The Study On The Effect Of Water Composition In Coolant To The Surface Condition Of Workspiece.
THE STUDY ON THE EFFECTS OF WATER
COMPOSITION IN COOLANT TO THE SURFACE
CONDITION OF WORKPIECE
NOORLAINIEWATI BINTI ABDULLAH
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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
THE STUDY ON THE EFFECTS OF WATER COMPOSITION IN
COOLANT TO THE SURFACE CONDITION OF WORKPIECE
This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) with Honours.
by
NOORLAINIEWATI BINTI ABDULLAH
FACULTY OF MANUFACTURING ENGINEERING 2009
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DECLARATION
I hereby, declared this report entitled “The effect of water composition in coolant to the surface condition of workpiece” is the results of my own research except as cited in references.
Signature : ... Author’s Name : Noorlainiewati binti Abdullah Date : 22nd May 2009
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APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of Universiti Teknikal Malaysia Melaka as a partial fulfilment of the requirements for the degree of Bachelor of Manufacturing Engineering (Manufacturing Process) with Honours. The member of the supervisory committee is as follow:
Signature : ... Supervisor’s Name : Mohammad Kamil bin Sued Date : 22nd May 2009
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ABSTRACT
In this study, an attempt has been made to investigate the effect of water composition in coolant to the surface condition in turning of low carbon steel using coated carbide cutting tool. The machining experiment is conducted on computer numerical control lathe machine and using water miscible cutting fluid as coolant. Three cutting parameters, cutting speed, feed rate and depth of cut are fixed at 107 mm/min, 0.05 mm/rev and 0.2 mm respectively. The composition of water in coolant is varied from 92%, 94%, 96% and 98%. The turning operation is done using the above-mentioned parameters and the result obtained is analyzed using surface profilometer for surface roughness and stereo microscope for rust formation. It is found that water composition in coolant is not giving any significant result to the surface roughness of a workpiece. The chip produced after every machining process is influenced by the machining condition and the rust formation area is increased with the respect to the time and it is also not influenced by the water composition in coolant.
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ABSTRAK
Dalam kajian ini, percubaan telah dilakukan untuk menentukan kesan komposisi air dalam kepekatan cecair pemotong terhadap keadaan permukaan keluli berkandungan karbon rendah menggunakan alat pemotong jenis karbaid tidak bersalut. Eksperimen pemesinan telah dilakukan di atas mesin larik kawalan komputer bernombor dan menggunakan cecair pemotong larut air sebagai penyejuk. Tiga parameter pemotongan, halaju memotong, kadar pemotongan dan kedalaman potongan telah ditetapkan pada 107 mm/min, 0.05 mm/putaran dan 0.2 mm. Operasi pemusingan dilakukan dengan menggunakan parameter yang dinyatakan di atas dan keputusan yang diperoleh dianalisis menggunakan profilometer untuk kekasaran permukaan dan mikroskop stereo untuk kawasan kemunculan karat. Komposisi air dalam penyejuk didapati tidak memberi sebarang keputusan bermakna terhadap kekasaran permukaan bahan kerja. Serpihan yang dihasilkan selepas setiap proses pemesinan dipengaruhi oleh keadaan pemesinan dan kemunculan karat adalah meningkat mengikut masa dan ia juga tidak dipengaruhi oleh komposisi air di dalam cecair pemotong.
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DEDICATION
To my beloved parents:
Encik Abdullah Musa & Puan Faridah Hussein
&
To my supportive siblings: Roslina
Mohd Fazlie Rosmalina Mohd Faiz Faizal
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ACKNOWLEDGEMENT
First and foremost, ALHAMDULILLAH, I have completed this study with the help of so many people. My most gratitude is for my supportive family, my supervisor, En. Mohammad Kamil Sued, my panels, En. Mohamadd Nizam Ayof, Dr. Zamberi Jamaludin and En. Wahyono Sapto Widodo and CNC lathe machine technician En. Fauzi. With their helps, comments, ideas and suggestion were helping me in the completion of this Projek Sarjana Muda. The knowledge and experiences I gained from this study is very valuable and will not be forgotten.
