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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

THE STUDY OF SIZE EFFECT ON SURFACE FINISH WHEN

HARD TURNING AISI D2 TOOL STEEL

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

MOHD AIZAT BIN A. HAMID

FACULTY OF MANUFACTURING ENGINEERING

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PSM

TAJUK: “The Study of Size Effect on Surface Finish when Hard Turning AISI D2 Tool Steel”

SESI PENGAJIAN: 2008/2009 Semester 2

Saya MOHD AIZAT BIN A. HAMIDmengaku membenarkan laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:

1. Laporan PSM / tesis adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis.2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan untuk tujuan pengajian sahaja dengan izin penulis.3. Perpustakaan dibenarkan membuat salinan laporan PSM / 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)

6, JALAN IKHLAS 7,BANDAR TUN RAZAK,56000 CHERAS, W. PERSEKUTUAN (KL)

Tarikh: _______________________

Cop Rasmi:

Tarikh: _______________________

* Jika laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.

APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a

partial fulfillment 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 of Supervisor)

……………………………………………..

(Official Stamp of Supervisor)

ABSTRACT

The introduction of hard turning has provided an alternative to the conventional

processing technology used to manufacture parts made from hardened steels. Shorter

product development time along with being more environmentally friendly are among

the benefits offered by hard turning, which potentially results in lower manufacturing

cost per part. However, common tool materials for hard turning applications are

expensive. Due to the continuous developments in cutting tool materials and coating

technology, inexpensive coated carbide cutting tools are being investigated to determine

the potential of using them for use in extreme conditions as in hard turning. TiN coated

carbide tool was selected to finish machine hardened steel. Performing hard turning at

various workpiece size revealed that the surface finish values of 0.68 µm that meet the

strict range of finish machining of workpiece diameter of 70 mm and 0.77 µm of finish

machining of workpiece diameter of 100 mm were obtained when finish machining

hardened steel of 45 HRC hardness. The results show that smooth surface finish was

influenced by workpiece diameter.

i

ABSTRAK

Pengenalan kepada larikan keras telah menyediakan satu alternatif untuk

teknologi pemprosesan yang konvensional untuk mengeluarkan bahagian-bahagian yang

diperbuat daripada keluli keras. Masa pembangunan produk yang lebih pendek bersama

dengan menjadi lebih mesra alam adalah antara faedah ditawarkan oleh larikan keras,

yang berpotensi mengakibatkan kos perkilangan lebih rendah setiap bahagian.

Walaubagaimanapun, bahan-bahan alat biasa untuk aplikasi-aplikasi larikan keras adalah

mahal, bersandarkan kepada pembangunan yang berterusan dalam bahan-bahan

perkakas pemotongan dan teknologi saduran, mata alat memotong karbida yang bersalut

adalah diselidiki untuk menentukan potensi menggunakannya untuk penggunaan dalam

proses pemesinan seperti yang terdapat dalam peralihan keras. TiN karbida bersalut

telah dipilih untuk menghabiskan proses pemesinan keluli keras. Hasil larikan keras

pada pelbagai saiz benda kerja menunjukkan nilai hasil permukaan 0.68 µm apabila

menjalankan proses pemesinan diameter benda kerja 70 mm dan 0.77 µm apabila

menjalankan proses pemesinan diameter benda kerja 100 mm telah diperolehi apabila

pemesinan akhir keluli keras yang mempunyai kekerasan 45 HRC. Keputusan

menunjukkan permukaan benda kerja yang baik dipengaruhi oleh diameter benda kerja.

ii

ACKNOWLEDGEMENT

The author wishes to express his most sincere appreciate to his supervisor, Dr.

Ahmad Kamely Bin Mohamad of the department of Manufacturing Process for

providing tremendous technical guidance, advices, continuous encouragement,

constructive criticisms, suggestions throughout this project and administrative support

during this project. Sincere thanks is extended wish to the general, his examiner, Dr.

