Effects of Tool Length In Milling Operation.

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Effects of Tool Length in Milling Operation

Thesis submitted in accordance with the partial requirement of the Malaysia Technical University of Malacca for the degree of Bachelor of Manufacturing Engineering (Manufacturing Process)

AHMAD FHADLI BIN SALLEH

Faculty of Manufacturing Engineering March 2008

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UTeM Library (Pind.1/2005)

UNIVERSITI TEKNIKAL MALAYSIA MELAKA (UTeM)

BORANG PENGESAHAN STATUS TESIS*

JUDUL: EFFECTS OF TOOL LENGTH IN MILLING OPERATION

SESI PENGAJIAN: 2007/ 2008

Saya AHMAD FHADLI BIN SALLEH

mengaku membenarkan t esis (PSM/ Sarj ana/ Dokt or Falsaf ah) ini disimpan di Perpust akaan Universit i Teknikal Malaysia Melaka (UTeM) dengan syarat -syarat kegunaan sepert i berikut :

1. Tesis adalah hak milik Universit i Teknikal Malaysia Melaka.

2. Perpust akaan Universit i Teknikal Malaysia Melaka dibenarkan membuat salinan unt uk t uj uan pengaj ian sahaj a.

3. Perpust akaan dibenarkan membuat salinan t esis ini sebagai bahan pert ukaran ant ara inst it usi pengaj ian t inggi.

4. **Sila t andakan (√) SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarj ah keselamat an at au kepent ingan Mal aysia yang t ermakt ub di dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang t elah dit ent ukan oleh organisasi/ badan di mana penyelidikan dij alankan)

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Disahkan ol eh:

(TANDATANGAN PENYELIA) Cop Rasmi:

Tarikh:

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Tel : 06-233 2421, Faks : 06 233 2414 Email : fkp@utem.edu.my

UNIVERSITI TEKNIKAL MALAYSIA MELAKA Karung Berkunci 1200, Ayer Keroh, 75450 Melaka

FAKULTI KEJURUTERAAN PEMBUATAN

Rujukan Kami (Our Ref) : 20 May 2008

Rujukan Tuan (Your Ref):

Pust akawan

Perpust akawan Universit i Teknikal Malaysia Melaka UTeM, Ayer Keroh

MELAKA. Saudara,

PENGKELASAN TESIS SEBAGAI SULIT/ TERHAD

- TESIS SARJANA MUDA KEJURUTERAAN PEMBUATAN (PROSES PEMBUATAN): AHMAD FHADLI BIN SALLEH

TAJUK: EFFECTS OF TOOL LENGTH IN MILLING OPERATION

Sukacit a dimaklumkan bahawa t esis yang t ersebut di at as bert aj uk “ Effect s of Tool Lengt h in Milling Operat ion” mohon dikelaskan sebagai t erhad unt uk t empoh lima (5) t ahun dari t arikh surat ini memandangkan ia mempunyai nilai dan pot ensi unt uk dikomersialkan di masa hadapan.

Sekian dimaklumkan. Terima kasih.

“ BERKHIDMAT UNTUK NEGARA KERANA ALLAH”

Yang benar,

WAN HASRULNIZZAM WAN MAHMOOD Pensyarah,

Fakul t i Kej urut eraan Pembuat an

(Penyel ia Bersama)

06-2332122

s. k. - Penyelia Ut ama:

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DECLARATION

I hereby, declare this thesis entitled “Effects of Tool Length in Milling Operation” is the results of my own research except as cited in the reference.

Signature : ………. Author’s Name : ………

Date : ………

AHMAD FHADLI BIN SALLEH 20 MAY 2008

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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

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ABSTRACT

Determination of the tool length effect in the milling operation is important due to its controlling influence on the surface roughness, tool wear and the quality of the machining parts. Numerous attempts have been made to approach the problem with different methods including experimental, analytical and also numerical analysis. The study is focused on determining the effect of the tool length to the surface roughness, tool wear and chip produced. The experiment was done by using the tool steel and Mild Steel 1020 as the workpiece material and also HSS Co 8 cobalt end mill cutter. The experiment was done by using two different tool lengths which is 12/18 and 14/18 from the total length with two different machining parameters i.e. speed and feed rate. The used speed for mild steel workpiece is 1400 mm/min and 900 mm/min and the feed rate is 500 mm/min and 200 mm/min. While for the tool steel workpiece, the used speed probably 850 mm/min and 550 mm/min and the feed rate is 350 mm/min and 150 mm/min. Experimental results indicate the different tool length of cutting tool affected to the surface finish obtained. The lower tool length (12/18) shows better surface roughness than higher tool length (14/18).

