DESIGN AND DEVELOPMENT OF THERMODYNAMICS APPARATUS
USING DESIGN FOR MANUFACTURE AND ASSEMBLY (DFMA)
METHODOLOGY
WAN ABD. RAHMAN ASSYAHID BIN WAN IBRAHIM
A project report submitted in partial fulfillment of the
requirements for the award of the degree of
Master of Mechanical Engineering
(Advance Manufacturing Technology)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
MAY, 2006
To my beloved wife Suriati Aliza bt. Ab. Samad
and my naughty kids; Wan Amirul Arif
I love you all.
v
ACKNOWLEDGEMENTS
I wish to express my sincere appreciation to my thesis supervisor, Tuan Haji
Dr. Ariffin Bin Abdul Razak, for encouragement, guidance, critics and friendship.
Without his continued support and interest, this thesis would not have been the same
as presented here.
Special thanks must go to Ahmad Humaizi Helmi and Ahmad Faizal Bin
Salleh for their truly support, co-operation and assistance. Thanks are also goes to
friends who had helped me directly or indirectly upon the project completion.
Finally, my very special, sincere and heartfelt gratitude goes to my beloved
wife and family for giving me tremendous courage while I was struggling with this
project. Their assistance and support was invaluable.
Wan Abd. Rahman Assyahid
May, 2006
vi
ABSTRACT
Thermodynamics is an essential subject in Mechanical Engineering
curriculum. The thermodynamics principles have been applied in many applications
to fulfill human needs. Mechanical engineers use thermodynamics principles in their
study to design a wide variety of energy system such as jet engines and rockets,
refrigeration system, air conditioning system, chemical process and power plant. This
would explain that thermodynamic was one of the critical areas which need to be
well understood. However, the majority of students perceive thermodynamics as a
difficult subject. By having the suitable experiment apparatus designed to
demonstrate thermodynamics process and system have been learned, such an
apparatus would enhance the teaching and learning of thermodynamics. Therefore,
an apparatus for this purpose is necessary to be developed. The apparatus should be
portable and mobilize which demonstration in both lecture and laboratory session is
possible. A Boothroyd-Dewhurst Design for Manufacturing and Assembly (DFMA)
Methodology had been applied to optimize the design apparatus. The application of
Boothroyd-Dewhurst (DFMA) Methodology will simplify the design through
minimizing the part component for ease of assembly and manufacture. In addition,
this methodology also provides analysis for selection of manufacturing process and
material for developed apparatus. Therefore, the overall development cost could be
minimized. The aim of this project is to successful develop an apparatus which could
demonstrate the 1st Law of Thermodynamics-closed system based on BoothroydDewhurst DFMA Methodology.
vii
ABSTRAK
Termodinamik merupakan salah satu mata pelajaran asas yang terpenting
dalam kurikulum kursus Kejuruteraan Mekanikal. Prinsip-prinsip termodinamik
diaplikasikan dalam penciptaan dalam
pelbagai peralatan
bagi
kemudahan
kehidupan manusia. Jurutera mekanikal menggunakan prinsip termodinamik untuk
mereka bentuk pelbagai jenis peralatan seperti enjin jet dan roket, sistem
penyejukan/pendinginan, sistem loji pemprosesan kimia dan sistem loji penjanaan
tenaga. Hal ini menjelaskan bahawa bidang termodinamik merupakan satu bidang
yang amat kritikal dan amat perlu dikuasai dengan sebaik yang mungkin oleh para
pelajar. Akan tetapi sehingga kini, kebanyakan pelajar masih menganggap bidang
termodinamik adalah satu bidang yang amat sukar untuk dipelajari. Dengan adanya
alat ujikaji yang bersesuaian bagi menerangkan proses termodinamik yang dipelajari,
maka sessi pembelajaran akan menjadi lebih menarik dan berupaya memudahkan
pemahaman para pelajar. Justeru itu, satu alat ujikaji termodinamik wajar
dibangunkan. Alatan ujikaji yang dibangunkan ini adalah bersifat mudah alih yang
boleh digunakan untuk demontrasi dalam kuliah dan juga dalam makmal. Bagi
mengoptimum reka bentuk alat ujikaji ini, kaedah Reka bentuk untuk Pembuatan dan
Pemasangan (DFMA) yang dipelopori oleh Boothroyd-Dewhurst telah digunakan.
Kaedah yang diguna pakai ini adalah bertujuan untuk memudah dan meringkaskan
reka bentuk alat ujikaji ini dengan meminimumkan jumlah komponen bagi
memudahkan kerja pemasangan dan pembuatan. Pemilihan bahan proses pembuatan
juga dapat ditentukan melalui kaedah ini. Kesan dari aplikasi kaedah ini adalah kos
keseluruhan produk dapat diminimakan. Matlamat akhir projek ini adalah untuk
membangunkan satu alat ujikaji makmal yang menggunakan prinsip Hukum Pertama
Termodinamik sistem tertutup dengan menggunakan kaedah Reka bentuk untuk
Pembuatan dan Pemasangan (DFMA) yang diperkenalkan oleh BoothroydDewhurst.
viii
TABLE OF CONTENTS
CHAPTER
1
TITLE
PAGE
ACKNOWLEDGEMENT
v
ABSTRACT
vi
ABSTRAK
vii
TABLE OF CONTENTS
viii
LIST OF TABLES
xiv
LIST OF FIGURES
xv
LIST OF SYMBOLS
xviii
LIST OF APPENDICES
xx
INTRODUCTION
1
1.1
Introduction to the Problem
1
1.2
Objective of Project
2
1.3
Scope of Project
2
1.4
Project Methodology
3
1.5
Significant of Findings
5
1.6
Report Structure
5
1.7
Summary
7
ix
2
LITERATURE REVIEW
8
2.1
Introduction
8
2.2
Thermodynamics Systems and Boundary
9
2.3
The 1st Law of Thermodynamics
11
2.4
Energy Balance
11
2.5
Energy Change in System
12
2.6
Mechanism of Energy Transfer, Ein and Eout
14
2.6.1
Heat Transfer
14
2.6.2
Work
14
2.6.3
Mass Flow
15
2.7
1st Law of Thermodynamics in
15
Piston Cylinder Analysis
2.8
Product Development Process
22
2.9
Identifying Customer Needs
24
2.10
Product Design Specifications (PDS)
25
2.11
Engineering Design Process
26
2.12
Concept Generation
27
2.13
Concept Selection
29
2.13.1 Concept Screening
30
2.13.2 Concept Scoring
32
2.14
Design for Manufacture and Assembly (DFMA)
35
2.15
Overview of Design For Manufacture (DFM)
36
2.16
DFM Methodology
37
2.17
Boothroyd-Dewhurst DFM Methodology
38
2.17.1 General Shape Attribute
40
2.17.2 Process Capabilities
41
DFM Guidelines
42
2.18.1 Design for Ease of Fabrication
42
2.18.2 Design within Process Capabilities
42
2.18
2.18.3 Simplify the Design and
Reduce Parts Number
43
2.18.4 Standardize and use common
parts and materials
2.19
Overview of Design For Assembly (DFA)
43
43
x
2.20
DFA Methodologies
44
2.20.1 The Boothroyd-Dewhurst DFA Method
44
2.20.1.1 Theory of Evaluation
45
2.20.1.2 Evaluation Procedure
45
2.20.2 The Hitachi Assemblablility
Evaluation Method
49
2.20.2.1 Theory of Evaluation
49
2.20.2.2 Evaluation Procedure
50
2.20.3 The Lucas DFA Method
2.21
2.22
3
51
2.20.3.1 Theory of Evaluation
51
2.20.3.2 Evaluation Procedure
51
DFA Guidelines
53
2.21.1 Reduce Part Count and Part Types
55
2.21.2 Eliminate Adjustments
56
2.21.3 Self Locating and Aligning
56
2.21.4 Consider Handling Part from Bulk
57
2.21.5 Consider Ease for Handling
58
2.21.6 Eliminate Threaded Fasteners
59
2.21.7 Minimize Variations, Use Standard Part
59
2.21.8 Easy Serviceability and Maintainability
59
2.21.9 Minimize Assembly Directions
60
2.21.10 Provide Easy Insertion and Alignment
60
Summary
61
CONCEPTUAL DESIGN DEVELOPMENT
62
3.1
Introduction
62
3.2
User Requirements
63
3.3
Prepare Product Design Specification
64
3.4
Concept Generation
65
3.4.1
Concept No. 1
65
3.4.1.1
Concept Description
66
3.4.1.2
The Advantage and Disadvantage
67
3.4.2
Concept No. 2
68
3.4.2.1
68
Concept Description
xi
3.4.2.2
3.4.3
3.4.4
3.5
4
The Advantage and Disadvantage
69
Concept No. 3
70
3.4.3.1
Concept Description
70
3.4.3.2
The Advantage and Disadvantage
71
Concept No. 4
72
3.4.4.1
Concept Description
72
3.4.4.2
The Advantage and Disadvantage
73
Selection Criteria
74
3.5.1
Ease of Handling
74
3.5.2
Low Cost
75
3.5.3
Safety
75
3.5.4
Ease of Manufacture
75
3.5.5
Lightweight
76
3.5.6
Portability
76
3.5.7
Ease of Maintenance
76
3.6
Concept Screening
77
3.7
Concept Scoring
78
3.8
Final Concept Selection
80
3.9
Summary
81
DESIGN FOR MANUFACTURE AND
ASSEMBLY (DFMA) ANALYSIS
82
4.1
Introduction
82
4.2
Product Structure and Part Quantity
83
4.2.1
Assembly Drawing
84
4.2.2
Exploded Drawing
85
4.2.3
Bill Of Material (BOM)
86
4.2.4
Part Function and Critics
87
4.3
Boothroyd-Dewhurst DFM Analysis
90
4.4
Boothroyd-Dewhurst DFA Analysis
93
4.5
Apparatus Animation
96
4.6
Summary
97
xii
5
FABRICATION AND ASSEMBLY
98
5.1
Introduction
98
5.2
Development –Phase 1
99
5.2.1
Cylinder Liner
99
5.2.2
Piston
101
5.2.3
Cylinder Liner Cover
103
5.3
5.4
6
103
5.3.1
Base Support
104
5.3.2
Cylinder Liner Support
105
Development – Phase 3
106
5.4.1
Cylinder Assembly
106
5.4.2
Thermometer Installation
108
5.4.3
Piston Indicator Assembly
109
5.4.4
Piston Installation
110
5.5
Complete Assembly
112
5.6
Summary
113
TESTING AND OPERATION WORK PROCEDURE
114
6.1
Introduction
114
6.2
Apparatus Preparation
115
6.3
Safety Instruction
117
6.4
Work Procedure
118
6.5
Data Collection
126
6.6
1st Law of Thermodynamics Analysis
128
6.6.1
Work Analysis, W
130
6.6.2
Total Internal Energy Analysis,
6.6.3
Net Heat Enter to System, Q
6.7
7
Development – Phase 2
U
Summary
131
134
135
DISCUSSION
136
7.1
Introduction
136
7.2
Product Development Approach
137
7.3
Design For Manufacture and Assembly Methodology
137
7.4
Fabrication and Assembly
141
xiii
8
7.5
Apparatus Testing and Functionality
142
7.6
Summary
142
CONCLUSIONS
143
8.1
Conclusion
143
8.2
Recommendation And Future Work
144
REFERENCES
APPENDICES
145
A1 - E
146 - 156
xiv
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Example of customer needs for the suspension fork
24
2.2
Example of concept screening matrix
30
2.3
Example of concept scoring matrix table
32
2.4
Concept rating
33
2.5
Shape Generation Capabilities of Processes
41
2.6
Boothroyd-Dewhurst DFA Evaluation table
46
2.7
Evaluation table of old piston assembly
47
2.8
Evaluation table of new design piston assembly
48
3.1
Product Specification
64
3.2
Screening matrix
77
3.3
Relative performance rating
78
3.4
Concept scoring matrix
79
4.1
Bill of Material of developed apparatus
86
4.2
Part functions
87
4.3
Shape attributes and material requirement data for cylinder
91
4.4
Process elimination for cylinder
92
4.5
Alpha ( ) and beta ( ) angle for each part
94
4.6
Computation Design Efficiency of the apparatus
95
6.1
Work Procedure for operating the apparatus
119
6.2
Table for data record
127
6.3
Testing data
128
xv
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
1.1
Project flowchart
3
2.1
Close system
10
2.2
Open system
10
2.3
Piston cylinder apparatus
15
2.4
Lifting the piston by steam pressure
16
2.5
Concept development phase
22
2.6
Five steps of concept generation
28
2.7
Generation of new concepts of potato peeler
29
2.8
Design flow in DFM
37
2.9
Compatibility matrix between processes and materials
39
2.10
Old design of piston assembly
47
2.11
New design of piston assembly
48
2.12
Example of AEM symbols and penalty scores
50
2.13
Application of DFA guidelines
54
2.14
Part reduction using DFA guidelines
55
2.15
Self locating and aligning parts
56
3.1
Design Concept No. 1
65
3.2
Design concept No. 2
68
3.3
Design concept No. 3
70
3.4
Design concept No. 4
72
3.5
Final design concept
80
4.1
Product structure
83
4.2
Assembly drawing of final design concept
84
4.3
Exploded drawing of final design concept
85
xvi
LIST OF FIGURES – CONTINUED
4.4
Step 1, piston at rest position
96
4.5
Step 2, piston start lift-up
96
4.6
Step 3, piston still lifting
96
4.7
Step 4, piston reach to final position
96
5.1
Cylinder Liner
99
5.2
Flow Chart of Cylinder Liner Fabrication Process
100
5.3
The Piston
101
5.4
Piston after modification
102
5.5
Aluminum sheet
103
5.6
Base support
104
5.7
Two inches angle iron
104
5.8
Cylinder liner support
105
5.9
Cylinder liner before assembly
106
5.10
Cylinder liner after assembly
106
5.11
Cylinder liner after wrapping with woven
107
5.12
Cylinder liner after assembled with aluminum cover
108
5.13
Thermometer installation
108
5.14
The assembly of indicator on piston
109
5.15
Ring Expander
110
5.16
Piston and ring
110
5.17
Special tool to insert piston to cylinder liner
111
5.18
Method to insert piston into cylinder
111
5.19
Complete Assembly of Apparatus
112
6.1
Lubrication oil is applied on the cylinder liner inner wall.
115
6.2
Complete apparatus arrangement
116
6.3
Hot surface sign on cylinder liner
117
6.4
Hot surface sign on base support
118
6.5
Complete Apparatus
119
6.6
Checking all fittings
119
6.7
Applying lubrication oil
119
xvii
LIST OF FIGURES – CONTINUED
6.8
Close bottom valve
120
6.9
Water is filled to cylinder
120
6.10
Initial temperature
120
6.11
Initial pressure
121
6.12
Initial piston position
121
6.13
Butane gas weight measurement
121
6.14
Installation of Butane gas container to gas stove burner
122
6.15
Placing gas stove burner
122
6.16
Flame directed to bottom of cylinder liner
122
6.17
Observation of temperature increasing
123
6.18
Temperature at 90° C
123
6.19
Ready to shut down gas burner
123
6.20
Piston slowly lifts up
124
6.21
Shut down gas burner
124
6.22
Piston lift to new position
124
6.23
Final water temperature
125
6.24
Piston final position
125
6.25
Final Pressure
125
6.26
Measurement final butane gas weight
126
6.27
Illustration of experimental process
129
7.1
Percentage of theoretical minimum parts
138
7.2
Comparison between parts that need special tool to total part
139
7.3
Percentage of assembly time
139
xviii
LIST OF SYMBOLS
E1
=
Initial energy
E2
=
Final energy
Ein
=
Total energy entering the system
Eout
=
Total energy leaving from system
∆Esystem
=
Change in the total energy in the system
Efinal
=
Energy at final state
Einitial
=
Energy at initial state
∆U
=
Change in internal energy
∆PE
=
Change in potential energy
∆KE
=
Change in kinetic energy
m
=
Mass of system, kg
u2
=
Specific internal energy at final state
u1
=
Specific internal energy at initial state
V2
=
Final velocity, m/s
V1
=
Initial velocity, m/s
g
=
Gravity acceleration, m/s2
z2
=
Final height, m
z1
=
Initial height, m
Q
=
Heat supplied to system, Joule
W
=
Work done by system, Joule
X1
=
Initial position, m
X2
=
Final Position, m
P
=
Pressure, Pa
V
=
Volume, m3
A
=
Area, m2
F
=
Force, kg / ms-2 or Nm
xix
LIST OF SYMBOLS (CONTINUED)
vf
=
Specific volume: Saturated liquid, m3/kg
vg
=
Specific volume: Saturated vapour, m3/kg
vfg
=
Specific volume: Evaporation, m3/kg
uf
=
Internal energy : Saturated liquid, kJ/kg
ug
=
Internal energy : Saturated vapour, kJ/kg
ufg
=
Internal energy : Evaporation, kJ/kg)
v1
=
Specific volume at initial state, m3/kg
v2
=
Specific volume at final state, m3/kg
x
=
Quality
Cv
=
Specific heat of Ideal gas, kJ/kg
T1
=
Temperature at initial state, ºC
T2
=
Temperature at final state., ºC
xx
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A1
Gantt Chart for Semester 1
146
A2
Gantt Chart for semester 2
146
B1
Te Standard Thermodynamics Properties
147
Table for water
B2
Example of Product Design Specification
148
B3
General Capabilities of a range of commonly
150
used manufacturing processes.
C
Data for estimated times for manual handling
154
(Boothroyd-Dewhurst)
D
Data for estimated times for manual insertion
155
(Boothroyd-Dewhurst)
E
Lucas DFA method - Manual Handling and
Manual Fitting Analysis
156
CHAPTER 1
INTRODUCTION
1.1
Introduction to the Problem
Thermodynamic is an essential subject in Mechanical Engineering
curriculum. The thermodynamics principles have been applied in many applications
to fulfill human needs. Mechanical engineers use thermodynamics principles in their
study to design a wide variety of energy system such as jet engines and rockets,
refrigeration system, air conditioning system, chemical process and power plant.
