ANALYSIS OF SPINDLE COOLING SYSTEM
NOEL CHRISTOPHER CHAN
Report submitted in partial fulfillment of the requirements
for the awards of Bachelor of Mechanical Engineering
Faculty of Mechanical Engineering
UNIVERSITI MALAYSIA PAHANG
JUNE 2013
vii
ABSTRACT
Modern technology has shown that machine tool has played great roles in
technology advances and is an ever-increasing productivity and competency throughout
ages. The vital developments in industrialize machining was the usage of high speed
machining which includes the motorized high speed spindle in manufacturing
industries. This development has break the problems regarding delayed time and lower
output in production line. However, heat was the primary enemy in this research.
Overheating or excessive heat generation has caused lack in accuracy and precision in
machining, exposure to wear and fatigue was the result of inefficient cooling system in
the spindle cooling system. Thus, an analysis on the spindle cooling system through
three parameters; different spindle operating speed, type of coolant and number of
radiators has experimented. The result shows that higher operating speed produces more
heat around the spindle. Moreover, results also demonstrate higher thermal stability in
Ethylene glycol and water (EGW) compared to water at the peak of 6th
and 12th
hour
respectively. In addition, EGW has a significant percentage of efficiency approximately
10% by using single and more than 15% using dual radiator at the minimal speed and
astonishing efficiency of more than 39% and 52% for single and dual radiators
respectively at speed, 18,000 rpm. In contrast, water only has below 10% of efficiency
in any condition of experiment. In conclusion, EGW with single radiator is
economically sufficient to remove heat generated in the spindle with efficiency of
between 10% and 39% with lower power consumption of 6 Watts.
viii
ABSTRAK
Teknologi moden telah menunjukkan bahawa alat mesin telah memainkan
peranan yang besar dalam kemajuan teknologi dan merupakan produktiviti yang
semakin meningkat dan kecekapan sepanjang zaman. Perkembangan penting dalam
industrialisasi pemesinan adalah penggunaan mesin kelajuan tinggi yang merangkumi
spindle bermotor pada kelajuan tinggi dalam industri pembuatan. Perkembangan ini
telah menyelesaikan masalah kesuntukan masa dan output yang rendah di barisan
pengeluaran. Walau bagaimanapun, haba adalah musuh utama dalam kajian ini.
Penjanaan haba terlampau panas atau berlebihan telah menyebabkan kekurangan dari
segi ketepatan dan kejituan dalam pemesinan. Pendedahan kepada haba yang terlampau
menyebabkan kehausan dan kerosakan akibat ketidakcekapan sistem penyejukan. Oleh
itu, analisis pada sistem penyejukan spindle melalui tiga parameter; kelajuan operasi
spindle yang berbeza, jenis penyejuk dan pengunaan radiator. Hasil kajian menunjukkan
bahawa kelajuan operasi yang lebih tinggi menghasilkan lebih banyak haba sekitar
spindle. Selain itu, keputusan juga menunjukkan kestabilan terma yang lebih tinggi
dalam etilena glikol dan air (EGW) berbanding dengan air di puncak jam ke-6 dan ke-
12 masing-masing. Di samping itu, EGW mempunyai peratusan kecekapan kira-kira
10% dengan menggunakan satu radiator dan lebih daripada 15% menggunakan dwi-
radiator pada kelajuan minimum. Manakala, kecekapan menakjubkan lebih daripada
39% dan 52% untuk radiator satu dan dwi-radiator pada kelajuan maksima 18,000 rpm.
