turning machinability assessment of hardened steel …

TURNING MACHINABILITY

ASSESSMENT OF HARDENED

STEEL USING UNCOATED

CARBIDE

Md. Abdul Jalil

DEPARTMENT OF MECHANICAL ENGINEERING

DHAKA UNIVERSITY OF ENGINEERING & TECHNOLOGY, GAZIPUR

GAZIPUR-1700

ii




CARBIDE

A Project

By

Md. Abdul Jalil

Department of Mechanical Engineering

Dhaka University of Engineering & Technology, Gazipur

Gazipur-1700

March 2016

iii




CARBIDE

A Project

By

Md. Abdul Jalil

Submitted to the Department of Mechanical Engineering, Dhaka University of

Engineering & Technology, Gazipur, in partial fulfillment of the requirements for the

degree of MASTER OF ENGINEERING IN MECHANICAL ENGINEERING


Dhaka University of Engineering & Technology, Gazipur

Gazipur-1700

March 2016

iv

The project titled “Turning Machinability Assessment of Hardened Steel Using

Uncoated Carbide”, submitted by Md. Abdul Jalil, Student No. 122301 (F) session

2012-2013, has been accepted as satisfactory in partial fulfillment of the requirements

for the degree of Master of Engineering in Mechanical Engineering on March 2, 2016.

BOARD OF EXAMINERS

1. Professor Dr. Md. Kamruzzaman

Professor

Chairman and

Supervisor


DUET, Gazipur.

2. Professor Dr. Mohammad Asaduzzaman Chowdhury

Head

Member

(Ex-officio)


DUET, Gazipur.

3. Professor Dr. Mohammed Alauddin Member

Professor


DUET, Gazipur.

4. Prof. Dr. Md. Arefin Kowser Member

Professor


DUET, Gazipur.

5. Prof. Dr. Mohammad Muhshin Aziz Khan Member

Professor

Department of Industrial & Production Engineering

Shahajalal University of Science & Technology (SUST)

Sylhet

(External)

v

Declaration

I do hereby declare that this work has been done by me and neither this project nor

any part of it has been submitted elsewhere for the award of any degree or diploma

except for publication.

Countersigned

Prof. Dr. Md. Kamruzzaman

Supervisor

&

Professor


DUET, Gazipur.

Md. Abdul Jalil

vi

This Project work is dedicated to

My beloved

Parents

vii

TABLE OF CONTENTS

Table of Contents vii

List of Figures ix

List of Tables x

Notations xi

Acknowledgement xii

Abstract xiii

CHAPTER 1 INTRODUCTION 1

1.1 Introduction 1

1.2 Literature Review 9

1.2.1 Hard Turning 9

1.2.2 Dry Machining 11

1.2.3 Machining with conventional cutting fluids 12

1.2.4 Liquid Nitrogen Technology/Cryogenic Cooling 15

1.2.5 High Pressure Coolant 16

1.2.6 Minimum Quantity Lubrication 18

1.3 Summary of review 34

1.4 Scope of the Present Work 40

1.5 Objectives of the Present Work 41

CHAPTER 2 EXPERIMENTAL INVESTIGATIONS AND RESULTS 43

2.1 Introduction 43

2.2 Experimental Setup 45

2.2.1 Near Dry Lubrication System 45

2.2.2 Experimental Procedure and conditions 49

2.3 Experimental Methodology 52

2.4 Experimental Results 53

2.4.1 Cutting temperature 53

2.4.2 Machining Chips 57

2.4.3 Surface roughness 61

2.4.4 Dimensional Deviation 63

CHAPTER 3 EXPERIMENTAL RESULTS AND DISCUSSION 66

3.1 Machining Chips 66

viii

3.2 Cutting Temperature 70

3.3 Product Quality 74

CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS 78

4.1 Conclusions 78

4.2 Recommendations 79

REFERENCES 81

ix

LIST OF FIGURES

No. Description Page no.

Fig. 1.1 Classification of Near Dry machining. 19

Fig. 1.2 Fishbone diagram showing cause and effect in MQL assisted

machining.

20

Fig. 1.3 Distribution of Fabrication costs in engineering. 37

Fig. 2.1 Photographic view of the Near Dry Lubrication applicator 47

Fig. 2.2 Schematic view of the Near Dry Lubrication applicator 47

Fig. 2.3 Photographic view of air nozzle for near dry lubrication for

Supplying high velocity air

48

Fig. 2.4 Schematic view of the near dry jet issuing and impinging system. 48

Fig. 2.5 Photographic view of surface roughness measuring technique 51

Fig. 2.6 Variation of Chip-tool interface temperature with different cutting

speed and feed rates at 1 mm depth of cut by using uncoated

carbide under dry, wet and near dry condition during machining

hardened AISI 1060 steel.

54


speed and feed rates at 0.50 mm depth of cut by using uncoated

carbide under dry, wet and near dry condition during machining


55


speed and feed rates at 1 mm depth of cut under dry, wet and near

dry condition during machining of hardened AISI 1060 steel by

using uncoated carbide insert.

56


speed and feed rates at 0.50 mm depth of cut under dry, wet and

near dry condition during machining of hardened AISI 1060 steel

by using uncoated carbide insert.

56

Fig. 2.10 Variation of Chip Thickness ratio (rc) with different cutting speed

and different feed rate under different conditions at 1 mm depth

of cut by using uncoated carbide during machining of hardened

AISI 1060 steel.

60

Fig. 2.11 Variation of Chip Thickness ratio (rc) with different cutting speed

and different feed rate under different conditions at 0.50 mm

depth of cut by using uncoated carbide during machining of


60

Fig. 2.12 Variation of Roughness (Ra) with different cutting speed and

different feed rate under different conditions at 1 mm depth of cut

by using uncoated carbide during machining of hardened AISI

1060 steel.

62

Fig. 2.13 Variation of Roughness (Ra) with different cutting speed and

different feed rate under different conditions at 0.50 mm depth of

cut by using uncoated carbide during machining of hardened AISI

1060 steel.

63

Fig. 2.14 Dimensional deviation observed after one full pass turning of

hardened steel by SNMG insert with different depth of cut under

dry wet and near dry conditions.

65

x

LIST OF TABLES

No. Description Page no.

Table 2.1 Experimental conditions 50

Table 2.2 Comparison of chip shape and color at different speed and feed

at depth of cut 1 mm under dry, wet and near dry conditions

during machining of hardened AISI 1060 steel by SNMG

uncoated carbide insert.

57

Table 2.3 Comparison of chip shape and color at different speed and feed

at depth of cut 0.50 mm under dry, wet and near dry conditions

during machining of hardened AISI 1060 steel by SNMG

uncoated carbide insert.

58

Table 3.1 Percentage increment in chip thickness ratio (rc) 69

Table 3.2 Average percentage increment in chip thickness ratio (rc) 70

Table 3.3 Percentage reduction in chip-tool interface temperature (θ) 72

Table 3.4 Average percentage reduction in θ 73

xi

NOTATIONS

AISI American Iron and Steel Institute

BUE Built-up edge

CBN Cubic boron nitride

HPC High Pressure Coolant

HSM High speed machining

MQL Minimum quantity lubrication

MRR Material removal rate

NDL Near Dry Lubrication

NIOSH National Institute of Occupational, Safety and Health

V Cutting Speed

d Depth of cut

f Feed rate

θ Temperature

rc Chip Thickness ratio

Ra Surface Roughness

xii

ACKNOWLEDGEMENT

At first the author expresses his heartiest thanks to the Almighty for giving his the

patience and capability to bring this project in light. The author is deeply indebted to

Prof. Dr. Md. Kamruzzaman, Professor of the Department of Mechanical

Engineering, and Director (Student Welfare), DUET for his continuous guidance,

perpetual help, endless support, valuable suggestions and encouragement throughout

the progress of the project work.

He also wants to thank especially to the Head of the Department of Mechanical

Engineering for the help rendered for allowing and providing Machine Shop facilities

to carry out the experiment whenever required. The help extended by the Director

(Research and Extension) for providing research fund is highly acknowledged.

The author is highly thankful to Engr. Hasan Mohammad Quamruzzaman, Principal

of Patuakhali Polytechnic Institute, he is also thankful to Engr. Md. Kamruzzaman

Khan, Instructor & Head of Civil Technology of the same Institute for their support

in various stages of this project research work. Also expresses his heartiest thanks to

Engr. Goutam Panday who helped the author to make this project work a successful

one. The author is deeply indebted to his elder brother for providing mental strength

to continue the study smoothly. A special word of thanks is due to all the staff

members of Machine Shop for their helps in conducting the experimental work.

Finally, the author offer his sincere thanks to all those who either directly or

indirectly helped him in various ways to complete this project.

March, 2016 Author

xiii

ABSTRACT

High cutting velocity and feed in metal machining generates large amount of heat as

well as high cutting temperature which shortens the tool life by increasing tool wear,

and deteriorates the product quality. Use of cutting fluid reduce this high cutting

temperature is a common belief. The conventional cutting fluids are ineffective in

such high production machining even is mixed with extreme pressure additives.

Further, the conventional cutting fluids are not environmentally friendly because it

contaminates air, water and soil. Performance of machining operations can be

changed by the lubrication, cooling and chip flushing functions of cutting fluid.

Recycling and reuse of conventional cutting fluids are also problematic. In this

decade, with increased environmental awareness, the researchers are striving to

develop environmentally friendly machining technology; one such technology is to

use minimum quantity lubrication with cutting oil. Minimum quantity lubrication

(MQL) or Minimum volume of oil (MVO) or Near Dry Lubrication (NDL) machining

presents itself as a possible alternative for machining with respect to tool wear, heat

dissertation and machined surface quality. This research compares the mechanical

performance of dry cutting without coolant, soluble cutting fluid as conventional

application and soluble cutting fluid as NDL for the turning of hardened AISI 1060

steel using uncoated carbide based on experimental measurement of cutting

temperature, Chips form (chip shape, chip color and chip thickness ratio, rc), Surface

finish (Ra) and Dimensional deviation.

Compared to the dry and conventional turning, the use of cutting fluid as NDL leads

to reduce surface roughness, decrease dimensional deviation and lower cutting

temperature, while also having favorable chip tool interaction.

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

The present and future manufacturing industries are required essentially to

address different challenges and needs, such as high production rate along with high

quality product and development of advanced materials, cost competitiveness and

environmentally friendly. The requirement of manufactured parts in terms of

complication, shape, material, size, etc. predictably enforces the manufacturing firms to

adapt new optimization strategies for the manufacturing processes, allowing the use of

latest manufacturing techniques. The part sequences in the manufacturing process are

generally diverse, and are directly linked to the part shaping process. Optimization

strategies can avoid or delete certain sequences, according to the initial shapes and the

necessary requirement of the final part. The actual optimization strategies aim at

increasing the productivity, quality, or the cost reduction by searching of optimal material

removal, improving machining accuracy, reduction of the number of operations and the

machining allowances and introducing of efficient and flexible sequences.

Producers of machined components and manufactured goods are continually

challenged to reduce cost, improve quality and minimize setup times in order to remain

competitive. Frequently the answer is found with new technology solutions. Such is the

case with grinding where the traditional operations involve expensive machinery and

generally have long manufacturing cycles, costly support equipment, and lengthy setup

2

times. The newer solution is a hard turning process, which is best performed with

appropriately configured turning centers or lathes [Noordin et al., 2007].

Machining is the broad term which describes the removal of material from a work

piece that typically involves the cutting of metals using different types of cutting speed,

feed and tools in which a tool removes material from the surface of a less resistant body.

The relative movement of the cutting speed, feed, tool and application of force and is

particularly useful due to its high dimensional accuracy, flexibility of process, and cost-

effectiveness in producing limited quantities of parts along with quality. The new

surfaces are break off from the work piece accompanied by a large consumption of

mechanical energy which in turn transformed into heat, leading to high temperature and

severe thermal conditions at the tool-chip interface due to removal of material in the form

of chips. The higher the tool-chip interface temperature, the faster the flank wears. The

cutting zone temperature reduces by its cooling effect, using of cutting fluids in the

machining processes and reduces the frictional heat generation due to its lubrication

effect. Also the cutting fluid serves is chip flushing or transportation of chips from the

cutting zone by the used / waste coolant stream.

Possibilities of controlling high cutting temperature in high production machining

by some alternative methods have been reported. Cutting forces and temperature were

found to reduce while machining steel with tribologically modified carbide inserts. High

pressure coolant injection technique was not only provided reduction in cutting forces

and temperature but also reduced the consumption of cutting fluid by 50%. Application

of CO2 in the form of liquid jet at high pressure also enabled some reduction in cutting

forces. Some works have recently been done on cryogenic cooling by liquid nitrogen jet

3

in machining and grinding some steel of common use. For the companies, the costs

related to cutting fluids represent a large amount of the total machining costs. Several

research workers state that the costs related to cutting fluids are frequently higher than

those related to cutting tools. Consequently, elimination on the use of cutting fluids, if

possible, can be a significant economic incentive. Considering the high cost associated

with the use of cutting fluids and projected escalating costs when the stricter

environmental laws are enforced, the choice seems obvious. Because of them some

alternatives has been sought to minimize or even avoid the use of cutting fluid in

machining operations. Some of these alternatives are dry machining and machining with

minimum quantity lubrication (MQL) and near dry lubrication (NDL) machining.

Manufacturers generally attempt to produce a product within the shortest possible

time keeping the cost of the product at a minimum level without affecting the quality of

the product as well. As, environmental regulations are being emerged and imposed, the

manufacturers are put to re-fabricate their manufacturing processes and reduce or

eliminate harmful chemicals, dusts and effluents associated with machining that can

deteriorate the environment. The harmful waste present in machining includes cutting

fluid, chip and worn out cutting tool.

The performance and service life of engineering component depends on their

material, dimensional or form accuracy and surface quality. The growing demand for

higher productivity, product quality and overall economy in manufacturing by machining

and grinding, particularly to meet the challenges of global cost competitiveness, insists

high material removal rate and high stability and long life of the cutting tools. But high

production machining with high cutting speed, feed, and depth of cut is inherently

4

associated with generation of large amount of heat and high cutting temperature. Such

high cutting temperature not only reduces dimensional accuracy but also impairs the

surface integrity of the product by inducing tensile residual stresses and surface and

subsurface micro cracks in addition to rapid oxidation and corrosion. In high speed

machining, conventional cutting fluid application fails to penetrate into the chip-tool

interface and thus cannot remove heat effectively [Paul et al., 2000]. Addition of extreme

pressure additives in the cutting fluids does not ensure penetration of coolant at the chip-

tool interface to provide lubrication and cooling [Cassin and Boothroyed, 1965].

Moreover, reaching to the boiling point conventional coolant vaporizes and makes a non-

conductive vapor barrier to enter the coolant effectively into the interface. With the

increase in cutting speed, feed and depth of cut this problem becomes acute and cooling

process become ineffective gradually.

