Optimization Of Machining Parameters In High Speed Milling Of Aluminum 6061.

(1)

UNIVERSITY TEKNIKAL MALAYSIA MELAKA

OPTIMIZATION OF MACHINING PARAMETERS IN HIGH

SPEED MILLING OF ALUMINUM 6061

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

LIM CHONG WEI

FACULTY OF MANUFACTURING ENGINEERING 2009

(2)

UTeM Library (Pind.1/2007)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS TESIS*

JUDUL: Optimization of machining parameters in high speed milling of Aluminum 6061._______________________

SESI PENGAJIAN: 2008/09___________________________________________________

SayaLIM CHONG WEI (B050510063)_________________________________________

mengaku membenarkan tesis (PSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hak milik Universiti Teknikal Malaysia Melaka .

2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan untuk tujuan pengajian sahaja.

3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan (√)

SULIT

TERHAD

√ TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

(TANDATANGAN PENULIS) Alamat Tetap:

3063, SRI TAMAN, JLN SULTANAH 05250, ALOR STAR,

KEDAH.

Tarikh: 08 APRIL 2009.

Disahkan oleh:

(TANDATANGAN PENYELIA) Cop Rasmi:

Tarikh: _______________________

* Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana secara penyelidikan, atau disertasi bagi pengajian secara kerja kursus dan penyelidikan, atau Laporan Projek Sarjana Muda (PSM). ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan

(3)

APPROVAL

This PSM submitted to the senate of UTeM and has been as partial fulfillment of the requirements for the degree of Bachelor of

Manufacturing Engineering (Manufacturing Process)

The members of the supervisory committee are as follow:

………

(Main Supervisor) (Official Stamp & Date)

(4)

DECLARATION

I hereby, declared this thesis entitled “Optimization of machining parameters in high

speed milling of aluminum 6061” is the results of my own research except as cited in references.

Signature : ……….

Author‟s Name : LIM CHONG WEI

(5)

ABSTRACT

This report presents the optimization of machining parameters in high speed milling of aluminum 6061. Aluminum is widely used in industry such as automation, aerospace and others industry. High speed milling is selected either than using conventional milling because it produce more precision final products and also mass production. The goal of research is to determine the possible effect of high speed milling by conducting the surface roughness test on workpieces that produced by different parameters setting. Consequently, the optimum parameters for surface roughness can be done. In this study, the RSM method was used to design and analysis the experiment. There are 20 trials conducted by using 3-axis high speed milling machine. The surface roughness produced was checked by using surface roughness tester. The surface roughness value was analysis in the Design Expert Software using RSM method. From the Design Expert software, quadratic model is suggested based on analysis the Box-Cox, Normal Plot and Predicted versus actual Graph. The significant parameters suggested were cutting speed and feed rate while depth of cut is not a significant factor. For the optimization section, the best predicted setting was cutting speed of 5000rpm, feed rate of 256mm/min and depth of cut of 0.25mm. The average deviation percentage value was about 30%. This might cause by cutting tool wear. More blocks were recommended so that noise effect will reduced and improved the surface quality. The objective was archived if the actual value is near to the predicted value Lastly, the particular study of new invention could improve help the industry to save a lot of unnecessary cost besides improve the products quality so that could increase the challengers in the global market.

(6)

ABSTRAK

Laporan ini menerangkan pengoptimuman parameter dalam „milling‟mesin untuk aluminum 6061. Aluminum digunakan dengan meluas dalam industri seperti automasi, aeroangkasa dan lain-lain industri. „High speed milling‟ dipilih kerana ia boleh menghasilkan produk secara besar-besaran dengan presis jika dibandingkan dengan mesin „milling‟ yang biasa. Objektif eksperimen ini adalah untuk menganalisis permukaan Aluminium dengan menggunakan „surface roughness

tester‟ untuk parameter setting yang berlainan seperti kelajuan spindle, kedalaman pemotogan dan kecepatan material dibuang. Dengan ini,optimum parameters boleh didapatkan. Dalam kerja kursus ini, cara untuk mengalisis adalah menggunakan RSM. Terdapat 20 percubaan akan dibuat dengan menggunakan tiga-axis mesin