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ABSTRAK

Penentuan terhadap kesan panjang mata alat yang digunakan ke atas operasi meraut adalah amat penting dalam mengawal pengaruh ke atas kekasaran permukaan bahan, kehausan mata alat dan juga juga kualiti bahan kerja tersebut. Pelbagai usaha digunakan untuk meyelesaikan masalah tersebut iaitu secara membuat ujikaji, analisis dan juga secara menggunakan pengiraan. Kajian ini difokuskan untuk menentukan kesan panjang mata alat terhadap serpihan bahan, kekasaran permukaan bahan dan kehausan mata alat yang digunakan. Eksperimen ini dijalankan dengan menggunakan bahan jenis (Tool Steel dan Mild Steel 1020) untuk diuji dan menggunakan mata alat pemotong jenis (HSS Co 8 Cobalt). Dua panjang mata alat yang berlainan iaitu 12/18 dan 14/18 daripada panjang mata alat sebenar di samping dua parameter yang berbeza turut digunakan iaitu kelajuan dan kadar meraut. Kelajuan yang diaplikasikan ketika menguji bahan (mild steel) adalah 1400 mm/min dan 900 mm/min manakala kadar meraut adalah 500 mm/min dan 200 mm/min. Bagi penggunaan bahan (tool steel), kelajuan yang digunakan adalah 850 mm/min dan 550 mm/min dan kadar meraut adalah 350 mm/min dan 150 mm/min. Keputusan eksperimen menunjukkan penggunaan panjang mata alat yang berbeza memberi kesan terhadap permukaan bahan yang diproses. Penggunaan panjang mata alat yang paling minima memberikan kesan yang lebih baik berbanding penggunaan panjang mata alat yang maksima.

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DEDICATION

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ACKNOWLEDGEMENTS

First and foremost, I would like to express my highest appreciation to my supportive academic supervisor, Mr. Raja Izamshah B. Raja Abdullah for his supervision and support in completing this thesis.

Mr Jaafar, the technician leader, for his eager assistance and for providing equipment that was required. Also, I want to thank Mr Afendy and Mr Fauzi for their help in conducting and teaching the CNC milling to fulfill this thesis.

I also would like to convey my biggest thanks to all UTeM staff especially to all staff at manufacturing department for supporting me throughout my PSM Project. The knowledge and experience I gained from you all will not be forgotten. I’m also obliged to everyone who had directly and indirectly involve through contributions of ideas, as well as materials and professional opinions.

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Abstract i

Abstrak ii

Dedication iii

Acknowledgment iv

Table of Contents v

List of Figures viii

List of Tables x

List of Abbreviations, Symbols, Specialized Nomenclature xi

1.0INTRODUCTION 1 1.1 Problem Statement 2

1.2 Objectives 3 1.3 Scope 3

2.0 LITERATURE REVIEW 4 2.1 Computer Numerical Control (CNC) milling machine 4 2.1.1 CNC Milling Operation 5

2.1.2 Selection for Milling Cutter 6

2.2 The Effect of the Surface and Tool in CNC Milling Operation 8 2.2.1 The Influence Factor of the Cutting Condition 8

2.2.1.1 High Speed Machining 9

2.2.1.2 Feed for Milling 9

2.2.1.3 Speed for Milling 10

2.2.1.4 The Cutter 10

2.2.2 Tool Deflection Test 11

2.2.2.1 Correlation of Deflection Experimental Value with Simple Model 12 2.2.2.2 Stiffness of the Shank and Tool Holder 13 2.2.2.3 Cutting Force Error Determination 14

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2.2.3 Influence of Tool Run-Out 15 2.2.4 Influence of Ploughing 15

2.3 Tool Wear 15

2.3.1 Type of Wear 16

2.3.2 Tool Wear Effect 17

2.3.2.1 Tool Run-Out Default 18

2.4 Chip 18

2.5 Surface Finish 19

2.5.1 Ideal Surface Finish 20 2.5.2 Impact of Milling Stability onto Machined Surface Roughness 20

2.5.3 Surface on Unstable Milling 21 2.5.4 The Factor Effect of the Surface Roughness 22 2.6 Overview Design Experiment (DOE) 24

2.6.1 The Role and Implication of DOE 24 2.6.2 Orthogonal Array (OA) 25

3.0 METHODOLOGY 27

3.1 Introduction 27

3.2 Study Tool Length Effect in Machining Operation 31 3.3 Design of Experiment 31 3.3.1 Tool Length 33 3.3.2 Feed Rate 34