These would explain that thermodynamic was one of the critical areas which need to
be well understood. However, the majority of students perceive thermodynamics as a
difficult subject. Failure to understand the fundamental of thermodynamics will
result negative thinking toward the subject. A proposal to integrate between
thermodynamics theories and applications during learning process is one of the
solutions to avoid negative paradigms among the students. Therefore, an
experimental apparatus that applied thermodynamics theory is needed to be
developed.
This project is carried out to design and develop an experimental
apparatus that can demonstrate thermodynamics theory. The aim of developing this
experimental apparatus is to integrate between theories learned in lecture room to the
real applications. The experimental apparatus had been developed is mainly focused
to demonstrate the 1st Law of Thermodynamics-closed system. Design for
Manufacturing and Assembly (DFMA) Methodology has been used during design
and development stages. The application of DFMA methodology during design and
2
development is to ensure the developed experimental apparatus is ease to
manufacture as well as ease to assemble in cost-efficient and at same time to achieve
higher product performance characteristics. As the end result, an experimental
apparatus is successful fabricated and ready to use in Thermodynamics laboratory.
1.2
Objective of Project
The objective of the project is to design and develop a portable experimental
apparatus based on the 1st Law Thermodynamics using Boothroyd-Dewhurst DFMA
Methodology.
1.3
Scope of Project
The scopes of the project are
1. Understanding the DFMA Methodologies for manual assembly.
2. Application of Boothroyd-Dewhurst DFMA during product assembly
analysis and manufacturing process selection.
3. The use of 1st Law Thermodynamics close system in the experimental
apparatus.
4. The use of water or gas as working fluid in experimental apparatus.
5. The animation of the proposed design using animation software.
3
1.4
Project Methodology
The project is conducted in two consecutive semesters which are summarized
in figure 1.1.
1st Semester
Start
Problem Definition
Literature Review on Product Development /
DFMA Methodologies and Thermodynamics
Prepare Product Design Specification
Concept Generation
Concept Selection
DFA Analysis of Final Design
DFM Analysis of Final Design
2nd Semester
Part Preparation and Fabrication
Animation Preparation
Testing and evaluation/ improvement
Discussion
Summary/Conclusion/Recommend
ation
END
Figure 1.1: Project Flow Chart
4
The project is accomplished in two semesters. The milestones of project
activities are shown in Gantt chart in Appendix A1 for semester 1 and Appendix A2
for semester 2.
In the first semester, the project starts by carrying out a literature review on
product development process, continued with Design for Manufacture and Assembly
(DFMA) and end up with 1st Law of Thermodynamics theory. The DFMA
Methodologies that being discussed are the Boothroyd-Dewhurst DFMA, the LucasHall Evaluation Method, and the Hitachi Assemblability evaluation Method (AEM).
The development process continues by preparing Product Design Specification
(PDS). The PDS was a product specification that being generated based on user
requirements. The next task is to generate several design concepts, then to select the
final design concept using concept screening and concept scoring method.
Preparation assembly and exploded drawing is also done for DFA analysis. The
Boothroyd-Dewhurst DFMA analysis is used to obtain design efficiency also to
determine the product material and manufacturing process.
In second semester, the project continues with material preparation and
fabrication. The experimental apparatus then will be tested. The evaluation and
improvement is carried-out during product testing. Finally, the product performance
is discussed and recommendations for future improvement are proposed.
5
1.5
Significant of Findings
The aim of DFMA methodology is to simplify the design. In other word,
DFMA target is to minimize components in experimental apparatus. Minimizing the
components means fewer components per unit product. Fewer components will lead
to reduce the overall production cost. Therefore, the experimental apparatus is
expected to be ease of fabrication and assembly. In other perspective, the
experimental apparatus will help students to understand the thermodynamics theory.
As the final result, student’s performance will increase and students may not more
perceive thermodynamics as a difficult subject but they will find that thermodynamics
is one of the interesting subjects.
1.6
Report Structure
The report consists of eight chapters. Chapter 1 is about introduction to the
project. An overall picture of the project can understand within this chapter. The
objectives and scopes are explained, while the significant of the project is described
at the end of chapter.
Chapter 2, deals with a literature review on 1st Law of Thermodynamics,
Product Development Process and DFMA Methodology. In 1st Law of
Thermodynamics review, the analysis of piston cylinder within close system is
clearly overview. Related equations and data are also been provide. Then, a Product
Development Process is explain touching steps for systematic of product
development is process such as identifying user needs, then generating the concept
design is clearly overviewed. The review ends with the concept selection procedure.
In DFMA review, three methodologies is described such as Boothroyd-Dewhurst
DFMA, Lucas DFA and Hitachi AEM. However, the Boothroyd-Dewhurst DFMA
Methodology is explained in details. The chapter concludes with a DFA guidelines
during product development process.
6
Chapter 3 focuses on the development process of the experimental apparatus.
This chapter starts with the user requirements, followed by preparation of Product
Design Specifications. Concept generation, selection and evaluation are done in this
chapter. At the end of the chapter a final design concept is proposed for further
development.
Chapter 4 focuses on DFMA analysis of proposed design concept. Starting
with preparing the assembly drawing and explode drawing, the DFMA analysis is
done using Boothroyd-Dewhurst Methodology. This chapter ends with DFM analysis
of main part of the experimental apparatus.
Material preparation and fabrication process of the experiment apparatus is
included in Chapter 5. The fabrication processes are showed in sequence using series
of photograph. This chapter ends with complete apparatus that ready to the tested.
Chapter 6 deals with development of operating procedure of the apparatus
and apparatus testing. The procedure is prepared step-by-step and there are
photographs included at every steps performed. To avoid any accident, a safety
instruction is given and potential hazards are identified with safety countermeasure.
The chapter ends with an analysis of 1st Laws of Thermodynamics using data during
testing.
A discussion of overall project is done in Chapter 7. Included in the
discussion are product development processes, DFMA application as well as the 1st
Laws of Thermodynamics applied in this project. Overall results from the project are
also been discussed to evaluate the performance of developed apparatus.
7
The final chapter gives an overall conclusion about undertaken project. The
project achievement is summarized and concluded by referring to the end results
gained during completing the project. This chapter ends with recommendation for
future work that could be done for further improvement of the apparatus.
1.7
Summary
The project to design and development a portable experimental apparatus that
demonstrate the First law of Thermodynamics is carried out in two consecutive
semesters. The aim of the apparatus is to integrate between thermodynamics theory
and application. Boothroyd-Dewhurst DFMA Methodology had been applied in
design stage in order to minimize product components as well as to simplify the
design for ease of assembly and manufacture. To systematic organize design and
development tasks; a project objective, scopes and methodology are prepared to
ensure the project started in the right direction until the end.
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
This chapter reviews on three major areas which are 1st Laws of
Thermodynamics, product development process and Design For Manufacture and
Assembly (DFMA). Literature review on these three areas is conducted because the
application of each area to undertaken project. The chapter starts with introduction to
thermodynamics system, boundary and energy balance before intensively discussed
on 1st Laws of Thermodynamics analysis. Then, review is done on product
development process which covers strategy such as identifying customer need,
preparing product design specification (PDS), concept generation and concept
selection. The chapter ends with review on Design For Manufacture and Assembly
(DFMA) Methodology.
9
2.2
Thermodynamics Systems and Boundary
Thermodynamics can be defined as the science of energy. The name
thermodynamics came from Greek words therme (heat) dynamis (power), which is
most descriptive of the early efforts to convert heat into power [1]. Thermodynamics
is a science in which the storage, transformation, and transfer of energy are studied
[2]. Energy is stored as internal energy kinetic energy, potential energy and chemical
energy. Energy is transformed from one of these forms to another; and it is
transferred across a boundary as either heat or work. The objective in studying
thermodynamics is to carry-out an analysis or design of a large-scale system
anything from an air conditioner to a nuclear power plant which dealings with
measurable parameters in thermodynamics such pressure, temperature and velocity.
A thermodynamics system is defined as a quantity of matter or a region in
space chosen for study. The mass or region outside the system is called the
surroundings. The real or imaginary surface that separates the system from its
surroundings is called the boundary. The boundary is contact surface shared by both
system and surroundings. The boundary of a system can be fixed or movable. The
boundary has zero thickness, and thus it can neither contain any mass nor occupy
any volume in space. Basically there are two major systems in thermodynamics
study which are closed-system and open system.
A closed-system also known as a control mass consists of a fixed amount of
mass and no mass can cross its boundary. There also no mass can enter and or leave
from closed system. In other words, no mass flow process happens inside the close
system, as shown in Figure 2.1. But energy in form of heat or work can cross the
boundary. The volume of a closed system does not have to be fixed.
10
Figure 2 .1: Closed system
An open-system (also known as control volume) consists of fixed volume but
mass can cross the boundary. Open system usually involves mass flow. Examples
include compressor, turbine or nozzle but the volume of the boundary must be fixed.
Figure 2.2 illustrates the open-system.
Figure 2.2: Open system
11
2.3
The 1st Law of Thermodynamics
The First Law of Thermodynamics simply states that energy can be neither
created nor destroyed (conservation of energy). Thus power generation processes and
energy sources actually involve conversion of energy from one form to another,
rather than creation of energy from nothing. The energy of the universe is constant.
However, energy can certainly be transferred from one part of the universe to
another. The energy transfer between different systems can be expressed as:
E1
=
E2
where
2.4
E1
=
initial
energy
E2
=
final energy
Energy Balance
The conservation of energy principle in first law makes use of the key
concepts of internal energy, heat, and system work which can express as, the net
change in the total energy of the system during a process is equal to the different
between the total energy total energy entering and total energy leaving the system
during that process. This statement could be summarized as [1]:
Total energy entering
-
the system
Ein
Total energy leaving
=
from system
-
Eout
Change in the total
energy in the system
=
∆Esystem
12
2.5
Energy Change in System
The determination of the energy change of a system during a process involves
an evaluation of energy in a system at beginning and at the end of the process, and
taking their difference. That is,
Energy change
=
Energy at final state -
Energy at initial state
or
∆Esystem
=
Efinal
-
Einitial
The energy change of a system is zero if the state of the system does not
change during the process. Also, energy can exist in numerous forms such as
internal, kinetic, potential, electric and magnetic energy. The change in the total
energy of a system during a process is the sum of the changes in its internal, kinetic,
and potential energies and can be expressed as [3]:
∆E
=
∆U
+
∆PE
+
∆KE
Where,
∆U
=
change in internal energy,
∆PE
=
change in potential energy, ½ m(V22- V12)
∆KE
=
change in kinetic energy,
m(u2-u1)
mg(z2 – z1)
When the initial and final states are specified, the values of the specified, the
values of the internal energies u1 and u2 can be determined directly from the proper
table or thermodynamic property relations. For stationary systems or closed system,
the changes in kinetic and potential energy are zero (that is, ∆KE = ∆PE = 0), and
13
the total energy change reduce to ∆E= ∆U. The 1st Law of Thermodynamics for a
closed system then could be simplified as:
Ein
-
Eout
=
∆Esystem
=
Change in the total
or
Total energy
-
Total energy
entering
leaving
energy in the
the system
from system
system
Heat supplied to
-
system
Work done
=
Change in internal
by system
energy
Q12
-
W12
=
U2 –U1
Q12
-
W12
=
m(u2 –u1)
Where ,
u2
= specific internal energy at initial condition, (kJ/kg)
u1
= specific internal energy at initial condition, (kJ/kg)
m
= working fluid mass (kg)
14
2.6
Mechanism of Energy Transfer, Ein and Eout
Energy can be transferred to or from a system in three forms: heat, work and
mass flow. Energy interactions are recognized at the system boundary as they cross
it, and they represent the energy gained or lost by a system during process. The only
two forms of energy interactions associated with fixed mass or closed system are
heat transfer and work. The 3 mechanism of energy transfer are [4]:
2.6.1
Heat Transfer
Heat transfer to a system increases the energy of the molecules and thus the
internal energy of the system will also increased. The symbol Q, denotes an amount
of energy transferred across the boundary of a system in heat interaction with the
system’s surroundings. Heat transfer into a system is taken to be positive and heat
transfer from system is taken negative. Heat transfer to system also known as energy
entering the system.
2.6.2
Work
An energy interaction that is not only caused by a temperature difference
between a system and its surroundings is work. A rising piston, a rotating shaft, and
an electrical wire crossing the system boundaries are all associated with work
interactions. Work transfer to a system increases the energy of the system, and work
transfer from a system (work done by the system) decrease if the energy transferred
out as work comes from the energy contained in the system. In piston cylinder,
internal energy is used to lift the piston. Therefore, works done to lift the piston is
known as energy leaving from system.
15
2.6.3
Mass Flow
Mass flow in and out of the system is the additional mechanism of energy
transfer. When mass enters a system, the energy of the system increases because
mass carries energy with it. Likewise, when some mass leaves the system, the energy
contained within the system decreases because the leaving mass takes out some
energy with it. Since in closed system doesn’t involve mass flow in or out from
system there is no energy leaving or entering to system because of mass flow.
2.7
1st Law of Thermodynamics in Piston Cylinder Analysis
First law of Thermodynamics for closed system is best to be studied using
piston cylinder apparatus. Figure 2.3 illustrates the piston cylinder apparatus. The
piston cylinder assembly consists of cylinder with insulating wall and piston. Water
is filled inside cylinder-piston assembly. A pressure gauge and temperature gauge
are also installed to measure the pressure and temperature.
Figure 2.3: Piston cylinder apparatus
16
In this system, the boundary is moving by up-down movement of the piston.
No mass can enter and exit from the piston cylinder assembly. A heat, Q is supplied
to system by heating the base plate. The temperature of water will rise and wet
steam will generate and trapped inside the cylinder. During the process, steam
pressure will exert a normal force on the piston surface as illustrated in Figure 2.4.
Therefore, the piston will move-up from position X1 to position X2.
Figure 2.4: Lifting the piston by steam pressure
Let (P) is the pressure acting on the piston and (A) is the area of piston
surface. The force (F) exerted by the steam to the piston is simply the product. The
work done by the system as the piston displacement a distance dx is [5]:
W
=
pA dx
The product (A dx ) is equal the change in volume of the system, dV. Thus the work
expression can be written as
W
=
p dV
17
Since dV is positive when volume increases, the work at the moving boundary is
positive when the steam is expanded. For a compression, dV is negative. For a
change in volume from V1 to V2 , the work is obtained by integrating :
Therefore, work done to move piston from position x1 to position x2 is given by :
W12
=
p (V2 –V1)
Knowing that, P = F/A, thus,
W12
=
F (V2 –V1)
A
But,
(V2 –V1)
=
(X2 - X1)
A
Therefore
Work done by system,
W12
=
F (X2 - X1)
……..Equation (1)
Where,
F
= Exerted force to piston
= Force by atmosphere pressure on piston + Weight of piston x gravity
(kg / ms-2 or Nm)
x1
= Piston at initial position (m)
x2
= Piston at final position (m)
18
Regarding to the 1st Law Of Thermodynamics for close system as explained in
section 2.5, given
Q12
-
W12
=
∆U
Q12
-
F (X2 - X1)
=
U2 –U1
Q12
-
F (X2 - X1)
=
m(u2 –u1)
….Equation (2)
To determine internal energy U2 and U1, the mass of working fluid and
temperature at initial and final condition need to be measured. Measurement of
temperature is done using thermometer. Regarding to above equation, the steam
pressure exerted to steam is not necessary to measure because the initial and final
pressure is equal due to the system have moving boundary (piston) and process is
called Isobaric process.
If water is used as the working fluid therefore, a Thermodynamics Properties
Table or Steam Table is needed to use to verify the thermodynamics properties at
initial stage and final stage. The Standard Thermodynamics Properties Table for
water is given in appendix B1.
Using Standard Thermodynamics Properties table, the properties of water at
initial stage and final stage could verify by following the below procedure.
i.
Check the initial stage of water temperature (T1) and pressure (P1).
ii.
Using Standard Thermodynamics Properties Table for water; Saturated
Pressure Entry, look at pressure column of value pressure P1. Then write
down the following value:
19
a. Specific volume: Saturated liquid, vf (m3/kg)
b. Specific volume: Saturated vapor, vg (m3/kg)
c. Specific volume: Evaporation , vfg (m3/kg)
d. Internal energy : Saturated liquid, uf (kJ/kg)
e. Internal energy : Saturated vapor, ug (kJ/kg)
f. Internal energy : Evaporation, ufg (kJ/kg)
iii. Calculate the specific volume at initial state (v1) using following formula:
v1
volume at initial stage (m3) ………Equation (3)
=
total weight (kg)
iv. Compare the value of v1
with vf , if
v1
< vf then water is called
100% sub-cooled which means no vapor present at this condition.
v.
Calculate the specific volume at final state (v2) using equation 3.
vi. Compare the value of v2 with vf and vg , if vf <
v2 < vg , means the
wet steam (combination of steam and water) occurs in cylinder. Therefore,
the quality (x) is needed to determine. Quality (x) means the ratio between
steam water inside the cylinder. Calculation of quality (x) is done using
following formula:
Quality (x) = Specific volume at final state - Specific volume saturated liquid
Specific volume evaporation
or
x
=
v2
vfg
vf
………Equation (4)
20
vii. Calculate the Internal Energy (u) at final stage. using following formula :
U2
=
Internal energy,
+
Quality
x
saturated liquid
U2
=
uf
Internal energy ,
Evaporation
x
+
x
ufg
…..Equation (5)
viii. Calculate Total Internal Energy ( U) using following formula :
U
=
total mass
x
in system
U
=
m
(Internal
-
Internal energy
energy at final
at initial
condition
condition)
x
(
U2
-
U1
)
…..Equation (6)
Note that internal energy at initial stage is u1 = 0 because no heat is added
or
no energy transfer during initial stage.
ix. Determine the net heat enter to system using equation 2.
If ideal gas is used instead of water in the piston cylinder, total internal energy ( U)
is given by following formula
U =
Cv (T2 –T1)
where.