I am also obliged to everyone who had directly and indirectly involve through the contributions of ideas, as well as materials and professional opinions. Finally, to all my dear friends who are always giving the support and opinion while I am struggling to complete this study.
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TABLE OF CONTENTS
Abstract i
Abstrak ii
Dedication iii
Acknowledgement iv
Table of Contents v
List of Tables viii
List of Figures ix
List of Abbreviations xi
CHAPTER 1 INTRODUCTION
1.1 Introduction of Study 1
1.2 Problem Statement 3
1.3 Objectives 3
1.4 Scope of Study 3
CHAPTER 2 LITERATURE REVIEW
2.1 Usage of Cutting Fluid/Lubricant in Machining Process 5 2.2 Turning Process 6
2.3 Cutting Tool 9
2.4 Material of Workpiece 12
2.5 Coolant 13
2.6 Chip Formation 16
2.7 Surface Finish 20
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vi CHAPTER 3 METHODOLOGY
3.1 General Procedure 28
3.2 Flow Chart 29
3.3 Tool and Equipment 30
3.3.1 HAAS SL Turning Center 30 3.3.2 Surface Profilometer 32 3.3.3 Zoom Stereo Microscope 33 3.4 Machining Preparation 34
3.4.1 Workpiece Material 34
3.4.2 Cutting Tool 35
3.4.3 Coolant 36
3.4.4 Experiment Setup 37
3.5 Machining Operation 38
3.5.1 Turning Process 38
3.6 Measurement Process 39
3.6.1 Surface Roughness 39
3.6.2 Chip Formation 40
3.6.3 Rust Formation 40
CHAPTER 4 RESULTS & DISCUSSION
4.1 Results 42
4.1.1 Surface Roughness 42
4.1.2 Chip Formation 47
4.1.3 Rust Formation 51
4.2 Discussion 54
4.2.1 Surface Roughness 54
4.2.2 Chip Formation 55
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CHAPTER 5 DICUSSION & RECOMMENDATIONS
5.1 Conclusion 58
5.2 Recommendation for Future Work 59
REFERENCES 61
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viii
LIST OF TABLES
4.1 Surface roughness values obtained after turning process with 2% of
coolant concentration 43 4.2 Surface roughness values obtained after turning process with 4% of
coolant concentration 44 4.3 Surface roughness values obtained after turning process with 6% of
coolant concentration 45 4.4 Surface roughness values obtained after turning process with 8% of
coolant concentration 46 4.5 Types of chip produced and their length after every machining process 47 4.6 Rust formation area in first week 51 4.7 Rust formation area in second week 52 4.8 Comparison between Week 1 and Week 2 53
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LIST OF FIGURES
2.1 Schematic illustration of the cutting process with a single-point tool 7 2.2 Modes of turning: (a) radial; (b) axial; (c) face 8 2.3 Schematic drawing of cutting tool angles 11
2.4 Mild Steel Rod 12
2.5 Methods showing proper and improper application of coolant in turning
process 15
2.6 Mechanics of chip formation by cutting with a tool 16 2.7 Types of chips obtained in metal cutting 17 2.8 Various surface profiles with the same surface roughness value 20 2.9 Surface produced by an angular tool 21 2.10 Surface finish terminology and symbols 22 2.11 Typical roughness values produced by various processes 23 2.12 Schematic diagram of corrosion process 25 2.13 Eight types of corrosion damage 26
3.1 Flow chart of proposed procedures used in this study 29 3.2 HAAS SL Turning Center 30 3.3 A Mitutoyo SJ-301 Surf Test 32 3.4 EMZ 13TR Zoom 33
3.5 Mild Steel Rod 34
3.6 The rod ends after sawing process 34 3.7 The rod ends after facing and center-drilling process 34 3.8 Diamond-shape cutting tool 35 3.9 SVJBR 2525 M16 Tool Holder 35
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3.10 Schematic drawing of cutting tool geometries 35
3.11 SYNCOOL 300G coolant 36
3.12 Mild steel rods before (lower) and after (after) turning process 38
3.13 Surface roughness measurement process for workpiece after turning process 39 3.14 Zoom stereo microscope for measuring rust formation area 40
3.15 Examples of corrosion area on the workpiece 41
4.1 Graph of surface roughness values for usage of 2% coolant concentration 43
