Simulation Of Cutting Force During High Speed End Milling Of Inconel 718.

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

SIMULATION OF CUTTING FORCE DURING HIGH SPEED END

MILLING OF INCONEL 718

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering

(Process) (Hons.)

HEMA NANTHINI A/P GANESAN B051110167

910103086322

FACULTY OF MANUFACTURING ENGINEERING 2015

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DECLARATION

I hereby declared this report entitled “Simulation of Cutting Force during High Speed End Milling of Inconel 718” is the results of my own research except as cited in

references.

Signature : ……….

Author’s Name : HEMA NANTHINI D/O GANESAN

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APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as partial fulfillment of the requirements for the degree of Bachelor of Manufacturing Engineering (Manufacturing Process) (Hons). The member of the supervisory committee is as follows.

……… Supervisor

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ABSTRAK

Dalam memahami proses asas pemotongan logam melalui kajian eksperimen mempunyai beberapa masalah dan batasan. Untuk mempunyai pemahaman yang lebih terpirinci mengenai proses pemesinan di bawah keadaan pemotongan yang berbeza , terdapat kaedah alternatif yang lain. Inconel adalah aloi yang berasaskan nikel, dan jelas dikenali sebagai bahan yang sukar untuk dipotong. Tujuan kajian ini adalah simulasi (FEM) daya pemotongan semasa HSM Inconel 718 di bawah keadaan pemesinan kering. Perkakas pemotong yang dipilih adalah jenis berbola yang dibuat dari tungsten karbida (WC-10%Co) dan disalut secara pengendapan wap fizik (PVD) dengan TiAlN dan CrAlN . Faktor yang diambil kira dalam ujian ini ialah halaju pemotongan, Vc (100-140 m / min), kadar suapan (0.1-0.2 mm / gigi) dan kedalaman pemotongan paksi (0.5-1.0 mm). DEFORM 3D software telah digunakan sebagai alat simulasi dalam kajian ini. Projek ini menerangkan kajian tentang kesan parameter terhadap daya pemotongan, daya suapan dan daya tujah semasa simulasi pemesinan Inconel 718. Keputusan yang diperolehi melalui simulasi yang telah dibandingkan dengan keputusan eksperimen sebenar yang pernah dijalankan oleh penyelidik sebelumnya untuk menentukan ketepatan keputusan. Perbandingan antara simulasi dan keputusan eksperimen menunjukkan bahawa, ralat purata daya pemotongan (Fx) adalah 258.34N, daya suapan (Fy) adalah 61.28N dan daya tujah (Fz) adalah 82.10N. Keputusan menunjukkan pada kedalaman pemotongan paksi dan kadar suapan yang rendah akan menjana daya yang rendah. Kombinasi parameter optimum yang menghasilkan sambutan yang paling dikehendaki ialah Vc = 120.58m/min, fz 0.13mm/tooth dan ap= 0.98mm.

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ABSTRACT

The essentials understanding of metal cutting processes over the experimental studies have several problems and restrictions. The understanding of machining process under different cutting parameters is better in machining modeling. Inconel is a nickel-based super alloy, prominently well-known as a difficult-to-cut material. It possesses great strength and corrosion resistant and withstand at elevated temperature (900 -1050◦ C). The main aim of this study is FEM simulation of cutting force during high speed end milling of Inconel 718 under dry machining condition. TiAlN/AlCrN-coated carbide inserts was used as the cutting tool for the machining simulation. The investigated milling parameters were cutting speed (100-140 m/min), feed rate (0.1-0.2 mm/tooth) and axial depth of cut (0.5 – 1.0 mm). The DEFORM 3D software is used as a simulation tool for achieved the goal of this study. This project describes a study on the cutting parameter effect on cutting force, feed force and thrust force during simulation of high speed end milling of Inconel 718. The simulation results on cutting force, feed force and thrust force are compared with experimental results to achieve the accuracy. The comparison made between simulation and experimental results specify that, the average error of cutting force (Fx) is 258.34N, feed force (Fy) is 61.28N and thrust force (Fz) is 82.10N. It was found that, the low cutting force was obtained during the lowest depth of cut and lowest feed rate. The significant parameter that can be used to obtain low cutting force, feed force and thrust force during high speed end milling of Inconel 718 are Vc = 120.58m/min, fz = 0.13mm/tooth and ap = 0.98mm.