Cv
=
specific heat of Ideal gas (kJ/kg)
T1
=
temperature at initial state. (ºC)
T2
=
temperature at final state. (ºC)
……Equation (7)
21
By calculating the work done by the system due to the movement of piston
and change of internal energy due to temperature rise from initial to final condition,
the heat supply to the system could be determined. In both cases, whether use water
or atmosphere as working fluid, the friction between cylinder wall and piston is
assume to be frictionless. The assumption is based on application of the lubrication
oil or grease on cylinder wall.
As the summary, 1st Laws of Thermodynamics states that energy cannot be
created or destroyed. In other words, 1st Laws of Thermodynamics could be defined
as energy entering a system is equal to energy leaving the system. In close system of
thermodynamics the kinetic energy and the potential energy is neglected. This is
because non-flow process happens in the system. In cylinder-piston assembly
analysis, the boundary is moving regarding to piston movement. The movement of
piston is due steam pressure cause by heat supply to the working fluid inside the
cylinder. As temperature increases, the internal energy of working fluid will also
increased. When the internal energy (U) is enough, it will push the piston to lift up.
The movement of piston from initial to final condition is called work (W) done by
the system or energy leaving from system. Heat supply (Q) to the system is known
as energy entering the system. In summarize, energy is supply in form of heat as
input to the system. Then the heat will increase the internal energy of working fluid
inside the system. When internal energy reaches its point it will lift the piston. The
piston movement could be understand as energy leaving from system which in form
of work. By calculating the changes of internal energy and work done by piston the
heat supply to system could be determined. This would verify the 1st Law of
Thermodynamics of closed system which stated that energy entering to system is
equal to energy leaving from the system.
22
2.8
Product Development Process
A product development process is the sequence of steps or activities which an
enterprise employs to conceive, design, and commercialize a product. Many of these
steps and activities are intellectual and organizational rather than physical. A design
process is the set of technical activities within a product development process that
work to meet the marketing and business vision. A concept development process is
set of activities include identified market opportunity, generate alternative products
concept and evaluate the concept. A concept is a description of the form, function,
and features of a product and is usually accompanied by a set of specifications.
Figure 2.5 shows the activities comprising the concept development process phase
[6]:
Figure 2.5 Concept development phase
Concept development could be divided into several phases. Each phase is explained
as the following.
a)
Identifying customer needs: The goal of this activity is to understand
customer’s needs and to effectively communicate them to the development
team. The output of this step is a set of customer need statements, organized
in a hierarchical list, with importance weightings for many or all of the
needs.
b)
Product Design Specifications: Specifications provide a description of what
a product has to do. They are the translation of the customer needs into
technical terms. Targets for the specifications are set early in the process
and represent the hopes to the final product. The output of this stage is a list
of target specifications. Each specification consists of metric, and marginal
and ideal values for that metric.
23
c)
Concept generation: The goal of concept generation is to explore the
product concepts that may address the customer needs. Concept generation
includes a mix of external search, problem solving and systematic
exploration of the various solutions in order to fulfill customer needs. The
result of this activity is usually a set of design concepts, each typically
represented by a sketch and brief descriptive text.
d)
Concept selection: Concept selection is the activity in which various
product concepts are analyzed and sequentially eliminated to identify the
most suitable concept.
e)
Concept testing: One or more concepts then are tested to verify that the
customer needs have been met. If the customer response is poor, the
development project may be terminated or some earlier activities may be
repeated as necessary.
f)
Setting final specifications: The target specifications set earlier in the
process are revisited after a concept has been selected and tested. At this
point, the product concept, limitations are identified through technical
modeling, and trade-offs between cost and performance.
g)
Project planning: In this final activity of concept development, the
designers creates a detailed development schedule, devises a strategy to
minimize development time, and identifies the resources required to
complete the project. The major results of the front-end activities can be
usefully captured in a contract book which contains the mission statement,
the customer needs, the details of the selected concept, the product
specifications, the economic analysis of the product, the development
schedule, the project staffing, and the budget.
24
2.9
Identifying Customer Needs
The process of identifying customer needs is an integral part of the larger
product development process and is most closely related to concept generation,
concept selection, competitive benchmarking, and the establishment of product
specifications. The philosophy behind the method is to create a high-quality
information channel that runs directly between customers in the target market and
the designers of the product. Identifying customer needs is itself a process which
forms in five-step method. The five steps are [7]:
1.
Gather raw data from customers.
2.
Interpret the raw data in terms of customer needs.
3.
Organize the needs into a hierarchy of primary, secondary, and tertiary
needs.
4.
Establish the relative importance of the needs.
5.
Reflect on the results and the process.
The key benefits of the applying the 5 methods of identifying customer need
are ensuring that the product is focused on customer needs and that no critical
customer need is forgotten; developing a clear understanding the needs of the
customers, developing a fact base to be used in generating concepts, selecting a
product concept and establishing product specifications. As example, Table 2.1
shows the customer needs for suspension fork of mountain bike:
Table 2.1: Example of customer needs for the suspension fork
No.
1
2
3
4
5
Item
Need
Imp.
The suspension
The suspension
The suspension
The suspension
The suspension
Reduces vibration to the hands.
Allows easy traversal of slow, difficult
Enables high-speed descents on bumpy
Allows sensitivity adjustment.
Preserves the steering characteristics of
3
2
5
3
4
25
2.10
Product Design Specifications (PDS)
The Product Design Specification (PDS) is a very important document in the
design process as it contains all the information necessary for designer to
successfully produce a solution to the design problem. A PDS splits the problem up
into smaller categories to make it easier to consider the problem. The aim of PDS is
to help designer to gain an understanding of the nature of the problem so that
designer can design a better solution to the problem. But there are other factors to be
considered such as materials available, the size of the user, or even the color they
customer wants the product to be. The more designer know about the problem, it
much easier to produce a final design that works first time and doesn'
t require
alterations at a later stage. Some of PDS characteristics:
i.
Splits the problem up into smaller categories to make it easier to consider the
problem.
ii.
The actual or intended customer should be consulted as fully as possible
while the PDS is being drawn up as their requirements are importance.
iii.
Any numeric properties in the PDS should be specified as exactly as possible
together with any tolerances allowed on their value.
iv.
The final document should cover as possible all the requirements that a
product must fulfill together with any constraints that may affect the product.
Various aspects relating to the product must be considered during PDS
preparation. The actual categories can vary, but a typical PDS may consist of the
following categories such as customer requirements, appearance, materials, product
dimensions, quality, ergonomics, performance, product cost, installation, testing,
maintenance, environment, quantity, packaging and transport, legislation, patents and
copyright, legal and safety implications, product disposal, documentation and
Standards. An example of PDS is given in Appendix B2 .
26
2.11
Engineering Design Process
Design decisions made during the early phases of design are especially
critical because it have a tremendous impact on total cost of product. Often, high
quality design decisions made during early stages of design can equal years of cost
reduction and design improvement made after design release. It is therefore
imperative that early design decisions be well thought out and carefully made.
Design decisions involve initial definition of the product'
s design. These
decisions are generally made during the engineering design process, which typically
involves following design activities [8]:
i.
Clarify and define product or design requirements.
ii.
Develop a working principle or physical concept for fulfilling required
product
functions.
iii. Decompose physical concept into subassemblies and components.
Determine the geometric arrangement (layout) of components. Establish
dimensional relationships between components.
iv. Decide which components are standard and which must be designed.
v.
Select general type of material (e.g., polymer, metal) and basic
manufacturing process (e.g., casting, machining) to be used for each
designed component, if not already determined.
vi. Determine configuration of each designed component. (i.e., size, shape,
external and internal geometric features) .
vii. Select a specific material and manufacturing process for each designed
component.
27
viii. Establish dimensions and tolerances for each designed component.
ix. Supply additional dimensions, tolerances, and detailed information
required for manufacture and assembly of the components.
The process begins by conceiving a physical concept for the product based on
customer needs and a product specification and then creating a preliminary layout of
the design that embodies the physical concept. This initial phase is often referred to
as the conceptual design which is done in concept generation phase
2.12
Concept Generation
Concept generations are activities to produce product concepts which are
approximately describe the technology, working principles and form of the product.
It is a description of how the product will satisfy the customer needs. A design
concept is usually expressed as a sketch or as a rough three or two dimensional
model. The concept generation process start with a set of customer needs and target
specifications and results in a set of product concepts from which the designers will
make a final selection. The concept generation normally consists of five steps [9]
which are shown in Figure 2.6.
28
Figure 2.6: Five steps of concept generation
i.
Clarify the problem. Understand the problem and decompose it into simpler
sub-problems.
ii.
Search externally. Gather information from lead users, experts, patents,
published literature, and related products.
iii. Search internally. Use individual and group methods to retrieve and adapt
the knowledge of the team.
iv. Explore systematically. Use classification trees and combination tables to
organize the thinking of the team and to synthesize solution fragments.
v.
Reflect on the solutions and the process. Identify opportunities for
improvement in subsequent iterations or future projects.
29
An example of concept generation is shown in Figure 2.7. These sketches are
being developed during generation the concept of new potato peeler [10].
Figure 2.7: Generation of new concepts of potato peeler
2.13
Concept Selection
Concept selection is the process of evaluating concepts with respect to
customer needs and other criteria, comparing the relative strengths and weaknesses
of the concepts, and selecting one or more concepts for further investigation, testing,
or development. The aim of concept selection is to develop the best concept for
further product development. Concept selection is often performed in two stages.
The first stage is called concept screening and the second stage is called concept
scoring. Each is supported by a decision matrix which is used by the designer to
rate, rank and select the best concept for further development.
30
2.13.1 Concept Screening
Concept screening is based on a method developed by the late Stuart Pugh in
the 1980s and is often called Pugh concept selection [9]. The purposes of this stage
are to narrow the number of concepts quickly and to improve the concepts. The
example of concept screening metric is shown in Table 2.2.
Table 2.2: Example of concept Screening Matrix
To generate concept screening matrix, six procedures need to be taken which are:
i
Prepare Selection Matrix
ii
Rate the Concepts
iii Rank the Concepts
iv
Combine and Improve the Concepts
v
Select One or More Concepts
vi
Reflect on the Results
31
Prepare Selection Matrix:
To prepare the matrix, the team selects a
physical medium appropriate to the problem at hand. Individuals and small groups
with a short list of criteria may use table as shown in Table 2.2.
Rate the Concepts: A relative score of "better than" (+), "same as" (0), or
"worse than" (-) is placed in each cell of the matrix to represent how each concept
rates in comparison to the reference concept relative to the particular criterion. It is
generally advisable to rate every concept on one criterion before moving to the next
criterion
Rank the Concepts: The concepts should be ranked. This is accomplished
by counting all the (+) as 1 point, (0) as 0 points, and (-) as -1 point. The remaining
scores are then ranked with the highest given 1 and ties receiving the same ranking.
The positive scores are selected; zero being a positive number, while the negative
scores are screened out of the process.
Combine and Improve the Concepts: Once the concepts are rated and
ranked the results should be checked to see if any concepts received a low ranking
due to one bad feature that could be possibly modified to improve the overall
concept. If two concepts can be combined than they should be combined into one
concept. In the table 2.2, concepts D and F could be combined to remove several of
the "worse than” ratings to yield the new concept DF in the section of concept
scoring. Concept G could be revised to improve its handling characteristic.
Select One or More Concepts: Once the designers satisfied with their
rankings they decide which concepts are to be selected for further refinement and
analysis. The number of concepts selected is limited to the resources available. In
this example, concepts A and E are selected. If too many concepts are selected, then
designers must decided whether to begin another round of the Concept Screening
process.
32
Reflect on the Results: It is important that designers are comfortable with
the outcome. If there is more than one designer in development group, the selected
concept shall satisfy all the designer members.
2.13.2 Concept Scoring
A concept scoring is a method of prioritizing the concept design. This method
uses a weighted sum of the ratings to determine concept ranking. Table 2.3
illustrates an example of scoring matrix use in this stage.
Table 2.3: Example of concept scoring matrix table
To prepare scoring matrix table, six procedures are need to be follows which are:
i
Prepare Selection Matrix
ii
Rate the Concepts
iii Rank the Concepts
33
iv
Combine and Improve the Concepts
v
Select One or More Concepts
vi
Reflect on the Results
Prepare Selection Matrix: Selection matrix is prepared by identified a
reference concept. As shown in example in Table 2.3, the concept which have been
identified for analysis are entered on the top of the matrix table and the selection
criterions are listed in left column of the table. After the criteria are entered, the
important weight is added. Several different schemes can be used to weight the
criteria, such assigning an important value from 1 to 5 or allocating 100 percentage
points among them. However for the purpose of concept selection the weight are
often determined subjectively by designer referring to customer needs.
Rate the Concepts: In the step rating the entire criterion will take part. The
concepts now will be rated individually. A rating scale could be from 1 to 5 but
rating 1 to 9 may also being used. The example of rating is shown in Table 2.4.
Table 2.4: Concept rating
Relative Performance
Rating
Much worse than reference
1
Worse than reference
2
Same as reference
3
Better than reference
4
Much better than reference
5
34
Rank the Concepts: Once the ratings are entered for each concept, weight
scores are calculated by multiplying the raw scores by criteria weight. The total
score for each concept is the sum of the weight scores. Finally, each concept is given
a rank corresponding to its total score.
Combine and Improve the Concept: There are possibilities to combine or
to improve the concept. The designer should look into the opportunities to combine
more than two concepts. Some combinations or improvements opportunity may
occur during the concept selection process as the designer realizes the inherent
strength and weakness of certain features of the product concepts.
Select One or More Concepts: Normally the highest score will be select as
final concept. However, based on the selection matrix, the designer may decide to
select the top two or more concepts. These concepts may be further developed,
prototyped and tested to elicit customer feed back.
Reflect on the Result: After the one or two concept is being selected,
designer should comfortable that all relevant criteria have been discussed, that the
selected concept has the greatest potential to satisfy customers and be economically
successful.
The success of product development depends on the designers ability to
identify the needs of customers and to quickly create products that meet these needs
and can be produced at low cost. Product development is the set of activities
beginning with the perception of a market opportunity and ending in the production,
sale, and delivery of a product. An enterprise must make two important decisions
about the way it carries out product development. It must define both a product
development process and a product development organization. A product
development process is the sequence of steps an enterprise employs to conceive,
design, and commercialize a product. A well-defined development process helps to
35
ensure product quality, facilitate coordination among designers, plan the
development project, and continuously improve the process. The concept
development phase requires tremendous integration across the different functions on
the development team. This front-end process includes identifying customer needs,
analyzing competitive products, establishing target specifications, generating
product concepts, selecting one or more final concepts, setting final specifications,
testing the concept, performing an economic analysis, and planning the remaining
project activities. The aim of the product development phase is to provide the
systematic approach by well organizing all design and development activities, so
that the well establishes product could be produced as the end result.
2.14
Design for Manufacture and Assembly (DFMA)
Design for Manufacture and Assembly (DFMA) is systematically approach
during product designs stage with the goal of reducing manufacture and assembly
costs, improving quality and speeding time to market. The word of DFMA is comes
from the combination of Design for Manufacture (DFM) and Design for Assembly
(DFA. Design for Manufacture (DFM) is a systematic approach that allows
engineers to anticipate manufacturing costs early in the design process, even when
only rough geometries are available on the product being developed. DFA
methodology is a complements of Design for Manufacture (DFM). Engineers use
DFA Methodology to reduce the assembly cost of a product by consolidating parts
into elegant and multifunctional designs. On the other hand, DFM allows the design
engineer quickly to judge the cost of producing the new design and to compare it
with the cost of producing the original assembly. Used together, DFM and DFA
methodology gives engineers an early cost profile of product designs, providing a
basis for planning and decision making. DFMA methodology leads to reduce part
count, shorter time-to-market, improved quality through assembly simplification,
and lowered overhead.
36
2.15
Overview of Design For Manufacture (DFM)
DFM (Design for Manufacturing) can be defined as a practice for designing
products, keeping manufacturing in mind. DFM starts by taking a plain sheet of
paper and identifying a product’s functional, performance, and other requirements. It
utilizes rules of thumb, best practices, and heuristics to design the part. Best
practices for a high-quality product design are to minimize the number of parts,
create multifunctional in the part, minimize part variations, and create ease of
handling. DFM involves meeting the end-user requirements with lower-cost design,
less material and quality fulfillment.
To effectively design the product, manufacturing knowledge needs to be
incorporated into product design. The designer should know how the process and
design interact. In general, the real challenge in designing composite products is to
develop a good understanding not only of engineering design techniques, but also of
processing and material information. The purposes of DFM are to:
i.
Narrow design choices to optimum design.
ii.
Minimize product development cycle time and cost
iii. Achieve high product quality and reliability
iv. Simplify production methods
v.
Increase the competitiveness of the company
vi. Have a quick and smooth transition from the design phase to the production
phase
vii. Minimize the number of parts and assembly time
viii. Eliminate, simplify, and standardize whenever possible
37
The design flow in DFM [11] is shown in Figure 2.8
Figure 2.8: Design flow in DFM
2.16
DFM Methodology
As design progress from the conceptual stage to production, the designer
would think the manufacturing process that involve. Changes in conceptual design
may affect the manufacturing process capability. In fact, there are many
manufacturing process that could applied, but selection of the most suitable process
become a challenge for the designer or manufacturing engineer. The product could
be produce in short time but the investment cost may be higher. In other hand, low
manufacturing cost could be applied, as result the product quality could be effect.
Therefore, process and material selection is a important part to be carefully
determine. To choose the suitable manufacturing process and to select the material,
the information on the initial selection material and process should be available.
Such information might include:
i.
Product life volume
ii.
Permissible tooling expenditure
iii. Possible part shape categories and complexity levels
iv. Service or environment requirements
v.
Appearance factors
vi. Accuracy factors.