4.2 Graph of surface roughness values for usage of 4% coolant concentration 44
4.3 Graph of surface roughness values for usage of 6% coolant concentration 45
4.4 Graph of surface roughness values for usage of 8% coolant concentration 46
4.5 WP1:155 mm 48
4.6 WP5: 18 mm 48
4.7 WP6: 90 mm 48
4.8 WP8: 90 mm 48
4.9 WP9: 55 mm 49
4.10 WP10:20 mm 49
4.11 WP11:93 mm 49
4.12 WP12:40 mm 49
4.13 WP2: 5 mm 50
4.14 WP3: 3 mm 50
4.15 WP4: 9 mm 50
4.16 WP7: 9 mm 50
4.17 Surface roughness value for all coolant concentration 54 4.18 Graph of comparison of rust formation area ratio between week 1 and week 2 56
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LIST OF ABBREVIATION
AISI - American Iron and Steel Institute BUE - Built-up Edge
C - Continuous
CNC - Computerizes numerically controlled d - Depth of cut
DC - Discontinuous f - Feed rate HSS - High speed steel
ISO - International Organization for Standardization LED - Light emitting diode
m/min - meter/minutes mm - millimeter
mm/rev - millimeter/revolution MRR - Material Removal Rate Ra - Average surface roughness RPM - Revolution per minute
SEM - Scanning electron microscope TiAlN - Titanium aluminum nitride TiC - Titanium carbide
TiCN - Titanium carbon nitride TiN - Titanium nitride
v - Cutting speed WC - Tungsten carbide WP - Workpiece
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CHAPTER 1
INTRODUCTION
1.1 Background
Machining is a process to cut, shape, or finish by machine. In cutting, the process may include drilling, forming, or grinding of a workpiece. Machining is also a group of processes that consist of the removal of material and modification of the surfaces of workpiece after it has been produced by various methods. Machining involves secondary and finishing operations. This study will discuss about one of three major types of material-removing processes which involving single-point and multi-point cutting tools that is turning operation.
A system of machining consists of workpiece, cutting tool, machine tool, and production personnel (Kalpakjian, 2006). The factors or variables that influenced machining can be divided into independent and dependent variables. The independent variables in cutting process are: tool material and coatings, tool shape, surface finish, and sharpness, workpiece material and conditions, cutting speed, feed rate, and depth of cut, cutting fluids, characteristics of the machine tool and work-holding and fixturing. The dependent variables in cutting are those that influenced by changes in the independent variables. They are: type of chip produced, force and energy dissipated during cutting, temperature rise in the workpiece, the tool and the chip, tool wear and failure, and surface finish and surface integrity of the workpiece.
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In machining process, there are various types of material being used. The common materials machined are carbon steel, aluminium, tool steel, high speed steel, brass, and etc. These materials are machined according to their application. Thus, surface roughness is an important aspect in determining the quality of the finish product. The value of surface roughness desired is small and as smooth as possible. Based on the product requirement, the smaller Ra value obtained, the surface finish of the product is better.
A lot of studies are done in order to determine the best cutting parameters to be used in order to produce the best surface finish. In previous studies, the value of surface roughness is determined by the cutting parameters such as depth of cut, cutting speed, feed rate, cutting force and etc. which had been varied in order to get the best result. The major influence in determining good surface finish is feed rate. The feed rate provides primary contribution in influences most significantly on the surface roughness while cutting speed has no significant effect on surface roughness (Lalwani et al. 2008) similar to the depth of cut (Kassab et al. 2007).