The challenge of modern machining industries is mainly focused on the

achievement of high quality, in terms of work part dimensional accuracy and surface

finish, high production rate and cost saving, with a reduced environmental impact. High

temperature generated during machining at high cutting speed and feed results in high

tool wear, reduced tool life, poor surface finish and dimensional accuracy and larger

force is required for machining. The temperature generation during machining is an

important factor since it affects the thermally activated mass transport phenomena in the

cutting tool-work-piece contact zone. While primarily dependent on the cutting speed and

the work-piece material properties, the cutting temperature is also affected by the cutting

tool properties. Almost all of the mechanical energy in metal cutting is transformed into

heat. The major portion of the produced heat is conducted into and removed with the

5

chips from the cutting region with nearly the entire remaining portion conducted into the

workpiece and cutting tool. At such elevated temperature the cutting tool if not enough

hard may lose their form stability quickly or wear out rapidly resulting in increased

cutting force, dimensional inaccuracy of the product and shorter tool life [Kitagawa et

al., 1997]. On the other hand, high cutting temperature accelerates the growth of tool

wear and also enhances the chance of premature failure of the tool by plastic deformation

and thermal fracturing.

The temperature at the cutting tool interface is one of the important factors

influencing the machining process. The primary function of cutting fluid is cooling and

lubrication to avoid the high temperature effect on a machined surface. A secondary

function of cutting fluid is to flash away chips and metal fines from the tool/work piece

interface to prevent a finish surface from becoming marred and also to reduce the

occurrence of built-up-edge (BUE). The surface quality of the machined parts also

deteriorate with the increase in cutting temperature due to built-up-edge formation,

oxidation, rapid corrosion and induction of tensile residual stress and surface micro

cracks. Such problems become more acute and serious if the work materials are very

hard, strong and heat resistive and when the machined or ground part is subjected to

dynamic or shock loading during their functional operations. Therefore, it is essential to

reduce cutting temperature as far as possible.

When carbide tools were introduced with other new methods of machining, the

efficiency of the metal cutting operations improved to a certain extent under normal

cutting conditions. Presently the high temperature problems are tried to be eliminated by

reducing heat generation and removing the generated heat from the cutting zone by using

6

the combination of optimum machining parameters along with the work and tool material

and application of effective cutting fluid. The foremost process parameters in this case

are the cutting speed, feed rate and depth of cut. Some recent techniques have enabled

partial control of the machining temperature by using heat resistant tools like coated

carbides, PCD, CBN, PCBN etc. However, diamond and CBN tools are very expensive

and the practices in the industry are still not wide spread. Machining productivity can be

significantly improved by employing the right combination of cutting tools, cutting

conditions and machine tool that prop up high speed machining without compromising

the integrity and tolerance of the machined components.

Over a long period the manufacturers have been trying to reduce cutting

temperature by applying water soluble cutting fluid from overhead position. This type of

cutting fluid not only cools the tool and job but also provides lubrication and handles the

chip to clean the cutting zone and protects the nascent finished surface from

contamination by the gases(such as; oxygen) present in the atmosphere. But these

conventional types of coolants and the methods of their application surely have some

limitations.

In turning process, single-point cutting tool that is nothing but insert can

complete the entire machining process in a single fixture, thereby reduced setup times

as well as lower costs. Also there is many optional thing to improve the turning

process rather than grinding process. In recent there is big problem for all industrialist for

achieving high quality products with more productivity within less machining time which

affects on surface roughness during turning of hardened steel. Even rough surfaces

wear more quickly & have high friction coefficient than smooth surfaces. As the surface

7

roughness increases then customer demand & quality of product goes on decreasing. So

that there should be bridge between quality and productivity. In short there should be

such optimum condition on which tool wear rate is minimum & maximum productivity

with maximum quality within less time. Generally hard turning requires large quantities

of coolants and lubricants. The cost associated with storage and disposal of coolants and

lubricants increases the total cost of production considerably.

Conventional cutting fluid application fails to penetrate the chip-tool interface and

thus cannot remove heat effectively due to which there is loss of surface finish and also

loss of tool life. This cooling system, the cutting zone is often flooded with coolant

without considering the requirements of the specific process. Scientific investigations and

industrial applications have indeed shown that the type of coolant and its supply

influence the quality of product and tool life to a great extent. But in some cases,

application of cutting fluids is considered undesirable, especially in machining some

alloys and heat treated materials.

To overcome this problem there are some solutions. Some of these alternatives

are dry machining and machining with minimal fluid application. Dry machining is now

of great interest and actually, they meet with success in the field of environmentally

friendly manufacturing. However, they are sometimes less effective when higher

machining efficiently, better surface finish quality and serve cutting conditions are

required. Minimal fluid application refers to the use of cutting fluids of only a minute

amount typically of flow rate of 50 to 500 ml/hour. The concept of minimal fluid

application sometimes referred to as near dry lubrication or micro lubrication.

8

In the recent years a lot of work has been done to avoid the cutting fluids from the

production system. Dry cutting and semi-dry cutting such as Minimum Quantity

Lubrication (MQL) have been favored by the industry. Dry and near-dry machining

operations are the key technology of environmentally friendly manufacturing process.

The conventional flood supply system demands more resources for operation,

maintenance, and disposal, and results in higher environmental and health problems.

MQL machining has many advantages in this regard. [Weinert et al., 2004]. By

abandoning conventional cooling lubricants and using the technologies of dry machining

or Minimum Quantity Lubrication (MQL), this cost can be reduced significantly. In fact,

the cooling lubricant performs several important functions, which, in its absence, must be

taken over by other components in the machining process. For instance cooling lubricants

reduce the friction, and thus the generation of heat, and dissipate the generated heat. In

addition, cooling lubricants are responsible for a variety of secondary functions, like the

transport of chips as well as the cleaning of tools, work pieces and fixtures.

Most investigations of using MQL have been focused mainly on turning and

drilling operations. Most research has concluded positive effects to its lubrication ability.

Thus, the aim to evaluate the use of soluble cutting fluid and insoluble cutting oil through

the application of MQL technique when turning AISI 1040 steel using solid uncoated

SNMG tool.

9

1.2 Literature Review

It appears that the high temperature in cutting zone is the main problem and hence

methods were tried out over the years to tackle this problem. Application of proper

cutting fluids at times, reduced the above problems to some extent through cooling and

lubrication of the cutting zone. The commonly used fluids are neat oil, semi synthetic and

synthetic fluids with or without additives and inorganic salts. The application procedures

of these fluids are generally by flood cooling, or in the form of jet or even mist. Ample

research has been done in various directions and is still going on aiming improvement in

overall machining efficiency through controlling the aforesaid problems.

1.2.1 Hard Turning

Hard machining makes a major contribution to search flexibility during the

machining of hard alloys or high mechanical strength materials. In fact, intermediate

operations such, as grinding operations can be eliminated. This, in most cases, leads to

substantial cost reduction in manufacturing, and therefore hard turning operations are

developing wide applications in industry. In order to change from grinding to hard

turning, three levels of substitution can be recognized: the first level substitutes rough

grinding; the second level substitutes fine grinding; and the last level includes

substitution of the honing operation. The more grinding and honing can be substituted,

the greater are the benefits of hard turning. In order to accomplish this, it is necessary to

have good knowledge of the surface integrity created by hard turning [Michael

Jacobson, 2002].

10

Hard turning is an emerging technology that can potentially replace many

grinding operations due to improved productivity, increased flexibility, decreased capital

expenses, and reduced environmental waste. The ultimate aim of hard turning is to

remove work piece material in a single cut rather than a lengthy grinding operation in

order to reduce processing time, production cost, surface roughness, and setup time, and

to remain competitive. So hard turning is a developing technology that offers many

potential benefits compared to grinding, which remains the standard finishing process for

critical hardened steel surfaces. High material removal rate and relatively low tool cost

are some of the economical benefits. To increase the implementation of this technology,

questions about the ability of this process to produce surfaces that meet required surface

finish and integrity requirements must be answered. Additionally, the economics of the

process must be justified, which requires a better understanding of tool wear patterns and

life predictions. The potential economic benefits of hard turning can be offset by rapid

tool wear or premature tool failure if the brittle cutting tools required for hard turning are

not used properly. Even steady, progressive tool wear can result in significant changes in

cutting forces, residual stresses, and micro-structural changes in the form of a rehardened

surface layer (often referred to as white layer) [Kevin Chou et al., 2003].

Precision hard turning applications have increased drastically in manufacturing

industry because it potentially provides an alternative to conventional grinding in

machining hardened components. This new technology significantly reduces the

production time, tooling costs and the capital investment, especially for low volume

production. Koning et al. [1993] also presented that turning of hardened steels have been

an attractive alternative to costly, yet environmentally harmful, grinding processes.

11

Benefits of hard turning over grinding have been reported including short cycle time,

process flexibility, part longevity, and less environmental impact. Scientific and

engineering issues of hard- turning, been frequently investigated, range from cutting

mechanics, tool wear surface integrity, to part accuracy [Davies, M.A., Chou et al.,

1996].

1.2.2 Dry Machining

Dry machining has been around for as long as traditional machining and

ecologically desirable. It will be considered as a necessity for manufacturing enterprises

in the near future and dry machining to enforce environmental protection laws for

occupational safety and health regulations. The advantages of dry machining include:

non-pollution of the atmosphere (or water); no residue on the swarf which will be

reflected in reduced disposal and cleaning costs; no danger to health; and it is non-

injurious to skin and is allergy free.

Dry machining is great interest and actually, they meet with success in the field of

environmentally friendly manufacturing. In reality, however, they are sometimes less

effective when higher machining efficiency, better surface finish quality and severe

cutting conditions are required. For these situations, semi-dry operations utilizing very

small amount of cutting lubricants are expected to become a powerful tool. Moreover, it

offers cost reduction in machining. Due to dry machining more heat is generated during

the machining process and without the coolant effect, it cannot be as efficiently removed

from the interface of the tool and the work piece. The dimensional accuracy is not as

good during dry machining because of the high temperature produced. Surface finish can

12

also be negatively affected. The increase in temperature increases the ductility of the

metal, changing the formation of chips [Klocke et al., 2006].

1.2.3 Machining with conventional cutting fluids

The primary function of cutting fluids is to reduce this cutting temperature and

increase tool life. In addition the cutting fluid has a practical function as a chip-handling

medium. Cutting fluids also help in machining of ductile materials by reducing or

preventing formation of a build-up-edge (BUE), which degrades the surface finish.

Conventional machining prevails [Ekinovic et al., 2005] plastically deformation in

generating chips whereas in high speed machining chip generation is followed by

segmentation process. Usually the high cutting temperature is controlled by profuse

cooling [Alaxender et al., 1998]. But such profuse cooling with conventional cutting

fluids is not able to solve these problems fully even when employed in the form of jet or

mist. With the advent of some modern machining process and harder materials and for

demand for precision machining, the control of machining temperature by more effective

and efficient has become extremely essential. Generally, suitable cutting fluid is

employed to reduce this problem through cooling and lubrication at the cutting zone. But

it has been experienced [Cassin ans Boothroyed, 1965] that lubrication is effective at

low speeds when it is accomplished by diffusion through the work piece and by forming

solid boundary layers from the extreme pressure additives, but at high speeds no

sufficient lubrication effect is evident. The ineffectiveness of lubrication of the cutting

fluid at high speed machining is attributed [Shaw et al., 2005] to the inability of the

13

cutting fluid to reach the actual cutting zone and particularly at the chip-tool interface due

to bulk or plastic contact at high cutting speed.

Most of the energy generated in the plastic deformation converts into heat, which

causes the temperature rise in the primary deformation zone. However a small amount of

heat transfer occurs between the work piece and tools due to very short time of the

deformation. Thus the temperature can be localized in some areas of chips. This

deformation and temperature localization will increase with increasing cutting speed.

Since vast amount of heat is generated during high speed machining, low pressure

conventional cutting fluid is vaporized due to high temperature when it comes in contact

with the work-tool-chip interface, makes a barrier (film).That’s why no cutting fluid

reach in the tool-chip interface or cutting zone [Ezugwu, 2004]. The film boiling

temperature of conventional cutting fluid is about 3500 [Ezugwu and Bonney, 2003].

The use of cutting fluids on machining operations has been questioned, due to problems

they may cause to the environment, due to damage to human health and also more due to

the severe laws regarding industrial waste that have been passed.

High machining of metal inherently generates high cutting zone temperature

causes dimensional deviation and premature failure of cutting tools. The application of

cutting fluid during machining operation reduces cutting zone temperature to prevent

overheating and increases tool life acts as lubricant as well. It reduces cutting zone

temperature either by removing heats as coolant or by heat generation as lubricant. It is

believed that heat is carried away from the tool and the work by means of cutting fluid

which at the same time reduce the friction between the tool and the chip and work and

also facilitates the chip formation.

14

The use of cutting fluids on machining operations has been questioned, due to

problems they may cause to the environment, due to damage to human health and also

more due to the severe laws regarding industrial waste that have been passed. Therefore,

industries are being forced to review the production processes aiming either, at

elimination or when it is not possible a sharp reduction in the use of these fluids. The

conventionally applied cutting fluid can do this job properly at normal cutting conditions

where the feed and depth of cut are very low. But the main problem with conventional

coolant is that it does not reach the real cutting area. In case of ductile material and under

high speed-feed condition conventionally applied coolant is completely ineffective to do

so as the bulk and progressive contact between tool face and the flowing chips cannot

allow the coolant to enter into the interface where maximum temperature attains.

Moreover water soluble coolant is a major source of environmental pollution, soil

contamination and carrier of bacteria borne diseases like lunch cancer, dermatitis and

others. Cutting fluids are important causes of occupational contact dermatitis which may

involve either irritant or allergic mechanisms. Water mixed fluids generally determine

irritant contact dermatitis, allergic contact dermatitis when they are in touch with workers

skin. Cutting fluids are widely used to reduce the cutting temperature. But the major

problems associated with the use of conventional methods and types of cutting fluids,

which are mostly oil based, are;

i. Ineffectiveness in desired cooling and lubrications.

ii. Health hazards due to generation of obnoxious gases and bacterial growth.

iii. Inconvenience due to un-cleanliness of the working zone.

15

iv. Need of storage, additional floor space, pumping system, recycling and

disposal.

v. Corrosion and contamination of the lubricating system of the machine

tools.

vi. Environmental pollution and contamination of soil and water.

The disposal of used chemical coolants involves incineration and partially

contributes to global warming. Also use of flood coolants does not inhibit the air

boundary layer and a protocol was made for further investigation of coolant flow

mechanism. The presence of chemical substances like sulfur, phosphorous, chlorine or

any other extreme pressure additives in the coolant introduces health hazard to the

operator. Skin exposure is the dominant route of exposure and it is believed that about 80

percent of all occupational diseases are caused by skin contact fluids.