38
The DFM methods may be applied at four stages of the design process:
1. The conceptual design stage: the product shape, design is unknown.
2. Assembly stage: manufacturing methods are unknown.
3. Selection of materials, processes: production processes are unknown.
4. Detail design: detailed manufacturing methods may be investigated.
There are various DFM methodologies that had been introduced. Among
them are Boothroyd-Dewhurst DFMA, The Lucas DFM methodology, CyberCut,
The Nippondenso Method, Feature Based-Gupta & Nau and Taguchi Method.
However, the Boothroyd-Dewhurst DFMA is well known and widely applied.
2.17
Boothroyd-Dewhurst DFM Methodology
This method developed by Boothroyd and Dewhurst, originated as a design
for assembly method but has developed since to include a wider range of activities
in the design process. DFA still plays a major role in this method; however, it is the
companion DFM methods within DFMA that help judge the contributions of DFA.
The following are the stages in the Boothroyd-Dewhurst DFM method:
•
DFA, with feedback to concept development stage about simplification of
product structure.
•
Selection of materials, processes and early cost estimation.
•
Detailed design for manufacture, on the best design concept.
Once DFA has been applied, an evaluation is carried out to assess part
manufacturing difficulties and part cost. The parts are designed and part costs are
estimated at early stages using various combinations of processes and materials. A
combination suitable for design is chosen and this makes way for a thorough
39
analysis for detailed design. The manufacturing analysis in Boothroyd-Dewhurst is
done using process/material compatibility matrix shown in Figure 2.9.
Figure 2.9: Compatibility matrix between processes and materials.
40
2.17.1 General Shape Attribute
Regarding to Boothroyd-Dewhurst, each process can be analyzed to
determine the range of its capabilities in terms of attributes of the part that can be
produced. There are eight general shape attributes for material and process selection.
The eight general attribute are [12]:
1. Depressions (Depress) are referring to the ability to form grooves in the
surfaces of the part. For example is machining, the direction of movement of
the tooling onto the work part.
2. Uniform Wall (Uniwall) is referring to uniform wall thickness.
3. Uniform Cross Section (UniSect) is refers to the parts where any cross
sections normal to a part axis are identical but excluding draft.
4. Axis of rotation (AxisRot). It refers to parts whose shape can be generated by
rotation about a single axis.
5. Regular Cross Section (RegXSec). Cross sections normal to the part’s axis
contain a regular pattern such as pipe hose.
6. Captured Cavities (CaptCav) is the ability to form cavities with reentrant
surfaces such as bottle.
7. Enclosed (Enclosd) is referring to parts which are hollow and completely
enclosed.
8. Draft Free Surfaces (NoDraft) is referring to the capability of producing
constant cross sections in the direction of tooling motion.
41
2.17.2 Process Capabilities
Each process has it own capabilities and limitations. These capabilities
determine whether a process can be used to produce the corresponding part
attributes. The knowledge of the capabilities and limitations of the process is very
necessary. This knowledge will be used in process and material compatibility
matrix. General capability of a range of manufacturing process is given in Appendix
B3, while Table 2.5 shows the shape generation capabilities of process.
Table 2.5: Shape Generation Capabilities of Processes
42
2.18
DFM Guidelines
The main objective of DFM is to minimize the manufacturing information
content in the product without sacrificing functional and performance requirements.
DFM can also be applied for a product that is already in production or on the
market. The main objective here will be to make the product more cost-competitive.
Some of the DFM guidelines are:
2.18.1 Design for Ease of Fabrication
Select processes compatible with the materials and production volumes.
Select materials compatible with production processes and that minimize processing
time while meeting functional requirements. Avoid unnecessary part features
because they involve extra processing effort and/or more complex tooling.
In
composite part fabrication, product design cannot be made effective without
knowledge of the manufacturing operations. Each manufacturing process has its
strengths and weaknesses. The product design should be tailored to reap the benefits
of the selected manufacturing process. For example, if close tolerances are required
on the inside diameter of a tube, then filament winding is preferred compared to a
pultrusion process. The design should be simplified as much as possible because it
helps in manufacturing and assembly and thus in cost savings. Workers and others
who are dealing with the products can easily understand simplified design.
2.18.2 Design within Process Capabilities
Know the production process capabilities of equipment and establish
controlled processes. Avoid unnecessarily tight tolerances that are beyond the
natural capability of the manufacturing processes. Otherwise, this will require that
parts be inspected or screened for acceptability,
43
2.18.3 Simplify the Design and Reduce Parts Number
As the number of parts goes up, the total cost of fabricating and assembling
the product also will goes up. Automation becomes more difficult and more
expensive when more parts are handled and processed. Costs related to purchasing,
stocking, and servicing also go down as the number of parts are reduced. Inventory
and work-in-process levels will go down with fewer parts.
2.18.4 Standardize and use common parts and materials
Use standard and common parts and material will facilitate design activities,
to minimize the amount of inventory in the system, and to standardize handling and
assembly operations. Common parts will result in lower inventories, reduced costs
and higher quality. Operator learning is simplified and there is a greater opportunity
for automation as the result of higher production volumes and operation
standardization.
2.19
Overview of Design For Assembly (DFA)
Design for Assembly (DFA) is a methodology for evaluating part designs and
the overall design of an assembly. It is a quantifiable way to identify unnecessary
parts in an assembly and to determine assembly times and costs. DFA recognizes the
need to analyze both the part design and the whole product for any assembly
problems early in the design process. DFA is a simple, structured analysis technique
which gives design teams the information they need to reduce product costs by:
•
Reducing the number of parts.
•
Simplifying parts handling.
•
Improving product assembly.
44
Using DFA approach, product engineers assess the cost contribution of each
part and then simplify the product concept through part reduction strategies. These
strategies involve incorporating as many features into one part as is economically
feasible. The outcome of a DFA-based design is a more elegant product with fewer
parts that is both functionally efficient and easy to assemble.
2.20
DFA Methodologies
DFA methodologies were developed to support the designer by generating
feedback on the consequences of design decisions on product assembly. The aim is
to help the designer to produce an efficient and economic design. The application of
DFA guides the designer towards a product with a minimum number of parts that
requires simple, cost-effective assembly operations and the most appropriate
manufacturing processes and materials for its components. The three best-known
DFA methods are the Boothroyd-Dewhurst System, the Lucas DFA Methodology
and the Hitachi Assemblability Evaluation Method.
2.20.1 The Boothroyd-Dewhurst DFA Method
The Boothroyd-Dewhurst method provides a quantitative measure called the
design efficiency based on analysis of the product. The efficiency compares the total
assembly time for a product with the total assembly time for an ideal product. The
efficiency can be used to compare various designs in term of their relative
efficiency.
This method is based on two principles which are:
i.
Determine the parts whether should be separate from all other parts or
combined.
ii.
Estimation of the handling and assembly time for each part using the
appropriate assembly process.
45
2.20.1.1 Theory of Evaluation
The evaluation is done by checking each part by following guidelines such as:
i.
During operation of the product, does the part move relative to all other
parts already assembled.
ii.
Must the part be of a different material than the parts already assembled.
[Only fundamental reasons associated with material properties are
acceptable.]
iii. Must the part be separate from all parts already assembled (because
otherwise necessary assembly/disassembly of other parts would be
impossible)?
If the answer to any of these questions is YES, the part is necessary part. If answer is
NO, then the part is under category un-necessary part and possible to be eliminated.
2.20.1.2 Evaluation Procedure
The purpose of evaluation criteria is to obtain design efficiency. Basically,
there two evaluation procedures involve. First is to determine the theoretical
minimum number based on the three guidelines. Necessary part will be given 1 and
un-necessary part will be given 0. The data is entered in column c9 in evaluation
table as shown in Table 2.6.
46
Table 2.6 : Boothroyd-Dewhurst DFA Evaluation table
The second part is evaluation on handling and insertion for each chart. For
this purpose Boothroyd-Dewhurst have develop DFA data tables as given in
appendix D and E. Table in Appendix D is data for estimated times for manual
handling and table in Appendix E is estimated times for manual insertion. Refer to
Table 2.6, data from column c3 and c4 is obtained from table for manual handling
code. Table for manual insertion will give data for c5 and c6. Then the cost of the
assembly process according to wage rate and overheads is to be determined. The
design efficiency or assembly efficiency (AE) is calculated using following equation:
AE
=
3 x NM / TM
where,
NM
=
Theoretical minimum number of part
TM
=
Total operation time
Example of calculating design efficiency is given below. Figure 2.10 shows the old
design of piston assembly.
47
Figure 2.10: Old design of piston assembly
Table 2.7 shows the evaluation of old design piston assembly. Old design efficiency
is about 29%.
Table 2.7 Evaluation table of old piston assembly
48
Figure 2.11 shows the new design of piston assembly after applied BoothroydDewhurst DFA Methodology.
Figure 2.11: New design of piston assembly
Table 2.8 shows the evaluation of new design piston assembly. New design
efficiency is about 90 %.
Table 2.8: Evaluation table of new design piston assembly
By applying the Boothroyd-Dewhurst DFA Methodology the design efficiency is
increased from 29 % to 90 %.
49
2.20.2 The Hitachi Assemblablility Evaluation Method
The Hitachi AEM analyses the motions and operations, called '
assembly
operations'
, necessary to insert and secure each component of the product. A simple
downward motion is considered to be the easiest and fastest assembly operation.
Hitachi AEM facilitate design improvement by identifying ‘weakness’ in the early
design process by using two indicators, score ratio (E) and cost ratio (K). An
assemblability evaluation score ratio (E) used to assess design quality by determining
the difficulty of operations. An assembly cost ratio (K) used to project elements of
assembly cost.
2.20.2.1
Theory of Evaluation
Penalty points are awarded for every motion or operation that differs from, or
is in addition to, this simple motion. The procedure begins by entering the motions
and operations necessary for assembly onto an AEM form. The form is used to
compare the assembly processes to the optimum, and given a penalty from the
synthetic assembly data. The Hitachi method offers a number of metrics as its
evaluation: assembly time (AT), assemblability evaluation score (E) which is a scale
of 0 (infinitely hard to assemble) to 100 (ideal assembly), assembly cost ratio (K)
that indicates the cost of a redesign as a ratio of the original cost, and simplicity
factor (SF) which is a combination of E and a measure of the design efficiency of an
assembly.
50
2.20.2.2 Evaluation Procedure
Evaluation procedure begins by each task is assigned a symbol indicated the
content of the task. Each of the element tasks is subject to a penalty score which
reflect the degree of difficulty of the task. Figure 2.12 shows the example of the
AEM symbols and penalty scores.
Figure 2.12: Example of AEM symbols and penalty scores.
The sum of the various penalty scores for a part are then modified by
attaching coefficient and subtracted from 100 points to give the assemblability
evaluation score for the part. Total assemblability evaluation score is then calculated.
Score of 80 is acceptable.
51
2.20.3 The Lucas DFA Method
The Lucas DFA method was developed in the early 1980'
s by the Lucas
Corp. in the U.K. The Lucas method is based on a "point scale" which gives a
relative measure of assembly difficulty. The method is based on three separate and
sequential analyses which known as assembly sequence flowchart (ASF):
2.20.3.1 Theory of Evaluation
The three sequential analyses or evaluation procedures by Lucas DFA are a
functional analysis, a handling or feeding analysis and a fitting analysis. The method
involves the assigning and summing of penalty factors associated with potential
design problems with the inclusion of handling (or feeding) as well insertion. These
penalty factors are combined with an assembly sequence flow chart to generate three
assimilability scores. The three scores; design efficiency, feeding/handling ratio and
fitting ratio are generated in three stages of the analysis.
2.20.3.2 Evaluation Procedure
At the beginning, all components of an assembly undergo functional
analysis. The table for manual handling analysis and manual fitting analysis is
shown in Appendix E. In this analysis, the components of the product are reviewed
only for their function. The components are divided into two groups. Parts that
belong to Group A are those that are deemed to be essential to the product'
s
function; Group B parts are those that are not essential to the product'
s function.
Group B functions include fastening, locating, etc. The functional efficiency of the
design can be calculated as: Ed = A/(A+B) x 100%, where A is the number of
essential components, and B is the number of non-essential components. Typically,
a design efficiency of 60% is targeted for initial designs. The next stage is feeding or
52
handling analysis. Similar to the Boothroyd-Dewhurst analysis, both the part
handling and insertion times are examined here. In the feeding analysis, the
problems associated with the handling of the part are scored using an appropriate
table. For each part, the individual feeding index is scored. Generally, the target
index for a part is 1.5. If the index is greater than 1.5, the part should be considered
for redesign.
Overall, all of the product'
s components should meet a "feeding ratio" defined as:
Feeding Ratio = (Total Feeding Index) / (Number of Essential Components)
The total feeding index is the sum of all the indices of all the parts. The
number of essential components is the value A from the functional analysis. An
ideal feeding ratio is generally taken to be 2.5.
The final stage is fitting analysis. The fitting analysis is calculated similarly
to the feeding analysis. Again, a fitting index of 1.5 is a goal value for each
assembly. However, it should be noted that there is usually greater variance in the
fitting indices than in the feeding indices. The fitting ratio is given by:
Fitting ratio = (Total Fitting Index) / (Number of Essential Components)
Again, an overall fitting ration of 2.5 is desired.
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2.21
DFA Guidelines
Assembly costs can be reduced by following well established DFA
guidelines. Components can be redesigned to simplify assembly operations, or
components can be eliminated entirely by integrating their functions into other
components. Thus, the general DFA guidelines proposed to be applied are:
i
Minimize part count by incorporating multiple functions into single parts.
ii
Design parts to be self-locating and self-aligning.
iii Standardize components, use common parts.
iv
Error-proof parts to make incorrect assembly impossible
v
Minimize the number of parts.
vi
Minimize the number and variety tools for assembly
vii Minimize the number of axes of insertion
viii Ensure clear vision and access for all assembly operations
ix
Minimize the number and complexity of adjustments
x
Eliminate the need to hold down, clamp or fixture parts
xi
Eliminate special assembly tools
xii Eliminate tangly parts.
xiii Prevent nesting of parts.
xiv Eliminate fasteners.
54
Figure 2.13 shows the example of application of DFA guidelines during mechanical
component.
Figure 2.13 Application of DFA guidelines
55
2.21.1 Reduce Part Count and Part Types
The needs to reduce part count are to lower material cost, reduced jigs/fixture
cost, improved quality, less documentation, small inventories, fewer suppliers, and
simplified production control, fewer inspections as well as less rework. The parts
could be reduced in such ways:
a) Check the need for the part’s existence.
b) Eliminate separate fasteners when possible.
c) Design multi-functional parts by maximum use of the capabilities
manufacturing processes. For example, use near-net shape moulding and
possible to reduce part count.
d) Eliminate product features that are of no value to the customer.
As example, Figure 2.14 shows the part is reduced:
Before : Two-component sub-assembly
After: Single component
Figure 2.14 : Part reduction using DFA guidelines.
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2.21.2 Eliminate Adjustments
Adjustments will require decision making during the assembly operation. The
decision making skill is different across operators. Failure to make standard
adjustment will cause quality accident. The product probably will not well work
properly or may not meet the specifications. Beside that an adjustment may lead to
malfunction after some usage by customer. Therefore eliminating the adjustment is
necessary to be carry-out. The good design should have not required adjustment
after product has been assembled.
2.21.3 Self Locating and Aligning
For ease of assembly, the part should be design to be self locating and
aligning. Figure 2.15 shows an example designing self locating and aligning parts.
Figure 2.15 Self locating and aligning parts
57
2.21.4 Consider Handling Part from Bulk
Parts tend to create a mess when mixed in large numbers, but easily handled
when alone. Therefore:
1. On parts that mate using interlocking tapers, include features that prevent
nesting.
2. On parts with combinations of holes, projections, gaps and cut-outs, there is
high probability of tangling. For a close gaps, enlarge projections, use
closed-end coil springs.
3. Avoid parts which are fragile or sharp, unless functionally necessary. If
necessary, include safe-handling features.
4. Avoid use of flexible parts. If flexible parts are needed, try using those that
retain shape when handled.
5. Avoid parts that require special tools for the worker to perform assembly.
58
2.21.5 Consider Ease for Handling
In an assembly plant, various parts are kept in separate boxes near the
assembly station. Workers pick up those parts and assemble them using adhesive
bonding or mechanical fastening or by slip-fit or interference-fit. Avoid using parts
such as springs, clips, etc., which are easy to nest and become interlocked. It
disrupts the assembly operation and creates irritation for the worker. For smooth
assembly operation and ease of handling, parts should not be heavy and should not
have many curves, thus reducing the potential for entanglement. To avoid physical
fatigue of the worker, part and assembly locations should be easy to access. Parts
should be symmetric to minimize handling and aid in orienting. Add features that
help guide the part to its desired location. The following suggestions can improve
part handling. These suggestions are more applicable for a high-volume production
environment.
i
Minimize handling of parts that are sticky, slippery, fragile, or have sharp
corners or edges.
ii
Keep parts within operator reach
iii
Avoid situations in which the operator must bend, lift, or walk to get the
part.
iv
Minimize operator movements to get the part. Avoid the need for two hands
or additional help to get the part.
v
Avoid using parts that are easy to nest or entangle.
vi
Use gravity as an aid for part handling.
59
2.21.6 Eliminate Threaded Fasteners
Avoid the use of screws, nuts, bolts, and other fasteners in the product. It is
estimated that driving a screw into the product costs almost 6 to 10 times the cost of
a screw. The use of fasteners increases inventory costs and add complexity in
assembly. Fasteners are used to compensate for dimensional variation, to join two
components, or for part disassembly. The use of fasteners creates the potential for a
part to become loose during service. Snap-fits are used with plastics or short fiber
composite parts and provides ease of assembly.
2.21.7 Minimize Variations, Use Standard Part
Part dimensional variations as well as property variation are the major
sources of product defects and nonconformities. Try to use standard parts off-theshelf and avoid the use of special parts. Eliminate part variations such as types of
bushings or O-rings, seals, screws, or nuts used in one application. The same size
would mean the same tool for assembly and disassembly. This guideline aims to
reduce part categories and the number of variations in each category, thus providing
better inventory control and part interchangeability.