Sebaliknya air hanya mempunyai kurang daripada 10% daripada kecekapan dalam
mana-mana eksperimen. Kesimpulannya, EGW dengan satu radiator adalah memadai
dari segi ekonomi untuk mengeluarkan haba yang dijana dalam spindle dengan
kecekapan dalam lingkungan 10% dan 39% dengan penggunaan kuasa yang rendah
pada 6 Watt.
ix
TABLE OF CONTENTS
Page
EXAMINER’S DECLARATION ii
SUPERVISOR’S DECLARATION iii
STUDENT’S DECLARATION iv
ACKNOWLEDGEMENTS vi
ABSTRACT vii
ABSTRAK vii
TABLE OF CONTENTS ix
LIST OF TABLES xii
LIST OF FIGURES xiv
LIST OF SYMBOLS xvii
LIST OF ABBREVIATIONS xviii
CHAPTER I INTRODUCTION
1.0 Introduction 1
1.1 Research Background 1
1.2 Problem Statement 3
1.3 Research Objective 3
1.4 Research Scope 3
CHAPTER II LITERATURE REVIEW
2.0 Introduction 4
2.1 Machining in Manufacturing Processes 4
2.2 Milling Machine 6
2.3 Milling Operations 7
2.3.1 Face Milling 7
2.3.2 Profiling 8
2.3.3 Drilling 9
2.3.4 Boring 9
2.4 Type of Milling Machine 10
2.4.1 Milling Machine Construction 11
2.4.2 Column-and-Knee Type Milling Machine 13
x
2.4.2.1 Plain Milling Machine 14
2.4.2.2 Universal Milling Machine 14
2.4.2.3 Vertical Spindle Milling Machine 15
2.4.3 Bed Type Milling Machine 16
2.5 Gantry Type Milling Machine 17
2.5.1 Construction of Gantry Type Milling Machine 18
2.6 Milling Machine Spindle 19
2.6.1 Structure of Spindle 20
2.6.2 Spindle Motor as Source of Heat 21
2.6.3 Energy Analysis of Steady Flow System 22
2.6.4 Thermal Expansion 22
2.6.5 Thermal Deformation in Spindle 24
2.6.6 Analysis of Heat Transfer through Motorized Spindle 25
2.7 Spindle Cooling System 26
2.7.1 Air-Cooled System 28
2.7.2 Liquid-Cooling System 29
2.7.2.1 Water as Fluid-Cooling System 30
2.7.2.2 Inhibited Glycols as Fluid-Cooling System 31
2.7.3 Radiator 32
2.7.3.1 Working Principles of Radiator 32
CHAPTER III METHODOLOGY
3.0 Introduction 33
3.1 Flow Chart Methodology 33
3.2 Material & Equipment Setup 35
3.2.1 Motorized High Speed Spindle 35
3.2.2 Type of Coolant 36
3.2.3 Temperature Sensor 37
3.2.4 Radiator and Fan 38
3.2.5 Pump 39
3.3 Standard Operating Procedure 41
3.3.1 Safety Precautions 41
xi
3.3.2 Procedure 41
3.3.3 Result Table 43
3.4 Summary 45
CHAPTER IV RESULT & DISCUSSION
4.0 Introduction 46
4.1 Result 46
4.1.1 Result with Water as Medium of Cooling Fluid 47
4.1.2 Result with EGW as Medium of Cooling Fluid 51
4.2 Discussion 56
4.2.1 Source of Heat 56
4.2.2 Effect of Load 58
4.2.3 Effect of High Speed 58
4.2.4 Thermal Behaviour 59
4.2.5 Effect of Cooling Fluid 61
4.2.6 Energy Effect of Steady Flow System 63
4.3 Efficiency of Medium Cooling Fluid 67
4.4 Power Consumption 69
CHAPTER V CONCLUSION
5.0 Introduction 71
5.1 Conclusion Summary 71
5.2 Recommendations 72
REFERENCES 73
APPENDICES
A1 Spindle Cooling System Machine 78
B1 Gantt Chart for FYP 1 79
B2 Gantt Chart for FYP 2 80
xii
LIST OF TABLES
Table No. Page
2.1 Thermal Expansion Coefficients for Materials used in
Machine Tool Structures and Work piece Materials
24
2.2 Material and Fluid Compatibility 30
2.3 Minimum Requirement for Good Quality Water 31
3.1 Result for Experiment I-No Flow Test at 50Hz 43
3.2 Result for Experiment II- Flow with Single Radiator
Fan at 6000 rpm
44
3.3 Result for Experiment III- Flow with Dual Radiator
Fan at 6000 rpm
44
4.1 Time vs. Temperature Rise at Operating Speed of
6,000 rpm using water as Cooling Fluid
47
4.2 Time vs. Temperature Rise at Operating Speed of
12,000 rpm using water as Cooling Fluid
49
4.3 Time vs. Temperature Rise at Operating Speed of
18,000 rpm using water as Cooling Fluid
50
4.4 Time vs. Temperature Rise at Operating Speed of
6,000 rpm using EGW as Cooling Fluid