1.2.4 Liquid Nitrogen Technology/Cryogenic Cooling

One solution to the problem of cutting fluid management currently under

development is the use of liquid nitrogen as a coolant and lubricant. The small flow rate

of liquid nitrogen makes this technique a very attractive alternative. There is no cutting

fluid to dispose as the nitrogen evaporates harmlessly into air. Reportedly, tool life and

finish quality are also improved by this technique due to high reduction of the tool-chip

interface temperature [Dhar et al., 2002]. But liquid nitrogen is hazardous to workers due

to its extremely low temperature. Exposure can result in mild to extreme frostbite.

Nitrogen that is stored in a sealed vessel will increase in pressure dramatically as it

warms, potentially resulting in a non-combustion explosion. Large spills can displace all

16

of the oxygen in a room in a short time. However, when proper equipment and handling

technique are used nitrogen is a very safe and environmental friendly alternative.

1.2.5 High Pressure Coolant

Coolants are used to reduce the amount of heat and friction at the point where a

tool cut into a metal work piece. This heat reduction allows the cutting tool to operate at

higher speeds and reduces tool wear. However, at the lower pressures typically used to

deliver cutting fluid, the coolant cannot effectively remove the majority of heat at the

cutting point because it does not reach the real cutting interface. Instead the coolant

washes over the tool holder and work piece, cooling the surfaces somewhat, but not

removing the intense heat within the cutting area, itself. In fact most of this heat is

conducted to the material around the shear zone and to the tooling. Thus the temperature

at the cutting point keeps higher than desired. By directing the coolant stream more

precisely and with the optimum amount of pressure and flow rate, more heat can be

removed dramatically. High pressure assisted cooling is one of the preferred

technologies, currently under exploitation especially in the aerospace and power plant

industries for machining exotic materials. The creditability of high-pressure coolant

assisted machining had been thoroughly investigated over the years [Ezugwu and

Bonney, 2004; Dhar et al., 2006 and Kamruzzaman, 2008]. This system not only

provides adequate cooling at the tool-work-piece interface but also provides an effective

removal (flushing) of chips from the cutting area. The coolant jet under such high-

pressure is capable of creating a hydraulic wedge between the tool and the work-piece,

penetrating the interface deeply with a speed exceeding that necessary even for very high

17

speed machining. The high-pressure coolant stream helps to break up chips and remove

them from the cutting zone area more effectively. The combination of reduced heat and

more efficient evacuation of chips prolong tool life and makes replacement more

predictable because the cutting tool wears out naturally, rather than failing prematurely

because of excessive heat or chip damage. Properly applied high-pressure coolant allows

users to achieve maximum performance. The coolant jet under such high-pressure is

capable of creating a hydraulic wedge between the tool and the work piece, penetrating

the interface deeply with a speed exceeding that necessary even for very high speed

machining. This phenomenon also changes the chip flow conditions [Kovacevic et al.,

1994]. The penetration of high- energy jet at the tool-chip interface reduces the

temperature gradient and minimizes the seizure effect, offering an adequate lubrication at

the tool-chip interface with a significant reduction in friction. It was found about the

performance of high-pressure coolant jet on grind ability of steel [Dhar et al., 2006]

based on the experimental results that high-pressure coolant jet reduces grinding zone

temperature significantly due to effective cooling and lubrication at the grinding zone

area. HPC grinding yields to less significant lamellar chips can be found due to change in

feed rate.

18

1.2.6 Minimum Quantity Lubrication

In MQL process, oil is mixed with high-pressure air and the resulting aerosol is

supplied near to the cutting edge. This aerosol impinges at high speed on the cutting zone

through the nozzle. Air in the aerosol provides the cooling function and chip removal,

whereas oil provides lubrication and cooling by droplet evaporation. The flow of

lubricant in MQL process varies from 10 to 100 ml/h and air pressure varies from 4 to 6.5

Kg/cm2 [Silva et al., 2005]. Different ranges for flow rate were also reported in literature

such as 50 to 500 ml/h [Dhar et al., 2006a] and 2 to 300 ml/h [Zhong et al., 2010].

However, in industrial applications consumption of oil is approximately in the range of

10-100 ml/h [Kamata and Obikawa, 2007]. When the flow rate of cutting fluid in MQL

is less than or equal to 1 ml/h it is termed as Micro-Liter Lubrication (μLL) [Obikawa et

al., 2008; Liu et al., 2011]. As the quantity of cutting fluid in MQL is very less (in ml/h

instead of l/min) in comparison to flood cooling, the process is also known as Near Dry

Machining. If oil is used as fluid medium in NDM, better lubrication is obtained with

slight cooling effect whereas, when emulsion, water or air (cold or liquid) were used,

better cooling is achieved with slight/no lubrication so, the processes were termed as

Minimum Quantity Lubrication and Minimum Quantity Cooling respectively [Weinert

et al., 2004; Tawakoli et al., 2010]. NDM can be classified on the basis of method of

aerosol spray and aerosol composition as shown in Fig. 1.1. Detailed description is

available with Astakhov, 2008.

In MQL, cooling occurs due to convective and evaporative mode of heat transfer

and thus is more effective than conventional wet cooling in which cooling occurs due to

convective heat transfer only. In addition, cutting fluid droplets by virtue of their high

19

velocity penetrates the blanket of vapor formed and provides more effective heat transfer

than wet cooling [Varadarajan et al., 2002]. However, according to Astakhov [2008]

aerosols do not acts as lubricants or boundary lubricants as they do not have access to the

tool-chip and tool-work-piece interfaces due to too low penetration ability. In addition,

the cooling action due to droplet evaporation is also small due to very small flow rate of

oil. MQL action on forming chip is also negligibly small as compared to high pressure

water soluble metal working fluids due to low mass of aerosol. Astakhov [2008]

suggested that the application of MQL enhances the rebinder effect and thus reduces the

work due to plastic deformation.

Fig. 1.1 Classification of Near Dry machining [Astakhov, 2008; Weinert et al., 2004]

20

Possible parameters and machining conditions affecting the performance of MQL

assisted machining are illustrated in fishbone diagram as shown in Fig. 1.2. As little

quantity of cutting fluid was utilized in MQL process, the cutting fluid should possess

significantly higher lubrication qualities than mineral oil. Vegetable oil and synthetic

ester oil are two viable alternatives. Vegetable oils are nontoxic as they are based on

extract from plants. Molecules of these oils are long, heavy and dipolar in nature and

provides greater capacity to absorb pressure.

Fig. 1.2 Fishbone diagram showing cause and effect in MQL assisted machining

Higher viscosity index provides stable lubrication in operating temperature range

and higher flash point provides opportunity to increase metal removal rate due to reduced

smoke formation and fire hazard [Krahenbuhl, 2002]. Wakabayashi et al. [2006]

introduced some synthetic esters, synthesized from a specific polyhydric alcohol. These

synthetic esters have high biodegradability, excellent oxidation stability, good storage

21

stability, and satisfactory cutting performance. Investigated synthetic esters were

suggested as satisfactory MQL cutting fluid on the basis of cutting performance and

optimal fluid for MQL machining on the basis of biodegradability, oxidation and storage

stability.

Some studies reported that application of MQL results in zero airborne mist levels

as the oil mist either vaporizes or clings to the work-piece or chips [Dasch and Kurgin,

2010]. However, Dasch and Kurgin [2010] found MQL mist level comparable to wet

application and proportional to the volume of oil entering the system. So, mass

concentration and particle size as well as composition and physical state of mist requires

serious attention. Advantages of MQL assisted machining are: fluid supplied to the

cutting tool is consumed at once so there is no need of fluid monitoring, maintenance or

disposal, reduction in solid waste by 60%, water use by 90%, and aquatic toxicity by 80%

due to delivery of lubricants in air instead of water [Clarens et al., 2008]; decreased

coolant costs due to low consumption of cutting fluid; reduced toxicity and hazardous

effects as mostly vegetable oils are used which are nontoxic and biologically inert [Khan

et al., 2009]; reduced cleaning cost and time due to low residue of lubricant on chip, tool

and work-piece, better visibility of cutting operation [Attansio et al., 2006].

Turning of AISI 52100 hardened steel was studied Diniz et al. [2003] using TiN

coated CBN inserts under dry cutting, wet cutting and minimum volume of oil (MVO).

Mostly similar values of flank wear and surface roughness were obtained with dry and

MVO cutting. Values of flank wear and surface roughness were always found better than

wet cutting. Based on study, dry cutting was concluded as the best technique for turning

22

of this material. The better performance of dry cutting was attributed to increased cutting

zone temperature that caused easier deformation and shearing of chip, reduced cutting

forces and vibration, and reduced tool wear. Attansio et al. [2006] studied tool wear in

finish turning of 100Cr6 normalized steel pieces under MQL and dry cutting conditions

using triple coated carbide tip (TiN outer layer, Al2O3 intermediate layer and TiCN inner

layer). MQL was applied on rake and flank face of the tool at constant cutting speed of

300 m/min and depth of cut of 1 mm, and at feed rate of 0.2 and 0.26 mm/rev with

cutting length of 50 mm and 200 mm. Equal or greater mean removed material was

reported with flank MQL as compared to dry and rake MQL. Tool life decreased with

feed rate in all cutting conditions however the tool life obtained in flank MQL was

highest. Tool life increases in flank MQL with increase in cutting length whereas it does

not influence tool life in dry and rake MQL. In rake MQL, lubricant was not able to reach

the cutting area as no elements indicating compounds from lubricant were seen on worn

surface of tool tip. Tool wear and surface roughness of AISI-4340 alloy was studied by

Dhar et al. [2006b] with uncoated carbide insert under MQL conditions. Principal flank

wear and auxiliary flank wear were selected to study the tool wear as former affects the

cutting force, and latter affects the surface finish and dimensional deviation. Reduced tool

wear and improved surface finish was achieved with MQL as compared to dry and wet

machining mainly due to effective reduction in cutting temperature.

In another study on same alloy, chip tool interface temperature and dimensional

deviation were also monitored along with surface roughness and tool wear. At low

cutting speeds the chip makes partially elastic contact with the tool but with increase in

cutting speed chip makes fully plastic or bulk contact with the rake face of the tool. So, at

23

low cutting speeds more effective cooling was observed as MQL was dragged due to

capillary effect in the elastic contact zone. While, at high cutting speed less reduction in

cutting temperature was observed due to reduction in time to remove accumulated heat

and due to fully plastic or bulk contact preventing the MQL to reach the hot chip-tool

interface. Decrease in feed improves the cooling effect to some extent particularly at low

cutting speed possibly due to slight lifting of the thinner chip. About 5 to 10% decrease in

average cutting temperature was recorded depending upon the level of cutting speed and

feed rate. Reduced dimensional deviation with machining time was observed with MQL

as compared to that in dry and wet turning [Dhar et al., 2007]. Rahman et al. [2009]

reported about 5 to 10% reduction in average cutting temperature in MQL turning of

AISI 9310 alloy depending upon the levels of cutting speed and feed.

In MQL turning of AISI-1040 with uncoated carbide, MQL jet was targeted on

the rake and flank face of the auxiliary cutting edge to achieve better dimensional

accuracy. With MQL application the cutting temperature is effectively reduced and blue

colored spiral shaped chips produced under dry and wet conditions became metallic

colored and half turn. Also the back surface of chip under MQL is much brighter and

smoother indicating the favorable chip tool interaction and elimination of built–up edge

formation. Reduced value of chip compression ratio and improved dimensional accuracy

was also achieved with MQL [Dhar et al., 2006a]. Similar improved results were also

reported in MQL turning of AISI-9310 and AISI-1060 alloy by using vegetable oil-based

cutting fluid [Khan and Dhar., 2006; Khan et al., 2009]. Physics based models for

MQL was developed by Li and Liang [2007] to predict the cutting temperature, cutting

force, tool wear and aerosol generation rate.

24

The models were validated with the experimental results obtained in turning of

AISI 1045 material. MQL was supplied on the flank face of the tool by a 0.762 mm

diameter opening in the tool holder. Cutting forces for MQL are found smaller than dry

cutting but higher than wet cutting. At lower cutting speeds lubrication was effective but

at high cutting speed (228.75 m/min) ineffective lubrication was observed. MQL was

most effective in reducing the tangential cutting force among the cutting force

components. MQL also reduced the cutting temperature for the entire range of speed and

provided a lower wear rate in comparison to dry cutting. However, it was expected that

MQL will generate more cutting fluid aerosol than flood cooling due to splash

mechanism. Tasdelen et al. [2008] investigated the affect of different cooling techniques

such as MQL, compressed air and emulsion on tool chip contact length in turning of

100Cr6 steel with different engagement times of inserts. Lower contact lengths were

observed with MQL and compressed air as compared to dry cutting. However, emulsion

assisted cutting provided the shortest contact length. For long engagement times, MQL

and compressed air have same contacts lengths, as the cooling effect was mainly from air

constituent in aerosol. For short engagement times, lubrication effect of oil drops

decrease the friction in the sliding region and overcomes the cooling effect resulting in

shorter contact lengths than compressed air. Also at short engagement times, increase in

quantity of oil decreases the contact length. More up curled chips were obtained with

emulsion than MQL and air assisted cutting. Chips obtained from MQL and compressed

air have almost same radius of curvature. Whereas, chips obtained from dry cutting have

largest radius of curvature. Chips obtained in dry cutting were wider than the chips

obtained with other methods due to side flow in the shear plane and have side curl due to

25

difference in speed at outer and inner diameter of work-piece. Shorter contact lengths

were observed with TiN coated tool due to different friction and temperature distribution

in the cutting zone. Effect of oil drops were found even at reduced engagement time for

TiN coating than uncoated carbides. On the basis of study it was concluded that for short

engagement time machining MQL is very suitable.

A study was conducted by Hwang and Lee [2010] to predict the cutting force and

surface roughness and to determine the optimal combination of cutting parameters in

turning of AISI 1045. To determine the significant parameters among supplied air

pressure, nozzle diameter, cutting speed, feed rate and depth of cut a two level fractional

factorial design is employed. It was reported that except supplied air pressure all the

parameters significantly affected the surface roughness. Models are then developed for

prediction of cutting speed and surface roughness in MQL and wet turning using Central

Composite Design. From the validation experiment cutting force equations are found

valid whereas surface roughness equations were not appropriate for accurate prediction.

The mismatch in experimental and predicted values was attributed to uncontrolled

parameters such as work material defect, lathe vibration and measuring errors. Nozzle

diameter of 6 mm, cutting speed of 361 m/min, feed rate of 0.01 mm/rev and depth of cut

of 0.1 mm were found optimal for MQL turning whereas nozzle diameter of 6 mm,

cutting velocity of 394 m/min, feed rate of 0.02 mm/rev and depth of cut of 0.1 mm were

found optimal for wet turning considering surface roughness and cutting forces

simultaneously. MQL turning was found to be more advantageous than wet turning when

only surface roughness and cutting forces were considered.

