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EFFECT OF PROCESS PARAMETERS ON SURFACE ROUGHNESS PRODUCED BY TURNING BORING OPERATION
AHMAD DZIA’UDDIN BIN MOHAMED
A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering (Mechanical - Advanced Manufacturing Technology)
Faculty of Mechanical Engineering Universiti Teknologi Malaysia
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DEDICATION
First of all, all the praises and thanks be to Allah S.W.T for His Love, This thesis is dedicated to my family,
To my beloved parents,
Mohamed bin Samat, Che Wa bt Yussof My supportive wife,
Asehara bt. Meor Ahmad My wonderful brothers and sister,
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ACKNOWLEDGEMENTS
I would like to thank Allah Almighty for blessing me and giving me strength to accomplish this thesis. A special thanks and deep gratitude to my supervisor, Professor Dr. Noordin bin Mohd Yusof who greatly helped in guiding and assisting me in every way throughout this entire project.
Many thanks to all the technicians and staff from KKTM Balik Pulau, Mr. Ashamudin Technician in Material Failure Testing and Mr. Mohzani lecturer Department Mechanical Engineering from USM, Mr. Zulkifli b. Mohamad HOD Mechanical Engineering and technical staff Alicona lab UiTM Shah Alam for their cooperation and assisting me in the various laboratory tasks.
I like to express my appreciation to my beloved wife Asehara bt Meor Ahmad and my three children, Nurulain, Nurul Izzati and Nurul Asyikin for their patience, support, encouragement, belief and trust. I will forever remain grateful for their sacrifices.
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ABSTRACT
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ABSTRAK
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF SYMBOLS xv
LIST OF APPENDICES xvi
1 INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 3
1.3 Objective of the Study 4
1.4 Significance of the Study 5
1.5 Scope of Study 6
1.6 Overview of the Methodology 7
1.7 Thesis Organization 8
2 LITERATURE REVIEW 9
2.1 Theory of Metal Cutting 9
2.1.1 Orthogonal Cutting 11
2.1.2 Oblique Cutting 12
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2.3. Tool Geometry 13
2.4 Turning Cutting Data 15
2.5 Boring Operation 18
2.6 Cutting Forces in Boring Operation 19
2.7 Holding the Boring Bar 21
2.8 Surface Roughness in Turning 25
2.9 Factors Affecting Surface Roughness 27
2.9.1 Nose Radius 26
2.9.2 Feed Rate 28
2.9.3 Depth of Cut 28
2.9.4 Cutting Speed 28
2.9.5 Built-Up Edge 29
2.9.6 Material Side Flow 28
2.9.7 Chip Morphology 30
2.10 Wear Mechanism 30
2.11 Chip Formation 33
2.12 Literature Review on Surface Roughness in 36 Turning Operation
2.13 Summary of Literature Review 44
3 METHODOLOGY 45
3.1 Introduction 45
3.2 Research Methods and Procedure 46
3.3 Machines and Equipment 47
3.4 Measurement Equipment and Setup 49
3.4.1 Surface Roughness Measurement 49
3.4.2 Tool Wear Measurement 51
3.5 Workpiece Material 53
3.6 Tool Cutting Material 55
3.7 Machining Parameters 57
3.8 Cutting Condition 57
3.9 Workpiece Preparation 58
3.10 Measure Surface Roughness 60
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3.12 Analyze of Chips Formation 62
3.13 Experimental Design 62
3.13.1 Test for Significance of the Regression Model 65 3.13.2 Test for Significance on Individual Model 65
Coefficient
3.13.3 Test for Lack-of-Fit 66
4 EXPERIMENTAL RESULTS 68
4.1 Introduction 68
4.2 Experimental Results 70
4.3 ANOVA Analysis 71
4.3.1 Confirmation Run 81
4.3.2 Optimization in Range of Surface Roughness 82
4.4 Tool Wear Mechanism 84
4.5 Chip Formation 88
5 DISCUSSION 94
5.1 Introduction 94
5.2 Surface Roughness in Turning Boring Operation 95
5.3 Tool Wear Mechanism 98
5.4 The Effect of Tool Wear on the Surface Roughness 101
6 CONCLUSION AND RECOMMENDATIONS 102
REFERENCES 105
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LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Summary of finding related to the boring operation 41 and surface roughness
3.1 Typical composition of aluminium alloy 6061 54 3.2 Physical properties of pluminium alloy 6061 54 3.3 Mechanical properties aluminium alloy 6061 54
3.4 Machining parameter 57
3.5 Level of independent variables 58
4.1 Experimental plan for surface roughness by turning 69 boring operation
4.2 Experimental result of surface roughness by turning 70 boring operation
4.3 ANOVA table for surface roughness 71
4.4 Experimental plan for confirmation run 81
4.5 Result of conformation test 81
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LIST OF FIGURES
FIGURE NO . TITLE PAGE
2.1 Basic machining operation and important parameter 10 2.2 Cutting process, (a) Orthogonal cutting (b) Oblique cutting 11
2.3 Conventional lathe machine 13
2.4 Turning tool nomenclatures 14
2.5 The main cutting data/tool elements for turning tool applications
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2.6 Internal turning operation 19
2.7 Radial and tangential cutting forces deflect the boring bar during machining, often necessitating cutting edge
compensation and tool damping.