„milling‟. Kekasaran permukaan yang dihasilkan akan diuji dengan menggunakan

„surface roughness tester‟. Nilai kekerasan akan dianalysis dalam software Design Expert dengan menggunakan cara RSM. Design Expert Software memberi mencadangkan quadratic model daripada analysis “Box-Cox” atau Graph Normal. ANOVA akan menunjukan parameters yang paling sensitive adalah kelajuan spindle dan kecepatan material dibuang manakala kedalaman pemotongan tidak memberi sensitive kesan kepada permukaan material. .Dalam seksen optimize, parameters yang diberi adalah kelajauan spindle dengan 5000rpm, kecepatan material dibuang adalah 256mm/min dan kedalaman pemotongan 0.25mm. Standard Deviation adalah 30% dan ini disebabkan ketumpulan cutting tool. Kekasaran permukaan akan diperbaiki dengan menjalankan lebih block untuk mengurangkan kebisingan.Objektif experiment ini akan tercapai jika permukaan yang dihasilkan adalah dekat dengan data ramalan. Akhirnya, rekaan baru ini boleh memperbaiki dan membantu industri untuk menjimat banyak kos selain memperbaiki kualiti produk-produk supaya boleh menyahut cabaran-cabaran dalam pasaran global.

(7)

DEDICATION

(8)

ACKNOWLEDGEMENT

Without involvement of many people, this project would not have been possible to complete. I would like to thank all of you especially to my supervisor, Ms Liew Pay Jun. Thanks for her guidance, advice, trust, sincere helping and excellent supervision in accomplishing this study. She is always willing to help me whenever I approach her.

Besides that, I would like to thank all my lecturers of Manufacturing Engineering Faculty and others that provided me with useful information and experience especially in contributing and sharing ideas toward this project.

Furthermore, I would like to extend my thankful to Manufacturing Engineering Laboratory of Universiti Teknikal Malaysia Melaka (UTeM) for providing me the equipments, time and always show their sincere kindness. Then, I also would like to thank my friend for sharing their time, ideas and comments to help me complete the experiment of this project.

Last but not least, I would like to thank my parents and family members for their love, care, support and understanding to carry out this project to the best of my ability.

(9)

TABLE OF CONTENT

Abstract i

Abstrak ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Tables vii

List of Figures viii

List of Abbreviations ix

1. INTRODUCTION 1

1.1 Introduction 1

1.2 Background of problem 2

1.3 Statement of problem 3

1.4 Objective 3

1.5 Scope 3

1.6 Important of study 3

1.7 Expected result 4

2. LITERATURE REVIEW 5

2.1 Milling Machine 5

2.1.1 Machining Center 6

2.1.2 Milling Machine Operation 8

2.1.2.1Peripheral Milling 8

2.1.2.2Face Milling 9

2.1.2.3End Milling 10

2.2 Milling Parameter 11

2.2.1 Cutting Speed 11

2.2.2 Feed Rate 12

2.2.3 Depth of Cut 12

(10)

2.4 Survey of appropriate cutting tool 16

2.5 Surface Roughness 18

2.6 Design of experiment(DOE) 20

2.6.1 Response surface methodology(RSM) 21

2.7 Summarize of journal 24

2.8 Conclusion 29

3. METHODOLOGY 30

3.1 RSM 30

3.2 Flow chart of study 31

3.2.1 Define the objective of the experiments 32

3.2.2 Determine the parameters speed at low level and high level 32

3.2.3 Identify the respond variable 32

3.2.4 Preparation of the experiments 32

3.2.4.1Workpiece preparation 33

3.2.4.2Cutting tool preparation 34

3.2.4.3Equipments and procedures 34

3.2.5 Running the experiments 35

3.2.5.1Testing 35

3.2.6 Define and analysis the results 36

3.2.7 Develop mathematical model of response surface with best fittings 36 3.2.8 Finding the optimal set of experimental parameters 36