51
4.5 Time vs. Temperature Rise at Operating Speed of
12,000 rpm using EGW as Cooling Fluid
53
4.6 Time vs. Temperature Rise at Operating Speed of
18,000 rpm using EGW as Cooling Fluid
55
4.7 Shaft Deformation at Three Operating Speed with
Water and EGW as Cooling Fluid
60
4.8 Summary of Physical Properties of Materials 63
xiii
4.9 Heat Transfer Rate of Water as Cooling Fluid 64
4.10 Heat Transfer Rate of EGW as Cooling Fluid 65
4.11 The Efficiency Effectiveness by Medium of Fluid 68
xiv
LIST OF FIGURES
Figure No. Page
2.1 Boring Mill from Wilkinson's iron works 5
2.2 Electrical-Discharge Machining (EDM) 6
2.3 Eli Whitney Milling Machine 6
2.4 Face Milling Operation 8
2.5 Profiling or Peripheral Cutting 8
2.6 Drilling Operation 9
2.7 Boring Operation 10
2.8 Vertical and Horizontal Milling Machine 11
2.9 Plain-type Milling Horizontal Machine 14
2.10 Universal type Horizontal Milling Machine 15
2.11 Vertical Spindle Milling Machine 16
2.12 Bed-type Milling Machine 17
2.13 Gantry-type Milling Machine 18
2.14 Structure of High Speed Motorized Spindle 21
2.15 The Trend of the Spindle Speed and Power 25
2.16 Temperature Distributions in Spindle Parts 26
2.17 Coolant Jacket in High Speed Motorized spindle 27
2.18 Basic Components in a Cooling System 28
2.19 Air-cooled Systems in Spindle that removes Heat through
Fins
29
xv
3.1 Process flowchart of Spindle Cooling System Experiment 34
3.2 1.5 kW water-cooled spindles with a variable frequency
drive (VFD) inverter used as a motorized spindle
36
3.3 Ethylene Glycol and water (EGW) to be used as a medium of
cooling fluid with corrosion protection
37
3.4 Digital Thermometer Temperature Sensors used to record
temperatures
38
3.5 AX240 Dual Fan Radiator that functions like a heat
exchanger in the cooling system
39
3.6 12V Phobya DC12-400 Water Pump & Reservoir Combo
used to circulate the fluid medium in the water-cooling
system
40
4.1 Time vs. Temperature Graph for 6,000 rpm with Water
as Cooling Fluid
47
4.2 Time vs. Temperature Graph for 12,000 rpm with Water
as Cooling Fluid
49
4.3 Time vs. Temperature Graph for 18,000 rpm with Water
as Cooling Fluid
50
4.4 Time vs. Temperature Graph for 6,000 rpm with EGW
as Cooling Fluid
52
4.5 Time vs. Temperature Graph for 12,000 rpm with EGW
as Cooling Fluid
54
4.6 Time vs. Temperature Graph for 18,000 rpm with EGW
as Cooling Fluid
55
4.7 Physical Model for Heat Source in Spindle System 57
4.8 Main Spindle Temperatures during 3.5 Working Hours 59
4.9 Speed vs. Heat Transfer Rate Graph with Water
as Cooling Fluid
64
xvi
4.10 Speed vs. Heat Transfer Rate Graph with EGW
as Cooling Fluid
66
4.11 Graph of Speed vs. Efficiency of Water and EGW 68
A1 Machine used in Spindle Cooling System Analysis 76
xvii
LIST OF SYMBOLS
α Thermal Expansion Coefficient
ρ Density
Δ Difference or Changes
Cp Specific Heat Capacity
K Thermal Conductivity
xviii
ABBREVIATIONS
AC Alternating Current
CNC Computer Numerical Controller
DC Direct Current
DOC Depth of Cut
EDM Electrical-Discharge Machining
EGW Ethylene Glycol and Water
ETVE Environmental Temperature Variation Error
ISO International Organization of Standards
LBM Laser Beam Machining
MQL Minimum Quantity of Lubricant
PAO Polyalphaolefin
PGW Propylene Glycol and Water
RE Radial Engagement
SOP Standard Operating Procedure
USM Ultrasonic Machining
VFD Variable Frequency Drive Inverter
CHAPTER I
INTRODUCTION
1.0 INTRODUCTION
This chapter introduces readers for a better understanding of this project. This
chapter compromise of research background, problem statement, research objectives
and research scope.