2.21.8 Easy Serviceability and Maintainability
Design the product such that it is easy to access for assembly and
disassembly. The part should be visible for inspection and have sufficient clearance
between adjacent members for scheduled maintenance using wrench, spanner, etc.
60
2.21.9 Minimize Assembly Directions
For product assembly, minimize assembly direction. While designing the
product, think about the assembly operations needed for various part attachments. It
is preferable to use one direction Z-direction assembly operation allows gravity to
aid in assembly. A one-direction assembly operation minimizes part movement as
well as the need for a separate assembly station. It is better in terms of an
ergonomics point of view as well.
2.21.10 Provide Easy Insertion and Alignment
When there are more than two parts in a product, the mating parts need to be
brought close by performing insertion or alignment. Some guidelines for easy
insertion and alignment are:
1. Provide generous tapers, chamfers, and radii for easy insertion and assembly.
2. Provide self-locating and self-aligning features where possible.
3. Avoid hindrance and obstruction for accessing mating parts.
4. Avoid excessive force for part alignment.
5. Design parts to maintain location.
6. Avoid restricted vision for part insertion or alignment.
DFMA is a tool for product design and development. The advantages are
ready to designer who applying DFMA methodology in their design stage. DFMA
could be applied at any design stage. However, for better result, DFMA is strongly
recommended to be start simultaneously during any stage of product design. DFMA
will simplify the product design without sacrifice the product function and quality.
The product components will be reduced by adapting DFMA methodology. In term
of cost, reducing product component will be rewarding with saving overall product
cost. Therefore, implementing the DFMA is a great opportunity that needs not to be
ignored. The DFMA methodology provides guidance during designing product
61
which end target is to simplify and minimizing product component as well as
minimizing overall product cost.
2.22
Summary
A review of 1st Law of Thermodynamics, product development process and
Design For Manufacture and Assemble are essential to be carried-out before
commencing any development works. Reviews done will give further information
about the apparatus, and ensuring all problems are identified. A product
development process, gives guidance on strategy and approach that should be
performs during development works. Meanwhile, Design For Manufacture and
Assembly (DFMA) is a value added in product development process by improving
overall design concept. Combination between product development method and
DFMA methodology promising a systematic and well arrange able procedure.
Finally, development a product is challenging work to need to carefully to be
carried-out. In order to minimize the failure, in turn to increase product success, the
methodology that been used must be identify and clearly understood.
CHAPTER 3
CONCEPTUAL DESIGN DEVELOPMENT
3.1
Introduction
The developed apparatus is one unit portable experimental apparatus for
demonstrating 1st Law of Thermodynamics closed system. The apparatus is targeted
to be used by undergraduate students who are taking thermodynamics subject for the
first time. Students will use this apparatus as a part of their laboratory experiment.
The apparatus will help student to understand the theory of the 1st Law of
Thermodynamics which are the basic knowledge in thermodynamics studies. The
idea to develop this experimental apparatus is proposed by one of the lecturer who
involve in teaching the thermodynamics subject. Based on his teaching experience,
the performance of students taken Thermodynamics subject is below expectation.
One of the factors contributing to this problem is the student did not really under
stand the 1st Law of Thermodynamics. The 1st Law of Thermodynamics is a first
topic in Thermodynamics that need to be well understood. Students who are not well
understood this topic will be omitted. They will also face difficulties to understand
the next topics. Therefore, one of the approaches to overcome this problem is to
enrich their understanding by providing them with an experiment apparatus.
Combination of theory and practical will directly enhance the teaching and learning
session. Beside, it also promotes student interest toward the subject.
63
3.2
User Requirements
It is important to consider all user requirements in order to develop successful
experimental apparatus. Based on conducted interview session, requirements for this
apparatus summarized as the followings:
i.
The apparatus must be able to clearly demonstrate the 1st Law of
thermodynamics closed system.
ii.
May use water or atmosphere air as working fluid.
iii. Provide a heat source.
iv. Preferred piston cylinder assembly.
v.
Simple design and low cost.
vi. Ease to operate or User friendly.
vii. Ease to measure the data.
viii. Ease of handling.
ix. The apparatus must be able measure temperature.
x.
The apparatus must portable type and can be move to lecture theater.
xi. Lightweight.
xii. Safety.
xiii. Attractive.
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3.3
Prepare Product Design Specification
Based on the above user requirements, the product design specification is
being prepared as shown in Table 3.1.
Table 3.1: Product Specification
No.
Matrix
Specification
1.
Weight
Not more than 10kg
2.
Safety
Provide heat insulation
3.
Attractive
Apparatus cover with stainless sheet
4.
Cylinder
Maximum diameter 15 cm, material cast iron.
standard part
5.
Piston
Suitable to the cylinder, material cast iron.
Standard part
6.
Temperature
Digital temperature sensor,
reading
range 10°C ~ 200 °C.
Standard part
7.
Displacement
0.5 meter Ruler with adequate indicator
reading
8.
Cost
Not more than RM 1500
9.
Source of heat
Portable gas stove
10.
Portable
Could be easily move.
65
3.4
Concept Generation
Four design concepts sketching had been developed. The concept’s sketches
are based on the user requirements. The sketch and description of each concept are
shown as following.
3.4.1
Concept No. 1
Figure 3.1 shows the design concept no. 1.
Figure 3.1: Design Concept No. 1
66
3.4.1.1 Concept Description
The first design concept consists of piston-cylinder assembly, which is
vertically arranged. Water will be supplied through inlet valve which is positioned at
the left side of the cylinder. At the bottom of cylinder there is an outlet valve to drain
out the water if the apparatus is not being used for a period of time. Temperature
sensor and Pressure Transmitter are being installed to cylinder using screw threaded
to prevent water and pressure leakage. On the left side of the apparatus there is
transparent level indicator for monitoring water level. At the bottom of the cylinder,
there is electric heat for the heating purpose. At the cylinder there is a stopper
positioned at the top and the bottom inside the cylinder wall. The purpose of these
stoppers is to limit the piston movement, so the piston will not fall outside of the
cylinder. A rod is connected to the piston. The rod is called a connecting rod. At the
top of the connecting rod there is an indicator, which is directed to the ruler for
measuring displacement. Lastly, the base and the frame are being installed to hold
and to balance the apparatus.
.
To demonstrate the 1st Law of Thermodynamics, firstly the water or gas must
be supplied to the cylinder through the inlet valve. If water is used, the weight of the
water is measured before it is supplied to the cylinder. Then, the initial temperature
inside the cylinder and the initial position of the piston is measured and recorded
using temperature sensor and ruler respectively. Then heat is supplied to the system
using a heater. After few minutes, the piston will move up. Once the piston move up
quickly shut-off the heater. The piston will move up and will stop at a new position.
At this new position, record the temperature and the new piston distance. Movement
of the piston from initial position to the final position means that the work is done by
system to lift the piston. The work done is resulted from changes of internal energy
of working fluid due to the heat supplied to the system.
67
3.4.1.2 The Advantage and Disadvantage
The advantages of concept design No. 1 are
i.
The temperature could be easily recorded.
ii.
The piston movement could be easily recorded.
iii. Easy to supply heat to system.
iv. Easy to operate.
The disadvantages are:
i.
Need to provide seven holes to the cylinder wall. More holes will
consume more machining time. Assembly time also will increase because
need to assemble 7 plugs to the cylinder.
ii.
Burn heater is difficult to replace for maintenance.
iii. Possibility of leaking at the heater assembly.
68
3.4.2
Concept No. 2.
Figure 3.2 shows the design concept no. 2 .
Figure 3.2 Design concepts No. 2.
3.4.2.1 Concept Description
The design concept No. 2 consists of two separate components that are
piston-cylinder assembly and the chamber assembly. Instead of supplying water
directly to the cylinder, it is supplied and heated in the chamber assembly unit. An
outlet valve located at the side of the cylinder is used to drain out the water. There
also an inlet valve connected to the temperature and pressure sensor. For piston cylinder assembly, the design is as concept No. 1. The portable gas stove burner is
introduced in concept no. 2 to replace the heater as a heat source. A hose is used to
69
connect between chamber and cylinder. There are one inlet and outlet at the chamber
assembly. The frame and base function is to stabilize the piston-cylinder position.
To demonstrate the 1st Law of Thermodynamics, the water is being supplied
to the chamber unit and being heat up using portable gas stove. Continuous heat
supply will increase the internal energy of the water. The internal energy then
changes water into wet steam inside the chamber. The wet steam then supplied to
piston-cylinder through a hose connection. The wet steam will accumulate inside the
cylinder until it has enough energy to push up the piston. Once the piston move, the
work is done by system. The work done is resulted from changes of internal energy
of working fluid due to the heat supply to the system.
3.4.2.2 The Advantage and Disadvantage
The advantages of concept design No. 2 are
i.
The temperature could be easily recorded.
ii.
The piston movement could be easily recorded.
iii. One inlet for temperature sensor and pressure sensor.
iv. Separate unit and ease to maintenance.
v.
Only 3 holes on the cylinder compare to design no. 1
The disadvantages are:
i.
More complicated than concept no. 1.
ii.
Consume large working space.
iii. Consist from many components, therefore will increase assembly time.
iv. Cost will increase due to many components
70
3.4.3
Concept No. 3
Figure 3.3 shows the design concept no. 3 .
Figure 3.3 Design concepts No. 3.
3.4.3.1 Concept Description
The design concept No. 3 consists of two main components, which are
cylinder and piston assembly. The heat source is gained from the portable gas stove
burner. Piston cylinder is arranged vertically. There are two holes at the cylinder,
first for water inlet together with the temperature and pressure sensor. The pressure
sensor could be replaced with the pressure gauge as an option. In piston assembly,
the indicator is connected to the ruler for measuring piston displacement. The frame
and base function is to stabilize the piston-cylinder position.
71
Procedure to demonstrate the 1st Law of Thermodynamics is similar to the
concept no. 1. The change is only using portable gas stove burner instead of electric
heater.
3.4.3.2 The Advantage and disadvantage
The advantages of concept design No. 3 are
i.
The temperature could be easily recorded.
ii.
Simple design.
iii. The piston movement could be easily recorded.
iv. Easy to supply heat to system.
v.
Easy to operate.
vi. Easy to maintenance.
vii. Only need to drill two holes on cylinder.
The disadvantages are:
i.
Need external gas stove burner to obtain heat supply to system.
72
3.4.4
Concept No. 4.
Figure 3.4 shows the design concept no. 4 .
Figure 3.4 : Design concepts No. 4.
3.4.4.1 Concept Description
The design concept No. 4 consists of piston-cylinder assembly which
horizontally arranged. Water will be supplied through the inlet valve which is
positioned at the right side of the cylinder. Similar method to be applied if air is used
as working fluid. There is outlet valve to drain out the water if this apparatus is not
to be used for a long period of time. Temperature sensor and Pressure Transmitter is
being installed to cylinder using thread to prevent leakage. The portable gas stove
burner is used for heating purpose. An indicator is connected to a connecting rod for
measuring the displacement of the piston. Lastly, the base and the frame are used to
hold and balance the apparatus.
.
73
To demonstrate the 1st Law of Thermodynamics, water or gas must be
supplied to the cylinder through the inlet valve. If water is used, measure the weight
of the water, but not necessary for atmosphere air. The initial temperature inside the
cylinder then is recorded. The initial position of the piston is recorded using indicator.
Heat is supplied to the system using portable gas stove burner. Within minutes, the
piston will move to left side. Once the piston begin move to the left side quickly
shut-of the heater. The piston will move, and then will stop at new position. At this
new position, record the temperature and the new piston distance. The movement of
the piston from initial position to the final position means that the work is done by
system. The work done is resulted from changes of internal energy of working fluid
due to the heat supply to the system.
3.4.4.2 The Advantage and disadvantage
The advantages of concept design No. 4 are
i.
The temperature could be easily recorded.
ii.
The piston movement could be easily recorded.
iii. Easy to supply heat to system.
iv. Easy to operate.
The disadvantages are:
i.
Need to drill 3 holes on cylinder.
ii.
Possibility of leaking because horizontal arrangement.
74
3.5
Selection Criteria
Other than the needs of technical product specification, a user requirement
which cannot be interpreted into technical term or translated into measurable quantity
is important things. The user requirements in this category could be define as the
features that will make user feel happy and comfortable to use it. Therefore, based on
the user requirements, several selection criteria are identified. The selection criteria
then are to be arranged started with the most important requirement and then
followed by others. Selection criteria under consideration are summarized as the
followings:
3.5.1
i.
Ease of handling
ii.
Low cost
iii.
Safety to use
iv.
Ease of manufacture
v.
Lightweight
vi.
Portability
vii.
Ease of maintenance
Ease of Handling
The most important criteria in experimental apparatus which required by user
is ease of handling. In other word, ease of handling could be defined as user friendly.
One of the factors contributing to ease of handling is to simplify the design. For
example, user will find that the apparatus is ease to handle if there is no much
complicated features such as setting buttons. Ease of handling also means that, the
customer could become familiar to operate the apparatus within short period of the
time. Some apparatus is easily operated so that the users need no instruction manual
in order to handle them. Ease of handling is the one of user requirements which
could influences user decision making during product selection.
75
3.5.2
Low Cost
The user tends to buy product at reasonable price. Therefore, any product
development will face the problems if they are not capable to meet this requirement.
The product cost should come along with the product quality. However, lowering
product cost didn’t mean sacrificing product quality. Most of the user will not
tolerate in quality issues. Thus, development of this experimental apparatus will
consider the product cost as well as product function and quality to satisfy the user.
The end target is to provide the reliable apparatus at affordable cost.
3.5.3
Safety
Any kinds of apparatus or product, users are very concern about the safety
issues. The development of this experimental apparatus will not compromise to the
any safety issues. As priority, any part of this experimental apparatus design shall not
harmful or potentially dangerous to the user. The entire hot surface will be fully
insulated. All the potentially dangerous part are taken care, so that the risk for
accidents as minimum as possible.
3.5.4
Ease of Manufacture
Complicated apparatus or product normally needs to undergo various
manufacturing process. The cost will increase if it requires special manufacturing
process to fabricate the apparatus. To avoid unnecessary cost, users require a product
which could be produce using common manufacturing process. Therefore
development of this experimental apparatus will consider all the manufacturing
aspect for ease of manufacturing.
76
3.5.5
Lightweight
Mobility or portability is one of user requirements into this experimental
apparatus. Therefore, the experimental apparatus need to be light weight as possible.
By having lightweight apparatus, handling and operation will become easier. In
addition, the apparatus could be easily to relocate from one location to other
location. .
3.5.6
Portability
To maximize the benefit gain from the experimental apparatus, developed
apparatus should be easily removed whether in laboratory or in lecturer theater.
Relocating the apparatus is expected to be done only by one person. The apparatus
also expected to be easily operated in different location.
3.5.7
Ease of Maintenance
After the apparatus have been used for some period of time, service and
maintenance is need to be done. This to ensure the apparatus performance is satisfy
and as well as to minimize repair cost. Therefore, user has put the maintenance factor
as one of their requirements. Product or apparatus which come with ease of
maintenance will have great advantage to be acceptable.
77
3.6
Concept Screening
Based on the selection criteria provided by the user, the concept screening
matrix had been develop to narrow the number of designs quickly. Concept screening
uses a reference concept to evaluate variants against selection criteria and narrow the
range of concepts under consideration. During screening process, design concept is
being rated using code '
+'for better than, '
0'same as and '
-'
for worse than. The
selection criteria are listed along the left hand side of the screening matrix. Table 3.2
shows screening matrix used during this stage. For the comparison purpose, the
design concept No. 1 is chosen as the references.
Table 3.2 Screening matrix
Concepts
Selection Criteria
1/ref.
2
3
4
Ease of handling
0
-
0
-
Low cost
0
-
+
+
Safety to use
0
0
0
0
Ease of manufacture
0
-
+
0
Lightweight
0
-
0
0
Portability
0
-
0
0
Ease of maintenance
0
-
+
-
Sum
+’s
0
0
3
1
Sum
0’s
7
1
4
4
Sum
–‘s
0
6
0
2
Net score
0
-6
3
-1
Rank
2
4
1
3
Yes
No
Yes
No
Continue?
Based on the screening matrix, the design concept 3 gives the highest score among
the other four design concept. Next score is design concept 1. Therefore design
concept 3 and design concept 1 is selected for further evaluation and assessment.
78
3.7
Concept Scoring
Concept scoring was a next process for evaluation and assessment of design
concept. Concept scoring use weighted selection criteria and a finer rating scale. The
weight for selection is being decided by designer refers to the priority of the user
requirements. The rating for relative performance for each criterion is done by
assigning the code as show in Table 3.3.
Table 3.3: Relative performance rating
Relative Performance
Rating
Much worse than reference
1
Worse than reference
2
Same as reference
3
Better than reference
4
Much better than reference
5
79
Table 3.4 shows the concept scoring matrix that had been done using relative
performance rating.
Table 3.4: Concept scoring matrix
Concept
1/reference
Selection
Weighted
3
Weighted
Weight
Rating
20%
3
0.6
3
0.6
Low cost
20%
3
0.6
4
0.8
Safety to use
15%
3
0.45
4
0.6
15%
3
0.45
4
0.6
Lightweight
10%
3
0.3
3
0.3
Portability
10%
3
0.3
3
0.3
10%
3
0.3
4
0.4
Criteria
Ease of
handling
Ease of
manufacture
Ease of
maintenance
score
Rating
score
Total score
3.00
3.60
Rank
2
1
Continue
No
Develop
Based on the scoring matrix, the highest score is achieved by the concept 3 compare
to concept 1. Therefore, further design development is based on design concept 3.
80
3.8
Final Concept Selection
The result obtained from concept screening and concept scoring show that,
the most potential concept to be developed is design concept 3. Although, concept 3
is selected, it didn’t means other concept is totally been eliminated. If there is
possibility to combine the features from other concept it can be done. However, the
concept combination could be done if there are relevant justifications such as
improving or producing better apparatus. The selected concept design 3 is again
shown in Figure 3.5.