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DEDICATION

Special thanks to my family members, supervisor, panels and friends for helping me throughout the project towards achieving my goals

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ACKNOWLEDGEMENT

I would like to give my deepest appreciation to my final year project supervisor, Dr. Mohd Shahir Bin Kasim for guiding me throughout the project. In addition to that, I also would like to express my sincere appreciation to Universiti Teknikal Malaysia Melaka (UTeM) for offering this Final Year Project (FYP) as a subject. The knowledge and experience gained is extraordinary and will be very useful for my future. Above all, I wish to thank my parents and family for their unconditional love and support throughout my degree course. Last but not least, I wish to thank God for giving me excellent health and chances in completing my project as well as my degree course.

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Abstrak ... i

Abstract ... ii

Dedication ... iii

Acknowledgement ... iv

Table of Contents ... v

List of Tables ... viii

List of Figures ... ix

List of Equation ... xi

List of Abbreviations ... xii

CHAPTER 1 : INTRODUCTION ... 1

1.1 Background of the Project ... 1

1.2 Problem Statement ... 3

1.3 Objectives ... 4

1.4 Scopes ... 4

CHAPTER 2 : LITERATURE REVIEW ... 5

2.1 Introduction ... 5

2.2 Machining Process ... 5

2.2.1 Milling Process ... 6

2.2.2 High Speed Machining (HSM) ... 7

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2.3.1 Machinability of Inconel 718 ... 10

2.4 Cutting tool ... 11

2.4.1 Characteristic of cutting tool ... 12

2.4.2 Cutting tool for Inconel 718 ... 12

2.5 Cutting forces ... 14

2.5.1 Merchant’s Model ... 15

2.6 Finite Element Models (FEM) ... 16

CHAPTER 3 : METHODOLOGY ... 17

3.1 Introduction ... 17

3.2 Flow Chart of Project ... 17

3.3 Simulation Material ... 21

3.3.1 Cutting Tool ... 22

3.3.2 Workpiece ... 24

3.4 Finite Element Method (FEM) Analysis ... 26

3.4.1 Simulation Control ... 26

3.4.2 Defining the Workpiece ... 26

3.4.3 Defining the Cutting Tool ... 27

3.4.4 Mesh Type ... 27

3.4.5 Generating Mesh ... 28

3.4.6 Boundary Condition ... 29

3.4.7 Assigning Movement Control ... 30

3.4.8 Contact Condition ... 32

3.5 Simulations ... 32

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vii

3.6 Compare the Results ... 34

3.7 Design of Experiment (DOE) ... 35

3.7.1 Historical Data Design ... 36

3.7.2 Analysis of Variance (ANOVA) ... 37

CHAPTER 4 : RESULT AND DISCUSSION ... 38

4.1 Introduction ... 38

4.2 Simulation of Machining ... 39

4.2.1 Entry Angle of Minimum and Maximum Force ... 42

4.3 Force Generation ... 44

4.3.1 The Cutting Parameter Effect on the Generated Resultant Force ... 46

4.4 Comparison between Simulation and Experiment ... 50

4.5 Analysis of Variance for Low Resultant Force ... 53

4.6 Optimization of Parameter Using RSM Method ... 54

4.6.1 Optimization of Resultant Force ... 55

CHAPTER 5 : CONCLUSION ... 57

REFERENCES ... 59

APPENDICES ... 65

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viii

LIST OF TABLES

2.1 Composition of Inconel According to Grade (METALS, 2011) 8

2.2 Characteristic of Inconel 718 9

3.1 Gantt Chart 20

3.2 Characteristic of Inconel 718 21

3.3 Cutting Tool Geometry 22

3.4 Geometry of Workpiece 24

3.5 Set of Parameter 31

3.6 Result of Previous Experiment with Actual Cutting Process 35

4.1 The Cutting Force, Feed Force And Thrust Force Obtain Through Simulation 46 4.2 Differences Between Simulation Force and Experiment Force 53

4.3 ANOVA for Resultant Force 54

4.4 Criteria for Obtaining the Optimum Response 55

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LIST OF FIGURES

2.1 Milling cutters: a) Up milling, b) Climb milling, c) Edge milling, d) Detail of Face Milling Windexable Inserts - (Courtesy of J.T. Black) 7

