP H2 BoB S C
CA 3 3 1 2 4 4 4 4 5 5 5 1 2
H1 2 2 1 2 3 3 3 3 4 4 4 1 2
S1 3 3 1 2 3 3 3 3 4 4 4 1 2
S2 3 3 1 2 3 3 3 3 4 4 4 1 2
H.1 2 2 1 1 3 3 3 3 4 4 4 2 3
H.2 2 2 1 1 3 3 3 3 4 4 4 2 3 H.3 2 2 1 1 3 3 3 3 4 4 4 2 3 Se 2 2 2 2 3 3 3 3 4 4 4 3 4
IC 1 1 2 2 2 2 2 2 3 3 3 3 3
BP 2 2 5 5 2 3 2 4 5 5 5 4 4 FP 1 1 4 4 1 2 1 2 3 3 3 4 4
SP1 2 2 5 5 2 3 2 3 4 4 4 5 5 SP2 2 2 5 5 2 3 2 3 4 4 4 5 5 BSP 2 2 5 5 2 3 2 3 4 4 4 5 5
R1 0 1 3 3 1 1 2 1 2 2 2 4 4
R2 1 0 3 3 1 1 2 1 2 2 2 4 4
P-E 3 3 0 1 4 4 4 4 5 5 5 1 2
S&H 3 3 1 0 4 4 4 4 5 5 5 2 3
S.Sp1 1 1 4 4 0 1 2 1 2 2 2 5 5 S.Sp2 1 1 4 4 1 0 2 1 2 1 2 5 5 L.Sp 2 2 4 4 2 2 0 1 1 1 1 5 5
KP 1 1 4 4 1 1 1 0 1 1 1 5 5
LP 2 2 5 5 2 2 1 1 0 1 1 6 6
JP 2 2 5 5 2 1 1 1 1 0 1 6 6
H2 2 2 5 5 2 2 1 1 1 1 0 6 6
BoB 4 4 1 2 5 5 5 5 6 6 6 0 1
SC 4 4 2 3 5 5 5 5 6 6 6 1 0
SBD 3 3 2 3 4 4 4 4 5 5 5 1 1
Light 0 0 0 0 0 0 0 0 0 0 0 0 0
Switch 0 0 0 0 0 0 0 0 0 0 0 0 0
Knob 0 0 0 0 0 0 0 0 0 0 0 0 0
E.C 2 2 2 3 3 3 3 3 4 4 4 2 2
OL 1 4 4 2 3 5 5 5 5 6 6 6 2 3
OL 2 4 4 2 3 5 5 5 5 6 6 6 2 3
66
S/H 3 5 5 3 4 6 6 6 6 7 7 7 3 4 Sp 1 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 2 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 3 5 5 3 4 6 6 6 6 7 7 7 3 4
Sp 4 5 5 3 4 6 6 6 6 7 7 7 3 4
93 93 99 114 113 117 113 115 146 145 146 111 128
Table 8 (c) Disassembly time calculation of an eco-toaster after material-wise separation
SBD Lt Swh Kb E.C OL1 OL2 S/H3 Sp1 Sp2 Sp3 Sp4
CA 2 0 0 0 2 1 1 2 2 2 2 2 103
H1 2 0 0 0 2 2 2 3 3 3 3 3 96
S1 2 0 0 0 2 2 2 3 3 3 3 3 98
S2 2 0 0 0 2 2 2 3 3 3 3 3 98
H.1 3 0 0 0 2 3 3 4 4 4 4 4 97
H.2 3 0 0 0 2 3 3 4 4 4 4 4 97 H.3 3 0 0 0 2 3 3 4 4 4 4 4 97 Se 4 0 0 0 2 4 4 5 5 5 5 5 112
IC 2 0 0 0 1 3 3 4 4 4 4 4 86
BP 3 0 0 0 2 4 4 5 5 5 5 5 127 FP 3 0 0 0 2 4 4 5 5 5 5 5 103
SP1 4 0 0 0 3 5 5 6 6 6 6 6 135 SP2 4 0 0 0 3 5 5 6 6 6 6 6 135 BSP 4 0 0 0 3 5 5 6 6 6 6 6 136
R1 3 0 0 0 2 4 4 5 5 5 5 5 93
R2 3 0 0 0 2 4 4 5 5 5 5 5 93
P-E 2 0 0 0 2 2 2 3 3 3 3 3 99
S&H 3 0 0 0 3 3 3 4 4 4 4 4 114
S.Sp1 4 0 0 0 3 5 5 6 6 6 6 6 113 S.Sp2 4 0 0 0 3 5 5 6 6 6 6 6 117 L.Sp 4 0 0 0 3 5 5 6 6 6 6 6 113
KP 4 0 0 0 3 5 5 6 6 6 6 6 115
LP 5 0 0 0 4 6 6 7 7 7 7 7 146
JP 5 0 0 0 4 6 6 7 7 7 7 7 145
H2 5 0 0 0 4 6 6 7 7 7 7 7 146
BoB 1 0 0 0 2 2 2 3 3 3 3 3 111
SC 1 0 0 0 2 3 3 4 4 4 4 4 128
SBD 0 0 0 0 1 3 3 4 4 4 4 4 112
Light 0 0 0 0 0 2 2 3 3 3 3 3 19
Switch 0 0 0 0 0 2 2 3 3 3 3 3 19
67
Knob 0 0 0 0 0 2 2 3 3 3 3 3 19
E.C 1 0 0 0 0 3 3 4 4 4 4 4 94
OL 1 3 2 2 2 3 0 1 1 1 1 1 1 120
OL 2 3 2 2 2 3 1 0 1 1 1 1 1 120
S/H 3 4 3 3 3 4 1 1 0 1 1 1 1 152 Sp 1 4 3 3 3 4 1 1 1 0 1 1 1 152
Sp 2 4 3 3 3 4 1 1 1 1 0 1 1 152
Sp 3 4 3 3 3 4 1 1 1 1 1 0 1 152
Sp 4 4 3 3 3 4 1 1 1 1 1 1 0 152