Figure 3.5: Final design concept.
81
3.9
Summary
Selection of the suitable design concept is one of the challenging tasks during
design and development activities. The generation of several design concepts is
needed to be carried out before chosen one of the concept for further development.
Generation of the design concepts is based on the Product Design Specification
which is being prepared based on customer or user requirements. Generating several
design concepts will provide different mechanism and characteristics. In order to
select the suitable design concept that fulfills user requirements, concept screening
and concept scoring is applied to select the most suitable design concept. Quickly
narrow the design concept is done by concept screening, while for finer selection the
concept scoring method was used. Four design concepts had been generated and
undergone evaluation process. During concept screening, comparison among the
design concept is done base on the design concept 1 which are set as reference design.
Base on concept screening evaluation and assessment, the highest score are obtained
from design concept 1 and concept 3. Therefore, concept 1 and concept 3 then
selected for evaluation using concept scoring method. Concept scoring method
evaluation is done by preparing concept scoring matrix. At this stage, design concept
1 and design concept 3 is evaluated again by given weighted to selection criteria
using relative performance rating. As the end result, the highest score is obtained
from design concept 3. Therefore, design concept 3 is selected for further
development.
CHAPTER 4
DESIGN FOR MANUFACTURE AND ASSEMBLY
(DFMA) ANALYSIS
4.1
Introduction
The analysis of the developed apparatus is done using Boothroyd-Dewhurst
DFMA Methodology. This method had been selected because this method is well
documented and mostly used by the industry. Beside that, much information about
Boothroyd-Dewhurst is available compared to the others methodology. DFMA is
applied after the design concept is being chosen. Evaluation in DFMA analysis
required in preparing product drawing for further analysis. Thus, several drawing
have been generated that based on the design concept no. 3. The Design for
Assembly (DFA) is done in order to obtain design efficiency. The Design for
Manufacture (DFM) analysis is done after DFA. The purposes of DFM analysis to
appropriate select the material and manufacturing process.
83
4.2
Product Structure and Parts Quantity
The apparatus consists of 13 parts, which includes two sub assemblies, piston
and cylinder sub-assemblies. The product structure is given in Figure 4.1.
Experimental Apparatus
Piston (1)
Connecting
rod
(1)
Piston
Pin
(1)
Cylinder (1)
Piston
Ring
(3)
Indicator
(1)
3-ways
Connector
Top (2)
Thermometer
(1)
Outlet
Valve
(1)
3-ways
Connector
Bottom (2)
Single
connector
(1)
L-connector
(1)
Pressure Gauge
(1)
Figure 4.1: Product structure
Inlet
Valve
(1)
84
4.2.1
Assembly Drawing
The assembly drawing for the selected final design concept is shown in
Figure 4.2.
Assembly drawing of apparatus with stand
Assembly drawing of apparatus without stand
Figure 4.2: Assembly drawing of final design concept
Based on selected final design concept, the experimental apparatus consist of
cylinder and piston assembly. The inlet and outlet for the working fluid had been
design on the cylinder. The DFMA analysis is done only to the piston-cylinder
apparatus which are the main focus of the design.
85
4.2.2 Exploded Drawing
To perform DFMA evaluation and analysis, exploded drawing for the pistoncylinder assembly had been prepared as shown in Figure 4.3.
1. Cylinder (1)
2. Piston (1)
3. Piston pin (1)
4. Piston ring (3)
5. Connecting rod (1)
6. Indicator (1)
7. 3-way connector (2)
8. Inlet valve (1)
9. Single connector (1)
10. L-connector (1)
11. Pressure gauge (1)
12. Thermometer (1)
13. Outlet Valve (1)
Figure 4.3: Exploded drawing of final design concept
86
4.2.3
Bill of Materials (BOM)
A Bill of Materials (BOM) describes a product in terms of its assemblies,
sub-assemblies and basic parts. Basically consisting of a list of parts, a BOM is an
essential part of the design and manufacture of any product. A bill of material can
define products as they are designed, as they are manufactured, as they are ordered,
as they are built, or as they are maintained. There are different types of bills of
material dependent upon the discipline that generates them and the purpose for which
they are intended. Table 4.1, shows the Bill of Material for developed apparatus.
Table 4.1: Bil of material of developed apparatus.
Part
Part Description
Qty
Material
Make/ Buy
ID
A1
B1
Cylinder
Piston
1
1
Carbon steel
Aluminum Alloy
•
Purchase
•
Modify
•
Purchase
•
Modify
B4
Piston pin
1
Aluminum
•
Purchase
B3
Piston ring
3
N/A
•
Purchase
B2
Connecting rod
1
Aluminum
•
Fabricate
B5
Indicator
1
Aluminum
•
Fabricate
A2
3-way connector
2
1” Stainless steel
•
Purchase
A7
Inlet valve
1
1” Stainless steel
•
Purchase
A6
Single connector
1
1” Stainless steel
•
Purchase
A8
L-connector
1
1” Stainless steel
•
Purchase
A9
Pressure gauge
1
N/A
•
Purchase
A4
Thermometer
1
N/A
•
Purchase
A5
Outlet Valve
1
1” Stainless steel
•
Purchase
C1
Base support
1
Mild Steel
•
Fabricate
87
4.2.4
Part Functions and Critics
Table 4.2 shows the function and critique of each part:
Table 4.2: Part functions
No.
Part
Function
1.
To allow piston slide up-down.
Theoretically necessary part since this is main
body.
Cylinder
2.
To be fitted inside the cylinder. Pressure is exerted
on the cylinder surface.
Theoretically necessary part because moveable
part.
Piston
3.
To attach the piston to connecting rod.
Theoretically
Piston Pin
necessary
maintenance reason.
part
because
for
88
Table 4.2: Part functions (continued)
No.
Part
4.
Function
To prevent leakage between piston and cylinder.
Theoretically necessary part because different
material and working in pressurize condition.
Piston Ring
5.
To hold the piston inside cylinder.
Theoretically necessary part because moveable
part and must be separate for reason of assembly.
Connecting Rod
6.
To point to the ruler.
Theoretically necessary part for ease of linear
displacement measurement
Indicator
7.
To connect to cylinder and to allow inlet for
working fluid.
Theoretically necessary part because must be
3-ways connector
separate for reason of assembly.
89
Table 4.2: Part functions (continued)
8.
As inlet of working fluid.
Theoretically necessary part because for reason of
operation.
Inlet valve
To connect to 3 ways connector and L-connector
9.
for pressure measurement.
Theoretically necessary part because for pressure
Single Connector
10.
measurement purpose.
To connect to pressure gauge
Theoretically necessary part because for pressure
measurement purpose.
L-connector
11.
To measure the pressure inside cylinder.
Theoretically necessary part because for purpose
of pressure measurement.
Pressure Gauge
12.
To measure the temperature inside cylinder.
Theoretically necessary part because for purpose
of temperature measurement.
Thermometer
90
Table 4.2: Part functions (continued)
13.
As inlet of working fluid.
Theoretically necessary part because for reason
of operation.
Outlet Valve
4.3
Boothroyd-Dewhurst DFM Analysis
The DFM analysis and evaluation were conducted by using Boothroyd
Dewhurst DFMA methodology. By applying DFM methodology, material and
process selection could be properly determine. As the end result DFM analysis will
provide the several suitable processes regarding to the selected material. DFM
analysis of the developed apparatus is only done to the cylinder part. The other parts
are assumed as standard part and being purchase.
Regarding to Boothroyd Dewhurst DFM Methodology, two categories of the
product needed to be evaluated. Firstly, the shape attributes and secondly the
material requirement. Table 4.3 shows cylinder data for DFM evaluation purpose.
91
Table 4.3: Shape attributes and material requirement data for cylinder
1. Part name : Cylinder
2. Shape attributes :
i.
Depressions
Yes
ii.
Uniform wall
Yes
iii. Uniform Cross section
Yes
iv. Axis of rotation
Yes
v.
Yes
Regular cross section
vi. Captured cavity
No
vii. Enclosed cavity
Yes
viii. No draft
Yes
3. Material requirement :
i.
Expose directly to flame.
ii.
Excellent heat transfer.
The DFM analysis is done by preparing the process elimination table
proposed by Boothroyd-Dewhurst. The elimination process is done on the table by
carry out analysis in sequence of shape attributes and material requirements. Table
4.4 shows the process elimination table for the cylinder.
92
Sand Casting
Investment Casting
Die Casting
Injection Molding
Structural Foam
Molding
Blow Molding (Ext.)
Blow Molding (Inj.)
Rotational Molding
Thermoset
Refraction Metals
Thermoplastics
Nickel and Alloys
Zinc and Alloys
Magnesium and
Alloys
Titanium and Alloys
Stainless Steel
Aluminum and
Alloys
Copper and Alloys
Alloy Steel
Cast Iron
Carbon Steel
Table 4.4: Process elimination for cylinder
Solidification
Processes
Impact Extrusion
Cold Heading
Closed Die Forging
Powder Metal Parts
Hot Extrusion
Rotary Swaging
Bulk
Deformation
Processes
Machining (From
Stock)
ECM
EDM
Material
Removal
Processes
Wire EDM
Profiling
Sheet Metal
(Stamp/bend)
Thermoforming
Metal Spinning
not applicable;
Sheet
Metal
Processing
normal practice;
less common.
93
The result shows that, there are three materials that suitable for cylinder
which is carbon steel, alloy steel and stainless steel. Chosen one of this material
should be done in terms of the cost involve. Regarding to low cost requirement by
user, carbon steel should come as priority to be selected compare to another two
materials. Refer to the manufacturing processes in the left column; clearly show that
machining process is the suitable manufacturing method to produce the cylinder
which made from carbon steel. Hot extrusion process is not selected because the
process is less common due to the bigger diameter of the cylinder, which can give
high tendency size deform during extrusion process.
4.4
Boothroyd-Dewhurst DFA Analysis
The DFA analysis and evaluation was conducted by using Boothroyd
Dewhurst DFMA methodology. By applying DFA methodology three quantitative
outputs will be generated which are assembly time, assembly cost and assembly
efficiency. The design efficiency or assembly efficiency is the end result of the DFA
analysis that can be used to compare various designs in terms of their relative
efficiencies for manual assembly. The DFA analysis and evaluation of begin with
determination of alpha ( ) and beta ( ) angle of each part of developed apparatus as
shown in Table 4.5.
94
Table 4.5: Alpha ( ) and beta ( ) angle for each part
No.
Part
Alpha ( º)
Beta ( °)
º+
1
Cylinder
360
360
720
2
Piston
360
180
540
3
Piston pin
180
180
360
4
Piston ring
180
0
180
5
Connecting rod
360
180
540
6
Indicator
360
180
540
7
3-way connector
180
180
360
8
Inlet valve
360
0
360
9
Single connector
180
180
360
10
L-connector
360
360
720
11
Pressure gauge
360
0
360
12
Temperature sensor
360
360
720
13
Outlet Valve
360
0
360
°
The analysis of manual handling will based on the difficulty of grasp and
manipulates the parts. The apparatus cylinder weight is assumed more that 10 lb and
piston weight is assumed less than 10lb. Both parts are large in size. Therefore, for
the purpose of handling the cylinder and piston need to use two hands. In manual
insertion analysis, the several parts had use screw-thread for the purpose of assemble.
Therefore the parts need to be screwed immediately after insertion. The use of thread
instead of snap fit is to prevent pressure leakage. In addition, all the part for the
apparatus is made from metallic material. The metal is used because the apparatus
will be exposed to heat during operation. The parts that need to be screwing during
insertion are 3-ways connector, inlet/outlet valve, single connector, L-connector,
pressure gauge and thermometer. For cost estimation purpose, assume that operator
wages is RM 2 per hour.
Table 4.6 shows the table computation of Design
Efficiency of the apparatus. Note that, C3 and C4 are columns for evaluation of
manual handling and C5 and C6 is for evaluation of manual insertion. The data is
obtained from table provided by Boothroyd-Dewhurst as in appendix ‘C’ and ‘D’.
95
Table 4.6: Computation Design Efficiency of apparatus
C7
C8
C9
Operator rate :
RM2/hr =
4
00
1.5
5.5
0.33
1
Cylinder
2
1
91
3
00
1.5
4.5
0.27
1
Piston
3
1
10
1.5
00
1.5
3.0
0.18
0
Piston pin
4
3
00
1.13
30
2
6.26
0.38
1
Piston ring
5
1
20
1.8
00
1.5
3.3
0.20
1
Connecting rod
6
1
20
1.8
00
1.5
3.3
0.20
1
Indicator
7
2
10
1.5
38
6
15
0.90
1
3-way connector
8
1
10
1.5
38
6
7.5
0.45
1
Inlet valve
9
1
10
1.5
38
6
7.5
0.45
1
Single connector
10
1
30
1.95
38
6
7.95
0.48
1
L-connector
11
1
10
1.5
38
6
7.5
0.45
1
Pressure gauge
12
1
30
1.95
38
6
7.95
0.48
1
Temp.sensor
13
1
10
1.5
38
6
7.5
0.45
1
Outlet Valve
C2(C4+C6)
95
Operation time
1
No. of parts
1
Part ID
Theoretical min. parts
C6
Operation cost 0.06C7
C5
Insertion time per part
C4
Manual insertion code
C3
Handling time per part
C2
Manual handling code
C1
0.06c/s
Name of
assembly:
Piston Cylinder
apparatus
Design
Efficiency
16
86.76
5.22
=
12 3NM/TM =
(3x12)/86.76 =
0.415 @ 41.5%
TM
CM
NM DE = 41.5%
Result from Boothroyd-Dewhurst DFA analysis shows that total operation
times about 86.76 second, operation cost to assemble one unit of apparatus is about
5.22 cent and design efficiency or assemble efficiency is about 41.5 percent.
96
4.5
Apparatus Animation
An animation of the apparatus is done purposely to illustrate apparatus
operation. A simple animation is prepared using animation software called
Macromedia Flash MX. Figure 4.4, 4.5, 4.6 and 4.7 shows four steps of animation
picture taken from Macromedia Flash MX.
Figure 4.4
Step 1, piston at rest position
Figure 4.5
Step 2, piston start lift-up
Figure 4.6
Step 3, piston still lifting
Figure 4.7
Step 4, piston reach to final position.
97
4.6
Summary
In Design For Manufacture and Assembly (DFMA) analysis, the first task is
to prepare the drawing of final design concept. Two types of drawing that had been
prepared which are assembly drawing and exploded drawing. Assembly drawing
shows the overall product features that assembly in one complete unit. The separated
part of the apparatus is shown by the exploded drawing. Next task is to determine the
functions of each part. Together with the critics of each part, the theoretical
necessary part is identified. Product structure had been prepared in order to group the
part into it subassembly. To obtain product design efficiency, Boothroyd-Dewhurst
DFA methodology had been applied. The result shows the design efficiency for
developed apparatus is about 41.5 percent. Material and process selection is done
based on Boothroyd-Dewhurst DFM Methodology. The DFM analysis and
evaluation is done to cylinder part as a sample. The material selections for remaining
parts are followed similar procedure. Result from DFM evaluation process show that
suitable material for cylinder is carbon steel and proposed manufacturing process is
machining process.
CHAPTER 5
FABRICATION AND ASSEMBLY
5.1
Introduction
This chapter describe on material preparation and fabrication work of
the apparatus. Fabrication is a process where the prototype is being fabricate and
prepared physically. Fabrication processes is done in work shop. In order to
systematically fabricate the developed apparatus the fabrication works are divided
into 3 major phases. Each phase will carry-out different fabrication work. For an
example in phase one, fabrication work is focused in the main body of the apparatus
which are cylinder-liner, piston and cover. The fabrication processes that involve in
each phase will be explained in detail with the series of photographs. The first two
phases will describe more on the fabrication process and the last phase will focus on
the assembly of the cylinder to base support, cover assembly and finishing works.
99
5.2
Development - Phase 1
The development in this phase involves the fabrication and acquisition main
apparatus components such as:
i.
Cylinder-liner
ii.
Piston
iii. Cover for cylinder liner
Material selection and preparation is done regarding the DFM analysis for example
material for piston is aluminum alloy and material for cylinder-liner is carbon steel.
5.2.1
Cylinder Liner
The most important component in the developed apparatus is a cylinder linear
as shows in figure 5.1.
Figure 5.1: Cylinder Liner
100
Cylinder-liner is made from cast steel. As a standard component in
automotive the cylinder-liner can be found easily in the automotive workshop at
standard size. A cylinder-liner that used in this project is not being fabricated but
purchased from automotive store. Inside diameter of cylinder is 10.87 cm and outside
diameter is 13 cm. Therefore cylinder-liner thickness is about 1 cm. The height of
cylinder-liner is about 38.4 cm. The flow chart for cylinder-liner manufacturing
process is shows in figure 5.2
Figure 5.2 Flow Chart of Cylinder Liner Fabrication Process
Refer to figure 5.2, the cylinder-liner is produced using centrifugal casting
operation, and then heat treated. Machining operations are then performed on the
liner, i.e., rough turning of outer diameter (OD), turning of external features to
manufacturer specifications, and rough boring of liner inner diameter (ID). Lastly,
finishing is done by boring and honing the cylinder liner wall surface.
101
5.2.2
Piston
A piston is described as a sliding piece moved by or moving against fluid
pressure which usually consists of a short cylinder fitting within a cylindrical liner
along which it can moves back and forth. Figure 5.3 shows the piston that used in
this project.
Figure 5.3: The Piston
The piston is made from aluminum alloy. There are two ways to produce the
piston which are die casting and forging. Die casting process requires the melting of
a special high silicon alloy in an electric furnace with extremely closely controlled
temperature. The molten alloy is then poured into a multi-piece die producing a very
accurate shape piston casting. The casting die is manufactured so that when the metal
has solidified the various pieces of the die can be extracted one by one. This means
that undercuts and relief can be produced in the casting to reduce the piston weight.
The forging process requires material to be brought in at closely controlled
diameters; this is then cut to billet size and all cut faces are machined to a smooth
finish.