2.2 Illustration of Depth of Cut During Machining 15

2.3 Merchant’s Orthogonal Cutting Model (Shaw, 1984) 16

3.1 Flow Chart 19

3.2 Geometry of Cutting Tool 23

3.3 Geometry of Actual Cutting Tool 23

3.4 Geometry of Workpiece with Depth of Cut 1.0m 24

3.5 Geometry of Workpiece with Depth of Cut 0.75mm 25

3.6 Geometry of Workpiece with Depth of Cut 0.5mm 25

3.7 Tetrahedral Mesh Element Constructed for the Ball Nose and the Workpiece 28

3.8 Velocity Boundary Condition 29

3.9 Heat Exchange with the Environment Boundary Condition of the Workpiece 30 3.10 Heat Exchange with the Environment Boundary Condition of Cutting Tool 30

3.11 Simulation of Machining Process of Inconel 718 33

3.12 Cutting Force Exerted on Cutting Tool In Y-Axis 34

3.13 Historical Data Design 36

3.14 Set of Parameter and Obtained Results 37

4.1 Chip Formation 39

4.2 Simulation of Material Removal 40

4.3 Graph of Thrust Force (Fz) 40

4.4 Graph of Cutting Force (Fx) 41

4.5 Graph of Feed Force (Fy) 41

4.6 Prediction of Maximum and Minimum Force 42

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4.8 Entry Angle of Minimum Force 43

4.9 Cutting Force During Simulation 45

4.10 Graph of Resultant Force 45

4.11 Graph of Average Force Against Depth of Cut 47

4.12 Graph of Average Force Against Feed Rate 48

4.13 Graph of Average Force Against Cutting Speed 50

4.14 Ploughing Effect 52

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LIST OF EQUATION

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xii

LIST OF ABBREVIATIONS

ap, DOC - Depth of Cut

DOE - Design of Experiment FEM - Finite Element Method Fx - Cutting Force in X-axis Fy - Feed Force in Y-axis Fz - Thrust Force in Z-axis

fz - Feed Rate

HSM - High Speed Machining

UTeM - Universiti Teknikal Malaysia Melaka

Vc - Cutting Speed

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CHAPTER 1

INTRODUCTION

1.1 Background of the Project

Machining can be defined as a chip formation process in fabricating engineering part. Machining process is a typical way to remove a material to form into desired geometry and also shape (M.S.H. Bhuiyan 2012). Machining process can be grouped into three major types. There are turning, milling and drilling. Milling is a process of a cutting operation. The cutting operation can be performed by rotating the cutting tool whereas the work piece is clamped on a table. Then the feed operation is achieved by moving the work piece toward the cutting tool (Trent & Wright, 2000).

High speed end milling process is applied for very hard material like nickel alloys, titanium alloys and others. High speed end ball milling operation is most widely used in aerospace and also nuclear reactorparts manufacturing industry (A. Li, Zhao, Zheng, & Pei, 2011). This is due to; the parts that used in aerospace industry must have low subsurface microstructure dislocation. During the machining, there is resultant force acting on three axes (x-axis, y-axis and z-axis) which known as cutting force, feed force and thrust force on the cutting tool. The cutting force exerted is varied according to nature of machining process.

Inconel is known as material hard to be machined. Flank wear, notch wear and crated wear that associated with cutting force abrasiveness of Inconel 718 (Çolak, 2012). Work

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2 hardening is contributing factor in premature tool life reported by (Zhang, Li, & Wang, 2012). The other problem of machining Inconel reported is flaking problem. That is related with cyclic load exerted onto rake face of cutting tool (Qian & Hossan, 2007). Those problems are associated with cutting force.

To overcome this problem is by changing machining strategy from conventional speed to high speed machining (HSM). High speed end milling process is applied for very hard material like nickel alloys, titanium alloys and others. The machine is also used to produce a complex geometry part. High speed end ball milling operation is most widely used in aerospace and also nuclear reactor parts manufacturing industry (A. Li, et al., 2011). In general, cutting speed is consider HSM when the cutting speed beyond 5000 RPM (Leigh, Tlusty, & Schueller, 1999). However, the most reasonable definition HSM specifically for Inconel is the cutting speed is ranging between 80 – 400 m/min (Thakur, Ramamoorthy, & Vijayaraghavan, 2009). HSM was claimed improve durability of cutting tool due to ability to reduce volume of removing material, hence reduce heat generated and cutting force.