As effect of water composition towards surface roughness is not widely discussed. So, this study has taken the opportunity to investigate the effect of water composition in coolant to the surface roughness. This effect will be studied through turning process with mild steel as the material. The surface roughness values will be analyzed after the workpiece being turned using different value of coolant concentration that varied from 2% to 8%. Each concentration will have three different workpiece with same dimension to be experimentally machined. So, total of the workpieces machined are twelve. The value of surface roughness will be compared to determine either they are directly proportional to the increment of coolant concentration or not.
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1.2 Problem Statement
Coolant is a cutting fluid that is widely used in machining process to reduce frictional heating, and removing chips produced by workpiece. It is also give an effect on the surface quality, shape, dimensional accuracy of a workpiece also the ability in enhancing the tool life, and protecting the workpiece from corrosion. But, the less usage of coolant will reduce operational cost and also create green machining environment. The previous researches mostly studied on the cutting parameters like cutting speed, feed rate and depth of cut on the surface roughness but not on the contribution and effect of coolant itself. This study will investigate the effect of the coolant with different concentration on the surface roughness values of the workpiece after being turned. After the machining process is done, there will be formation of rust on the material as mild steel is widely known have high tendency of corrosion. The area ratio on the workpiece also will be determined. Beside that, the chip formation for every workpiece also being observed after every turning process in order to investigate the types of chip produced.
1.3 Objectives
The objectives of this study are to:
1. Compare the surface finish of workpiece when water composition is varied; 2. Observe the chip formation produced after machining process; and
3. Observe the rust formation on the workpiece.
1.4 Scope of Study
This study main emphasis is to investigate the surface roughness on mild steel after turning operation using coated carbide as cutting tools. The process is done on the HAAS SL Turning Center in the room temperatures. During the machining operation, cutting parameters that are feed rate, cutting speed and depth of cut are not varied and
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are constant and uniformed. The only parameter that is varied is coolant concentration in the cutting fluid. There are twelve samples used to complete the concentration and to test for the surface roughness analysis. The percentages of coolant diluted with water are varied from 2% to 8%. Chip and rust formation are observed in order to determine the types of chip formed and the percentage formation of corrosion area.
A profilometer or surface roughness tester, Mitutoyo SJ-301 is used to measure and identify the surface roughness and it values. This will determine the surface roughness of the material after completing the turning operations. Thus, effect of coolant concentration on the surface roughness is identified after the materials have been machined. Zoom Stereo Microscopes is used to evaluate the area ratio of the rust formed on the workpiece.
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CHAPTER 2
LITERATURE REVIEW
2.1 Usage of Cutting Fluid/Lubricant in Machining Process
The aims of cutting fluid application are as cooling and lubrication in metal cutting (Adler et al., 2006). In addition, cutting fluids can help to dispose the chips and control chip formation (Sokovic and Mijanovic, 2001) because it will decrease contact length between chip and tool, and this situation has a positive effect on chip braking (Shaw, 1996). Thus, it can help to achieve better tool life and surface finish. However, it is stated that cutting fluid application can either aggravate (Seah et al. (1995), Rakic and Rakic (2002)) or improve tool life (Avila and Abrao, 2001) depending on cutting conditions. Cutting fluids are used throughout industry in many metal cutting operations and they are usually classified into three main categories: neat cutting oils, water-soluble fluids and gases (El Baradie, 1996). Cutting fluids can be applied to the work-chip, tool-chip or tool-work interfaces (Shaw, 1986) in a metal cutting.
Lubrication using coconut oil is proved to be more effective when turning austenitic stainless steel using carbide tool. It can reduce tool wear and surface roughness value (Xavior and Adithan, 2008). Good surface quality can be obtained when using minimum quantity lubrication (MQL) when turning AISI4340 steel (Dhar et al., 2006). Other researchers have stated that dry machining is a success in the fields of manufacturing environmental-friendly. But, it is less effective when higher machining efficiency, better surface finish quality and severe cutting condition are required.
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Khan et al. (2006) describe that using vegetable oil as cutting fluid through MQL technique provides the benefits mainly by reducing the cutting temperature, improving the surface finish, dimensional accuracy and cutting force. In other study, Machado and Wallbank (1997) show the results of preliminary tests using very low quantities of cutting fluids while machining steel. The low quantities are applied in a fast flowing air stream. The results are compared to traditional flood cooling. The results indicate that surface finish, chip thickness and force variation are all affected beneficially with the low coolant volume compared to flood cooling.