102
The billet is pre-heated in an air-circulating furnace to a temperature quite
close to the operating temperature of the piston crown when the engine is operating
at full power. This temperature is critical and cannot be disclosed. This together with
tightly controlled speed of the forging process gives a dense and very fine grain
structure to the forging. After forging, any excess material is removed and the
forgings are then heat-treated followed by wet blast cleaning.
In this project, piston is purchased as standard part which suit to cylinderliner. In order to use piston in apparatus, a modification is made to piston. The piston
is cut at back face (hole for connecting rod pin) to reduce it height. The cutting
process of piston is done using cutting jaw. Figure 5.4 shows the piston after the
modification. This modification take part is to provide maximum travel distance of
piston inside cylinder liner.
Figure 5.4: Piston after the modification
103
5.2.3
Cylinder Liner Cover
The aluminum sheet is use for preparing cylinder liner cover. The cover is
prepared in over to cover the cylinder body which are originally black color. Beside
that cover also covered the insulation layer which are located between cylinder liner
external wall and the cover it self. The cover is made manually using conventional
sheet metal process. The material is aluminum sheet metal which need to cut
regarding to cylinder liner circumference and insulation layer. Figure 5.5 shows
aluminum sheet metal before and after undergone cutting and forming process.
Figure 5.5: Aluminum sheet
5.3
Development – Phase 2
The development in phase two involves the fabrication the components such
as:
i.
Base support
ii.
Cylinder support
These supports are made from the inch angle iron from the stock. All fabrication
works are done manually in work shop.
104
5.3.1
Base Support
Base support is fabricated as stand for developed apparatus. As shown in
figure 5.6, base support is design lowest as possible to keep center of gravity at
lowest position possible. However, there is ample space for gas burner or heater to be
place at the bottom of piston-cylinder liner for heating purpose.
Figure 5.6: Base support
Base support should provide rigidity and stability to support piston–cylinder
liner weight. Therefore, base support is design to have wide opening for stability
purpose. The material for base support should strong enough to support cylinder liner
and piston weight, thus two inch angle iron (mild steel) as shown in figure 5.7 is used
for this purpose. The fabrications works involves cutting the angle iron according to
dimension then joining angle iron bar by welding process. Finally, the base support is
painted for better appearance.
Figure 5.7: Two inches angle iron
105
5.3.2
Cylinder Liner Support
The purpose of cylinder support is to hold the cylinder liner, so that cylinder
liner could stand vertically. The cylinder support is important because, the support
would prevent an-accident to user due to the fall of cylinder liner during operation.
To ensure the design is simplest as possible and to fulfill DFMA guidelines, the
support is designed so that the support is attached to base support. For this purpose a
mild steel hollow square bar half inch size is used. An attachment of this done to
base support is done through welding process. The height of support is designed to
not exceeding to the cylinder height. The cylinder liner is tie-up to support using
steel belt. Figure 5.8 shows cylinder liner support attached to base support.
Figure 5.8 : Cylinder liner support
106
5.4
Development –Phase 3
The development in phase three involves the assembly the component in the
apparatus such as:
i.
Cylinder Liner Assembly
ii.
Thermometer Installation.
iii. Piston Indicator assembly
iv. Piston installation
5.4.1
Cylinder Liner Assembly
The cylinder linear before assembly is shown in figure 5.9, and the assembly
cylinder is shown in figure 5.10.
Figure 5.9: Cylinder liner
Figure 5.10: Cylinder liner
before assembly
after assembly
107
The assembly of cylinder liner is consist from one unit pressure gauge, two
unit hand valve, two unit T-pipe and one unit elbow. There are two threaded holes
diameter 1 inch each that already been drilled during acquiring the cylinder liner.
The T-pipes are inserted to the both hole. For the bottom hole, the hand valve is
fitted so that, the valve opening is facing down position. The purpose of the valve is
to drain the water out from the apparatus after the experiment is finish. At the top
hole, the hand valve is fitted so that the valve opening in facing up position. The
purpose of upper valve is to receive water thru its opening. At above hole, there is
one unit analog pressure valve fitted to the T-joint pipe. The T-joint, hand valve and
pressure gauge is fitted after applying white tape to the thread.
Next step is to isolate the cylinder using heat resistance woven in order to
reduce heat transfer from the cylinder liner to surrounding. The woven is wrapping to
the cylinder surface as shown in figure 5.11. The wrapping is done for the entire
external circumference surface of the cylinder. Care should be taken to ensure that
the wrapping thickness is event to ensure optimum heat isolation.
Figure 5.11: Cylinder liner after wrapping with woven.
108
After wrapping process is done, the cylinder liner is now to be cover-up with
the external cover which is made from aluminum sheet metal. The purpose of the
aluminum cover is to give better appearance to the cylinder liner. Figure 5.12 shows
the cylinder liner after being assembled with aluminum cover.
Figure 5.12: Cylinder liner after assembled with aluminum cover.
5.4.2
Thermometer Installation
Temperature measurement is done through direct reading from the
thermometer installed to right side of T-pipe on the cylinder. The thermometer is
fitted to T-pipe after applying white tape to the thread. Figure 5.13 shows the
installation of the thermometer to T-joint on the cylinder liner.
Figure 5.13: Thermometer installation
109
5.4.3
Piston Indicator Assembly
Figure 5.14 shows an assembly of indicator on the piston. The purpose of
piston indicator is carry-out measurement of piston movement during the operation.
The indicator is made from the aluminum strip. To attach the indicator to the piston,
a steel epoxy is used. Steel epoxy is been selected because it can withstand to
temperature up to 120 °C. During operation, the apparatus will be heated by heat
source until the water is boiling to wet saturated steam. This means that the water
will boil and temperature at this point (wet saturated steam) by referring to steam
table is 109.8 °C. Therefore the used of steel epoxy is to ensure that the indicator is
still remain stick to piston.
Figure 5.14: The assembly of indicator on piston.
110
5.4.4
Piston Installation
Installation of piston involve two tasks which fitting the piston rings and
insert the piston into the cylinder liner. The piston that used in this apparatus comes
with the 3 grooves of for different piston rings. Two grooves for compression ring
and another groove for oil ring. Fitting the rings is done by using special tool called
ring expander as shows in figure 5.15, and the piston after fitted the rings is shows in
figure 5.16.
Figure 5.15: Ring Expander
Figure 5.16: Piston and ring
111
After rings are fitted to piston, next task is to insert piston to cylinder liner
using a special tool as shown in figure 5.17, while figure 5.18 shows installation
method of piston.
Figure 5.17: Special tool to insert piston to cylinder liner
Figure 5.18: Method to insert piston into cylinder
112
5.5
Complete Assembly
The complete assembly of the apparatus is shows in figure 5.19.
Figure 5.19: Complete Assembly of Apparatus
113
5.6
Summary
The fabrication and assembly works is divided into three phases. Each phase
will focused on different component. As example, the first phase focuses on the
fabrication main components such as cylinder, piston and cover. Second phase
involve fabrication of the base support and cylinder support. The fabrication process
and the material used also discussed in the phase two. The last phase describes the
assembly process among the components to produce a complete apparatus. For each
phase, the explanation is done by using series of photograph. By the aids of
photographs, the fabrication and assembly process is expected to be clearly
explained. Beside that an overall process involve to produce complete apparatus is
well presented.
CHAPTER 6
TESTING AND
OPERATION WORK PROCEDURE
6.1
Introduction
A testing is carry-out to investigate the apparatus performance. Through the
testing, the apparatus mechanisms and operation could be observed. A testing done is
able to ensure that all the components are well function as well as to counter measure
the problems arise. During the testing, the step by step procedure on operating the
apparatus could be prepared systematically and at the same time can identify the
safety issued during the operation. Safety consideration is done in order to avoid any
accident to the user and to avoid damage to the apparatus. In the other view, the
collected data during the testing then to be analyzed and compare to standard steam
table. Comparison the collected data is to be carry-out because to confirm the data
relevancy. The relevancy of the data is important because it represent the apparatus
performance whether it is achieving the expectation or not. At this stage if the data is
not relevant as expected, a fine tune and adjustment to the apparatus needed to be
done. This chapter, mainly explains on testing the apparatus in order prepare the
standard operating procedure as well as data verification through analysis using
standard steam table and lastly to confirm the apparatus performance.
115
6.2
Apparatus Preparation
Preparation the apparatus involves three main aspects which are:
i.
Piston-Cylinder liner lubrication
ii.
Base support to cylinder body
iii.
Pipes and thermometer fitting condition
iv.
Gas burner preparation.
The major aspect is the preparation of complete assembly of the apparatus
which are done early. In this stage, cylinder liners inner wall is need to be lubricating
using lubrication oil. This action is necessary to be carry-out because to reduce the
friction between cylinder liner inner wall and the piston rings. If not, the piston could
be stuck inside the cylinder liner due to high friction. Application a lubrication oils
on cylinder liner inner wall is shown in figure 6.1.
Figure 6.1: Lubrication oil is applied on the cylinder liner inner wall.
116
The next step is to check pipe fittings and ensure it is well tighten. Then pay
attention to thermometer fitting and condition. Ensure that, thermometer bulb in good
condition and not broken and the cylinder liner assembly and base support is well
tightening. Lastly, check and ensure that butane fuel cartridge is at less half in
cartridge container. A complete apparatus preparation and arrangement which is
ready for experiment is shown in figure 6.2.
Figure 6.2: Complete apparatus arrangement
117
6.3
Safety Instruction
Operation the apparatus involves heating the water using portable stove
burner that using butane gas fuel. During the operation, a flame produce by stove is
directed to the bottom of cylinder liner. Therefore, heat transfer process is happen
from the flame to cylinder liner bottom wall. As heat continued supplied, the cylinder
liner become hotter until water is boiled. Boiled temperature of water is 100°C and
the cylinder liner temperature will have the same temperature. Although there is heat
insulation between the cylinder liner wall and aluminum cover, the cover may also
being heated but it’s temperature is lower than cylinder liner temperature. For safety
purpose the user is advice not to touch aluminum cover during operation. As
reminder, a sign about hot surface is attached to aluminum cover as shows in figure
6.3.
Figure 6.3: Hot surface sign on cylinder liner.
Care should also be taken not to touch the base support of the cylinder liner.
This is because the base support may also hot due to convention heat transfer from
the flame.
118
A same hot surface sign as attached to cylinder is applied on base support as
shows in figure 6.4.
Figure 6.4: Hot surface sign on base support
6.4
Work Procedure
The work procedure or step by step operation is prepared during testing of the
apparatus. The work procedure is a method to correctly operate the apparatus. The
work procedure should be follow sequentially. Failure to follow work procedure
would damage the apparatus and cause injury to user. This is because the apparatus
work with wet steam which temperature at 100°C. The table 6.1 describes step by
step procedure to operate the apparatus.
119
Table 6.1: Work Procedure for operating the apparatus
Step
1.
Procedure
Check
the
Photograph
apparatus
arrangement, ensure that all
component
is
completely
assembled. Refer to figure
6.5.
Figure 6.5: Complete Apparatus.
2.
Check pipe fittings, tighten
the
fittings
if
necessary.
Ensure that piston is located
at the bottom stopper by
pushing down the piston.
Refer to figure 6.6.
3.
Figure 6.6: Checking all fittings.
Apply lubrication oil on
cylinder liner inner wall.
Refer to figure 6.7.
Figure 6.7: Applying lubrication oil.
120
Table 6.1 continued
4.
Close the bottom valve and
then open top valve. Refer to
figure 6.8.
Figure 6.8: Close bottom valve.
5.
Slowly, fill 0.5 liter water
into cylinder liner through
top valve, then close the
valve. Refer to figure 6.9.
Figure 6.9: Fill water to cylinder.
6.
Record
initial
water
temperature (T1).
Refer to figure 6.10.
Figure 6.10: Initial temperature.
121
Table 6.1 continued
7.
Record
initial
cylinder
pressure (P1).Refer to figure
6.11. Piston is exposed to
atmosphere; therefore gauge
pressure will give zero.
Figure 6.11: Initial pressure.
8.
Record initial piston position
(X1).Refer figure 6.12.
Figure 6.12: Initial piston position.
9.
Measure
Butane
gas
container weight (MB1) using
weighing scale. Refer figure
6.13
Figure 6.13: Butane gas weight
measurement.
122
Table 6.1 continued
10.
Install butane gas container
to the gas stove burner. Refer
figure 6.14
Figure 6.14: Installation of Butane gas
container to gas stove burner.
11.
Place a gas stove burner at
the bottom of cylinder liner.
Refer figure 6.15
Figure 6.15: Placing gas stove burner.
12.
Light
up
the
gas
stove
burner. Adjust the flame
directly to bottom of cylinder
liner. Refer figure 6.16
Caution: DO NOT OPEN THE
UPPER AND LOWER VALVE
BY YOUR SELF UNTIL END
OF EXPERIMENT.
Figure 6.16: Flame directed to bottom of
cylinder liner.
123
Table 6.1 continued
13.
Observe the temperature of
the water. The temperature
will increase. Refer figure
6.17.
Figure 6.17: Observation of temperature
increasing.
14.
Wait until the temperature is
about 90° C, at this moment
adjust gas stove so the flame
is smaller. Refer figure 6.18.
Figure 6.18: Temperature at 90° C .
15.
When the temperature just
reached 100° C, be ready to
shut down gas burner.. Refer
figure 6.19.
Figure 6.19: Ready to shut down
gas burner.
124
Table 6.1 continued
16.
Observe the piston. At this
moment piston will slowly
lift up. Refer figure 6.20.
Figure 6.20: Piston slowly lifts up.
17.
Once piston nearly touch
upper stopper, Quickly, shut
down the gas burner to stop
the piston movement. Refer
figure 6.21.
Figure 6.21: Shut down gas burner.
18.
Wait until piston is complete
stop the new position. Refer
figure 6.22.
Figure 6.22: Piston lift to new position.
125
Table 6.1 continued
19.
Record final temperature of
water inside cylinder. (T2).
Refer figure 6.23.
Figure 6.23: Final water temperature.
20.
Record
final
position
of
piston (X2). Refer figure
6.24.
Figure 6.24: Piston final position
21.
Record final pressure (P2).
Refer figure 6.25. Process is
Isobaric (constant pressure),
therefore
no
changes
in
initial pressure and final
pressure. Only atmosphere
pressure involves. So, gauge
pressure reading will give
zero.
Figure 6.25: Final Pressure
126
Table 6.1 continued
22.
Measure
final
weight
of
Butane gas (MB2). Refer
figure 6.26.
Figure 6.26: Measurement final
butane gas weight
23.
6.5
End of experiment.
Data Collection
During the operation the data that need to record is divided into two stages,
which are at initial operation and at the end of operation. The data that need to be
record are:
Before start Operation
i.
Water volume in liter (l).
ii.
Initial Water Temperature (ºC)
iii. Initial position of piston (mm)
iv. Initial Pressure (Pa)
v.
Initial weight of Butane gas (g)
127
At the end Operation
i.
Final Water Temperature (ºC)
ii.
Final position of piston (mm)
iii. Final Pressure (Pa)
iv. Final weight of Butane gas (g)
The data collection is simplified recorded using table 6.2.
Table 6.2: Table for Data record
Condition
No.
Parameter
Unit
1.
Water volume
Liter
2.
Water Temperature
ºC
3.
Piston Position
mm
4.
Pressure
Bar
5.
Butane gas weight
gram
Before heating
After heating
(Initial position)
(final position)
Remark
128
1st Law of Thermodynamics Analysis
6.6
The sample of experiment data taken from the testing is shows in table 6.3.
Base of the data the analysis of 1st of Thermodynamics is done.
Table 6.3: Testing data
Remark
Condition
No.
Parameter
1.
Water volume
2.
Unit
Before heating
After heating
(Initial position) (final position)
Liter
0.5 liter
-
-
Water Temperature
ºC
30ºC
100ºC
-
3.
Piston Position
mm
1cm
12.5cm
-
4.
Pressure
Pa
1 atm = 1bar
1 atm = 1bar
Isobaric
pressure gauge= 0
pressure
process
gauge= 0
5.
Butane gas weight
gram
357 gram
308 gram
Additional information:
1. Piston diameter : 10.94 cm
2. Piston height : 6.53 cm
3. Piston weight : 1240 gram
4. Inner diameter of cylinder liner : 10.87 cm
5. Outside diameter of cylinder liner : 13.0 cm
6. Cylinder liner height : 37.5 cm
To understanding the process, the illustration of the process is need to be redraw. The
illustration for initial condition and final condition is shows in figure 6.27.
129
Figure 6.27: Illustration of experimental process
At initial condition where pressure is 1 atm. or 1 bar and temperature of water
is 25º C, water is called subcooled liquid (or compressed liquid). This condition no
heat is transferred to system. As heat is transferred to water, the temperature
increased. When the temperature reaches 100º C, additional heat transfer results in
boiling and a change of phase. Water is about to boil is called a saturated liquid. As
heat is supplied to vaporize the water, its temperature and pressure remain constant
while its specific volume increases. During this stage, the phase is called a saturated
liquid-vapor mixture and the liquid and vapor phase coexist in equilibrium.
Additional heat will increase the volume of vapor and piston to be pushed up to final
position. At the final position the pressure is constant where P1 = P2. This is because
developed pressure is used to lift up the piston to final position. At final position, the
pressure inside cylinder is equal to pressure outside of cylinder. This process called
as Isobaric process where there no changes in pressure at initial and final position.
The analysis of 1st Law of Thermodynamics in this system shows the following.