The study done by (Qian & Hossan, 2007) indicate resultant force is mostly contributed by depth of cut followed by feed rate and cutting speed. However, their study merely on experiment without simulation. From the findings, Fx is mostly contribute to the resultant force. Thus, this project is initiated to simulate the effect of cutting parameter on the resultant force and to compare with the experiment. Therefore Deform 3D software is used to simulate the high speed end milling of Inconel 718.

Then the expected results will be compare with the actual experiment result which done by previous researcher. The simulation will investigate about the cutting force, where the cutting forces are affected by several of parameter. This is explaining why the application of FEM 3D software is used in order to obtain more accurate results.

In this 3D Deform software, by using the simulation will investigate the force exerted on cutting tool in tree axis of direction (Fx,Fy,Fz) accurately. In additional, the simulations allow the complex machining operation and also there is zero cost to conduct the machining operation via simulation method.

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1.2 Problem Statement

Basically nickel alloys are known as strongest materials. This nickel alloys have higher resistance to corrosion and also to high temperature. Inconel 718 is a one of the example of a nickel-based alloy. These Inconel 718 alloys are highly resistance to heavy corrosive substances. Those properties of this alloys lead to applied widely in aerospace, gas turbine, nuclear reactor, chemical and petrochemical industries. The material that used in aerospace industry must have less surface microstructure dislocation. It is very important for the part that used in aerospace industry to have low surface microstructure dislocation (Wessel, 2004).

Inconel 718 is well known as a difficult-to-cut material, so usually there is higher cutting force acting on the Inconel 718 during the machining as compared to other less harder material (Devillez, Schneider, Dominiak, Dudzinski, & Larrouquere, 2007). The higher cutting force will cause the material to have higher surface microstructure dislocation especially in normal milling and turning machines (Thakur, et al., 2009). Therefore, the high speed machining (HSM) is introduced in order to reduce the cutting force on the cutting tool. The HSM was claimed low cutting force during the machining operation. The depth of cut, feed rate and cutting speed are those several factors which act as main parameters of machining (Soo, Aspinwall, & Dewes, 2004). These parameters are very important in machining process to obtain a good surface finish. During the machining operation of Inconel 718, several of cutting force will produce due to change in the cutting parameter. The major problem faced by machinist during HSM of super alloys is short tool life. The force acting on the cutting tool leads to short tool life. The range of cutting tool life span is between 0.5min to 90min (Huang & Liang, 2005). According to (Qian & Hossan, 2007) stated that, notch wear, pitting, chipping, flanking are associated with cutting force.

By applying the finite element method (FEM) in machining processes is one of the best way to investigate the different cutting force due to the changes in cutting parameters. The high speed end ball milling of Inconel 718 is can stimulate by using 3D Deform

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4 software and the simulation results can used to determine the most significant parameter to produce lower cutting force. It is very difficult to decide the optimization of cutting parameters in real machining process due to a lot of cutting experiments need to be executed. The simulation is run based on the real machining operation.

1.3 Objectives

1) To model the cutting process of Inconel 718.

2) To compare the parameters effect on cutting force between simulation and experiment.

3) To identify the best cutting parameter to produce lower cutting force.

1.4 Scopes

The scope of the research, including:

1) This project will focus on the dry machining only. 2) The material for work piece is just Inconel 718. 3) High speed milling machine is used.

4) The material for cutting tool only focuses the PVD coated of TiAlN and AlCrN ball nose tungsten carbide (WC- 10 % Co).

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2

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

In this chapter, the review of pass journals is done. Literature review is essentially examined according to the sources and described to justify the statements with proof of research or study in related subject.

2.2 Machining Process

Machining operation is act as a main body of manufacturing industry revolution. Machining is a process where there is an occurrence of material removal. The material of a workpiece is removed by cutting tool to form the workpiece into desired shape under specified condition (Rao, 2011). Turning, milling and drilling are the most common machining process that widely using in mechanical manufacturing process (Childs, Maekawa, Obikawa, & Yamane, 2000).