Kumar et al. (2008) have study about the performance of TiCN and TiAlN tools in machining hardened steel under dry lubricating condition. As comparison, the wet and minimum fluid application also being study. The result showed that both tools performed better with minimal fluid application when compared with dry and wet machining. Better surface finish is obtained when using TiAlN tool. Che Harun et al. (2001) have done a study about wear of coated and uncoated carbides in turning tool steel. The use of dry machining technique and the performance of carbide tools in this dry lubrication machining is better. But, for the uncoated carbide tool, the performance is better in wet machining. Both coated and uncoated tools decrease in a short time at higher cutting speed.
2.2 Turning Process
Turning is the removal of metal from the outer diameter of a rotating cylindrical workpiece in order to produce straight, conical, curved or grooved workpiece, such as shafts spindles, and pins. Turning is used to reduce the diameter of the workpiece, usually to a specified dimension, and to produce a smooth finish on the metal. Often the workpiece will be turned so that adjacent sections have different diameters. The majority of turning process involved the use of simple singe-point cutting tools, with the geometry of a typical right-hand cutting tool. Each group of material has an optimum set of tool angles, which have been developed largely through experience. Such tool is
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described by a standardized nomenclature. The cutting process using a single-point tool is illustrated in figure 2.1
Figure 2.1: Schematic illustration of the cutting process with a single-point tool (Kalpakjian, 2006)
When turning, a piece of material is rotated and a cutting tool is traversed along two axes of motion to produce precise diameters and depths. Turning can be either on the outside of the cylinder or on the inside to produce tubular components to various geometries. Facing is part of the turning process. It involves moving the cutting tool across the face or end of the workpiece and is performed by the operation of the cross-slide, if one is fitted, as distinct from the turning. It is frequently the first operation performed in the production of the workpiece, and often the finishing process. The bits of waste metal from turning operations are known as chips.
The material removal rate (MRR) in turning is the volume of material removed per unit time in mm3/min. For each revolution of the workpiece, a ring-shaped layer of material is removed. The MRR in turning process can be calculated using equation 2.1.
MRR = π × Davg × d × f × N (2.1)
where; Davg : Average diameter
N : Rotational speed of the workpiece F : Feed rate
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Figure 2.2: Modes of turning: (a) radial; (b) axial; (c) face (Whitehouse, 2002)
The forces acting on a cutting in turning are important in the design of machine tools. The machine tool and its components must be able to withstand these forces without causing significant deflections, vibrations, or chatter during the operation. There are several modes of turning process, radial, axial and face as illustrated in figure 2.2. There are three principal forces during a turning process: cutting force, thrust force and radial force.
i. The cutting force acts downward on the tool tip allowing deflection of the workpiece upward. It supplies the energy required for the cutting operation. ii. The thrust force acts in the longitudinal direction. It is also called the feed force
because it is in the feed direction of the tool. This force tends to push the tool away from the chuck.
iii. The radial force acts in the radial direction and tends to push the tool away from the workpiece.
Several considerations are important in designing parts to be machine by turning operations. Because machining in general takes considerable time, wastes materials and not economical, it must be avoided if possible. When turning operation is necessary, the following general guidelines should be followed:
i. Parts should be designed so that they can be fixture and clamped easily in work-holding devices.
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ii. The dimensional accuracy and surface finish specified should be as wide as permissible for the part to still function properly.
iii. Sharp corners, tapers, steps, and major dimensional variations in the part should be avoided.
iv. Workpiece to be machined should be as close to final dimensions as possible to reduce production cycle time.
v. Parts should be designed so that cutting tools can travel across the workpiece without obstruction.
vi. Design features should be such that commercially available standard cutting tools, inserts, and tool-holders can be used.
vii. Workpiece material should be selected for their machinability as much as possible.