26

The cutting fluids are used in machining processes to improve the characteristics

of tribological processes, which are always present on the contact surfaces between tool

and work pieces. Due to several negative effects, a lot of works have been done in the

recent past years to minimize or even completely avoid the use of cutting fluids [Sokovic

and Mijanovic, 2001]. A number of attempts were made in the past to improve

cooling/lubrication in high speed machining and in the case of machining of difficult -to-

machine materials by the use of a minimum quantity lubricant jet to overcome these

problems. The results achieved by these investigators were very encouraging

[Wakabayashi et al., 1998; Suda et al., 2004; McCabe and Ostaraff, 2001]. Cutting

forces were reduced, chip shape, surface quality and tool life improved, thereby

increasing the metal removal rate and improving the overall performance of the

machining operation. In particular, Minimum Quantity Lubrication (MQL) machining

has already played a significant role as successful near-dry machining in a number of

practical applications [Sutherland et al. 2000; Rahman et al., 2002]. Minimum

Quantity Lubrication (MQL) in machining is an alternative to completely dry or flood

lubricating system, which has been considered as one of the solutions for reducing the

amount of lubricant to address the environmental, economical and mechanical process

performance concerns [Heinemann et al., 2006]. The concept of MQL sometimes

referred to as near dry machining that is based on the principle of total use, without

residues, applying lubricant between 10 to 100 ml/h at a pressure from 4 to 6.5 Kg/cm2

[Silva et al., 2005]. The minimum quantity lubricants have the advantages of advanced

thermal stability and lubricating capability over conventional cutting fluids. In this

technology, the lubricating function is ensured by the oil and the cooling function is

27

provided mainly by the compressed air. From the viewpoints of environment, safety,

health, performance and cost, the vegetable based oils are considered as alternatives to

petroleum-based metalworking cutting fluids because of its high biodegradability, high

viscosity indexes and good thermal stability. The vegetable-based oils could produce

better results than the mineral reference oil in view of increased machining performance

as well as renewable sources. Many researchers [Rahman et al., 2002; Khan and Dhar,

2006; Heinemann et al., 2006] have conducted various machining investigations using

MQL with both synthetic oils and vegetable oils. Many researchers have suggested the

MQL techniques in machining processes [Rahman et al., 2001; Davim et al., 2006].

They applied this technique in reaming process of grey cast iron and aluminum alloy with

coated carbide tools. The significant reduction in tool wear and improvement in surface

quality of the holes have been observed using MQL technique when compared to dry

cutting. Dhar et al. [2006] employed MQL technique in turning of AISI 1040 steel and

the results clearly indicated that a mixture of air and soluble oil machining is better than

conventional flood coolant system.

Braga et al. [2002] reported that the holes obtained during drilling of aluminium–

silicon alloys with uncoated and diamond coated K10 carbide tools using MQL technique

presented either similar or better quality than those obtained with flood lubricant system.

The investigations carried out by Kelly and Cotterell [2002] on aluminium alloy revealed

that the MQL technique is preferable for higher cutting speeds and feed rates. Davim et

al. [2007] carried out experimental investigations on machining of brass under different

conditions of lubricant environments. The primary function of cutting fluid is cooling and

lubrication. The cooling and lubricating properties of cutting fluids are critical in

28

decreasing tool wear and extending tool life. Cooling and lubrication are also important

in achieving the desired size, finish and shape of the workpiece. In respect of profit,

safety and convenience a number of alternatives to traditional machining are currently

under development. Minimum quantity lubrication (MQL) is an obvious and very

intricate balance between dry machining and traditional methods. MQL (Minimum

Quantity Lubricant) technique, a very small quantity of oil is applied to the cutting point

and it improves the cutting performance as compared to dry cutting. Some investigations

have been performed to examine the effect of MQL technique on the reduction of tool

wear and the improvement of surface roughness of work materials, but there are few

studies which have investigated the influence of MQL technique on the tool temperature

[Byrne et al., 2003].

The reduced utilization of cooling lubricants, in order to improve environmental

protection, safety of machining processes and to decrease time and costs related to the

number of machining operations, can be pursued performing machining processes with

the MQL (minimum quantity of lubricant) technique or without any cutting fluid (dry

cutting) [Diniz et al., 2003]. Such approaches can allow the obtaining of the product

specifications, in terms of surface roughness and dimensional accuracy, by the shortening

conventional process cycles (i.e. avoiding grinding). The effect of the lubrication-cooling

condition on the surface quality of the machined part strongly depends on the type of

machining operation to be performed (e.g. turning, milling, etc.), as well as on the

process parameters to be used. In particular, in face milling operations cutting takes place

with high frequency tooth impacts, depending on the cutting speed, and discontinuously

due to the presence of several teeth; for such reasons dry and MQL face milling can be

29

performed over a wide field of workpiece materials [Weinert et al. 2004, Vieira et al.

2001]. In line with growing environmental concerns involved in the use of cutting fluids

in machining processes, as reported by several researchers and manufacturers of machine

tools, strong emphasis is being placed on the development of environmentally friendly

technology, i.e., on environmental preservation and the search for conformity with the

ISO 14000 standard. On the other hand, despite persistent attempts to completely

eliminate cutting fluids, in many cases cooling is still essential to the economically

feasible service life of tools and the required surface qualities. This is particularly true

when tight tolerances and high dimensional and shape exactness are required, or when the

machining of critical, difficult to cut materials is involved. This makes the minimum

quantity of lubrication an interesting alternative, because it combines the functionality of

cooling with an extremely low consumption of fluids (usually < 80ml/h). These minimal

quantities of oil suffice, in many cases, to reduce the tool’s friction and to prevent the

adherence of materials. The minimization of cutting fluids has gained increasing

relevance in the past decade [Dorr & Sahm, 2000]. This small amount of fluid suffices

to reduce friction in cutting, diminishing the tendency of adhesion in materials with such

characteristics. A comparison with conventional cooling revealed numerous advantages

[Dorr and sahm 2000 and Diniz and Micarony 2002]. However, compared with the

conventional technique, MQL involves additional costs to pressurize the air and

technological supports needed in the process in order to overcome the technological

restrictions of the MQL technique. For instance, special techniques for transporting chips

may be necessary, and productivity may decrease due to the thermal impact on the

machined components. Oil vapor, mist and smoke generated during the use of MQL in

30

machining can be considered undesirable byproducts, since they contribute to increase

the index of airborne pollutants. This has become a factor for concern, requiring a

adequate exhaustion system in the machine tool. A compressed air line that works

intermittently during the process is used for atomization. These compressed air lines

generate noise levels that usually exceed the legally established limits [Machado &

Diniz, 2001]. Based on the known costs of wet machining and MQL machining, a

comparison was made of the costs of investments and annual fixed and proportional costs

at the BMW company. The comparison of the total investment costs in the transfer line,

results of the process still merit further in-depth studies. Minimum quantity lubrication

systems employ mainly cutting fluids that are no soluble in water, especially mineral oils.

Due to the very small amounts of cutting fluids used, one must consider that the costs

should not prevent the use of high technology compositions in the field of basic and

additive oils. Vegetal-based materials are being increasingly used. These oils, inhaled in

the form of aerosol, reduce the health hazard factor [Novaski & Dorr, 1999].

Kamata and Obikawa [2007] investigated finish turning of Inconel 718 under

MQL with three types of coated carbide tool (TiCN/Al2O3/TiN (CVD), TiN/AlN

superlattice (PVD) and TiAlN (PVD)). Biodegradable synthetic ester was supplied with

compressed air on both the rake and flank face of the tool. On the basis of tool life and

surface finish, TiCN/Al2O3/TiN (CVD) and TiN/AlN superlattice (PVD) were found

suitable for finish turning of Inconel 718 with MQL. They reported that optimization of

air pressure is required for appropriate application of MQL in finish turning of Inconel

718. They also reported that carrier gas plays a vital role in cooling of cutting point as

short tool life were obtained with argon gas as compared to air. Increase in cutting speed

31

from 1m/s to 1.5 m/s resulted in drastic decrease of tool life and worse surface finish for

both the coatings under MQL condition. Also, increase in lubricant quantity, increased

the tool life and surface roughness for TiCN/Al2O3/TiN coating, whereas it decreased the

tool life and surface roughness slightly for TiN/AlN coated tool.

Su et al. [2007] used cooled air (at a temperature of -200C) with MQL at a

pressure of 6 bar in finish turning of Inconel 718 alloy. Application of cooled air and

cooled air with MQL resulted in 78% and 124% improvement respectively in tool life

over dry cutting. Improvement in tool life was attributed to reduction in cutting

temperature resulting in reduced abrasion, adhesion and diffusion wear. Surface

roughness was also reduced drastically in both conditions due to reduction in tool wear.

Significant improvement in chip shape was also reported as short continuous tubular

chips were obtained under both conditions.

Obikawa et al., [2008] observed that control of oil mist flow and decrease in

distance between nozzle and tool tip enhances the cutting performance of MQL

particularly in Micro-liter lubrication range (oil consumption less than 1 ml/h). Finish

turning of Inconel 718 was investigated in micro-liter lubrication (μLL) range with

biodegradable ester using three different types of nozzles: ordinary type, cover type for

normal spraying and cover type for oblique spraying.

Effectiveness of MQL (eMQL) was computed by the relation (1)

eMQL=

TMQL - Tdry

Twet- TWet - Tdry

......... (1)

32

where TMQL, Tdry and Twet are tool life for MQL, dry and wet turning.

Ordinary nozzle and cover type nozzle for normal spraying are not found suitable

for μLL. Values of eMQL decreased to 0.50, 0.47 and 0.36 as oil consumption (Q)

decreased to 1.1 , 0.5 and 0.2 ml/h for ordinary nozzle whereas with cover type nozzle

for normal spraying increase in eMQL is 0.22 and 0.18 for Q =0.50 and 0.20 ml/h over

ordinary nozzle. The cover type nozzle for oblique spraying provided significant

improvement as value of eMQL was 0.80,0.94 and 0.97 for Q =0.2, 0.5 and 1.1 ml/h

respectively. Good surface finish and tool life of 47 min was obtained at an oil

consumption of 0.5 ml/h and cutting speed of 1.3 m/s.

A study on effects and mechanisms in MQL intermittent turning of Aluminum

alloy (AlSi5) was conducted by Itoigawa et al. [2006]. MQL was studied with oil and oil

film on water droplet using rapeseed oil and synthetic ester as lubricant. MQL with

rapeseed oil showed only a small lubrication effect in light loaded machining conditions.

MQL with synthetic ester shows a lubrication effect but there was significant tool

damage and aluminum pick-up on the tool surface. MQL with water droplets using

synthetic ester provided good lubrication. They reported that influence of water for good

frictional performance depends not on the film chemi-sorption process but on water’s

chilling effect to sustain boundary film strength. In MQL machining of 6061 aluminum

alloy the quantity of adhered material to the tool was more as compared to flooded

coolant and less as compared to dry cutting. No considerable reduction in material

adhesion and flank wear was observed by increasing the lubricant quantity to two times.

33

Significant increase in flank wear was reported with increase in cutting speed. Cutting

forces were found highest under dry cutting and lowest under flooded condition. The

variation of cutting forces with different machining strategies is attributed to the amount

of adhesion. Surface roughness obtained by MQL is found to lie between dry cutting and

flooded condition [Sreejith, 2008].

Davim et al. [2007] conducted a study on turning of brass with MQL to study the

effect of the quantity of cutting fluid. They compared the cutting power, specific cutting

force, surface roughness and chip form with MQL at Q =50, 100, 200 ml/h and with

flood cooling at Q =2000 ml/h. Cutting parameters in the experimental test are cutting

speed (v) =100, 200 and 400 m/min, feed rate (s) =0.05, 0.10, 0.15 and 0.2 mm/rev, depth

of cut (t) =2 mm. Slightly higher cutting power was observed with MQL lubrication at 50

ml/h and flood lubrication at 2000 ml/h whereas almost same power is noticed with MQL

at flow rate of 100 and 200 ml/h. This suggests that similar/better cutting conditions can

be achieved with MQL as compared to flood lubrication. The specific cutting force is

found lower at a cutting velocity of 200 m/min except for fluid lubrication and reported it

to be a critical speed for brass machining. At Q =200 ml/h specific cutting force is found

to be lowest. Surface roughness decreased with increase in flow rate. Similar surface

roughness is observed with MQL at Q =200 ml/h and flood lubrication. Also for all the

machining conditions the relation between Rt and Ra was found maintained. Similar chip

forms were observed MQL and flood lubrication. In further work by Gaitonde et al.

[2008] quantity of lubricant, cutting speed and feed rate were determined for

simultaneously minimizing surface roughness and specific cutting force by using Taguchi

method and utility concept. They reported that Q =200 ml/h, v =200 m/min and s =0.05

34

mm/rev are optimal process parameters. Feed rate is found to be most significant factor

followed by quantity of MQL lubricant and cutting speed in optimizing the machinability

characteristics.

Effect of dry cutting, flood coolant, and minimum quantity lubrication were

studied in continuous and interrupted turning of Ti-6Al-4V alloy with uncoated carbide

inserts. It was reported that in continuous cutting, MQL seems to be more effective than

flood cooling at high cutting speed and feed rate due to its better lubrication ability. In

interrupted cutting MQL was also found more effective than dry and flood coolant

particularly in two slots cutting [Wang et al., 2009]. The main problem with machining

of titanium alloys is related to high heat generation at tool-chip interface due to which

machining of these alloys is recommended only with copious amount of cutting fluid. As

the main concern in titanium alloy machining is to remove the heat generated during the

process, Minimum quantity cooling (MQC) seems to be more appropriate than MQL. A

sequential procedure for determining operating parameters in MQC assisted turning of

Ti-6Al-4V alloy is presented in following section.

1.3 Summary of Review

During machining temperature is the apprehensive element and it is essential to

control this cutting temperature for better surface finish. Cutting fluid reduces cutting

temperature and also provides lubrication effect between the tool and work-piece

interface. There are different types of lubrication as well as cooling system available to

minimize the cutting temperature. Many researchers also made their investigations using

these different types of cooling and lubrications systems like flood cooling, near dry

35

cooling, or micro lubrication, high pressure jet cooling, cryogenic cooling and MQL

cooling. Flood cooling reduces temperature to some extent by bulk cooling but is not

very much effective because it cools only the top surface of the job and this is due to its

overhead application. It has some bad effects too, when cutting/cooling fluid comes in

contact with the human body it creates skin irritation, lung cancer etc. Near dry cooling is

based on air coolant, a little amount of temperature is reduced. Cryogenic cooling

effectively reduces temperature from the cutting zone but it is very costly and in nitrogen

rich atmosphere notch wear of the tool takes place. High pressure coolant has been

reported to provide quickly reduction in cutting temperature [Aronson, 2004]. It reduces

temperature very quickly due to high pressure jet coolant reaches very easily in the chip-

tool interface. It has been experienced that lubrication is effective at low speeds when it is

accomplished by diffusion through the work piece and by forming solid boundary layers

from the extreme pressure additives, but at high speeds no significant lubrication effect in

evident. The ineffectiveness of lubrication of the cutting fluid at high speed machining is

attributed to the inability of the cutting fluid to reach the actual cutting zone and

particularly at the chip-tool interface due to bulk or plastic contact at high cutting speed.