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2.2.1 Milling Process

The workpiece’s material is removed away by feeding the workpiece past a rotating multiple tooth cutters is known as milling process. The fast method of machining is achieved by the many teeth’s cutting action around the milling cutting. The workpiece can be machined into various shapes like flat, angular, curved or combinations of shape. Milling process is disturbed cutting action: during every revolution, the teeth of the cutting tool is enters and exit as shown in Figure 2.1. The disturbed cutting operation is focusing the cutting tool to an impact force cycle and thermal shock on each rotation. When designing the cutting tool material and its geometry must follow these conditions (Groover, 2007).

The disturbed milling’s action produces variable thickness of chips by the tooth of the cutting tool. The milling machine will encounter problem where it face difficulty in machining further during machining the high strength material like nickel alloy, due the material hardening effect. The workpiece will be pushed rather than it cut if the cutting edge of the cutting tool is not sharp enough (H. Z. Li, Zeng, & Chen, 2006). This phenomenon will produce high cutting force.

The every action of cutting edge is discontinues which is an important aspect in every milling process. The period of each tooth to cut is less than half of a revolution of cutter. Every edge is exposed to impacts which make the cutting tool to have contact with workpiece. When designing the cutting tool of milling, the designer must consider the problem of free of the chips (Trent & Wright, 2000).

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Figure 2.1: Milling cutters: a) Up milling, b) Climb milling, c) Edge milling, d) Detail of face milling windexable inserts (Courtesy of J.T. Black)

2.2.2 High Speed Machining (HSM)

High speed machining (HSM) is one of the best important technologies used in advanced manufacturing. HSM is not only decreases the machining process time, it is also decreases the production cost and as well as increases the production level without the secondary process which produced a good surface finishing (Dolinsek, Sustarsic, & Kopac, 2001). The chips formation at high speed is short and thinner than the chips formed in turning process (Tschätsch, 2008).

The HSM average machining speed is three to four times faster than conventional machine’s machining speed. However the quality of the machined surface is not affected and the desired dimension is achieved within the tolerance (Leigh, et al., 1999). The other advantages of HSM is, the machining process time is lower which lead to

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8 maintain at lower temperature (Liao, Lin, & Wang, 2008). The other definition by Schultz & Moriwaki (1992), also mentioned that, HSM, have low cutting force, high material removal rate, and lower lead time. They also stated that the distortion in work piece is lower which resulted from the chip removal dissipation heat. This is will lead to produce a part with good surface finish and higher precision.

2.3 Inconel 718

Inconel 718 is a hardened with the nickel-chromium precipitation. It has Nickel, Iron and Chromium as main elements, little amount of Columbium, Molybdenum, Titanium and Aluminum. The Inconel 718 has higher strength without heat treatment which cause by the additional elements of niobium which reacts with molybdenum in alloy metrics hardening (METALS, 2011). The other differences in Inconel grades are the compositional dominated by nickel and chromium, which are shown in Table 2.1.

Table 2.1: Composition of Inconel according to grade (METALS, 2011)

Inconel 600 625 718

Nickel 72 58 50.0-55.0

Chromium 14.0-17.0 20.0-23.0 17.0-21.0

Iron 6.0-10.0 5 Balance

Molybdenum 8.0-10.0 2.8-3.3

Niobium 3.15-4.15 4.75-5.5

Cobalt 1 1.0

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Copper 0.5 0.2-0.8

Aluminum 0.4 0.65-1.15

Titanium 0.4 0.3

Silicon 0.5 0.5 0.35

Carbon 0.15 0.1 0.08

Sulfur 0.015 0.015 0.015

Phosphorus 72 0.015 0.015

Boron 14.0-17.0 58 0.006

This nickel alloy can be found in many forms like coil, bar, sheet and wire (Alloys, 2011). The properties of nickel alloy like ability to maintain the strength and ductility and also the oxidation at elevated temperature lead to use in industries of gas turbine, nuclear reactor and aerospace. The Inconel 718 was used in space ship due to its temperature which is lower than the freezing temperature (METALS, 2011). Table 2.2 shows the Inconel 718 characteristic.

Table 2.2 : Characteristic of Inconel 718

Characteristic Value

Melting point 1425 ᶱC

Thermal expansion 13 µm/m ᶱC(20-100 ᶱC) Thermal conductivity 0.15 W/cm. ᶱC

Density 8.19 g/cm 3

Modulus of rigidity 77.2kN/mm2 Modulus of elasticity 204.9kN/mm2

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