3.3.3 Speed 34

3.4 Prepare the Sample 34

3.4.1 Mild Steel 35

3.4.2 Tool Steel 35

3.5 Machine Selection 35

3.5.1 G- Code 37

3.5.1.1 Machining Process 38

3.5.2 Cutting Tool 40

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3.6.1.1 Surface Roughness Measurement 41 3.6.2 The Metallurgy Microscope 42

3.6.3 Dial Caliper 43

3.7 Analyze the Data 44

4.0 RESULTS/ANALYISIS 45

4.1 Introduction 45

4.2 Surface Roughness Result 45 4.2.1 Analysis for Significant Parameter 47 4.2.2 Surface Roughness Analysis for Mild Steel Material 47 4.2.3 Surface Roughness Analysis for Tool Steel Material 51

4.3 Chip Thickness Result 56

4.3.1 Chip Thickness Analysis for Mild Steel 57 4.3.2 Chip Thickness Analysis for Tool Steel 58 4.4 Observation of Tool Wear 60

5.0 DISCUSSIONS 64

5.1 Tool Length 64

5.2 Speed and Feed Rate Factor 65

5.3 Tool Wear 66

6.0 CONCLUSION AND RECOMMENDATIONS 67

6.1 Conclusion 67

6.2 Recommendation 68

REFERENCES 69

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LIST OF FIGURES

2.1 Effect milling cutting diameter workpiece travel 7 2.2 Tool path direction in three-axis ball-end milling of an inclined surface 8

2.2a Up- ramping 8

2.2b Down ramping 8

2.2c Down-cutting contouring 8

2.2d Up-cutting countering 8

2.3 Type of milling cutter 11 2.4 Deflection test on the machine and result for ball-end mill Ø 8mm. 11 2.5 Deflection verification test of the cantilever beam model, and points

where the deflection is measured 12 2.6 Diagram representing the tests performed on the machine 13 2.7 Slot C and Hole B cutting test along X axis in forward direction. 14 2.8 Representative scanning electron microscopy (SEM) figures of tool wear 17 2.9 Chip Form Produced in Machining Operation 19 2.10 Profile of the machined surface and workpiece simulation deflected

during unstable milling 22

2.11 Pair means comparison for spindle levels 23 2.12 Pair means comparison for depth levels 23

3.1 Methodology Flow Chart 28

3.2 Workpiece 34

3.3 HAAS CNC Milling machine 35

3.4 Jig use 38

3.5 Set the programme code 39 3.6 Tool length Measurement 39 3.7 Machine operation to the workpiece 39

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3.10 Portable Surface Roughness Tester 41 3.11 Surface roughness measurement 42

3.12 Metallurgy Microscope 42

3.13 Dial Calliper 43

3.14 Measure the chip thickness 44

4.1 Estimated effects and coefficients for Ra 47 4.2 Normal probability plot of the standardized effects 48 4.3 Pareto chart of the standardized effects 54 4.4 Main effects plot (data means) for Ra 49 4.5 Interaction plot (data means) for Ra 50 4.6 Estimated effects and coefficients for Ra 52 4.7 Normal probability plot of the standardized effects 52 4.8 Pareto chart of the standardized effects 53 4.9 Main effects plot (data means) for Ra 54 4.10 Interaction plot (data means) for Ra 55 4.11 Estimated effects and coefficients for chip thickness 57 4.12 Normal probability plot of the standardized effects 58 4.13 Estimated effects and coefficients for Chip Thickness 59 4.14 Graph normal probability plot of the standardized effect 59 4.15 Observation before milling operation 61

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LIST OF TABLES

2.1 Classical Array 26

2.2 Taguchi Arrays 26

3.1 Gantt Chat for PSM 1 29 3.2 Gantt Chat for PSM 2 30 3.3 The Level of Process Parameter for Mild Steel 31 3.4 The Level of Process Parameter for Tool Steel 32 3.5 Orthogonal Array table for experiment use Mild Steel workpiece 32 3.6 Orthogonal Array table for experiment use Tool Steel workpiece 33 3.7 Machine Specification of CNC Milling Machine 36 3.8 The machining G-Code programme 37