112 19 19 19 94 120 120 152 152 152 152 152 4316
Total Path Length (TPL) = ∑ Mij 4316
Average Path Length APL = TPL/ n(n-1) 3.069701
Path Length Density = APL/ No. of Relationships (51) 0.047226
Disassembly Time (ta) = APL * n^(1.185 + [PLD]) 271.4856
The selective disassembly time for the eco-friendly toaster is estimated as
271 seconds.
5.9 Results
Using the methodology described in chapter 4, the disassembly time for
both standard and eco-friendly toasters were calculated both before and after
material-wise separation. The results are tabulated as follows:
Table 9 Disassembly time results
Type Disassembly
time
(seconds)
Standard toaster before material-wise
separation
197.3
Standard toaster after material-wise
separation
167.7
Eco-friendly toaster before material-wise
separation
297.9
Eco-friendly toaster after material-wise
separation
271.4
68
Chapter 6 – Conclusion and Future Work
The contributions, limitations and future work will be summarized in the
following sections in this chapter.
6.1 Contributions
A method for selective disassembly time computation was
developed. This method is applicable for most electronic and
automobile products.
The use of this method was demonstrated through two case studies,
i.e., a standard and an eco-friendly toaster. Their corresponding
disassembly times were calculated and compared with each other
before material-wise separation and also the environmental
impacts and selective disassembly time for two similar products
were compared after material-wise separation.
This methodology can be very useful in reducing the total
disassembly time and the costs associated with total disassembly,
because by selectively disassembling a product to components or
subassemblies, the time spent in complete disassembly is
considerably reduced and use of manpower involved in total
disassembly is also reduced which in turn minimizes the costs
associated with disassembly.
69
Although this methodology is very useful there are certain limitations.
6.2 Limitations
The percentage error is within 16% of that of Boothroyds‟ method.
The types of assembly joints are not considered in this method.
This method can be applied only for recycling. This method has
not be applied for reuse and remanufacturing.
This method has been tested only with electronic products.
6.3 Future Work
Future work should focus on automating the selective disassembly
time computation using a CAD software.
Develop an equation or formula in such a way that the error
percentage is minimum when compared with Boothroyd method.
Focus on how to account for assembly joints.
The application of the proposed methodology can be investigated
for reuse and re-manufacturing of components.