130
1st Law of Thermodynamics state that
Total energy
-
Total energy
entering
leaving
the system
from system
-
Ein
=
Change in the total energy
in the system
Eout
=
∆Esystem
=
Change in internal energy
Or
Heat enter to
-
Works done
system
by system
of system
(energy in)
(energy out)
(from initial to final
condition)
Q12
6.6.1
-
W12
=
∆U
Works Analysis, W
The work (W) is given by the formula
W = F (X2-X1) , equation (1) where F is the force acting on the piston
surface
F = Atmosphere Pressure x Piston Surface Area + Piston Weight x Gravity
F =
F =
Patm x Ap
1x 105 x
+
(0.10922)
4
F
= 949 Newton
Mp x g
+
1.24 x 9.81
131
Therefore, using equation (1)
W
=
949 (0.125 – 0.01)
W
=
109.1 Nm or Joule
Piston travel from initial position ( X1 = 1cm) to final position (X2=12.5cm),
work done by system is 109.1 Nm @ Joule .
6.6.2
Total Internal Energy Analysis, U
At initial condition, the water temperature is 30 °C and pressure is at 1 bar =
1 x 105 Pascal or 100 kPa. Refer to table B.1.2: Saturated water pressure entry
(Appendix F). At 100 kPa given data are:
i.
Temperature = 99.62 °C.
ii.
Specific volume, saturated liquid vf = 0.001043 m3/kg
iii. Specific volume, saturated vapor vg = 1.69400 m3/kg
iv. Specific volume, Evaporation vfg
v.
= 1.69296 m3/kg
Internal energy, saturated liquid uf = 417.33 kJ/kg
vi. Internal energy, saturated vapor ug = 2506.06 kJ/kg
vii. Internal energy , Evaporation ufg
= 2088.72 m3/kg
At initial condition, the cylinder liner is filled with 0.5 liter water. No vapor is
present at this moment. The water is 100% sub-cooled liquid. Because of water
density of water is 1000kg/m3 . Therefore, the volume of 0.5 liter water is equal to
0.0005 m3. The state of water at initial condition can be proven as the following:
132
Using equation (3) , A specific volume at initial condition (v1 ) is
v1
volume at initial stage (m3)
=
total weight (kg)
v1
=
0.0005
0.5
v1
0.001m3/kg
=
Compare between v1 and vf , find that
v1<
vf ,this result prove that water at
initial condition is in 100% sub-cooled.
At final condition, the water temperature is 100 °C and pressure is at 1 bar =
1 x 105 Pascal or 100 kPa because the process is isobaric process. Mass of the system
still 0.5 kg because the system is isolated, but consist of water and wet steam.
Volume of system at final condition (V2) = water volume + wet steam volume
V2
=
(0.1094)2 x (0.115)
0.0005 +
4
V2
=
0.00158 m
3
Therefore,
Specific volume at final condition (v2) is given by :
v2
=
0.00158
0.5
v2
=
0.00316 m3/kg
133
Compare among v2 ,vf and vg , find that vf < v2 < vg , this result prove that
system at final condition is in saturated liquid-vapor mixture, where liquid and vapor
phase coexist in equilibrium. The quality (x) of the saturated liquid-vapor mixture is
calculated using equation (4).
Quality (x) = Specific volume at final condition - Specific volume saturated liquid
Specific volume evaporation
x
=
v2 - v1
vfg
x
=
0.00316
- 0.001043
1.69296
x
=
0.00125
Thus, Internal energy at final condition, U2 is calculated using equation (5),
u2 = Internal energy, saturated liquid + Quality x Internal energy , Evaporation
u2 = uf
+ x (ufg )
u2 = 417.33
u2 = 419.9 kJ
+ 0.00125 (2088.72)
134
Thus, total internal energy is calculated using equation (6),
U
=
m x ( u2 -u1)
U
=
0.5 x (419.9)
U
=
209.95 kJ
Result shows that total internal energy in the system is 209.95 kJ
6.6.3 Net Heat Enter to System, Q
From the 1st Law of Thermodynamics, the net heat (Q) enter to system is
calculated equation (2) ,
Net heat enter to system
= Total internal energy
+ Work done
Q
=
+
W
Q
=
209.95 kJ
+
0.10912 kJ
Q
=
210.059 kJ
U
Therefore Net heat enter to system is 210.059 kJ.
135
6.7
Summary
This chapter mainly discusses on the apparatus preparation, testing and
development of operation work procedure. Safety aspect during operation is also
identified and an instruction to counter measure this problem is proposed. On the
other hand, step by step operation procedure of the apparatus is prepared sequentially
with the photographs for better understanding. To collect the data, a table is proposed
and then a sample of 1st Law of Thermodynamics analysis is done. The result show
that the much energy is used to increased the internal energy of the water compare to
energy used to carry-out work. This is because the water needs to be heated from 25º
C until 100º C before the work could be done. Heating the water will absorb much
energy from the supplied energy. Therefore the portion of supplied energy is mainly
used to increase the water temperature or in other word, increase the internal energy
of the water. As the conclusion, the carried-out testing is successfully performed. The
achievement could be prove through moving mechanism which, piston is being lift up
as predicted and all other components are well function.
CHAPTER 7
DISCUSSION
7.1
Introduction
This chapter discusses on overall process and results obtained during
development the apparatus. To complete the project, two manufacturing technology
approaches have been used which are Product Development Approach and Design
For Manufacture and Assembly (DFMA). The first approach is conducted during
early stage of the project, followed by DFMA analysis for determination of design
efficiency. A fabrication work starts after the final design is finalized. The complete
fabricated an assembled apparatus is tested purposely for evaluation of its
functionality and performance. The data recorded during the testing is then being
analyzed using 1st Law of Thermodynamics with the aid of Standard
Thermodynamics Properties Table or Steam Table for data verification. This chapter
mainly discusses on the Product Development Process, DFMA application, product
fabrication and testing, finally results obtained during development of the
137
7.2
Product Development Approach
The product development approach applied in this project is essential to
ensure development works are systematically run on the right direction. To develop a
product, many criteria are needed or must carefully been considered. These criteria
are necessary to be identified and considered in order to fulfill the customer demands
besides minimizing product failure once the product is fabricated or after the product
reach to customer. A survey done at early stage is purposely to list out and identify
the requirements from the users.
Information obtained from survey is used to
prepare Product Design Specification (PDS). Based on PDS, four design concepts are
generated. The final design concept selected after carried-out concept screening and
concept scoring matrix. Concept screening method or often called Pugh method is
used purposely to narrow the number of design concepts quickly as well as to
improve the concept. Meanwhile the concept scoring matrix used to prioritize and
ranking the design concept through weight rating. The advantages of application of
Product Development Process are to provide a systematic approach by well
organizing all design and development activities, so that the well establishes product
could be produced as end result.
7.3
Design For Manufacture And Assembly (DFMA) Methodology
Design for Manufacturing and Assembly (DFMA) methodology is applied
after selected final design concept. Application of DFMA is applied in order to
further improvement of design concept. The goal of DFMA are reducing
manufacture and assembly cost, improving quality and speeding time to market. The
element Design For Manufacture (DFM) is useful during material and process
selection. Through the DFM, the selection of suitable material and manufacturing
processes is properly determined. The material and process selection are done
through the compatibility matrix. In the developed apparatus, determination of
manufacturing process and material are done based on DFM method. As the result, a
fabrication process are easy and quickly to be performed. In fact that, proposed
138
manufacturing process and material are economical, available and within normal
practice.
The final design concept is improved by applying Design For Assembly
(DFA) method. Design For Assembly (DFA) identify unnecessary parts in assembly
through three guidelines proposed by Boothroyd-Dewhurst. The DFA result is
showed through Design Efficiency (DE) or also known as Assembly Efficiency
(AE). Assembly Efficiency determination is based on two criteria which are
estimation of the handling time and estimation of assembly time.
Assembly Efficiency for developed apparatus is 41.5 percent. Two factors
contribute to the calculation of the design efficiency. Firstly, the theoretical
minimum parts and the other one is total assembly time. In detail, total minimum
number is 12 from the 16 parts. The theoretical minimum number is acceptable
because it covers 75 percent from the total parts. The highest theoretical minimum
number is achieved due to consideration of DFA guidelines during carry-out
improvement to final design.
Figure 7.1 shows the percentage of theoretical
minimum part compared to total parts.
Figure 7.1: Percentage of theoretical minimum parts
139
Meanwhile, total assembly time from same analysis is 86.76 seconds. The
assembly time is considered high because of 7 parts from total 16 parts are using
thread and screw for assembly on cylinder liner. Therefore, a special tool is needed
for screw tightening after insertion. The use of thread-screw and special tool will
consume much time compared to an assembly without any tool. Figure 7.2 shows the
number of part that used thread and screw of assembly method.
Figure7:2: Comparison between parts that need special tool to total part.
In term of time consumption, the part required tool consumes 60.9 seconds from total
time 86.76 seconds. The percentage of time portion is shows in figure 7.3.
Figure7:3: Percentage of assembly time
140
Based on DFA guidelines, a snap fit feature is preferred during assembly
process because it will consume less time compared to thread and screw method.
However, snap-fit cannot be used in developed apparatus due to the following
reasons:
1. As water is used as working fluid inside the cylinder liner, it is impossible to
avoid the leakage if snap fit is used.
2. The technical requirement of developed apparatus needs the system to be
isolated from the surrounding. A snap-fit feature is not capable to meet this
requirement.
3. Snap fit is best to be used for plastic parts. During operation, the apparatus is
exposing directly to flame to boil water inside cylinder liner. The entire
apparatus body will become hot. Therefore, the snap fit feature will deform.
Finally, application of DFMA methodology gives advantages in term part
reduction and assembly efficiency analysis. The higher assembly efficiency value is
better than lower value. Higher assembly efficiency shows that handling and
assembly time is lower. By reducing assembly time, overall product assembly
efficiency is expected improved. In this project, total part number is reduced at same
time theoretical minimum number is higher compare to total parts. However
assembly time is high and resulting 41.5% in assembly efficiency. The higher
assembly time is due to 70% part or 7 parts from 16 parts need tool for purpose of
assembly because of technical requirement of the apparatus.
141
7.4
Fabrication and Assembly
A fabrication of final design is done after DFMA analysis. Fabrication of the
apparatus is divided into 3 phases. The first phase involves material preparation and
fabrication of the cylinder liner, piston and cylinder cover. Due of availability in
market, a cylinder liner and piston are purchased from automotive retailer. To fit to
apparatus application, modifications are done to cylinder-liner and piston. Cylinderliner is totally sealed at it bottom, and this is done by using round carbon steel plate
with same cylinder diameter. Meanwhile, a piston height is reduced by cutting the
piston at piston pin hole. To produce cylinder cover, an aluminum sheet is used. The
fabrication of cylinder cover is done using sheet metal forming process.
Second phase involves fabrication of base support and cylinder-liner support.
The arc welding process is used for both parts. The material is made from two inch
mild steel angle iron for base support and half inch mild steel hollow square bar for
cylinder liner support. Finally, these parts then are painted for better appearance.
An assembly of fabricated parts was done in third phase. All the parts are
assembled in sequence. The tool is used to assemble some parts. A thermometer,
pressure gauge and pipes fittings need a wrench, meanwhile to insert the piston ring,
a tool called ring expander is needed.
Overall tasks perform during fabrication and assemblies of the apparatus
require knowledge’s on fabrication process together skills to handle the materials and
machines. Although, the machines used are conventional and fabrication processes
involve a normal workshop practice, the fabrication works are perfectly done as
proposed by DFM analysis. In addition, by using available parts and common
materials combined together with conventional fabrication process, the development
time and cost could be reduced.
142
7.5
Apparatus Testing and Functionality
A testing is conducted after complete apparatus is fabricated and assembled.
As the result, all parts are perfectly functioning as expected. No major modification
required or no major rework job is needed. A well function apparatus shows that, the
development work is efficacious. The testing data is used for an analysis of 1st Law
of Thermodynamics by aid of Standard Thermodynamics Properties table or often
called Steam Table. As a result, the energy balance in analysis shows that energy
balance is accepted, by changes of internal energy of studied system is higher than
the works done by system. However, any changes of internal energy must not equal
or beyond total energy or heat supply to system because some energy is losses to
surrounding during the operation. Finally, after gone through stages of development
work, an expected apparatus is successful developed, fabricated and ready to be used
in practical session in Thermodynamics laboratory.
7.6
Summary
The development of piston cylinder apparatus that demonstrate a 1st Law
Thermodynamics involved in theoretical and practical aspect. The early stages of
development are focused on methodology of product development strategy and
Design For Manufacture and Assembly (DFMA). Through these two approaches a
design concept is developed. A final design concept is to be fabricated and tested. A
practical aspect is now focused. Fabrications the apparatus require knowledge on
materials, machines and manufacturing processes, which are suitable and economical
without sacrificing product quality.
CHAPTER 8
CONCLUSIONS
8.1
Conclusion
A development an apparatus for Thermodynamics is successful conducted.
The well function apparatus is fabricated and tested. Implementing product
development strategy ensures that all development activities are systematically
planned. Conceptual design is beneficial at early of development stage because it
give a primary idea on apparatus. Further brain-storming of conceptual design
resulted developing several design concepts to be chosen. A chosen final design
concept is then is improve using Design for Manufacture and Assembly (DFMA)
methodology. The DFMA implementations are beneficial in-term of part reduction
design simplification. Design for Manufacture (DFM) analysis gives proper materials
and manufacturing process selection. Meanwhile, Design For Assembly (DFA)
provide a guideline on reduction part number and determination of assembly
efficiency through analysis on manual handling time and manual insertion time.
Assembly efficiency is used purposely for design comparison at same apparatus.
Higher value of assembly efficiency means less time required to assemble the
product. Combination of product development strategy together with DFMA
methodology in developed apparatus gives advantages in term of part reduction and
overall project organization. As overall conclusion, the project objective is achieved
and project scopes are fulfilled.
144
8.2
Recommendations for Future Work
To improve the apparatus design and performance, the following
considerations for future work should be taken into account:
1. To up-grade the apparatus using computer interface. The apparatus operation
could be controlled via computer screen. Measurable parameters are to be
upgraded using digital sensors instead using conventional method.
2. Increase assembly efficiency by reducing assembly time. A study is needed to
be carried-out by eliminating the part that use thread and screw for isolated
cylinder.
3.
To improve heating element method. The gas stove burner could be replaced
using other method of heating elements for example by using electric heater.
145
REFERENCES
1. Yunus A. Cengel, Robert H. Turner. Fundamentals of Thermal-Fluid
Sciences.2nd edition. New York: McGraw Hill. 2005
2. Michael J. Moran, Howard N. Shapiro. Fundamentals of Engineering
Thermodynamics. 5th edition. N.J: John Wiley & Sons, Inc. 2004
3. Richard.E.Sonntag, Claus Borgnakke, Gordon J. Van Wylen. Fundamentals of
Thermodynamics.6th edition. N.J.: John Wiley & Sons, Inc. 2003
4. Irving Granet, Maurice Bluestein. Thermodynamics and Heat Power. 7th edition.
N.J:
Pearson Prentice Hall. 2004
5. Merle C. Potter and Elaine P. Scott. Thermal Science: An Introduction to
Thermodynamics, Fluid Mechanics and Heat Transfer. Belmont, USA:
Brooks/Cole Inc. Thomson Learning. 2004
6. J.D Booker, M.Raines, K.G. Swift. Designing Capable and Reliable Products.
Oxford: Butterworth Heinemann. 2001
7. Kevin N. Otto, Kristin L. Wood. Product Design: Techniques in Reverse
Engineering and New Product Development. N.J.: Prentice-Hall. 2001
8. Henry W. Stoll . Product Design Methods and Practices. New York: Marcel
Dekker, Inc. 1999
9. Karl T. Ulrich, Steven D. Eppinger. Product Design and Development. 3rd
edition.
NY.: McGraw Hill. 2004
10. Mike Baxter. Product Design: A Practical Guide to Systematic Methods of New
Product Development. Cheltenham,U.K.:Stanley Thornes Publishers Ltd. 1999
11. Beno
Benhabib.
Manufacturing,
Design,
Production,
Automation
and
Intergration. New York.: Marcel Dekker, Inc. 2003
12. G. Boothroyd, Peter Dewhurst and Winston Knight. Product Design for
Manufacture and Assembly.2nd edition. New York.: Marcel Dekker, Inc. 2002
146
APPENDIX
Appendix A1
Appendix A2
147
Appendix B1
148
Appendix B2
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Appendix B3
151
Appendix B3 – continued
152
Appendix B3 – continued
153
Appendix B3 – continued
154
Appendix C
Data for estimated times for manual handling (Boothroyd-Dewhurst)
155
Appendix D
Data for estimated times for manual insertion (Boothroyd-Dewhurst)
156
Appendix E
Lucas DFA method - Manual Handling Analysis
Handling Index = A+B+C+D
A. Size & Weight of Part
One of the following
Very small - requires tools
Convenient - hands only
Large and/or heavy
requires more than 1 hand
Large and/or heavy
requires hoist or 2 people
C. Orientation of Part
One of the following:
Symmetrical, no orientation req'd
End to end, easy to see
End to end, not visible
B. Handling difficulties
All that apply
1.5
1
1.5
3
Delicate
Flexible
Sticky
Tangible
Severely nest
Sharp/Abrasive
Untouchable
Gripping problem / slippery
No handling difficulties
D. Rotational Orientation of Part
One of the following
0 Rotational Symmetry
0.1 Rotational Orientation, easy to see
0.5 Rotational Orientation, hard to see
0.4
0.6
0.5
0.8
0.7
0.3
0.5
0.2
0
0
0.2
0.4
Lucas DFA method - Manual Fitting Analysis
Fitting Index = A+B+C+D+E+F
A. Part Placing and Fastening
One of the following
Self-holding orientation
Requires holding
Plus 1 of the following
Self-securing (i.e. snaps)
Screwing
Riveting
Bending
1.3
4.0
4.0
4.0
B. Process Direction
One of the following
Straight line from above
Straight line not from above
Not a straight line
E. Alignment
One of the following
0 Easy to align
0.1 Difficult to align
1.6
C. Insertion
One of the following
F. Insertion Force
One of the following
0 No resistance to insertion
0.7 Resistance to insertion
1.2
Single
Multiple insertions
Simultaneous multiple insertions
D. Access and/or Vision
One of the following
1.0 Direct
2.0 Restricted
0
1.5
0
0.7
0
0.6