3.2.7 Confirmation runs 36

3.2.8 Conclusion 37

4. RESULT AND DISCUSSION 38

4.1 Result 38

4.2 Analysis 40

4.2.1 Fit Summary 40

4.2.2 ANOVA 44

4.2.3 Model Graphs 46

4.3 Optimization 55

4.3.1 Numerical 56

(11)

4.4.1 Average Deviation Percentage Value 60

5.0 RECOMMANDATION AND CONCLUSION 61

5.1 Conclusion 61

5.2 Recommendation of Method Used 62

5.3 Recommendation of Safety 63

References 64

Appendix 68

(12)

LIST OF TABLES

2.1 Al 6061 chemical composition (%) 14

2.2 Mechanical properties at room temperature 15

2.3 Standard tempers and its definitions 15

2.4 Chemical properties of High Speed Steel (HSS) 17

3.1 Factors and their entire unit and speed 32

3.2 Data guide to run the experiments 35

4.1 Surface Roughness Value Of Different Setting 38

4.2 Sequential Model Sum of Square [Type 1] 41

4.3 Lack of fit test 41

4.4 Model Summary Statistic 42

4.5 Analysis of variance table [Partial sum of squares - Type III] 44

4.6 Summarize value of Analysis of variance table 45

4.7 Solution Value Suggested By Design Expert Software 56

4.8 Surface Roughness Value for Random Trail 59

4.9 The Value Of The Kerfs Width And Surface Roughness From The 60 Comfirmation Trials & The deviation of the result with the predicted values.

(13)

LIST OF FIGURES

2.1 VCM with parts name 7

2.2 Movement of the VCM machine 7

2.3 Conventional milling 8

2.4 Climb milling 9

2.5 Face mill with indexable inserts 9

2.6 End Milling 10

2.7 Range of cutting speed for difference materials 13 2.8 Different Cutting Tool with Different Hardness and Fracture Strength 16 2.9 Definition of the arithmetic average height (Ra) 19 2.10 Three spots for taking surface roughness measurements 19 2.11 Principle of a stylus instrument profilometer 20 2.12 Relationship between a response variable and the two independent 22 variables x1 and x2.

3.1 Phase of experiments 30

3.2 Flow Chart of conducting experiments 31

3.3 Flow chart of workpiece preparation 33

3.4 HSS end mill diameter 6mm 34

3.5 HAAS VF Series Vertical Machining Center 34

(14)

4.1 Graph Box-Cox Plot for Power Transform 40 4.2 Predicted Versus Actual Graph For Quadratic Model 42 4.3 Predicted Versus Actual Graph For Linear Model 42

4.4 Normal Plot of Residuals For Quadratic Graph 43

4.5 Normal Plot of Residuals For Linear Graph 43

4.6 One Factor graph of cutting speed (A) versus surface roughness 46 4.7 One Factor graph of feed rate (B) versus surface roughness 48 4.8 One Factor graph of depth of cut (C) versus surface roughness 50

4.9 Perturbation graphs of Factor A, B and C 52

4.10 3D modeling and Contour graph of cutting speed (A) and depth of cut (C) 53 to respond of surface roughness

4.11 3D modeling and Contour graph of cutting speed (A) and feed rate (B) 54 to respond of surface roughness

4.12 A Cube Box Show The Interaction Between Cutting Speed (A),Feed Rate 55 (B) And Depth of Cut

4.13 Ramp Function Graph 57

4.14 3D modeling and Contour graph of cutting speed (A) and feed rate (B) 57 to the desirability.

(15)

LIST OF ABBREVIATIONS

UTeM - University Teknikal Malaysia Melaka PSM - Project Sarjana Muda

DOE - Design of experiment

CNC - Computer Numerical Control ATC - Automatic tool changer VCM - Vertical machining centers RPM - Revolutions per minute

FPT - Feed per tooth

Al - Aluminum

Cr - Chromium

Cu - Copper

Fe - Ferum

Mg - Magnesium

Si - Silicon

Ti - Titanium

Zn - Zinc

CBN - Crystalline Boron Nitride

HSS - High Speed Steel

CLA - Centre line average RMS - Root Means Square

RSM - Respond Surface Methodology

vs - Versus

Prob - Probability

(16)

CHAPTER 1 INTRODUCTION

This chapter describes the introduction to the title of the project and briefly explains on the problem faced on the industry and also the planning of completing PSM 1 .This chapter also includes the scope and important of carried this project.