2.3 Cutting Tool
The selection of cutting tool materials for a particular application is almost important factors in machining operation. The cutting tool material must possess the following characteristics: hot hardness, toughness and impact strength, thermal shock resistance, wear resistance, and chemical stability and inertness. Hardness and strength are important with regard to the hardness and strength of the workpiece material to be machined, the impact strength is important in making interrupted cuts in machining, melting temperature of the tool material is important versus temperatures developed in the cutting zone, and the physical properties of thermal conductivity and coefficient of thermal expansion are important in determining the resistance of the tool materials to thermal fatigue and shock.
Tool materials generally are divided into the following categories: high-speed steel, cast-cobalt alloy, carbides, coated tools, alumina-based ceramics, cubic boron nitride, silicon-nitride-based ceramics, diamond, and whisker-reinforced materials and nano-materials. For this study, coated carbide tool is used. Carbides are among the most
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are constant and uniformed. The only parameter that is varied is coolant concentration in the cutting fluid. There are twelve samples used to complete the concentration and to test for the surface roughness analysis. The percentages of coolant diluted with water are varied from 2% to 8%. Chip and rust formation are observed in order to determine the types of chip formed and the percentage formation of corrosion area.
A profilometer or surface roughness tester, Mitutoyo SJ-301 is used to measure and identify the surface roughness and it values. This will determine the surface roughness of the material after completing the turning operations. Thus, effect of coolant concentration on the surface roughness is identified after the materials have been machined. Zoom Stereo Microscopes is used to evaluate the area ratio of the rust formed on the workpiece.
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CHAPTER 2
LITERATURE REVIEW
2.1 Usage of Cutting Fluid/Lubricant in Machining Process
The aims of cutting fluid application are as cooling and lubrication in metal cutting (Adler et al., 2006). In addition, cutting fluids can help to dispose the chips and control chip formation (Sokovic and Mijanovic, 2001) because it will decrease contact length between chip and tool, and this situation has a positive effect on chip braking (Shaw, 1996). Thus, it can help to achieve better tool life and surface finish. However, it is stated that cutting fluid application can either aggravate (Seah et al. (1995), Rakic and Rakic (2002)) or improve tool life (Avila and Abrao, 2001) depending on cutting conditions. Cutting fluids are used throughout industry in many metal cutting operations and they are usually classified into three main categories: neat cutting oils, water-soluble fluids and gases (El Baradie, 1996). Cutting fluids can be applied to the work-chip, tool-chip or tool-work interfaces (Shaw, 1986) in a metal cutting.
Lubrication using coconut oil is proved to be more effective when turning austenitic stainless steel using carbide tool. It can reduce tool wear and surface roughness value (Xavior and Adithan, 2008). Good surface quality can be obtained when using minimum quantity lubrication (MQL) when turning AISI4340 steel (Dhar et al., 2006). Other researchers have stated that dry machining is a success in the fields of manufacturing environmental-friendly. But, it is less effective when higher machining efficiency, better surface finish quality and severe cutting condition are required.
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Khan et al. (2006) describe that using vegetable oil as cutting fluid through MQL technique provides the benefits mainly by reducing the cutting temperature, improving the surface finish, dimensional accuracy and cutting force. In other study, Machado and Wallbank (1997) show the results of preliminary tests using very low quantities of cutting fluids while machining steel. The low quantities are applied in a fast flowing air stream. The results are compared to traditional flood cooling. The results indicate that surface finish, chip thickness and force variation are all affected beneficially with the low coolant volume compared to flood cooling.
Kumar et al. (2008) have study about the performance of TiCN and TiAlN tools in machining hardened steel under dry lubricating condition. As comparison, the wet and minimum fluid application also being study. The result showed that both tools performed better with minimal fluid application when compared with dry and wet machining. Better surface finish is obtained when using TiAlN tool. Che Harun et al. (2001) have done a study about wear of coated and uncoated carbides in turning tool steel. The use of dry machining technique and the performance of carbide tools in this dry lubrication machining is better. But, for the uncoated carbide tool, the performance is better in wet machining. Both coated and uncoated tools decrease in a short time at higher cutting speed.