So, if we automate the selective disassembly time computation, this
method can be applied to a given product that demands more material
recovery/components recovery/subassemblies recovery which can be computed
by automatically predicting the suitable end-of-life options such as recycling,
reuse and remanufacturing for a product thereby minimizing the time spent in
deciding the right end-of-life option for recovery from a given product. Once the
right end-of-life has been applied to the given product the selectively
70
disassembled/recovered sub-assemblies or whole components that can be reused
in manufacturing of a new product which replaces the cost to manufacture the
same component/sub-assemblies for a new product.
71
References
[1] USEPA. The United States Environmental Protection Agency.
[2] ISO 14040 (2006): Environmental management - Life cycle
assessment -Principles and framework, International Organisation for
Standardisation (ISO), Geneve.
[3] Product Environmental Life-Cycle Assessment Using Input-Output
Techniques. Satish Joshi, James Madison College, Michigan State University,
East Lansing, MI USA.
[4] Gupta, S. M. and Taleb, K. N., 1994, Scheduling disassembly.
International Journal of Production Research, 32, 1857-1866.
[5] Navin-Chandra, D., 1994, The recovery problem in product design.
Journal of Engineering Design, 5, 65-86.
[6] DeRon,A. and Penev,K., 1995, Disassembly and recycling of
electronic consumer products: an overview. Technovation, 15, 363-374.
[7] Penev, K.D. and deRon, A. J., 1996, Determination of a
disassembly strategy. International Journal of Production Research, 34, 495-
506.
[8] Gupta, S.M. and McLean, C. R., 1996, Disassembly of products.
Computers and Industrial Engineering, 31, 225-228.
[9] Gungor, A. and Gupta, S.M., 1997, An evaluation methodology for
disassembly processes. Computers and Industrial Engineering, 33, 329-332.
72
[10] Gungor, A. and Gupta, S. M., 1998a, Disassembly sequence
planning for complete disassembly in product recovery. Proceedings of the
Northeast Decision Sciences Institute - 27th Annual Meeting, Boston, MA,
25-27 March, pp. 250-252.
[11] Gungor, A. and Gupta, S. M., 1998b, Disassembly sequence
planning for products with defective parts in product recovery. Computers and
Industrial Engineering, 35, 161-164.
[12] Veerakamolmal, P., Gupta, S. M. and McLean, C. R., 1997,
Disassembly process planning. Proceedings of the International Conference
on Engineering Design and Automation, Bangkok, Thailand, 18±21 March,
pp. 162-165.
[13] Moore, K. E., Gungor, A. and Gupta, S. M., 1998a, Disassembly
process planning using Petri nets. Proceedings of the IEEE International
Symposium on Electronics and the Environment, Oak Brook, IL, pp. 88-93.
[14] Moore, K. E., Gungor, A. and Gupta, S.M., 1998b, A Petri net
approach to disassembly process planning. Computers and Industrial
Engineering, 35, 165-168.
[15] Moore, K. E., Gungor, A. and Gupta, S. M., 2001, Petri net
approach to disassembly process planning for products with complex
AND/OR precedence relationships. European Journal of Operational Research,
135, 428-449.
73
[16] Veerakamolmal, P. and Gupta, S. M., 1998, Optimal analysis of
lot size balancing for multi-products selective disassembly. International
Journal of Flexible Automation and Integrated Manufacturing, 6, 245-269.
[17] Veerakamolmal, P. and Gupta, S.M., 1999, Analysis of design
efficiency for the disassembly of modular electronic products. Journal of
Electronics Manufacturing, 9, 79-95.
[18] Zussmann, E., Krivet, A. and Seliger, G., Disassembly oriented
assessment methodology to support design for recycling. Annals CIRP, 1994,
34, pp. 9–14.
[19] Kroll, E., Beardsley, B. and Parulian, A., A methodology to
evaluate ease of disassembly for product recycling. IIE Trans., 1996, 28, pp.
837–845.
[20] Wiendahl, H.P., Seliger, G., Perlewitz, H. and Burkner, S.,
General approach to disassembly planning and control. Prod. Plan.Cont., 1999,
10, pp. 718–726.
[21] Salomonski, E. and Zussman, E., On-line predictive model for
disassembly process planning adaptation. Robot. Comput. Integ. Manuf., 1999,
15, pp. 211–220.