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2.8 The way a boring bar is clamped is decisive as regards performance and result
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2.9 Solid bars overhang 23
2.10 Chip evacuation is a critical factor for successful boring. 24
2.11 Tool wear phenomena 32
2.12 Features of single-point wear in turning. (ISO proposed standard)
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2.13 Three basic types of chips 34
2.14 Chips are broken (a) on their own (b) against the tool (c) against workpiece
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2.15 Chip formation varies with depth of cut, entering angle, feed, material and tool geometry
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xii 3.2 An internal turning setup with a workpiece clamped in a
shuck to the left and a boring bar clamped in a clamping housing to the right
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3.3 Machine CNC Turning DMG CTX 310 48
3.4 Surface roughness tester 50
3.5 Measuring setup 50
3.6 Optical Nikon microscope c/w Image analyzing software 51
3.7 Optical 3D measurement Infinite Focus 52
3.8 Solid steel boring bar with cermet insert 55
3.9 Cermet insert Specification 55
3.10 Boring bar specification 56
3.11 U-drill and insert specification 56
3.12 Dimension of workpiece before experiment cut 59
3.13 View of boring operation on a workpiece 59
3.14 Machining the workpiece 60
3.15 Surface roughness measurement of work sample 61 4.1 Normal probability plots of residuals for surface
finish in turning boring operation.
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4.2 Plots of residuals vs. predicted response for surface finish in turning boring operation.
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4.3 Outlier T plot for surface finish in turning boring operation.
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4.4 Cutting speed factor influence on Ra in turning boring operation
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4.5 Feed rate factor influence on Ra in turning boring operation
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4.6 Boring bar length factor influence on Ra in turning boring operation
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4.7 Boring bar diameter factor influence on Ra in turning boring operation
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in turning boring operation.
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4.9 Perturbation graph for Ra in turning boring operation. (bd = 12 mm)
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4.10 Perturbation graph for Ra in turning boring operation. (bd = 16 mm)
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4.11 Surface and contour plot on Surface finish 80 4.12 Plot for optimum cutting parameter in range. 83 4.13 Initial tool wear for boring bar Ø16 mm with tool
overhang 55 mm.
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4.14 Initial tool wear for boring bar Ø16 mm with tool overhang 60 mm.
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4.15 Initial tool wear for boring bar Ø16 mm with tool overhang 65mm.
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4.16 Initial tool wear for boring bar Ø12 mm with tool overhang 55mm.
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4.17 Initial tool wear for boring bar Ø12 mm with tool overhang 65mm.
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4.18 Initial tool wear for boring bar Ø12 mm with tool overhang 60mm.
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4.19 ISO-based chip forms classification 88
4.20 Chips formation using bar diameter 16 mm, bar length 55 mm.
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4.21 Chips formation using diameter 16 mm, bar length 65mm. 90 4.22 Chips formation with cutting data Diameter 12 mm,
Bar length 55 mm
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4.23 Chips formation using Diameter 12, Bar length 65 92
4.24 Chips formation using bar length 60 93
5.1 Surface finish result using cutting data cs=150 m/min, f=0.1 mm/rev, doc = 0.1 mm, bd=16 mm, bl=55 mm.
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5.2 Surface finish result using cutting data cs=250 m/min, f=0.2 mm/rev, doc = 0.25 mm, bd=12 mm, bl=655 mm.
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5.3 Material stick on top face insert 99
5.4 Built up edge on rake side 100
5.5 Crater wear on rake side 100
5.6 Marks on surface finish cause of material adhered on to the tool continuously ploughed on the machined surface
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LIST OF SYMBOLS
ANOVA - Analysis of Variance
Al - Aluminium
ECEA - End Cutting Edge Angle SCEA - Side Cutting Edge Angle
Sqrt - Square root
doc - Depth of Cut
cs - Cutting Speed
f - Feed rate
bd - Bar Diameter
bl - Bar Length
F - Force
Fc - Cutting Force
Ft - Tangential Force
Fr - Radial Force
N - Revolution per Minute Ra - Surface Roughness
T - Tool Life
V - Cutting Speed
C - Taylor’s constant
n - Taylor’s exponential
α - Rake Angle
Ø - Diameter
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LIST OF APPENDICES
APPENDIX TITLE PAGE
A-1 Unmodified ANOVA table for turning boring operation 105 B-1 Box-cox plot for turning boring operation 106 B-2 Initial tool wear for cutting Al 6061, times 6s. 107 B-3(a) Surface finish after turning boring operation sequence
followed experimental plan
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B-3(b) Surface finish after turning boring operation sequence followed experimental plan
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B-4 Result of chip formation 110
C-1 Chip formation chart 111
C-2 Recommendation of tool overhang for internal turning 112 C-3 Factor that effect vibration tendencies positively and
negatively, vibration tendency grow towards the right
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C-4(a) Table of tool wear 114
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CHAPTER 1
INTRODUCTION
1.1 Background
In machining operation, the quality of surface finish is an important requirement of many bored work pieces and parameter in manufacturing engineering. It is characteristic that could influence the performance of mechanical parts and the production cost. Various failure, some time catastrophic, leading to high cost, have been attribute to the surface finish of the component in question. For these reasons there have been research developments with the objective of optimizing the cutting condition to obtain a surface finish.