Bagas Wardono and fellow friends for their corporation and help during the period of

this project. The author always appreciates to the Faculty of Manufacturing Engineering,

Universiti Teknikal Malaysia Melaka (UTeM) for providing the facilities for this

project.

iii

DEDICATION

Specially dedicated for my beloved father, A. Hamid Bin A. Rahman and my mother, Siti

Rohani Binti Che Omar who are very concerns, understanding patient and supporting.

Thank you for everything to my supervisor, Dr. Ahmad Kamely Bin Mohamad, my

sisters, my brothers and all my friends. The work and success will never be achieved

without all of you

iv

TABLE OF CONTENT

Abstract i

Abstrak ii

Acknowledgement iii

Dedication iv

Table of Content v

List of Tables viii

List of Figures ix

List of Abbreviations xi

1. INTRODUCTION 1

1.1 Background 1

1.2 Problems Statement 2

1.3 Objectives 3

1.4 Scope of Work 3

1.5 Significance of the Study 3

v

2. LITERATURE REVIEW 4

2.1 Introduction 4

2.2 Hard Turning 5

2.2.1 Parameters in Hard Turning 6

2.3 Hard Turning Using TiAIN Coated Carbide Tool 7

2.4 Hard Turning of Stainless Steel Using Wiper Coated Carbide Tool 8

2.5 Performance of Coated Carbide Tools in Hard Turning 10

2.6 Wear 11

2.7 Coating 13

2.8 Surface Finish 14

2.9 The Relationship Between the Work Piece Extension Length/Diameter 19

Ratio and Surface Roughness in Turning Applications

2.10 Dynamic Instability of the Hard Turning Process 21

3. RESEARCH METHODOLOGY 23

3.1 Introduction 23

3.2 Cutting Condition 24

3.3 Tool Wear Standard 25

3.4 Workpiece Material 27

3.5 Surface Roughness Measurement 30

PSM 1 Gantt Chart 32

vi

4. RESLUTS AND DISCUSSION 33

4.1 Surface Finish 34

4.2 Influence of the Tool Nose Radius 38

4.3 Influence of the Dry Cut Finishing 39

4.4 Influence of the Workpiece Diameter 40

4.5 Motion Capability and Machine Accuracy 41

5. CONCLUSION AND RECOMMENDATION 42

5.1 Conclusion 42

5.2 Recommendation 43

GANTT CHART 44

REFERENCES 55

LIST OF APPENDICES 53

vii

LIST OF TABLES

3.1 Tools technical details and cutting conditions (Tool’s catalogue). 25

3.2 Properties of tungsten carbide and coating materials (Tool’s catalogue). 25

3.3 Recommendations used in industrial practice for limit of flank wear VBB

for several cutting materials (Astakhov and Davim, 2008). 27

3.4 AISI D2 properties (Tool’s catalogue). 28

3.5 Cutting data parameters for turning (Tool’s catalogue). 29

4.1 Results of surface roughness of cutting parameter. 35

4.2 Results of surface roughness of cutting parameter. 35

LIST OF FIGURES

viii

2.1 Typical wear pattern and pertinent terminology. 12

2.2 Illustration of surface roughness. 15

2.3 Surface roughness vs. tool wear. 16

2.4 Surface roughness (Ra and Rmax) and flank wear vs. 17

length of cutting.

2.5 Surface roughness vs. cutting length (lc) for different 17

cutting speeds.

2.6 Surface roughness measurements vs. cutting speed. 18

3.1 f = feed, r = corner radius and Ra = surface finish. 24

3.2 Types of tool wear according to standard ISO 3685:1993. 26

3.3 Progressive die made of AISI D2. Long run tooling for 29

blanking of parts in thin sheets.

3.4 Center drilling the work pieces. 30

3.5 Profilometer of Surface roughness Tester Mitutoyo SJ-301. 31

4.1 The diagram of average surface roughness value (Ra) obtained by 34

processing AISI D2 tool steel with coated carbide cutting tool at

200 mm/min cutting speed and 0.16 mm/rev feed rate.