1.1 RESEARCH BACKGROUND
Manufacturing constitutes the economic background of an industrialized nation
and, is the key factor in industrial and equipment evolution, and as such, sustaining a
country’s economic position and improving man’s quality of life. Throughout the
centuries, machine tools have been manufactured, evolved and perfected to meet a
current market challenge which is seen as a catalyst for changes in manufacturing
technologies and system.
In the past thirty years, machines have been revolutionized with the
incorporation of numerical control, which is a treat to traditional machines, such as
lathes, milling machines, grinders and etc. However, with highly sophisticated
knowledge-based systems, these traditional machines have evolved into a more capable
multi-task machine of milling, grinding, drilling turning and etc., all in one system
(López L. N. and Lamikiz A., 2009). Through rapid developments of machine tools, the
lathe was evolved through time, developments and numerical control into a more
functioning milling machine based on the spindle axis itself. As of today, the vertical
2
milling machine is the most commonly used machinery in manufacturing industry
compared to the horizontal, boring and lathe milling machine and etc.
Moreover, industries have shifted towards high speed machining and advanced
machining for a more advanced digital control, higher speeds, precise accuracy and
greater flexibility that encourages technological competitiveness of productivity and
manufacturing processes. Besides that, importance of high speed machining (HSM) is
assumed to assist industries in striving to raise their production demand and revenue by
increasing the machineries cutting speed and manufacturing processes in the same
amount of time.
Motorized high speed machining has help industries to overcome many
problems with low output on production floor. Long operating hours on machining has
become a common aspect in manufacturing industries, however, the risk in shorting the
lifespan of the machine is at stake. In various milling machine operations, the spindle
functions to shape the work piece into desired designs of products. However, to meet
tight datelines, the motorized high speed spindles operating continuously causes
excessive heat generation and thermal deformation in spindles.
Nevertheless, excessive heat generation and thermal deformation in spindles
contributes to low accuracy and precision in machining, lack of flexibility, and reduces
lifespan of the bearings and the whole spindle system. A spindle cooling system is the
solution to this dilemma. A spindle cooling system is divided into air-cooled and liquid-
cooled system. Liquid cooling system has proven advantages and contribution over air-
cooled system.
A research on liquid-cooling system based on three parameters; different
operating spindle speed, type of coolant and number of radiators are studied to
overcome this heat generation build-up in motor spindle to fully-utilized the usage of
spindle in machining.
3
1.2 PROBLEM STATEMENT
A common problem in manufacturing industries is the heat generated in
motorized components, for example, the heat generation motorized high speed spindle
in milling machine operation. The spindle works to shape and perform material removal
on raw materials by computer numerical control (CNC) system into desired end
products. However, operating at long hours puts the spindle in risk of spindle failure
(Zitney E., 2012). Thus a research to study and optimize the spindle cooling system
with standard parameters is required. Moreover, experimental researches on the effect of
different operating speed with radiator are investigated. Then, a conclusion is drawn to
validate the efficiency of the optimum spindle cooling system.