1.1 Introduction

High speed machining was first develop by German inventor during year 1920 and now widely spread in variety of manufacturing industry included aerospace and automotive sectors where to produce high precession and accuracy parts. Major advantages of high speed machining are high material removing rate, reduction of lead time and the most important is increase parts precision and surface finish. Many industry nowdays facing challenge to improve the quality of products and processes with minimum cost and time constraints.

Commonly, surface roughness is using to determine and evaluate the quality of product, so controlling the parameters in high speed milling are very important to produce a perfect surface finish without damaging machine and cutting tools. Surface roughness also effect several functional attributes of parts such as contact causing surface friction, wearing, light reflection, heat transmission or resisting fatigue. Therefore the desired finish surface is usually specified and the appropriate processes are selected to reach the required quality. The dynamic and widespread of high speed machining operations in the coming decade have raised a need for seeking a systematic solution that can help to

(17)

solve the problem of surface roughness. It is advance to select the parameters of cutting speed; spindle speed and depth of cut because these are the main factors that affect the surface roughness and also can be controllable.

The goal of the research is to determine the possible effect of high speed milling on the aluminum surface by conducting the surface roughness test of the workpieces that produce. This included using the surface roughness tester to check for the surface roughness produce by different speed of cutting and the defects on the surface may lead to major changes in the mechanical properties of the material such as reduction in fatigue life. The results from this research will assist to replace the traditional ―trial and

error‖ method by DOE method which may lead to the improvements in manufacturing

of aircraft and manufacturing industry. Aluminum 6061 is chosen as the material to test because it is widely used for construction of aircraft structures, such as wings and fuselages, more commonly in automation precision parts.

1.2 Background of Problem

For the industry nowadays, mostly the machine operator using ―trial and error‖ method to approach set up for high speed milling and this method is not effective and also very time consuming process. Commonly, machinists have to set the different speed according to their experience with just eye inspection on the surface roughness and this could not get the perfect surface finish. Besides, this method are not effective because they using several type of cutting speed, hence it is difficult to control the tolerance causing low quality of the products. Furthermore, the wrong setting of parameters such as depth of cut without guideline will wasting the cutting tool life hence producing poor surface finish while damaging to the cutter and machine. The industrial also facing challenges to improve the quality of products and process with minimum cost and time constrains because this involve manpower and details research to solve the problem that faced. Hence there is a great need for the author to investigate the effect of feed rate,

(18)

spindle speed and depth of cut to the surface roughness by using RSM method in order to get the best optimum parameter setting for surface roughness.

1.3 Statement of Problem

 What is the effect of different parameters setting such as depth of cut, spindle speed and feed rate to the surface roughness?

 What is the best setting of parameters to get the perfect surface roughness?

1.4 Objective

 To analyze the effect of feed rate, depth of cut and spindle speed to the surface roughness of Aluminum.

 To determine the optimum parameters of surface roughness.

1.5 Scopes

For this experiment, the factors that involved are spindle speed, depth of cut and also feed rate. Material that will be used is Aluminum 6061.RSM method will apply to get the optimum speed of parameters. Cutting tool involved is high speed steel with diameter 6mm. The factors that would not cover are material used, tool geometry, cutting tool diameter, voltage of high speed machining tool design and others.

1.6 Importance of Study

The invention of better surface finish using high speed milling by controlling the parameters could help the automation and aircraft industry to produce better quality parts and increase the challenges in the global markets. Besides, the DOE method could

(19)

help the industry to save time and cost compare to the previous ―trial and error‖ method which need experience machinist to test the surface finish using different of parameters speed.

1.7 Expected Result

The surface roughness produce by high speed milling can be improved by controlling the main parameters such as depth of cut, spindle speed and also feed rate. Different spindle speed, feed rate and depth of cut will produce different type of surface roughness. Besides, by applying DOE method in this experiment, the optimum of machining parameters will be obtained to produce the best surface finish.