On the other hand the cooling and lubricating affects of cutting fluid influence each other

and diminish with increase in cutting velocity. The machining temperature could be

reduced to some extent by improving the machinability characteristics of the work

material metallurgical, optimizing the tool geometry and by proper selection of process

parameters. Some recent techniques have enabled partial control of machining

temperature by using heat resistance tools like coated carbides, CBN etc. the thermal

deterioration of the cutting tools can be reduced by using CBN tools. But CBN tools are

36

very expensive. Although the modified inserts offer reduced cutting force, their beneficial

effect on surface finish is marginal. Some recent techniques have enabled partial control

of machining temperature by using heat resistance tools like coated carbides, CBN etc

while dry cutting. The thermal deterioration of the cutting tools can be reduced by using

CBN tools. But CBN tools are very expensive. It was reported that [Alaxender et al.,

1998] that coolant injection offers better cutting performance in terms of surface finish,

tool force and tool wear when compared to flood cooling.

Coolants are frequently used in machining processes. They reduce tool wear,

dissipate heat from the work piece and machine, assist in the removal of swarf and

release cutting residues attached to the work piece, tool and equipment. The increased use

of coolants in recent years has caused a considerable increase in costs for procurement,

maintenance and disposal. The compatibility of coolants with the environment and the

potential health risks to the machine operator generated by the latter have increasingly

become the subject of criticism. The disposal of used coolants is not entirely sound

ecologically and is also causing rising costs. These costs are often underestimated

because they are mainly included in general overheads. Thus in fabrication operations

with centralized systems, they reach a level of 7 to17 % of the total fabrication costs. In

comparison with the latter, the tool costs in general amount to just 2 to 4 % of overall

costs (Figure 1). Minimizing lubricant consumption therefore has to be the ecological and

economic objective of a fabrication operation which looks towards the future. Against the

background of modern cutting materials and advanced coatings, the question arises as to

whether machining without lubricant i.e. “dry” is possible on an industrial scale.

37

Fig. 1.3 Distribution of Fabrication costs in engineering

The influence of cutting speed and feed rate on machinability aspects were

studied and concluded that flood lubrication can be successfully replaced by MQL type

of lubrication. However, in manufacturing machining industries, the temperature and its

detrimental effects are generally reduced by:

i. Proper selection of process parameters and geometry of the cutting tools.

ii. Proper selection and application of cutting fluid.

iii. Using heat and wear resistant cutting tool materials like carbides, coated

carbides and high performance ceramics (CBN and diamond are extremely

heat and wear resistive but those are too expensive and justified for very

special work materials and requirements where other tools are not

effective.

38

Coolant plays a significant role in improving lubrication as well as minimizing

temperature at the tool-chip and tool-work interfaces, consequently seizure during

machining. Flood cooling is not effective in terms lowering cutting temperature when

machining exotic materials. The coolant does not readily access the tool-work and tool-

chip interfaces that are under seizure condition as it is vaporized by the high cutting

temperature generated close to the tool edge. Machining of medium carbon based alloys

at high-speed conditions can therefore be achieved by combination of the appropriate tool

material, machining technique and the choice of a suitable cooling technology. Minimum

quantity lubrication is one of the preferred technologies currently under exploitation.

In general, when machining steel with coated carbide tools different tool wear

mechanisms occur, such as: abrasion, adhesion, oxidation and even some diffusion,

which act simultaneously and in proportions depending mainly on the temperature. The

task of defining which of those mechanisms is the predominant one has become a very

complex task. However, some researches relating wear mechanisms to the cutting speed

have been made and some important results have been published. For example, the raise

in temperature at the cutting zone occurs basically due to the cutting speed increase. The

abrasion phenomenon occurs predominantly at low cutting speeds, adhesion at medium

ones, and oxidation/diffusion at high ones. The limit of growing for cutting speed

depends on several other factors, such as tool-work combination, contact time between

them and the presence of cutting fluids. However, those findings are only indications and

may not offer more than recommendations for practical applications. By superimposing

wear mechanisms and their relations with cutting speed, it is possible to explain most of

the tool wear observed in practice; although in some cases the causes may depend on

39

some other factors occurring at the cutting zone and tool/work piece contact area,

[Arsecularatne et al., 2006]. In machining of steels the use of proper coating structure

can contribute to substantial reduction of the friction action between the rake and chip

and result in a decrease in heat generation and lower the tool-chip interface temperature.

The selection of work piece material with low thermal conductivity and low heat capacity

and a coating material with low thermal conductivity leads to a reduction in the contact

length, resulting in the effect of a thermal barrier. As a consequence, heat is concentrated

within the thin top layer of the coating to protect the tool against diffusion.

The application of MQL or dry cutting techniques requires that the functions of

the cooling lubricant are carried out by the other components of the machining system.

To this purpose, the cutting material and tool coating play a key role. In the last decades,

research has led to the development of cutting materials with improved performances,

such as ultra-fine grain cemented carbides, cermets, ceramics, cubic boron nitrides and

diamond, in order to withstand the higher temperatures occurring under MQL and dry

machining conditions, and provide a longer tool life. A further contribution has been

given by the development of tool coatings that can compensate for the lack of the cooling

lubricant; in particular, they can improve the tool wear behavior, reduce the thermal load

of the cutting tool by acting as thermal barrier and improve the sliding behavior on the

flank and rake faces by acting as a solid lubricant. Improvements in coating technology

have led to the development of multilayer coatings, nanolayer coatings, supernitrides,

self-lubricating coatings, CBN coatings and diamond coatings [Zhang et al. 2007;

Belmonte 2003].

40

At present, industry and researchers are looking for ways to reduce the use of

lubricants because of ecological and economical reasons. Therefore, metal cutting is to

move toward dry cutting or semi-dry cutting. This project presents an investigation into

MQL (Minimum Quantity Lubrication) machining with the objective of deriving the

optimum cutting conditions for the turning process of 42CrMo4. To reach these goals

several finish turning experiments were carried out, varying cutting speed, feed rate and

Cutting fluid with MQL. The surface roughness and tool wear results of tests were

measured and the effects of cutting conditions were analyzed by the graphical

presentation. From the experimental results, it is found that a better surface roughness can

be obtained by decreasing oil quantity and feed rate.

1.4 Scope of the Present Work

There are lot of scope and necessary to carry out extensive research and

development work for more effective and efficient machining of such increasingly used

steels. Such research and development work through understanding of mechanism and

mechanics of machining of this critical steel will essentially enable enhanced

productivity, product quality, tool life and overall economy in machining though

optimum selection of process parameter, tool material and geometry and environment.

Chapter 1 comprises with Introduction and Literature Review of the previous works. The

objective of the present work is included at the end of the chapter.

Chapter 2 comprises with Experimental set-ups, Experimental procedures, data collected

and Investigations on experiment.

41

Chapter 3 comprises with the detail Discussion on Experimental Results. The

experimental results are plotted or tabulated where necessary and presented in this

chapter.

In Chapter 4 pin pointed conclusions are drawn from the research outcomes.

Finally a list of reference is provided in separate Chapter.

1.5 Objectives of the present work

The main objectives of the present work is to make an experimental investigation

on the role of soluble cutting fluid as conventional application and as NDL and applied

the conventional coolant and Near Dry Lubrication (NDL) in continuous turning of

hardened steel (likely hardened AISI-1060 steel) using uncoated carbide insert on the

major mach inability characteristics in respect of

i. Cutting Temperature such as average chip-tool and work-tool interface

temperature. Monitoring of cutting zone temperature by tool-work thermocouple

technique. A tool-work thermocouple technique is developed and used to measure

the average chip-tool interface temperature. It is obvious that chip-tool interface

temperature is reduces drastically by the application of cutting fluid as NDL

because of its effective cooling and lubrication.

ii. Chip morphology such as chip shape, color and chip thickness ratio. The

machining chips is collected during all the treatments for studying their shape,

colour and nature of interaction with the cutting insert at its rake surface. It is

42

expected that application of cutting fluid as NDL is changed the chip colour and is

changed the mode of chip formation.

iii. Surface finish (Ra). The surface roughness and variation in finished diameter

along the job-axis is monitored by a Roughness checker (usually Talysurf,

surtronic 25) and precision dial gauge respectively. As application of cutting fluid

as NDL is protect the cutting edges during gradual wear regime surface roughness is

reduced and as a result deviation in diameter is also reduced.

iv. To check the dimensional accuracy.

in machining hardened steel by the industry used uncoated carbide tool (SNMG

120408) at different speeds and feeds combination. In this study, the Near Dry

Lubrication (NDL) was provided with a spray of air and soluble cutting fluids in which

air at a pressure of 15 bar and lubrication at atmospheric pressure through an externally

fitted metering unit at lubricant flow rate of 35 ml/hr. The results indicated that the use of

the very small amount Lubrication by soluble cutting fluid leads to reduced surface

roughness and lowered cutting temperature significantly in compare to other

environments.

These results are being expected to improve machinability due to reduction in cutting

zone temperature enabling favorable chip formation and chip-tool interaction. It is also

provide reduction in tool wear which is enhance the tool life, surface finish and

dimensional deviation. It is expected that the use of cutting fluids leads to reduce surface

roughness, increase dimensional accuracy, and lower cutting temperature, while also

having favorable chip tool interaction.

43

CHAPTER 2

EXPERIMENTAL INVESTIGATION

2.1 Introduction

The high cutting temperature generated during machining of hardened steel is

not only reduces tool life but also impairs the product quality. The temperature becomes

more intensive when cutting speed and feed are increased for higher MRR and the work

materials are relatively difficult to machine for their high strength, harden-ability and

lesser thermal conductivity. Cutting fluids are widely used to reduce the cutting

temperature. But the major problems associated with the use of conventional methods. It

has already been observed through previous research that proper application of reduced

amount of lubricant may play vital role in providing not only environment friendliness

but also some techno-economical benefits.

The machining responses have been studied and evaluated for assessing the

machinability characteristics of the steel specimen under dry, wet and NDL with soluble

cutting fluid conditions by using uncoated carbide insert. The economy of machining

steel is strongly related to effective chip control, for higher utilization of machines and

temperature reduction in the tool, for raising the rates of metal removal. Cutting with the

excess amount of cutting fluids is still very common in conventional machining to control

high cutting temperature which adversely affects, directly and indirectly, chip formation,

cutting forces, tool life and dimensional accuracy and surface integrity of the products.

The effectiveness, efficiency and overall economy of machining any work material by

44

given tool depend largely on the machinability characteristics of the tool-work material

under the recommended conditions. The conditions are

i. Cutting temperature; which affects product quality and cutting tool

performance

ii. Chip formation

iii. Magnitude of cutting forces; which affects power requirements, vibration

and dimensional accuracy

iv. Surface finish

v. Tool wear and tool life

For achieving substantial technological and economical benefits in addition to

environmental friendliness, Near Dry Lubrication system needs to be properly designed

considering the following important factors:

i. Effecting cooling by enabling cutting liquid along with air jet reach as close

as to the actual hot zones as possible.

ii. Avoidance of bulk cooling of the tool and the job, which may cause

unfavorable metallurgical changes.

iii. Minimum consumption of cutting fluid by pin-pointed impingement and

only during chip formation.

The machining responses have been studied and evaluated for assessing the

machinability characteristics of the hardened steel specimen under dry, wet and near dry

conditions by using uncoated carbide insert.

45

2.2 Experimental Setup

2.2.1 Near Dry Lubrication System

The aim of the present work is primarily to explore and evaluate the beneficial

role of Near Dry Lubrication system on machinability characteristics of commonly used

tool-work combinations mainly in terms of cutting temperature, surface finish and chip-

forms, which governs productivity along with quality and overall economy.

Typically a very small amount coolant and/or lubricant supply system consists of

a compressor, small container for cutting fluid, fluid supply system, nozzle, separate

device and pipes for supply of cooling lubricant and air for their independent adjustment.

However, the components of the near dry lubrication system may vary depending upon

the type of fluid delivery system and atomization. The photographic view of the

experimental set-up fabricated at Machine Tool Laboratory, Dhaka university of

Engineering & Technology, Gazipur is presented in Fig. 2.1. In order to deliver metered

supply of air at desired pressure, pressure regulator is fitted in air supply line. The

pressurized air from nozzle can be directed on rake face depending upon experimental

requirement. The very important factor is design of near dry mixing system for supplying

lubricant on tool-work interface. First of all it is necessary to mix air and lubricant to

obtain the mixture to be spread on the cutting surface. There are two different types of

mixing methods can be used: mixing inside nozzle and mixing outside nozzle. Using the

mixing outside nozzle equipment, pressurized air and lubricant are mixed outside the

nozzle by create vacuum pressure due to dropping nozzle high pressure to atmospheric

pressure and increasing its velocity. The fluid pressure line was blocked by turning the

46

knobs of the set-up developed by Mr. Makinuzzaman Shahadat at Machine tool lab of

DUET under the supervision of same supervisor for MQL delivery. A separate fluid

chamber fitted with controller was used to store and deliver the coolant to outlet orifice of

the nozzle. A very precise wheel type metering system usually used in intravenous fluid

application apparatus traditionally known as saline pushing device is used to measure a

small amount of fluid that in turn was applied externally to the flowing stream of high

velocity air jet delivered from the specially designed nozzle at 15 bar. The high velocity

stream atomized the lubricant delivered as a feebler stream from the dispenser towards

the cutting interface as a pin pointed impingement. Figure 2.1 and figure 2.2 show the

photographic view of high velocity air supply system and schematic views of mixing

system for near dry lubrication supply system. A commercially available flexible tube

and wheel type flow controller was used to control the supply of cutting fluid to outlet

orifice of the nozzle. A special designed nozzle was used to impinge aerosol at high

velocity in the cutting zone. The lubrication is obtained by the lubricant, while a minimal

cooling action is achieved by the pressurized air that reaches the cutting surface. Several

advantages derive applying this method. Mist and dangerous vapors are reduced and the

mixture setting is very easy to control.

47

Fig. 2.1 Photographic view of the Near Dry Lubrication applicator

Fig. 2.2 Schematic view of the Near Dry Lubrication applicator

48

Fig. 2.3 Photographic view of air nozzle for near dry lubrication for Supplying high

velocity air

Fig. 2.4 Schematic view of the near dry jet issuing and impinging system

Figure 2.1 to Figure 2.4 show the photographic and schematic views of near dry

lubrication applicator, Photographic view of air nozzle for supplying high velocity air

and Schematic view of near dry jet issuing and impinging system respectively.

49

2.2.2 Experimental Procedure and conditions

In this experiment, Near Dry Lubrication conditions are used during machining to

compare the results with the same by dry and wet condition. For Near Dry Lubrication

supply the positioning of nozzle tip is very important and that has been settled after a

number of trials. During machining the Near Dry Lubrication jet is directed along the

auxiliary cutting edge over the tool rake face and partially under the flowing chips to the

cutting edges.