4.2 The average surface roughness (Ra) obtained by processing the 36

AISI D2 tool steel with different cutters at constant cutting speeds

and at chosen 0.16 mm/rev feed rates.

4.3 The average surface roughness (Ra) obtained by processing 36

the AISI D2 tool steel with different spindle speed (rpm)

ix

LIST OF ABBREVIATIONS

x

CNC - Computer Numerical Control

CBN - Cubic Boron Nitride

VB - Average Wear Land Width

VBmax - Maximum Wear Land Width

PVD - Physical Vapor Deposition

ISO - International Standard Organization

Fe3C - Ferum Carbide

TiC - Titanium Carbide

TiN - Titanium Nitride

Al2O3 - Aluminum Oxide

TiO2 - Titanium Oxide

AA - Arithmetic Average

Vb - Flank Wear

Ra - Surface Roughness

VA - Front face wear

µm - micron meter

xi

CHAPTER 1

INTRODUCTION

1.1 Background

In the manufacturing industries, mold and die making usually refers to the parts

produced that are asymmetrical in shape. Sheet metal components are of various shapes,

and injection molded plastic parts range from household appliances to consumer

electronics. Hard turning is applied to make a die and mold to produce variety of plastic

parts.

Hard turning is a single point machining process, is carried out on a lathe and

carried out on hard materials which have Rockwell C hardness greater than 45. The

process is intended to replace or limit traditional grinding operations that are expensive,

environmentally unfriendly, and inflexible. Hard turning, when applied for purely stock

removal purposes, competes favorably with rough grinding. However, when it is applied

for finishing where form and dimension are critical, grinding is superior.

First introduced around 1926, cemented carbides are the most popular and most

common high production tool materials available today (Metals Handbook, 1980). The

productivity enhancement of manufacturing processes imposes the acceleration of the

1

design and evolution of improved cutting tools with respect to the achievement of a

superior tribological attainment and wear resistance (Bouzakis, 2000).

One important aspect that is being vigorously researched and developed is the

hard coating for cutting tools. These hard coatings are thin films that range from one

layer to hundreds of layers and have thickness that range from few nanometers to few

millimeters. These hard coatings have been proven to increase the tool life by as much

as 10 folds through slowing down the wear phenomenon of the cutting tools. This

increase in tool life allows for less frequent tool changes, therefore increasing the batch

sizes that could be manufactured and in turn, not only reducing manufacturing cost, but

also reducing the setup time as well as the setup cost (Nouilati, 2002).

Surface finish influences not only to the dimensional accuracy of machined parts

but also their properties and their performance in service. The term surface finish

describes the geometry features of a surface, and surface integrity pertains to material

properties, such as fatigue life and corrosion resistance, which are strongly influenced by

the nature of the surface produced. The quality of machined surface is characterized by

the accuracy of its manufacture with respect to the dimensions specified by the designer.

Every machining operation leaves characteristic evidence on the machined surface. This

evidence in the form of finely spaced micro irregularities left by the cutting tool. Each

type of cutting tool leaves its own individual pattern which therefore can be identified.

This pattern is known as surface finish or surface roughness.

In addition to increasing the tool life, hard coating deposited on cutting tools

allows for improved and more consistent surface roughness of the machined work piece.

The surface roughness of the machined workpiece changes as the diameter of the

workpiece changes due to cutting speed in revolutions per minute (rpm).

1.2 Problems Statement

In machining of parts, surface quality is one of the most important that specified

customer requirements. Major indication of surface quality of machine parts is surface

2

roughness. Roughness is often closely related to the friction and wear properties of a

surface. There are various machining parameters that have an effect of the surface

roughness, but size effect has not been adequately quantified.

1.3 Objectives

The objective of this study is to investigate the influences of the workpiece size on

surface finish when hard turning AISI D2 tool steel of 45 HRC with carbide cutting tool.

Besides that, the influence of size effect on surface morphology is also been deserve.