(20)

CHAPTER 2 LITERATURE REVIEW

This chapter describes the theory of milling machine and how the parameters are selected by referring to the journal .Besides that, the machining, tool, workpiece properties and summary of journal are also explained and show in this chapter.

2.1 Milling Machine

Milling machine is capable of performing a variety of cutting operations and is among the most versatile and useful machine tools. The first milling machine was built in 1820 by Eli Whitney (1765-1825). Its basic form is that of a rotating cutter which rotates about the spindle axis (similar to a drill), and a table to which the workpiece is affixed. The workpiece is held securely on the work table of the machine or in a holding device clamped to the table. It is then brought into contact with a revolving cutter. [1]

Used for general purpose milling operation, column and knee type machines are the most common milling machines. It can be used in one, two, three planes (X, Y, Z axes). The spindle on which the milling cutter is mounted may be horizontal for peripheral milling or vertical for face and end milling, boring, and drilling operations. A wide selection of typical standard milling machine with numerous features is now available. However, these milling machine and operations are now being replaced with computer controls and machining centers. It can be highly automated in order to increase the productivity, and it is indeed the principle behind transfer lines. [1]

(21)

2.1.1 Machining Center

A machining centers is an advanced, computer controlled machine tools that is capable of performing a variety of machining operations on different surfaces and different orientations of a workpiece without having to remove it from its workholding device or fixture. The workpiece is generally stationary, and the cutting tools rotate as they do in milling, drilling, honing, tapping, and similar operations. Whereas in transfer lines or in typical shops and factories the workpiece is brought to the machine, note that in machining centers, it is the machining operation that is brought to the workpiece. CNC machine allow more operation to be done on a part in one setup instead of moving from machine to machine for various operations. These machines greatly increase productivity because the time formerly used to move a part from machine to machine is eliminated. [1]

There are three main types of machining centers which is horizontal, the vertical spindle and universal machines. They are available in many types and sizes which may determine by following factors:

 The size and weight of the largest piece that can be machined.

 The maximum travel of the three primary axes (X, Y, Z).

 The maximum speed and feeds available.

 The horsepower of the spindle.

 The number of tools that the automatic tool changer (ATC) can hold.

Vertical machining centers (VCM) are capable to performing various machining operations on parts with deep cavities, such as in mold and die making. A vertical-spindle machining center is a saddle-type construction with sliding bedways that use a sliding vertical head instead of a quill movement and it is shown in Figure2.1. The tool magazine is on the left of the figure and all operation and movements are directed and modified through the computer control panel. Because the thrust forces in the vertical machining are directed downward, such machines have high stiffness and produces parts with good dimensional accuracy. [2]

(22)

Figure 2.1: VCM with parts name

The vertical machining center operates on three axes which show in Figure2.2:

 The X axis controls the table movement left or right.

 The Y axis controls the table movement toward or away from the column.

 The Z axis controls the vertical movement (up or down) of the spindle or knee.

(23)

2.1.2 Milling machining operation

There are three basic types of milling operations, which is a) Peripheral milling

b) Face milling c) End milling

2.1.2.1Peripheral milling

Peripheral milling also called plain milling which the axis of cutter rotation is parallel to the workpiece surface as show in figure. The cutter body which generally is made of high speed steel has a number of teeth along its circumference; each tooth acts like a single-point cutting tool. Cutter of peripheral milling may have straight or helical teeth, resulting in orthogonal or oblique cutting action.

There are two type of peripheral milling:

 Conventional milling

 Climb Milling

(24)

Figure 2.4: Climb milling

2.1.2.2Face milling

The cutter is mounted on the spindle having an axis of rotation perpendicular to the workpiece surface and removes material as in figure 2.5. Because of the relative motion between the cutter teeth and workpiece, face milling leaves feed marks on the machined surface. The surface roughness of the workpiece depends on the corner geometry of the inserts and feed per tooth. In typical face-milling operation, the ratio of the cutter diameter, D to the width of cut, w should be not less than 3:2. [1]

(1)