[22] Santochi, M., Dini, G. and Failli, F., Computer-aided disassembly
planning: State of the art and perspectives. Annals CIRP, 2002, 51, pp. 507–
530.
[23] Homem DM., Anderson A.C., AND/OR graph representation of
assembly plans, IEEE Trans. Robot. Autom., 1990, 6, pp. 188-199.
74
[24] Baldwin, D.F., Abell, T.E., Lui, M.M., De Fazio, T.L. and
Whitney, D.E., An integrated computer aid for generating and evaluating
assembly sequences for mechanical products. IEEE Trans. Robot. Autom.,
1991, 7, pp. 78–79.
[26] B. R. Fox and K. G. Kempf, "Opportunistic scheduling for
robotics assembly," in Proc. IEEE Inf. Conf. Robotics Automat., 1985.
pp.880-889.
[27] G. Boothroyd and L. Alting, “Design for Assembly and
Disassembly,” CIRP Annuls 1992 Manufacturing Technology, 1992, 41, 2, pp.
625-636.
[28] Geoffrey Boothroyd, Assembly Automation and Product design,
Second Edition ed. Boca Raton,FL, USA: Taylor & Francis, 2005.
[29] G. Boothroyd and J. Walker, “Design for Assembly,” in
Handbook of Manufacutring Engineering, Jack Walker, Ed.New York, NY,
USA: Marcel Dekker 1996, 1, pp. 1-50.
[30] G. Boothroyd and P. Dewhurst, “Product Design for Manufacture
and Assembly,” Manufacturing Engineering, pp. 42-46,April 1998.
[31] G. Boothroyd and P. Dewhurst, “Product Design for Assembly,”
Wakefield, RI, USA: Boothroyd and Dewhurst Inc., 1980.
[32] John Priest and Jose Sanchez, Product Development and Design
for Manufacturing. New York, NY, USA: Marcel Dekker, 2001.
75
[33] H.J Warnecke and R. Babler, “ Design for Assembly – Part of the
Design Process,” CIRP Annuls 1988 Manufacturing Technology, 37, 1, pp. 1-
4, August 1988.
[34] Curran MA (2004)., “The status of life-cycle assessment as an
environmental management tool,” Environ Prog 23: pp 277–283.
[35] Kuo TC, Zhang HC, Huang SH., “A graph-based disassembly
planning for end-of-life electromechanical products.” Int. J. Prod. Res.
2000;38(5):993–1007.
[36] T.C. Kuo, “Enhancing disassembly and recycling planning using
life-cycle analysis.” Int. J. Robotics and Computer-Integrated Manufacturing
22 (2006), pp. 420–428.
[37] Landfills: A Solid Waste Management Plan – American Field
Guide.
[38] D-H Lee, J-G kang, P Xirouchakis., 2001, “Disassembly planning
and scheduling: review and future research”. Proc Instn Mech Engnrs, Vol
215 Part B.
[39] I. Barclay and Z. Dann, "New-product-development performance
evaluation: a product-compexity-based methodology," IEE Proceedings in
Scientific Measurement Technology, vol. 147, no. 2, pp. 41-55, march 2000.
[40] J. Casti, Connectivity, Complexity, and Catastrophe in Large-
Scale Systems, International Series on Applied Systems Analysis ed. New
York, NY, USA: John Wiley & Sons, 1979.
76
[41] F Ameri, J.D. Summers, G.M. Mocko, and M. Porter,
"Engineering design complexity: an investigation of methods and measures,"
Research in Engineering Design, vol. 19, no. 2-3, pp. 161-179, November
2008.
[42] J. Mathieson and J. Summers, "Relational DSMs in Connectivity
Complexity Measurement," Greenville, SC, 2009
[43] I. Pramanick and H. Ali, "Analysis and experiments for a parallel
solution to the all pairs shortest path problem," in 1994 IEEE International
Symposium on Circuits and Systems, vol. 1, New York, NY, USA, 1994, pp.
479-82.
[44] J. Mathieson, B. Wallace, J. Summers, “Assembly Time
Modeling through Connective Complexity Metrics,” in 2010 International
Conference on Manufacturing Automation.