1.4 Scope of Work

This study will aim an experimental investigation with coated carbide tools in turning

hardened AISI D2 steel of 45 HRC, aiming at determining the most suitable parameters

and material characteristics. To achieve this goal, turning tests were conducted with a

CNC lathe using commercially available carbide cutting inserts. The surface finish of the

workpiece will be measure by using surface roughness profilometer.

1.5 Significance of the Study

Many factors will affect the performance of a component. Some of the more commonly

discussed factor is surface finish. The surface finish has a significant effect on fatigue

strength of a component such as bearing. Fortunately, the study of size effect on surface

finish is still not adequate and need to be research for further understanding.

3

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

The introduction of hard turning has provided an alternative to the usual processing

technology used to manufacture parts made from hardened steels. Shorter product

development time along with being more environmentally friendly are among the

benefits offered by hard turning, which potentially results in lower manufacturing cost

per part. However, common tool materials for hard turning applications are expensive.

Due to the continuous developments in cutting tool materials and coating technology,

inexpensive coated carbide cutting tools are being investigated to determine the potential

of using them for use in extreme conditions as in hard turning. Coated carbide tool was

selected to finish machine hardened steel. Performing hard turning dry at various cutting

conditions, that is, cutting speed and feed rate, revealed that suitable tool life and surface

finish values that meet the strict range of finish machining were obtained when finish

machining hardened steel of 58 HRC hardness (Noordin, 2007).

4

2.2 Hard Turning

One of the reasons hard turning is coming to the forefront of manufacturing is because

people are trying to reduce the lead times it takes to get a part from raw material to the

customer. It’s a lean manufacturing initiative. The thing that can do with hard turning,

that is difficult to do with grinding, is hard turning can start with a solid blank material

and produce a finished component complete on one machine. In hard turning, it can start

with a pre hardened material and machine it and can skip several steps and actually cut

days out of the process.

Choosing hard turning is really application driven, because it’s dependent on the part.

Grinding is better suited if it have really thin walled parts or parts that are delicate from

a crushing perspective. If it have a surface finish that requires a different type of texture,

for example, when turning, it will creating a thread and when grinding it will get a

checking. If look at it under a microscope, it would be a pitted surface finish. When

honing, it will get cross checking surface finish. If this part has oil lubrication near it or

running across the surface, the turned part would actually screw the oil through from one

side to another. With grinding, the oil would be held there because it’s pitted or cross

checked.

Places where hard turning is very well suited is when it have complex figures, such as

contour radii, angles and diameters all on one part. Hard turning can do that in one

setting. Besides the actual process and efficiency of hard turning, this type of machining

is gaining popularity because the overall function is less expensive today. It’s becoming

more popular because hard turning is usually less expensive to do because it is faster, the

machines cost less and operator learning curve is less. The operator has to learn the one

machine and the one machine does it all. Hard turning also offers smaller benefits that

can be time saving and environmentally friendly. When grinding, it will get a lot of fine

particles and have to clean it out and have a special filtration unit on which to have to

5

clean regularly. With turning, it will producing steel chips, which are much easier to

dispose of or recycle (Ferguson, 2004).

2.2.1 Parameters in Hard Turning

Four typical characteristics of hard turning as opposed to grinding have been stated

below:

a. The significantly higher cutting force.

b. The omission of coolant.

c. The single point form generation.

d. The minimum value of the depth of cut.

The cutting force occurring in hard turning is higher than conventional turning or

grinding. The passive force occurring in hard turning is the component perpendicular to

the cutting speed and is a multiple of the main cutting force, while in traditional turning

it is only a fraction of this value. The extraordinarily high passive force, which

contributes to the material removal, significantly loads the elements of the machining

system. The disadvantageous effect of the high passive force must be compensated for

by an increase in machine tool rigidity.

Hard turning can be done in dry conditions at relatively high speed. The relative high

friction coefficient and the passive force cause a significant friction force which

transforms into heat. The other source of the generated heat is the high cutting speed.