2.2 Turning Process
Turning is the removal of metal from the outer diameter of a rotating cylindrical workpiece in order to produce straight, conical, curved or grooved workpiece, such as shafts spindles, and pins. Turning is used to reduce the diameter of the workpiece, usually to a specified dimension, and to produce a smooth finish on the metal. Often the workpiece will be turned so that adjacent sections have different diameters. The majority of turning process involved the use of simple singe-point cutting tools, with the geometry of a typical right-hand cutting tool. Each group of material has an optimum set of tool angles, which have been developed largely through experience. Such tool is
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described by a standardized nomenclature. The cutting process using a single-point tool is illustrated in figure 2.1
Figure 2.1: Schematic illustration of the cutting process with a single-point tool (Kalpakjian, 2006)
When turning, a piece of material is rotated and a cutting tool is traversed along two axes of motion to produce precise diameters and depths. Turning can be either on the outside of the cylinder or on the inside to produce tubular components to various geometries. Facing is part of the turning process. It involves moving the cutting tool across the face or end of the workpiece and is performed by the operation of the cross-slide, if one is fitted, as distinct from the turning. It is frequently the first operation performed in the production of the workpiece, and often the finishing process. The bits of waste metal from turning operations are known as chips.
The material removal rate (MRR) in turning is the volume of material removed per unit time in mm3/min. For each revolution of the workpiece, a ring-shaped layer of material is removed. The MRR in turning process can be calculated using equation 2.1.
MRR = π × Davg × d × f × N (2.1)
where; Davg : Average diameter
N : Rotational speed of the workpiece F : Feed rate
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Figure 2.2: Modes of turning: (a) radial; (b) axial; (c) face (Whitehouse, 2002)
The forces acting on a cutting in turning are important in the design of machine tools. The machine tool and its components must be able to withstand these forces without causing significant deflections, vibrations, or chatter during the operation. There are several modes of turning process, radial, axial and face as illustrated in figure 2.2. There are three principal forces during a turning process: cutting force, thrust force and radial force.
i. The cutting force acts downward on the tool tip allowing deflection of the workpiece upward. It supplies the energy required for the cutting operation. ii. The thrust force acts in the longitudinal direction. It is also called the feed force
because it is in the feed direction of the tool. This force tends to push the tool away from the chuck.
iii. The radial force acts in the radial direction and tends to push the tool away from the workpiece.
Several considerations are important in designing parts to be machine by turning operations. Because machining in general takes considerable time, wastes materials and not economical, it must be avoided if possible. When turning operation is necessary, the following general guidelines should be followed:
i. Parts should be designed so that they can be fixture and clamped easily in work-holding devices.
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ii. The dimensional accuracy and surface finish specified should be as wide as permissible for the part to still function properly.
iii. Sharp corners, tapers, steps, and major dimensional variations in the part should be avoided.
iv. Workpiece to be machined should be as close to final dimensions as possible to reduce production cycle time.
v. Parts should be designed so that cutting tools can travel across the workpiece without obstruction.
vi. Design features should be such that commercially available standard cutting tools, inserts, and tool-holders can be used.
vii. Workpiece material should be selected for their machinability as much as possible.
2.3 Cutting Tool
The selection of cutting tool materials for a particular application is almost important factors in machining operation. The cutting tool material must possess the following characteristics: hot hardness, toughness and impact strength, thermal shock resistance, wear resistance, and chemical stability and inertness. Hardness and strength are important with regard to the hardness and strength of the workpiece material to be machined, the impact strength is important in making interrupted cuts in machining, melting temperature of the tool material is important versus temperatures developed in the cutting zone, and the physical properties of thermal conductivity and coefficient of thermal expansion are important in determining the resistance of the tool materials to thermal fatigue and shock.
Tool materials generally are divided into the following categories: high-speed steel, cast-cobalt alloy, carbides, coated tools, alumina-based ceramics, cubic boron nitride, silicon-nitride-based ceramics, diamond, and whisker-reinforced materials and nano-materials. For this study, coated carbide tool is used. Carbides are among the most