The photographic view of the experimental setup is shown in Figure 2.1. In the

figure it is shown that a jet of air along with a very amount of lubricant was injected

through the tool rake face, consists of a compressor, Near Dry Lubrication applicator,

USSR made engine lathe of Model 16K20, tool-work thermocouple and experimental

hardened steel. In this study, the Near Dry Lubrication was provided with a spray of air

and cutting fluids at a pressure 15 bars and coolant flow rate of 35 ml/hr.

The experiment was carried out on lathe, which has a 7.5 kW motor and

maximum spindle speed of 1600 rpm. The work material was hardened AISI 1060 steel

having diameter of 105 mm and length of 840 mm. The uncoated SNMG 120408 WIDIA

made inserts were clamped in a PSBNR-2525 M12 (Drillco) type tool holder. The tool

holder provided negative 6° side and back rake angles and 6° side cutting-edge and end

cutting-edge angles. The ranges of the cutting velocity (V), feed (f) and depth of cut (d)

were selected based on the tool manufacturer’s recommendation and industrial practices.

The following cutting conditions were employed in this investigation, shown in Table

2.1.

50

Table 2.1 Experimental conditions

• Machine tool : Engine Lathe, 7.5 kW, 1600 rpm, model 16K20, made in

Rusia (USSR)

• Work material : Hardened AISI 1060 steel

• Chemical Composition : Chemical Composition by weight percent

AISI 1060 steel (C-0.55-0.66 , Fe- 98.35-98.85, Mn-

0.60-0.90, P- ≤ 0.040 and S ≤ 0.050)

• Cutting insert : Uncoated Carbide, SNMG 120408 , WIDIA

Geometry : -6°,-6°,6°,15°,75°,0.8 mm

Process parameters

• Cutting speed, V : 41, 53, 66 and 82 m/min

• Feed, f : 0.09, 0.10 and 0.125 mm/rev

• Depth of cut, d : 0.50 mm and 1mm

• Coolant type : Soluble Cutting Fluid

• Coolant delivery methods : Near Dry Lubrication with a spray of air and cutting fluids

(in which air at a pressure of 15 bars and lubricant flow

rate of 35 ml/hr under atmospheric pressure)

• Environment : i. Dry

ii. Wet

iii. Near Dry

A number of cutting velocity V and feed rate f have been taken over relatively wider

ranges keeping in view the industrial recommendations for the tool-work materials

51

undertaken and evaluation of role of variation in V and f on the effectiveness of Near Dry

Lubrication.

Figure 2.5 Photographic view of surface roughness measuring technique

A tool-work thermocouple technique is developed and used to measure the

average chip-tool interface temperature. Calibration of tool-work thermocouple is taken

from the previously done research work of Kamruzzaman and Dhar, 2007. A polynomial

regression analysis is done for the set of temperature and milivolt data obtained by him

using a small crucible and a tiny junction of carbide rod and sample steel rod. Regression

equation is derived and the obtained result of mV under different process parameters and

conditions are put into that equation. Results of temperature readings are plotted against

cutting speed to visualize the trend of graph and effectiveness of different conditions.

The thickness of the chips directly and indirectly indicates the nature of chip-tool

interaction influenced by the machining environment. The chip samples were collected

during short run machining for the V-f combinations under dry, wet with soluble fluid

and Near Dry Lubrication with soluble fluid conditions. Cutting temperature as mV was

measured by a reliable tool-work thermocouple technique. The thickness of the chips was

repeatedly measured by a slide caliper to determine the value of chip thickness ratio. The

52

surface roughness of the machined surface after each cut was measured by a Talysurf

(Surtronic 25), rank Hobson, UK using a sampling length 4 mm and cut-off 0.8 mm,

shown in Figure 2.5. The results are documented and plotted against various

environments having different combinations of velocities and feeds.

2.3 Experimental Methodology

The research work is mainly experimental in nature. The methodology would be as

follows:

i. A 60 grade traditional used steel specimen of solid bar stock (840 mm X φ

107 mm) is hardened above critical hardness for carbide insert i.e. 33 HRC

keeping in mind that avoidance of case hardening also while cooling brine

solution mixed with ice may cause surface hardening. The hardening process

is carried out from Bangladesh Industrial and Technical Assistance center

(BITAC) because of absence of gas furnace in DUET.

ii. Monitoring of cutting zone temperature by tool-work thermocouple technique.

A tool-work thermocouple technique is developed and used to measure the

average chip-tool interface temperature.

iii. The machining chips is collected during all the treatments for studying their

shape, colour and nature of interaction with the cutting insert at its rake surface.

The surface roughness and variation in finished diameter along the job-axis is

monitored by a Roughness checker (usually Talysurf, Surtronic 25, Rank Hobson, UK)

and precision dial gauge having 0.1 μm accuracy respectively.

53

2.4 Experimental Results

2.4.1 Cutting Temperature

High production machining associated with high velocity (V), feed rate (f) and

depth of cut (d) inherently generates high heat as well as high cutting zone temperature.

The cutting temperature if not controlled properly, cutting tools undergo severe flank

wear and notch wear, lose sharpness of the cutting edge by either wearing or become

blunt by welded built-up edge and weaken the product quality. In normal cutting condition

all such heat sources produce maximum temperature at the chip-tool interface, which

substantially influence the chip formation mode; cutting forces, tool life and product quality.

High production machining needs to increase the process parameters further for meeting up

the growing demand and cost competitiveness. Cutting temperature is increased with the

increase in process parameter as well as with the increase in hardness and strength of the

work material. Therefore, attempts are made to reduce this detrimental cutting temperature.

In the Present work, the average cutting temperature was measured by tool-work

thermocouple technique with proper calibration under all the machining conditions. The

evaluated role of NDL on average chip-tool interface temperature in turning hardened AISI

1060 steel by uncoated carbide inserts at different V, f and d combinations in compare to

dry, wet and near dry condition have been shown in Fig.2.6, Fig.2.7, Fig.2.8 and Fig.2.9

respectively.

54

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800

Feed rate 0.09 mm/revAvera

ge c

hip

-tool in

terf

ace tem

pera

ture

, oC

Cutting speed, m/min

Dry

Wet

Near Dry

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800


ge c

hip

-tool in

terf

ace t

em

pera

ture

, oC


Dry

Wet

Near Dry

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800


ge c

hip

-tool in

terf

ace tem

pera

ture

, oC


Dry

Wet

Near Dry

Fig. 2.6 Variation of Chip-tool interface temperature with different cutting speed at feed

rates and 1 mm depth of cut by using uncoated carbide under dry, wet and near

dry condition during machining hardened AISI 1060 steel.

55

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800

Feed rate 0.09 mm/revAve

rag

e c

hip

-too

l in

terf

ace t

em

pe

ratu

re,

oC


Dry

Wet

Near Dry

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800


rag

e c

hip

-too

l in

terf

ace t

em

pe

ratu

re,

oC


Dry

Wet

Near Dry

38 63 8825 50 75 100

450

550

650

750

400

500

600

700

800


rag

e c

hip

-too

l in

terf

ace t

em

pe

ratu

re,

oC


Dry

Wet

Near Dry


rates and 0.50 mm depth of cut by using uncoated carbide under dry, wet and

near dry condition during machining hardened AISI 1060 steel.

56


rates at 1 mm depth of cut under dry, wet and near dry condition during

machining of hardened AISI 1060 steel by using uncoated carbide insert.


rates at 0.50 mm depth of cut under dry, wet and near dry condition during

machining of hardened AISI 1060 steel by using uncoated carbide insert.

57

2.4.2 Machining Chips

Machining is a process of shaping by the removal of material which results in chips

and the geometrical and metallurgical characteristics of these chips are very

representative of the performance of the process because the form (Shape, color) and

thickness of the chips directly and indirectly indicate the nature of chip-tool interaction

influenced by the machining environment. In general chip formation in machining can be

categorized as forming continuous, discontinuous or serrated chips.

In the present work, the chip samples are collected while turning of the hardened

AISI 1060 steel by uncoated carbide insert at different speed-feed and depth of cut

combinations under dry, conventional coolant and Near Dry Lubrication conditions by

the soluble cutting oil, have been visually examined and categorized with respect to their

shape and color. The form and color of all these chips were noted down based on ISO

3658-1977 (E) standard chip forms. The results of such categorization of the chips

produced at different environments have been shown in Table 2.2 and Table 2.3.

Table 2.2

Comparison of chip shape and color at different speed and feed at depth of cut 1 mm

under dry, wet and near dry conditions during machining of hardened AISI 1060 steel by

SNMG uncoated carbide insert.

Feed (f)

Cutting

Velocity

(V)

Dry Wet Near Dry

Chip

Shape Color

Chip

Shape Color

Chip

Shape Color

0.09

41 Long

Tubular Metallic

Small

Tubular Metallic

Small

Helical Metallic

53 Helical Burn Blue Small

Tubular Metallic

Small

Helical Metallic

66 Long

Helical Burn Blue

Small

Tubular Metallic

Small

Tubular Metallic

82 Long

Helical Burn Blue

Long

Helical Goldish

Small

Helical Metallic

0.10

41 Long

Tubular Metallic

Small

Tubular Metallic

Small

Helical Metallic

53 Tubular Metallic Small

Tubular Metallic Loose Arc Metallic

66 Long Burn Blue Small Metallic Small Metallic

58

Helical Helical Tubular

82 Long

Helical Burn Blue

Long

Helical Goldish

Small

Helical Metallic

0.125

41 Long

Helical Metallic

Small

Tubular Metallic

Long

Helical Metallic

53 Tubular Goldish Small

Tubular Metallic Loose Arc Metallic

66 Helical Burn Blue Small

Helical Metallic Loose Arc Metallic

82 Long

Helical Burn Blue

Long

Helical Goldish

Small

Helical Metallic

Chip Shape

Group Loose Arc Chips Long Tubular Snarled Tubular

Chips Snarled Ribbon

Table 2.3

Comparison of chip shape and color at different speed and feed at depth of

cut 0.50 mm under dry, wet and near dry conditions during machining of

hardened AISI 1060 steel by SNMG uncoated carbide insert.

Feed (f)

Cutting

Velocity

(V)

Dry Wet Near Dry

Chip

Shape Color

Chip

Shape Color

Chip

Shape Color

0.09

41 Small

Helical Goldish

Small

Tubular Metallic

Small

Helical Metallic

53 Small

Helical Bluish

Small

Tubular Metallic

Small

Helical Metallic

66 Small

Helical Bluish

Long

Tubular Metallic

Long

Helical Metallic

82 Snarled Blue Long

Tubular Metallic

Long

Helical Metallic

0.10

41 Small

Helical Bluish

Small

Tubular Metallic

Long

Helical Metallic

53 Small

Helical Bluish

Small

Tubular Metallic

Long

Helical Metallic

66 Long

Helical Blue

Long

Tubular Metallic

Long

Helical Metallic


Tubular Metallic

Long

Helical Metallic

0.125

41 Small

Helical Bluish

Small

Tubular Metallic

Long

Helical Metallic

53 Small

Helical Blue

Long

Tubular Metallic

Long

Helical Metallic

59

66 Long

Helical Blue

Long

Tubular Metallic

Long

Helical Metallic


Tubular Metallic

Small

Helical Metallic

In machining another important machinability index is chip thickness ratio, rc

(ratio of chip thickness before and after cut). For a given tool geometry and cutting

conditions, the value of rc depends upon the nature of chip-tool interaction, chip contact

length and chip form all of which are expected to be influenced by Near Dry Lubrication

conditions to the level of speed and feed. The thickness of the chips was repeatedly

measured by a digital slide caliper to determine the value of chip thickness ratio, rc (ratio

of chip thickness before and after cut). The variation in value of chip thickness ratio (rc)

with speed and feed at dry, wet and Near Dry Lubrication condition has been plotted

which are shown from Fig. 2.10 and Fig. 2.11 respectively.

40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

Environment: Dry

Ave

rag

e C

hip

Th

ickn

ess R

atio

(rc

)


0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Wet

Ave

rag

e C

hip

Th

ickn

ess R

atio

(r c

)


60

40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Near Dry

Ave

rag

e C

hip

Th

ickn

ess R

atio

(r c

)


Fig. 2.10 Variation of Chip Thickness ratio (rc) with different cutting speed and different

feed rate under different conditions at 1 mm depth of cut by using uncoated

carbide during machining of hardened AISI 1060 steel.

40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Dry

Ave

rag

e C

hip

Th

ickn

ess R

atio

(r c

)


40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Wet

Ave

rag

e C

hip

Th

ickn

ess R

atio

(r c

)


40 45 50 55 60 65 70 75 80 85

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev


Ave

rag

e C

hip

Th

ickn

ess R

atio

(r c

)


Fig. 2.11 Variation of Chip Thickness ratio (rc) with different cutting speed and different

feed rate under different conditions at 0.50 mm depth of cut by using uncoated

carbide during machining of hardened AISI 1060 steel.

61

2.4.3 Surface Roughness

Quality of the product is very crucial issue. The performance and service life of

any machined parts mainly vary by the quality of that product. For a given material

quality is generally assessed by dimensional and form accuracy and surface integrity of

the product in respect of surface roughness, oxidation, corrosion, residual stresses and

surface and subsurface micro-cracks.

To evaluate the quality of the product only the surface roughness and the

dimensional deviations on diameter have been investigated in this present work. This

investigation is carried out under different cutting environment at various V-f

combinations. But depth of cuts are 1.0 mm and 0.50 mm.

Finished Surface is a very vital consideration for product quality. This important

index of machinability is substantially influenced by the machining environment for

given tool-work pair and speed-feed conditions. So the development of surface roughness

in continuous machining processes like turning, is caused by

i. vibration in the machining system

ii. improper machine set-up

iii. gradual wear of the cutting tool

Surface roughness has been measured after a few seconds of machining with the

sharp tool while recording the cutting temperature. Here the surface finish has been

measured by a Talysurf (Surtronic 25, Rank Taylor Hobson) by the machining of the

hardened steel bar by the coated carbide insert at different V-f combination under dry,

62

wet and Near Dry Lubrication with soluble oil conditions using a sampling length of 4

mm along with cut-off 0.80 mm.

The surface roughness, Ra attained of machining of hardened AISI 1060 steel by

the sharp uncoated carbide (SNMG 120408, Widia) insert at various V-f combinations

under dry, Near Dry Lubrication with soluble oil, conditions are shown in Fig.2.12 and

Fig.2.13 respectively.

40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Dry

Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Wet

Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev


Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


Fig. 2.12 Variation of Roughness (Ra) with different cutting speed and different feed rate

under different conditions at 1 mm depth of cut by using uncoated carbide

during machining of hardened AISI 1060 steel.

63

40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Dry

Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev

Environment: Wet

Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


40 45 50 55 60 65 70 75 80 85

2.5

3.0

3.5

4.0

4.5

5.0

0.09 mm/rev

0.10 mm/rev

0.125 mm/rev


Ave

rag

e S

urf

ace

Ro

ug

hn

ess R

a(µ

m)


Fig. 2.13 Variation of Roughness (Ra) with different cutting speed and different feed rate

under different conditions at 0.50 mm depth of cut by using uncoated carbide

during machining of hardened AISI 1060 steel.