The high temperature generated during material removal causes thermal expansion of

the work piece.

The surface generating element of hard turning is the single point tool tip, which shapes

the surface of the work piece and is accompanied by significant force and heat effects.

Under such conditions is the single point tool tip reacts sensitively to any irregularities.

The last parameter discussed for hard turning is the depth of cut. In hard turning this

cannot be reduced significantly, although this is possible in grinding. Because of the

necessity of a minimum depth of cut, hard turning is followed by higher forces than in

grinding, even in the finest smoothing operations. (Kundrak, 2006).

6

2.3 Hard Turning Using TiAIN Coated Carbide Tool

Components made from hardened steels are increasing in numbers driven by the need

for high performance. Hardened steel’s properties of high wear resistance and

compressive strength meet the demands in automotive, tool and die industries. Machine

shop being an integral portion of the manufacturing system needs to modify the

machining process flow in order to be able to machine parts made from these hard to cut

materials more effectively. The usual technique to manufacture hardened parts involves

three sequential steps, that is, rough machining of unhardened steel, heat treating the

steel to the required hardness and finish machining to the required dimensional accuracy.

Normally, heat treatment is being done externally thereby leading to longer lead times.

The introduction of hard turning using tools with high hot hardness (Polycrystalline

Cubic Boron Nitride (PCBN) and ceramic) has simplified the process flow by allowing

the steel blank to be machined to its final dimension in the hardened state (Poulachon et

al., 2003). Hard turning refers to the turning of hardened steels with a hardness of

beyond 45 HRC. The hardness can even reach 68 HRC. This technique became a

profitable alternative for finish machining due to advantage in economical and

ecological aspects. High material removal rate and relatively low tool cost compared to

the incumbent grinding as the finishing operation are some of the economical benefits.

Additionally, stricter health and environment regulations and also post production cost

consideration led to the minimized use of coolant whenever feasible and hard turning

has been successfully performed in dry condition (Mamalis et al., 2002).

Despite its significant advantages, the lack of data concerning surface quality and tool

wear for the many combinations of work piece and cutting tool impedes the acceptance

of hard turning by the manufacturing industry (Pavel et al., 2005). Moreover, the

common tools used in hard turning, PCBN and ceramic, are relatively high in price.

Some applications in the mould and die industry have been identified to require parts

made of hardened steels within the moderate range of hard turning (45–48 HRC). Using

advanced and consequently expensive cutting tools for these moderate hardness ranges

7

may hinder the economical benefit of hard turning. Previous hard turning of stainless

steel (43–45 HRC) has been successfully performed using coated carbide tool (Noordin

et al., 2007). It is likely that coated carbide tool has the potential to turn steels of even

higher hardness within the moderate range of hard turning. This is because of the

continuous development of carbide tool taking place in the form of fine grained

substrate, better binder that optimizes strength and toughness and improved coating

using Physical Vapor Deposition (PVD) technique. Therefore, the potential of using

inexpensive coated carbide cutting tools needs to be investigated.

In order to encourage machine shops to fully adopt hard turning, assessments should be

made to clarify the aspects of the tool life and machined surface’s quality. The

machining cost per part is a function of tool life and, thus, machine shops demand long

tool life. Additionally, finish machining should produce fine surface finish as requested

by the users of the machined parts to meet the specific requirements of certain

application (Gillibrand et al., 1996). Therefore, in order to generate information on the

performance of coated carbide tool and the resulting machined surface, hard turning was

conducted using various cutting parameters within finish machining parameters.