4.1 The result for Mild Steel material 46 4.2 The result for Tool Steel material 46 4.3 Mean value of surface roughness for Mild Steel 1020

for each 2- way interaction 51 4.4 Mean value of surface roughness for Tool Steel

for each 2- way interaction 55 4.5 Chip thickness result for Mild Steel 56 4.6 Chip thickness result for Tool Steel 57 4.7 Tool wear of cutting tool 60 4.8 Tool wear micro picture for Mild Steel material at 12/18 tool length 61 4.9 Tool wear micro picture for Mild Steel material at 14/18 tool length 62 4.10 Tool wear micro picture for Tool Steel material at 12/18 tool length 62 4.11 Tool wear micro picture for Tool Steel material at 14/18 tool length 63

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LIST OF ABBREVIATIONS, SYMBOLS, SPECIALIZED

NOMENCLATURE

% - percent µ - micro

µm - micro meter cm - centimeter

CAM - computer aided manufacturing CNC - computer numerical control DOE - design of experiment DoF - degree of freedom in - inch

LF - distance to the force application point m - meter

mm - millimeter OA - orthogonal Array PC - personal computer Ra - arithmetic mean value

Rq - root mean square average

Rt - peak to peak surface rughness

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CHAPTER 1 INTRODUCTION

1.0 Introduction

The CNC Milling is one of the advanced machining that can automatically operate without too many operator handled. However the most important thing in CNC machining operation is the code of programming and the tool set up. The tool set up is a crucial step as it will influence the quality of machined part.

There are many factors that influence the results of machining operation such as the coolant, type of tools, materials, speed and feed rate. These problems may happen when the machining operation does not refer to the suitable schedule of operation and choose the wrong parameters. Before any machining operations are run, all related parameters must take into account. This is because it can avoid any waste in any product produced and increase the capability of machine and tool life. Besides, it can reduce any redundant of cost to any companies by producing a quantity of quality products.

The research on the effect of tool length is to obtain the suitable tool length used during milling operation. There are many ideas from people of choosing the suitable tool length set up to the tool holder. However, the different tool length will also give some effects to the surface finish and will increase the tool wear.

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The vibration of the cutting tool will be generated during the machining if the tool is tied at short length. This situation may happen due to the force of the mill increase while the tool stands in poor condition. The tool may be broken when the force is increased or during high speed.

The result of this experiment can be obtained by taking measurements of surface roughness on the workpiece, chip produced and also rate of tool wear. The Portable Surface Roughness Tester will be utilised to take the measurement of the surface roughness and the thickness of the chips will be recorded. All the measurements taken will be determined by using appropriate graphs to monitor the effects of tool length with the variable parameters involved in this experiment.

1.1 Problem Statement

Usually, the tool length will be set up by inserting the tool into the tool holder until it will fit and lock. So, the tool length of this experiment will be divided into two values which are 12/18 and 14/18 of the overall tool length. These values may influence the effect of the surface roughness, chips produced and as well as tool wear. The vibration and the force during the machining are also the dominant factors that influence the results.

The increased of temperature during the machining process can be considered as one of the sources of tool wear produced and poor surface finish. Therefore, the goal of this experiment is to suggest the optimum tool length value with the controlling the machining programme (surface finish and tool wear).

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1.2 Objectives

The purposes of this project are:

i. To find the suitable tool length value of cutter during milling operation. ii. To find the effects of surface roughness for different tool length in milling.

iii. To find the significant machining parameters that influences the surface roughness in milling.

1.3 Scope

The scopes of this project are:

i. To machine Mild Steel and Tool Steel using different tool length and machine parameters.

ii. To obtain the surface roughness by milling operation. iii. To observe the tool wear using metallurgy microscope.

iv. Apply the design of experiment (DOE) to analyze the most significant factors that influence the machining performance.

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CHAPTER 2 LITERATURE REVIEW

2.1 Computer Numerical Control (CNC) Milling Machine

Computer numerical control (CNC) is the machines that can operate automatic refer to the program that was setting and the code inserted to the PC and it will transfer to

the machine. Other, CNC milling machines or machining centers is computer

controlled vertical mills with the ability to move the spindle vertically along the Z-axis.Usually; the CNC Milling can perform the functions of drilling and often turning. CNC machines today are controlled directly from files created by CAM software packages, so that a part or assembly can go directly from design to manufacturing without the need of producing a drafted paper drawing of the manufactured component.

CNC milling uses a computer program written in a notation called G-code, which conforms to the EIA-274-D standard. CNC milling machines feature a rotating cylindrical cutter with multiple flutes, known as an endmill. The endmill is capable of traveling along multiple axes and is used for machining techniques such as slots, pockets, and profiles (Ananymous, 2005a).

Other types of machining centers are primarily milling and boring machines which can perform a variety of other operation such as drilling, reaming, and tapping without changing the part set up. They are sometime referred to as multitasking machines (Stephenson and Agapiou, 2006).