1.3 RESEARCH OBJECTIVES
The objectives of this research are as follow;
To conduct a fundamental studies on milling machine operations.
To study the spindle cooling system in milling machine.
To develop an optimum result of liquid-cooled spindle cooling system using
suggested parameters.
To test the water-cooling system’s efficiency.
1.4 RESEARCH SCOPE
The spindle cooling system is the primary focus of this research. The spindle
structure and spindle cooling system were investigated. Next, experiments based on
suggested parameters are considered. The proposed parameters; such as medium of
fluid-cooling system, different operating speed (rpm) and usage of radiators were tested
experimentally to study the effects on increasing spindle speed with temperature rise.
Moreover, the outcomes validated were the trend of temperature rise, optimum medium
of fluid in liquid-cooled spindle cooling system and percentage efficiency of the liquid-
cooling system.
CHAPTER II
LITERATURE REVIEW
2.0 INTRODUCTION
Today’s development and prosperity of the world was governed and judged by
transformation, improvement and upholding of the standard of living and challenges in
manufacturing industries. Manufacturing activities has contributes to a country’s
economic position; which now becomes a modern rivalry in technology development.
Manufacturing process is as a value added processes where raw materials are
removed into high utility and valued products with distinct shape and sizes, surface
quality and functionality. Manufacturing incorporates a variety of processes which
includes casting, molding, forming, machining, joining, rapid manufacturing and etc.
2.1 MACHINING IN MANUFACTURING PROCESSES
Machining is one of the most important elements in manufacturing processes as
it drives the economic system towards mass production with increasing demands from
consumers. Traditional machining and advanced machining has embark on a journey for
better precision, quality and functionality as the industry faces challenges to fulfill
consumers requirements and specifications. By definition, machining is one of the
various processes of material removal of raw materials into desired shape and sizes in
the form of chips, and was collectively themed as subtractive manufacturing.
Apart from that, conventional machining started back in the 18th
century when
an Englishman, John Wilkinson’s “boring mill” that was water-powered; over time, this
5
space for improvement gives alternatives for machines to be steam-powered, leather
belts gearing system and finally electric-powered. The next important development in
machining was the milling machine. As machining process improves, processes such as;
turning, boring, drilling, milling, broaching, sawing, shaping, planning, reaming, and
tapping became more essential.
Figure 2.1: Boring mill from Wilkinson's iron works, Bersham, Wales, 1775
Source: Science & Society (2012)
By contrast, the advent of new technologies makes advanced machining seem
slightly valuable as industries begin strive to escalate their production and revenue. One
of the importances of advanced machining is the need to machine newly developed
materials with special properties into intrinsic part geometries, without having surface
damages that can be found through conventional machining. To be precise, advanced
machining processes includes Electrical-Discharge Machining (EDM), Laser Beam
Machining (LBM), Ultrasonic Machining (USM), Water jet Machining, Photochemical
machining and etc.
6
Figure 2.2: Electrical-Discharge Machining (EDM)
Source: CIM Industries (2010)
2.2 MILLING MACHINE
The milling machine was one of the most important developments in the history
of machine tools. The milling machine was evolved from the practice or rotary filing in
the headstock of a lathe which, dated back in 1760. Between 1912 and 1916, Eli
Whitney was the first to invent and developed the true milling machine to produce
interchangeable musket parts with the help of power feed, but there were limitations
towards Whitney’s milling machine; the lack of provision to lift the worktable and lack
standardization of measurements at that moment.
Figure 2.3: Eli Whitney milling machine dated back to circa 1818
Source: www.robinsonlibrary.com (2012)
7
Besides the limitation’s on Whitney’s design, the milling machine had an
advantage of duplicating the part that could not been manufactured using a file; which
was, maintaining the accuracy and uniformity of the design. The advent of technologies
have brought a wide varieties of cutting operations on the milling machine, which made
the milling machine to have more variations compared to any other family of machine
tools.