2.4 Hard Turning of Stainless Steel Using Wiper Coated Carbide Tool

Hard turning has been explored as an alternative to grinding for finish machining of

machine parts made of hardened steels. The introduction of tools with high hot hardness

(Polycrystalline Cubic Boron Nitride (PCBN) and ceramic) has contributed in enabling a

hardened steel blank to be finish machined by single point turning process. Hard turning

simplifies the current technique to manufacture hardened parts which involve three

sequential steps, for example, rough machining of unhardened steel, heat treating to the

required hardness and finish machining to the required dimensional accuracy. Potential

advantages in economical and ecological aspects have made hard turning a profitable

alternative to the incumbent grinding as the finishing operation. High material removal

rate and relatively low tool cost are some of the economical benefits. Nevertheless, the

drive to minimize the use of coolant whenever feasible has advantaged hard turning

8

which has been successfully performed in dry condition (Mamalis et al., 2002 and

Noordin et al., 2007).

Along with developing researches and studies, types of materials being cut by hard

turning method are growing in numbers and applications. Stainless steel is among the

materials being investigated to employ hard turning method due to its wide application

in automotive, tool and die industries. High wear resistance and compressive strength

are some properties required for some high performance parts. Martensitic stainless steel

seems the appropriate type of stainless steel since it is hardenable by quenching and

tempering and therefore can achieve high strength and hardness levels (Sourmail and

Bhadeshia, 2005).

However, the advanced tools commonly used in hard turning, PCBN and ceramic, are

relatively high in price. The need for lower cost tool materials to perform hard turning is

still on demand. Coated carbide tool is the proposed alternative for some applications

within moderate range of hard turning. Recent development has provided commercially

available coated carbide tools very fine substrate grain size, modified binder that

optimizes strength and toughness, and improved coating using Physical Vapor

Deposition (PVD) technique which may ensure reasonable tool life at minimal cost per

cutting edge (Jindal et al., 1999).

Finish machining is intended to achieve high level of surface finish and is characterized

with low feed and depth of cut (Shaw, 2005). In order to improve the productivity, tools

with wiper geometry have been provided by tool manufacturers. This tool geometry has

wiper radii adjacent to the nose radius and has little or no clearance angle to improve

finish by burnishing action by the flank face of the insert (Shaw, 2005). This

modification can double the current feed and still achieve surface finishes comparable to

conventional inserts. Alternatively, if surface finish is the most important consideration,

then the same feed can be maintained to achieve better surface roughness values

(Castner, 2000).

2.5 Performance of Coated Carbide Tools in Hard Turning

9

The use of coating materials to enhance the performance of cutting tools is not a new

concept. The first coated carbide indexable inserts for turning were introduced in 1969

and had an immediate impact on the metal cutting industry (Soderberg, 2001). The boost

in wear resistance gave room for a significant increase in cutting speed and thereby

improved productivity at the machine shop floor. And today, 70% of the carbide tools

used in the industry are coated (Abdullah, 1996).

In development of modern materials, the functionality is often improved by combining

several materials of different properties into composites. Many classes of composites

exist, most of which are addressing improved mechanical properties such as stiffness,

strength, toughness and resistance to fatigue. Coating composites are designed to

specifically improve tribological and chemical functions. It is thus natural to select the

bulk of a component to meet the demands for stiffness, strength, toughness, formability,

cost, and then modify or add another material as a thin surface layer. This surface layer

or coating is the carrier of virtually all other functional properties. Application of

coatings on tools and machine elements is, therefore, a very efficient way of improving

their friction and wear resistance properties (Hogmark, 2000).

The combined substrate coating properties ultimately determine the important properties

such as wear, abrasion resistance and adhesion strength of a coating. A hard wear

resistant coating cannot perform well unless complimented by a hard and tough

substrate. Thus, a hard coating deposited on a soft substrate leads to poor properties

(Deevi, 2003).

Due to their significantly higher hardness, carbide cutting tools are more widely used in

the manufacturing industry today than high speed steels. Coated and uncoated carbides

are widely used in the manufacturing industry and provide the best alternative for most

turning operations (Haron, 2001). Due to their heat resistance, coated carbides can be

used in very hot applications and all types of PVD and CVD processes can be used to

deposit coatings (Armarego, 2002).

Physically and chemically vapor deposited coatings offer today a powerful alternative to

improve further the cutting performance of the cutting materials (Bozakis, 2000).

10