2.4.4 Dimensional Deviation

Dimensional accuracy often affects the performance and service life of the

machined component. The diameter of the machined part during the straight turning in an

engine lathe is generally found to increase along length of cut due to gradual wear of the

tool tip; decrease due to thermal expansion and subsequent cooling of the job if the job

temperature rises significantly during machining and increase due to system compliance

of the machine-fixture-tool-work (M-F-T-W) system under the action of the cutting

64

forces. So the development of dimensional deviation in continuous machining processes

like turning, is caused by

iv. vibration in the machining system

v. improper machine set-up, tool

vi. excessive heat development

vii. gradual wear of the cutting tool

The order of dimensional deviations possible due to thermal expansion of the

job even under dry machining and due to compliance of the M-F-T-W system were

calculated for the steel specimens being machined under the present conditions and the

values appear to be extremely small (less than 1 µm) compared to that possible due to

wear of the tool tips. Therefore, in the present study, the dimensional deviations are

considered to be mainly due to wear of the tool tips.

The gradual increase in dimensional deviations on diameter observed along the

length of cut on the hardened AISI 1060 steel after one full pass of machining at cutting

velocity of 82 m/min, 0.15 mm/rev feed and 1.0 mm depth of cut under dry, wet and Near

Dry Lubrication conditions have been considered. For Near Dry Lubrication

environment only the water soluble oil has been applied. Dimensional deviation of the

machined work piece has been measured by fitting a dial gauge of least count 10 µm on

the carriage of the machine tool under a complete pass of machining. During machining

gauge reading has been taken in 10 mm interval and plotted in Fig.2.14.

65

50 150 2500 100 200 300

50

150

250

350

0

100

200

300

400

Depth of cut: 1 mm

Devia

tion in D

imensio

n,

m

Length of cut, mm

Dry

Wet

Near Dry

50 150 2500 100 200 300

50

150

250

350

0

100

200

300

400

Depth of cut: 1 mm

De

via

tion

in D

ime

nsio

n,

m

Length of cut, mm

Dry

Wet

Near Dry

Fig. 2.14 Dimensional deviation observed after one full pass turning of hardened steel by

SNMG insert with different depth of cut under dry wet and near dry conditions.

66

CHAPTER 3

EXPERIMENTAL RESULTS AND DISCUSSION

3.1 Machining Chip

Chip morphology and thickness of the chips directly and indirectly indicate the nature

of chip-tool interaction influence by the machining environment. The pattern of chips in

machining ductile metals are found to depend upon the mechanical properties of the work

material, tool geometry particularly rake angle, levels of V and f, nature of chip-tool interaction

and cutting environment. In absence of chip breaker, length and uniformity of chips increase with

the increase in ductility and softness of the work material, tool rake angle and cutting velocity

unless the chip-tool interaction is adverse causing intensive friction and built-up edge formation.

From Table 2.2 and Table 2.3 it is stated that under dry condition most of the chips

produced are long tubular in nature and the colour of the chips are bluish, blue or burn blue.

Under lower speed –feed conditions where temperature is not more severe the chips produced are

lighter in colour but with the changing incremental interfacial temperature due to increase in

speed-feed as the metal becomes ductile, chips produced got incremental shapes like helical as

well as chip morphological changes takes place, more darker coloured chips are produced with

the incremental change in speed-feed. Wet condition changes the mode of chip formation due to

its cooling effect. Bulk cooling changes the shape the shape of the chips from long tubular to

small helical or small tubular or loose arc also colour changes to goldish or metallic that also an

indication of decrease in cutting temperature due to application of cutting fluid though in bulk

amount. Under Near Dry condition the shape of all most all the chips are small helical that is near

to loose are and morphologically metallic in colour. But when V=82 m/min ie. the highest speed

employed for this experiment at all the feed range, the shape of the chips are small helical under

67

the application of near dry lubrication. Again from Table 2.2 and Table 2.3 it is clear that when V

and f increase, the chip-tool interface temperature increases. Thus chip become much deeper, i.e.

from metallic to golden to blue or even burn blue. Again the colour of the chips have also become

much lighter depending upon V and f due to reduction in cutting temperature by wet and Near

Dry condition. At dry condition the colour of the chips are very deeper, i.e. blue due to high

temperature. Wet condition changes the colour to golden by reducing temperature and Near Dry

condition changes the colour to metallic by reducing the cutting temperature by effective and

efficient cooling and lubrication as well as pin pointed impingement of the cooling jet to the

actual cutting interface.

The chip-thickness ratio (rc) is an important index of chip formation and specific energy

consumption for a given tool-work combination. It is evaluated from the ratio,

22

1c

a

φsin f

a

ar == (3.1)

Where,

rc = Chip thickness ratio

a1 = Chip thickness before cut = f sinφ

a2 = Chip thickness

f = Feed rate

φ = Principal cutting edge angle

68

During the machining of the metals and alloys, continuous chips are produced and the

value of rc is generally less than 1.0 because chip thickness after cut (a2) becomes greater than

chip thickness before cut (a1) due to almost all sided compression and friction at the chip-tool

interface. Smaller value of rc means larger cutting forces and friction and hence is undesirable.

Chip thickness depends on almost all the parameters involved in machining. The degree

of chip thickness which is measured by chip thickness ratio, plays an important role on cutting

forces and hence on cutting energy requirements and cutting temperature. The effect of increase

in V and f and the change in environment on the value of chip-thickness ratio (rc) obtained during

turning hardened AISI 1060 steel are shown in figure from Fig. 2.10 and Fig. 2.11 which depict

some significant facts;

i. values of rc has all along been less than 1.0

ii. the value of rc has increased by the application of minimum quantity of lubricant

iii. the value of rc increases with increase in V and f

Figure 2.10 and Figure 2.11 show that Near Dry condition has increased the value of

chip thickness ratio for all V-f combinations due to reduction in friction at the chip-tool interface,

reduction in built-up-edge formation and wear at the cutting edges. In all V-f combinations Near

Dry condition by cutting fluid shows more effectiveness than that of conventional application of

cutting fluid and completely absence of cutting fluid ie, dry cutting. The figures from Fig. 2.10

and Fig. 2.11 clearly show that throughout the present experimental domain the value of rc

gradually increased with the increase in V and f in different degree under dry, wet and Near Dry

conditions. Among these three conditions, NDL has shown the best performance, because the

value of rc has increased more than the other conditions, i.e. dry and wet. The value of rc usually

increases with the increase in V particularly at its lower range due to plasticization and shrinkage

of the shear zone for reduction in friction and built-up edge formation at the chip-tool interface

69

due to increase in temperature and sliding velocity. In machining steels by tools like carbide,

usually the possibility of built-up edge formation and size and strength of the built-up edge, if

formed gradually increase with the increase in temperature due to increase in V and also f and

then decrease with the further increase in V due to too much softening of the chip material and its

removal by high sliding speed.

The percentage increment in chip-thickness ratio, rc attained by Near Dry for different

cutting velocity and feed have been calculated from the previous figures and shown in Table 3.1

for hardened AISI 1060 steel. For ease of comparison, the ranges and averages of percentage

increment in rc has been separately shown in Table 3.2 which visualizes how the beneficial role of

Near Dry varied with different cutting conditions.

Table 3.1 Percentage increment in chip thickness ratio (rc)

Feed rate, f,

mm/rev

Cutting velocity,

V,

m/min

Percentage increment in rc

for depth of cut 1.0 mm

Percentage increment in rc


Wet Near Dry Wet Near Dry

0.09

41 0.95 20.24 12.05 4.79

53 4.99 22.51 12.86 4.74

66 5.77 20.41 11.54 5.97

82 9.92 16.67 11.11 6.62

0.10

41 7.35 15.58 11.57 5.70

53 8.70 17.59 12.11 4.53

66 11.82 16.71 11.02 9.41

82 13.93 13.34 10.80 10.88

0.125

41 11.81 15.11 12.52 7.99

53 11.57 17.14 11.55 5.95

66 14.03 16.73 14.24 7.75

82 12.05 14.90 11.13 10.94

70

Table 3.2 Average percentage increment in chip thickness ratio (rc)

Savings Average Percentage increment in rc


Average Percentage increment in rc



Range 0.95-14.03 13.34-22.51 10.80-12.86 4.53-10.94

Average 9.41 17.24 11.88 7.11

From Table 3.1 the percentage of increment in chip thickness ratio for the stated V-f

combinations for wet and Near Dry by traditional cutting fluid over dry condition are 1~14%, and

13~23% respectively for depth of cut 1 mm and 10~13%, and 4~11% respectively for depth of

cut 0.50 mm. It can also show that at low feed and low cutting speed increase in chip thickness

ratio is more. But if feed increases better result is shown at 82 m/min cutting speed.

3.2 Cutting Temperature

During hard turning the maximum heat generated at the chip-tool interface, as a result

temperature of chip-tool interface is increased quickly. This machining temperature at the cutting

zone needs to be controlled as far as possible. Cutting temperature increases with the increase in

specific energy consumption and material removal rate (MRR). Such high cutting temperature

adversely affects, directly and indirectly, chip formation, cutting forces, tool life and dimensional

accuracy and surface integrity of the products. That is why, attempts are made to reduce this

detrimental cutting temperature. In some cases dry cutting is preferable in machine to hard

materials at low speed. But in case of high speed machining cutting fluids may apply.

Conventional cutting fluid application may, to some extent, cool the tool and the work piece in

bulk but cannot cool and lubricate expectedly and effectively at the chip-tool interface where the

71

temperature is maximum. This is mainly because the flowing chips make mainly bulk contact

with the tool rake surface and may be followed by elastic contact just before leaving the contact

with the tool. Bulk contact does not allow the cutting fluid to penetrate in the interface. Elastic

contact allows slight penetration of the cutting fluid only over a small region by capillary action.

The cutting fluid action becomes more and more ineffective at the interface with the increase in V

when the chip-tool contact becomes almost fully plastic.

Therefore, application of Near Dry Lubrication at chip-tool interface is expected to

improve machinability characteristics that play vital role on productivity, product quality and

overall economy in addition to environment-friendliness in machining particularly when the

cutting temperature is very high. The average chip-tool interface temperature has been

determined by using the tool work thermocouple technique and plotted against different cutting

velocity, V under dry, wet and Near Dry environment in turning hardened steel by uncoated

SNMG 120408 insert.

The variation in average chip-tool interface temperature at different cutting velocity,

feed and environment combinations are shown Fig. 2.6 and Fig. 2.7. The cutting temperature

generally increases with the increase in V and f though in different degree due to increased

energy input. So, for high-speed machining it is very important to control the cutting temperature.

It could be expected that Near Dry Lubrication would be more effective at higher values of V and

f. Fig. 2.6 and Fig. 2.7 show that Near Dry Lubrication is better than dry and wet machining for

all the V-f combinations.

It is evident from Fig. 2.6 and Fig. 2.7 that as the cutting velocity and feed rate

increases, the percentage reduction in average cutting temperature decreases. It may be for the

reasons that, the bulk contact of the chips with the tool with the increase in V and f do not allow

significant entry of air-coolant jet. Only possible reduction in the chip-tool contact length by the

72

Near Dry coolant jet particularly that which comes along the auxiliary cutting edge can reduce the

temperature to some extent particularly when the chip velocity is high due to higher V. So, at

industrial speed-feed conditions, this amount of reduction in average cutting temperature is quite

significant in pertaining tool life and surface finish.

The percentage saving in average chip-tool interface temperature θ attained by Near

Dry Lubrication for different V-f combinations have been extracted from the previous figures and

shown in Table 3.3 for hardened AISI 1060 steel. For convenience of comparison, the ranges and

averages of percentage savings in θ have been separately shown in Table 3.3 which visualizes

how the beneficial role of Near Dry Lubrication varied with different cutting conditions.

Table 3.3 Percentage reduction in chip-tool interface temperature (θ)

Feed rate, f,

mm/rev

Cutting velocity,

V,

m/min

Percentage reduction in (θ)

doc 1 mm

Percentage reduction in (θ)

doc 0.50 mm


0.09

41 15.13 4.75 4.93 4.32

53 14.58 4.08 6.65 8.51

66 7.13 7.36 10.33 15.36

82 5.78 9.93 9.80 15.75

0.10

41 9.75 7.51 5.74 3.78

53 6.77 2.60 5.25 9.18

66 7.23 3.02 12.21 6.69

82 4.18 5.32 6.12 14.22

0.125

41 6.89 3.53 6.46 10.17

53 4.36 2.99 6.17 12.79

66 2.86 5.15 10.20 9.49

82 2.20 3.71 8.39 7.63

73

Table 3.4 Average percentage reduction in θ

Savings

Average percentage reduction in θ for

depth of cut 1.0 mm

Average percentage reduction in θ



Range 2 16 3 10 5 11 4 16

Average 7.24 5.00 7.69 9.82

From the Table 3.3 and Table 3.4 it is found that, in case of Near Dry Lubrication by

cutting fluid among all V-f combinations the reduction in cutting temperature for V=82m/min and

f=0.09 mm/rev is more. In this V-f combination temperature reduction under wet and Near Dry

Lubrication by cutting fluid varies from 2~16% and 3~10% respectively for depth of cut 1 mm

and 5~11%, and 4~16% respectively for depth of cut 0.50 mm. It can be noticed that with the

increase in feed rate Near Dry Lubrication becomes less effective at higher cutting velocity but it

shows better performance at lower cutting velocities. This may be due to the increase in chip load

and increase in plastic contact length during cutting prevents the Near Dry Lubrication jet to enter

into the chip-tool interface. More over, it shows best reduction at higher velocity for lower feed

rate. Again Table 3.4 presents that the average percentage reduction in chip-tool interaction

temperature under wet and Near Dry Lubrication by cutting fluid and soluble oil are 7.24% and

5% respectively for depth of cut 1 mm and 7.69%, and 9.82% respectively for depth of cut 0.50

mm. Therefore, in all the tests through out the entire experiment, Near Dry Lubrication with

cutting fluid shows the best performance due to its better cooling and lubrication irrespective of

speed feed and depth of cut.

74

3.3 Product Quality

The value of any machined product of given material is generally assessed by surface

integrity and dimensional accuracy, which govern the performance and service life of that

product. For the present study, only dimensional accuracy and surface finish have been

considered for assessment of quality of product under dry, wet and Near Dry machining

conditions.

Surface finish is an important index of mach inability or grind ability because the

quality of any machined product of given material is generally assessed by dimensional accuracy

and surface integrity, which govern the performance and service life of that product. Generally,

good surface finish, if essential, is achieved by finishing processes like grinding but sometimes it

is left to machining. The major causes behind development of surface roughness in continuous

machining processes are:

i. regular feed marks left by the tool tip on the finished surface

ii. irregular deformation of the auxiliary cutting edge at the tool-tip due to chipping,

fracturing and wear

iii. vibration in the machining system

iv. built-up edge formation, if any

Even in absence of all other sources, the turned surface inherently attains some amount

of roughness of systematic and uniform configurations due to feed marks. The peak value of such

roughness depends upon the value of feed, f and the geometry of the turning inserts. Nose radius

essentially imparts edge strength and better heat dissipation at the tool tip but its main

contribution is drastic reduction in the aforesaid surface roughness as indicated by the simple

relationship,

75

r8

fh

2

m = (3.2)

Where,

hm = Peak value of roughness caused due to feed marks

r = Nose radius of the turning inserts

f = Feed rate

In actual machining, particularly at high feed and cutting velocity, the peak value, hm

may decrease, due to rubbing over the feed mark ridges by the inner sharp edge of the flowing

chips. Further deterioration of the cutting edge profile takes place due to chipping, wear etc.