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CNC milling is a technology whereby a machine tool is driven by a computer to produce a desired shape. The Computer Numerical Control computer is programmed to drive the motors attached to each of the machines moving axes in a discrete manner to create the cutting action, which will produce the desired shape in a work piece

2.1.1 CNC Milling Operation

A milling machine is a machine tool used for the complex shaping of metal and other solid materials. Its basic form is that of a rotating cutter or endmill which rotates about the spindle axis as similar to a drill and a movable table to which the workpiece is affixed. That is to say, the cutting tool generally remains stationary while the workpiece moves to accomplish the cutting action. Milling machines may be operated manually or under computer numerical control. Some machines might even make 1000 parts on a weekend with no operator, checking each part with lasers and sensors.

The function of CNC Milling machine can refer to the G-Code that transfer to the control panel. This code will make the machine run refer to the program that had download to the control panel. The several types of instruction will do of this machine were:

a) Movement: The most basic motion for a controller is to move the machine

tool along a linear path from one point to another. Some machine tools can only do this in XY, and have to accept changes in Z separately. Some have two further axes of rotation to control the orientation of the cutter, and can move them simultaneously with the XYZ motion.

b) Tool Changes: Originally there would be a G-code instruction telling the

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of different tools which they can change themselves pneumatically, hydraulically, and electromechanically.

c) Drilling: A tool can be used to drill holes by pecking to let the sward out. Using a special tapping tool and the ability to control the exact rotational position of the tool with the depth of cut, it can be used to cut screw threads.

d) Drilling Cycle: A drilling cycle is used to repeat drilling or tapping operations on a workpiece. The drilling cycle accepts a list of parameters about the operation, such as depth and feed rate. To begin drilling any number of holes to the specifications configured in the cycle, the only input required is a set of coordinates for hole location. The cycle takes care of depth, feed rate, retraction, and other parameters that appear in more complex cycles. After the holes are completed, the machine is given another command to cancel the cycle, and resumes operation.

e) Parametric Programming: A more recent advancement in CNC interpreters is

support of logical commands, known as parametric programming. Parametric programs incorporate both G-code and these logical constructs to create a programming language and syntax similar to basic comment.

2.1.2 Selection for Milling Cutter

There were very important to choose the suitable during the machining process. It will avoid any defect the machine and the product produce. Figure 2.1, show the effect of cutting diameter during the machining process. Consider the following when choosing milling cutters:

a) 45° angular cuts may either be made with a 45° single angle milling cutter while the workpiece is held in a swivel vise, or with an end milling cutter while the workpiece is set at the required angle in a universal vise.

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b) Use a coarse-tooth milling cutter for roughing cuts and a finer-toothed milling cutter for light cuts and finishing operations.

c) When milling stock to length, the choice of using a pair of side milling cutters to straddle the workpiece, a single side milling cutter, or an end milling cutter will depend upon the number of pieces to be cut.

d) High-speed steel, stellite, and cemented carbide cutters reamer shank. In this case, one or two side milling have a distinct advantage of being capable of rapid cutters, a fly cutter, or an end milling cutter may be used roduction when used on a machine that can reach the proper speed.

e) The milling cutter should be small enough in diameter so that the pressure of the cut will not cause the workpiece to be sprung or displaced while being milled.

Figure 2.1: Effect milling cutting diameter workpiece travel (Stephenson and Agapiou, 2006).

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2.2 The Effect of the Surface and Tool in CNC Milling Operation

The tool length also effects the machining operation of the surface roughness of the workpiece. This machining process also influence by the speed rate, dept of cut and feed rate. This situation will show the effect by the chip produce and result of the surface roughness.

According to the Raksiri, (2004) on his studies the other major cause of inaccuracy in CNC milling machine is error due to cutting force. The error in workpiece is caused either by excessive deformation at the tool and workpiece interface due to cutting action or by deformation of machine tool structure.

2.2.1 The Influence Factor of the Cutting Condition

There were many direction of milling cutting during produce the product or any machining part. The cutting condition can be the factor of the surface roughness result in milling operation. Refer to the Dudzinski, (2007) on his studies about the cutting force in ball-end milling with tool-surface and predictive force. Figure 2.2 shows direction cutting influence force in milling operation.

Figure 2.2: Tool path direction in three-axis ball-end milling of an inclined surface. (a) Up- ramping, (b) down ramping, (c) down-cutting contouring, and (d) up-cutting countering. (Source: Dudzinski et al. 2007)

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