2 In internal turning, the metal-cutting process is carried out in pre-drilled holes or holes in cast, etc. The dimensions of the work-piece hole generally determine the length and limit the diameter or cross-sectional size of the boring bar. Usually, a boring bar is long and slender and is thus sensitive to excitation forces introduced by the material deformation process in the turning operation. The boring bar is generally the weakest link in the boring bar – clamping system of the lathe. The boring bar motion may vary with time. This dynamic motion originates from the deformation process of the work material. The motion or vibration of the boring bar influences the result of the machining in general, and the surface finish in particular.
With external turning, the tool overhang is not effect by the length of work piece, and the size of tool holder is selected to withstand the forces and stresses which arise during the operation. With boring – internal turning, the choice of tool very much restricted by the component’s hole diameter and length, as the depth of the hole determines the overhang.
A general rule, which applies to all machining is to always minimize tool overhang and to select the largest possible tool size in order to obtain the best possible stability and thereby accuracy. The stability is increased when the larger boring bar diameter is used, but possibilities are often limited, since the space allowed by the diameter of the hole in the component must be taken into consideration for swarf evacuation and any radial movement.
3 Previous studies proved the significant impact of DOC, machining speed, and rake angles on surface roughness. The few studies that have studied boring bar length that effect of cutting stability or vibration during boring operation. But very few researchers have studied the interaction effect of boring bar length and bar diameter. The combination of both of these factors suggests a significant weight in the relationship. All the previous studies on predicting surface roughness have not included boring bar diameter as a major factor that affects surface roughness.
1.2 Problem Statement
The determination of optimal cutting condition for specified surface roughness and accuracy of product are the key factors in the selection of machining process. In Turning operations, and especially boring operations, are associated with serious vibration-related problems. To reduce the problem of vibration and ensure that the desired shape and tolerance are achieved, extra care must be taken with production planning and in the preparations for the machining of a work-piece. A through investigation of the vibrations involved is therefore an important step toward solving the problem.
4 In turning operation, the performances of cutting tools are depending on a few cutting conditions and parameters. The proper selection of feed rate has direct effect to the product surface roughness. Turning process by maximizing cutting speed and depth of cut will optimize the cutting process and minimize the production cost. The tool life, machined surface integrity and cutting forces are directly dependent on cutting parameters and will determine the cutting tool performances. The study of surface roughness form will resolve the characteristic and phenomena happening during the machining process. The questions to be answered at the end of the study are how does the boring bar tool length and diameter influence the surface roughness during internal turning operation?
1.3 Objective of the Study
The study was carried out to evaluate the effects of different cutting tool length on workpiece for internal cutting profile with turning operation, where the surface roughness values were statistically comparable and to find out the optimum cutting condition by analyzing the different cutting tool length to get the lowest surface roughness in turning an Aluminium alloy 6061 solid bar.
Objective of this study are follow:
• To evaluate the effects of different process parameter on internal turning operation.
• To develop a mathematical model for predicting surface roughness for internal turning operation by using design of experiment approach. • Study the initial tool wear during internal turning operation.
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1.4 Significance of the Study
Machining operations tend to leave characteristic evidence on the machined surface. They usually leave finely spaced micro-irregularities that form a pattern known as surface finish or surface roughness. The quality of the finished product, on the other hand, relies on the process parameters; surface roughness is, therefore, a critical quality measure in many mechanical products.
In the turning operation especially boring operation, chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. In order to achieve sufficient process stability, the metal removal rate is often reduced or the cutting tool changed. But as productivity is normally a priority in manufacturing, this is the wrong route to go.
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1.5 Scope of the Study
The study has been conducted on the following scopes:
(i) CNC Turning machine will be employed.
(ii) Aluminum alloy solid bar Al 6061 will be used as workpiece material. (iii) Two different diameters boring bar size 16 .0 mm and 12.0 mm with
carbide cutting tool insert will be used at various tool lengths.
(iv) Cutting speed, feed and depth of cut are the other process factors investigated.
(v) Performance will be primarily in terms of surface roughness, chip formation and initial tool wear will also be briefly discussed.
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1.6 Overview of the Methodology
The following methodology has been used as a guide in the study to achieve the study objectives.
(i) Selecting the proper cutting parameters based on literature reviews and manufacturer recommendations.
(ii) Plan and design reliable experimental techniques. (iii) Workpiece preparation
Using CNC Turning and purpose tooling to machine the workpiece. (iv) Experimental trials consisting of:
Surface finish measurement using stylus instrument.
Chip morphology and tool wear mechanism studies using microscope (v) Data analysis and validation.
Evaluate the effect of tool length on the surface finish
Evaluate the effect of diameter boring bar on the surface finish Evaluate the initila tool wear
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1.7 Thesis Organization