In addition, improvements and development of the milling machines and
components have made the milling machine to improvise on material removal rate
(MRR), high accuracy and precision, increasing quality finishing, minimizing errors,
and reducing component wear life.
2.3 MILLING OPERATIONS
According to the National Machine Tool Builders Association (2011), milling
machine is sold nearly 80 percent in North America as milling is the central issue in
machining. As of today, the milling machines can perform a wide range of tasks
compared to their primary duty, which was to create flat and square surfaces. Moreover,
they shape metal by rotating the cutter and moving it along an axis through the work
piece manually. As of today, there are 12 common operation that are divided into four
main types; facing, profiling, drilling and boring as explained below.
2.3.1 FACE MILLING
Face milling is the most basic operation in milling machine operation. Basically,
face milling is a process of cutting a flat surface using end of the cutter teeth by
lowering the cutter below the working surface to the depth of cut (DOC), then setting
the engaging of work at a given portion of it diameter, called radial engagement (RE).
The most desirable RE is at 66 percent to lengthen the tool life.
8
Figure 2.4: Face milling operation
Source: CustomPart.Net (2009)
2.3.2 PROFILING
Peripheral cutting is also known as profiling. Profiling is a process of cutting
around the outside or inside surface of the workpiece or a part by using the side teeth of
the cutter. Usually, end mill is used as the cutter in any profiling milling operations.
Figure 2.5: Profiling or Peripheral Cutting
Source: CustomPart.Net (2009)
9
2.3.3 DRILLING
Drilling or reaming is a process of performing a hole or hollow opening. Hole-
drilling is usually performed on the milling machine when the hole’s position tolerance
is tighter than the drill press accuracy. The advantages using the milling machine to drill
is that the mill spindles are more rigid compared to drill press and it does not require a
center drill to aid the location accuracy as the position of work piece are lock onto the
working table.
Figure 2.6: Drilling operation
Source: CustomPart.Net (2009)
2.3.4 BORING
Boring is a process done after drilling to give the best location solution by using
a rotating, adjustable cutter called boring head. In this operation, a hole is first milled or
drilled, then workpiece are taken by dialing the boring tool outward to a bigger radius,
then machining passing through a hole. A single-point tool and several passes are used
to eliminate out-of-roundness and mis-positioning of the rough hole as boring process
tends to machine the hole precisely on the location, very round and straight through the
work, without wandering from initial position.
10
Figure 2.7: Boring operation
Source: CustomPart.Net (2009)
Besides that, the milling machine has other operational methods; such as, step
and pocket milling, angular cutting, forming cuts, arbor cutter work, indexed and spaced
work, and rotary table work. Moreover, this machine operation can be done over the
horizontal or vertical milling machine.
2.4 TYPE OF MILLING MACHINE
Milling machines are difficult to classify as there are various categories of
milling machine, and the machines tends to merge within one another. However, they
are basically classified into horizontal and vertical milling machine based on the axis of
the milling machine spindle.
In horizontal spindle milling machine, the cutters are fit onto an arbor mounted
in the milling machine on an axis parallel to the working table. Multiple cutters can also
be mounted onto the spindle for some machining operations. However, cutters on the
vertical spindle milling machine are placed perpendicular to the working table; but on
some occasions, the spindles can be tilted to perform angular cutting operation on the
milling machine.
11
The milling machine are also classified into groups as bed-type, knee-type, ram-
type and planer-type milling machines. These machines have their own self-sufficient
electric drive motor, coolant system, variable spindle speed and power operated table
feeds.
Figure 2.8: Vertical and Horizontal Milling Machine
Source: American Machine Tools Corporation (2012)
2.4.1 MILLING MACHINE CONSTRUCTION
The principle parts of a milling machine (See Figure 2.8) are as follow;
Base. The base serves as the foundation member for all parts that rests on it. It
also carries the column at one end while in some machines; the base is left
hollowed and works as a reservoir for cutting fluid.
Column. The box shaped that mainly supports the frame that is mounted
vertically on the base. The column is heavily ribbed on the inside and houses all