Formation of built-up edge may also worsen the surface by further chipping and flaking of the

tool materials and by overflowing to the auxiliary flank at the tool-tip.

For the present study, only surface finish has been considered for assessment of quality

of product under dry, wet and Near Dry machining conditions. Surface roughness is an important

measuring criterion of machinability because performance and service life of the machined

component are often affected by its surface finish, nature and extent of residual stresses and

presence of surface or subsurface micro-cracks, if any, particularly when that component is to be

used under dynamic loading or in conjugation with some other mating part. However, it is evident

that Near Dry improves surface finish depending upon the work-tool materials and mainly

through controlling the deterioration of the auxiliary cutting edge by abrasion, chipping and built-

up edge formation.

76

Feed force as well as chip thickness ratio is responsible for surface roughness along the

longitudinal direction of the turned job. Usually surface roughness decreases with the increase in

cutting velocity as cutting force decreases and chip thickness ratio increases with the increase in

cutting speed. Fig 2.12 and Fig. 2.13 show the variation of the values of surface roughness, Ra

attained of machining of hardened AISI 1060 steel by the sharp SNMG 120408 Widia inserts at

various V-f combinations under dry, wet and Near Dry conditions. The surface roughness

increases with the increase in feed, f and decreases with the increase in V. Increase in f raises Ra

mainly. Reduction in Ra with the increase in V may be attributed to smoother chip-tool interface

with lesser chance of built-up edge formation in addition to possible truncation of the feed marks

and slight flattening of the tool-tip. Increase in V may also cause slight smoothing of the abraded

auxiliary cutting edge by adhesion and diffusion type wear and thus reduces surface roughness.

So, cutting velocity, V influences on surface roughness under dry, wet and Near Dry machining

conditions. It is clear that the surface roughness quite decreases with increasing cutting velocity

under dry machining. In case of Near Dry machining, surface roughness faster decreases with

increases cutting velocity. This is mainly because of formation of built-up edge frequently and

behaviour of materials to be machined in dry machining compared that of Near Dry machining.

It appears from Fig 2.12 and Fig. 2.13 that surface roughness grows quite fast under dry

machining due to more intensive temperature and stresses at the tool-tips. Near Dry condition

appeared to be effective in reducing surface roughness. However, it is evident that Near Dry

improves surface finish depending upon the work-tool materials and mainly through controlling

the deterioration of the auxiliary cutting edge by abrasion, chipping and built-up edge formation.

It has been also observed that the roughness of the machined surfaces is high at high feed rates

and vice versa, under dry, wet and Near Dry Lubrication conditions. The factors influence in that

phenomenon is the irregular deformation of the auxiliary cutting edge at the tool-tip due chipping,

fracturing and wear.

77

Figure 2.14 shows the effect of Near Dry Lubrication by cutting fluid on the

dimensional accuracy of the turned job. The finished job diameter generally deviates from its

desired value with the progress of machining, i.e. along the job-length mainly due to change in

the effective depth of cut for several reasons which include wear of the tool nose, over all

compliance of the machine-fixture-tool-work system and thermal expansion of the job during

machining followed by cooling. Therefore, if the machine-fixture-tool-work system is rigid,

variation in diameter would be governed mainly by the heat and cutting temperature. With the

increase in temperature the rate of growth of auxiliary flank wear and thermal expansion of the

job will increase. Near Dry Lubrication takes away the major portion of heat and reduces the

temperature resulting from decrease in dimensional deviation.

78

CHAPTER 4

CONCLUSIONS AND RECOMMENDATIONS

4.1 CONCLUSIONS

The following conclusions can be deduced from the experiments performed:

i. The present NDL systems enabled reduction in average chip-tool interface

temperature upto 16% by using water soluble cutting fluids and even such

apparently small reduction, unlike common belief, enabled significant

improvement in the major machinability indices.

ii. The form and color of the hardened steel chips became favorable for more

effective cooling due to NDL application.

iii. Reduction of cutting temperature has not been more effective for those tool-work

combinations and cutting conditions, which provided lower value of chip

thickness ratio, rc for adverse chip-tool interaction causing large friction and

build-up-edge formation at the chip-tool interface.

iv. Surface finishes also improved mainly due to reduction of wear and damage at the

tool tip by the application of NDL.

The dimensional deviation is less in near dry lubrication (NDL) condition

compared to dry machining by using uncoated SNMG insert due to fewer breaks

in wear or initial wear and absence of notching at the auxiliary flank of the insert.

79

4.2 RECOMMENDATIONS

As the research work is experimental in nature, the measurements should be taken

with not only a great care but also should use more precision tools and instruments.

i. Temperature is measured by using tool-work thermocouple technique.

Though this technique is reliable, infrared technique or XRD can be used

to compare the measured data. Data acquisition system for temperature

reading may be incorporated along with tool-work thermocouple.

ii. Measuring the chip thickness is a very difficult task. Riz produced on the

top surface can create some obstacle to take proper measurement by slide

caliper. More precision technique can be used.

iii. Under NDL only one jet is used along auxiliary cutting edge over the rake

face at an angle of 15 to 20 degree. Another one jet may be used along

principal cutting edge. Bore better performance third jet may be used from

the bottom side targeting the nose if the cutting insert. In this situation

summation of the lubricant amount for all these jets will be less than 50

ml/hr as prescribed for NDL.

iv. Various types of lubricant may be used for checking the performance and

comparative study among the lubricants. Synthetic, semi-synthetic,

insoluble oil, vegetable oil and olive oils may be tested for this purpose.

v. A high pressure pump either normal or common rail type may be used to

inject a very small amount oil into the flowing stream for proper

atomization and mixing.

80

vi. Formation of aerosol can be measured in parts per million and concluded

whether it is harmful for operators health or environment.

81

REFERENCES

Alaxender, A., Varadarajan, A. S. and Philip, P. K., “Hard Turning with Minimum

Cutting Fluid: A Viable Green Alternative on the Shop Floor”, Proceeding of the

18th AIMTDR, pp.152-155, 1998.

Aronson, R. B., “Using High-Pressure Fluids, Cooling and Chip Removal are Critical”,

Manufacturing Engineering, June 2004, Vol.132 (6), 2004.

Arsecularatne, J. A., Zhanga, C., Montross, C., “Wear and Tool Life of Tungsten

Carbide, PCBN and PCD Cutting Tools”, International Journal of Machine Tools

& Manufacture, Vol. 46, No. 5, pp. 482-419, 2006.

Astakhov, V.P., “Ecological Machining: Near-Dry Machining”, Machining Fundamentals

and Recent Advances, Springer, London, 2008.

Attanasio, A., Gelfi, M., Giardini C. and Remino C., “Minimal Quantity Lubrication in

Turning: Effect on Tool Wear”, Wear, Vol. 260, pp.333-338, 2006.

Belmonte, M., Perro, P., Fernandes, A.J.S., Costa, F.M., Sacramento, J. and Silva, R.F.,

“Wear Resistant CVD Diamond Tools for Turning of Sintered Hardmetals”,

Diamond and Related Materials, Vol. 12, pp. 738–743, 2003.

Braga, D., Diniz, U., Miranda, A. E., and Coppini, W., “Using a Minimum Quantity of

Lubricant (MQL) and a Diamond Coated Tool in the Drilling of Aluminum–

Silicon Alloys”, Journal of Material Processing Technology, Vol. 122, pp. 127–

138, 2002.

Byrne, G., Dornfeld, D. and Denkena, B., “Advancing Cutting Technology”, Annals of

CIRP, Vol. 52(2), pp. 483–507, 2003.

82

Cassin, C. and Boothroyed, G., “Lubrication action of cutting fluids”, Journal of

Mechanical Engineering Science, Vol. l7, No. 1, pp.67–81, 1965.

Clarens, A.F., Zimmerman, J. B., Keoleian, G. A., Hayes, K. F. and Skerlos, S. J.,

“Comparison of Life Cycle Emissions and Energy Consumption for

Environmentally Adapted Metalworking Fluid System”, Environmental Science

and Technology, Vol. 42(22), pp. 8534-8540, 2008.

Dasch, J. M., and Kurgin, S. K., “A Characterization of Mist Generated from Minimum

Quantity Lubrication (MQL) Compared to Wet Machining”, International Journal

of Machining and Machinability of Materials, Vol. 7(1/2), pp. 82-95, 2010.

Davies, M.A., Chou, Y. and Evans, C.J., “On Chip Morphology, Tool wear and Cutting

Mechanics in Finish Hard Turning”, Annals of CIRP, vol.45(1), pp.77-82, 1996.

Davim, J.P., Sreejith, P.S., Gomes, R., and Peixoto, C., “Experimental Studies on Drilling

of Aluminium (AA1050) Under Dry, Minimum Quantity of Lubricant and Flood-

Lubricated Conditions”, Proc. ImechE Part B: J. Eng. Manuf., Vol. 220, pp.

1605–1611, 2006.

Davim,, J. P., Sreejith,, P.S. and Silva, J., “Turning of Brasses Using Minimum Quantity

of Lubrication (MQL) and Flooded Lubricant Conditions”, Materials and

Manufacturing Processes, Vol. 22, pp. 45-50, 2007.

Dhar N. R. and Kamruzzaman, M., “Effect of High-Pressure Coolant on Tool Wear, Tool

Life and Surface Roughness in Turning Medium Carbon Steel by SNMG Insert”,

9th Cairo University International Conference on Mechanical Design and

Production (MDP-9), Cairo, pp. 555-565, January, 2008.

83

Dhar, N. R., Nandakishore, S. V., Paul, S. and Chattopadhyay, A. B., “The Effects of

Cryogenic Cooling on Chips and Cutting Forces in Turning of AISI 1040 and

AISI 4320 Steels”, Journal of Engineering Manufacture (IMechE-2002), Part B,

Vol. 216, pp. 713-724, 2002.

Dhar, N., Kamruzzaman, M., and Ahmed, M., “Effect of Minimum Quantity Lubrication

(MQL) on Tool Wear and Surface Roughness in Turning AISI-4340 Steel”, J.

Mater. Processing Technol., Vol. 172, pp.299–304, 2006.

Dhar, N.R., Islam, M. W., Islam, S., and Mithu, M.A.H., “The Influence of Minimum

Quantity of Lubrication (MQL) on Cutting Temperature, Chip and Dimensional

Accuracy in Turning AISI-1040 Steel”, Journal of Materials Processing

Technology, Vol.171 (1), pp. 93-99, 2006.

Dhar,, N.R., Islam,, M.W. Islam,, S. and Mithu,, M.A.H., “ The influence of Minimum

Quantity of Lubrication (MQL) on Cutting Temperature, Chip and Dimensional

Accuracy in Turning AISI-1040 Steel”, Journal of Materials Processing

Technology, Vol. 171, pp. 93-99, 2006a.

Dhar,, N.R., Islam,, S. & Kamruzzaman,, M., “Effect of Minimum Quantity Lubrication

(MQL) on Tool Wear, Surface Roughness and Dimensional Deviation in Turning

AISI-4340 Steel”. G.U. Journal of Science, Vol. 20(2), pp. 23-32, 2007.

Dhar,, N.R., Kamruzzaman,, M. and Mahiuddin,, A., “Effect of Minimum Quantity

Lubrication (MQL) on Tool Wear and Surface Roughness in Turning AISI-4340

Steel”. Journal of Materials Processing Technology, Vol. 172, pp. 299-304,

2006b.

84

Diniz, A. E. and Micaroni, R., “Cutting Conditions for Finish Turning Process Aiming:

the use of Dry Cutting”, International Journal of Machine Tools & Manufacture,

Vol. 42, pp. 899-904, 2002.

Diniz, A. E., Ferreira, J. R., and Filho, F.T., “Influence of Refrigeration/Lubrication

Condition on SAE 52100 Hardened Steel Turning at Several Cutting Speeds”,

International Journal of Machine Tools and Manufacture, Vol. 43, pp. 317–326,

2003.

Dorr, J. and Sahm, A., “The Minimum Quantity Lubricant Evaluated by the Users”,

Machines and Metals Magazine, Vol. 418, Brazil, Nov, pp. 20-39, 2000.

Ekinovic, S., Dolinsek, S. and Begovic, E., “Machinability of 90MnCrV8 Steel during

High-Speed Machining”, Journal of Materials Processing Technology, Vol. 162–

163, pp. 603–608, 2005.

Ezugwu, E. O. and Bonney, J., “Effect of High-Pressure Coolant Supply when Machining

Nickel-Base, Inconel 718, Alloy with Coated Carbide Tools”, Journal of

Materials Processing Technology, Vol. 153–154, pp. 1045–1050, 2004.

Ezugwu, E. O. and Bonney, J., “Effect of High-Pressure Coolant Supply when Machining

Nickel-Base, Inconel 718, Alloy with Coated Carbide Tools”, International

Conference on Advances in Materials and Processing Technologies (AMPT),

Dublin City University, Dublin, Republic of Ireland, pp. 787–790, 8–11 July,

2003.

Gaitonde,, V. N., Karnik,, S. R. and Davim,, J. P., “Selection of Optimal MQL and

Cutting Conditions for Enhancing Machinability in Turning of Brass”. Journal of

Materials Processing Technology, Vol. 204, pp. 459-464, 2008.

85

Heinemann, R., Hinduja, S., Barrow, G., and Petuelli, G., “Effect of MQL on the Tool

Life of Small Twist Drills in Deep-Hole Drilling”, International Journal of

Machine Tool and Manufacturing, Vol. 46, pp. 1–6, 2006.

Hwang,, Y. K. and Lee,, C. M., “Surface Roughness and Cutting Force Prediction in

MQL and Wet Turning Process of AISI 1045 using Design of Experiments”.

Journal of Mechanical Science and Technology, Vol. 24(8), pp. 1669-1677,

2010.

Itoigawa,, F., Childs,, T.H.C., Nakamura,, T. and Belluco,, W., “Effects and Mechanisms

in Minimal Quantity Lubrication Machining of an Aluminum Alloy”, Wear, Vol.

260, pp. 339-344, 2006.

Kamata,, Y. and Obikawa,, T., “High Speed MQL Finish-Turning of Inconel 718 with

Different Coated Tools”, Journal of Materials Processing Technology, Vol. 192-

193, pp. 281-286, 2007.

Kelly,, J.F., and Cotterell,, M.G., “Minimum Lubrication Machining of Aluminium

Alloys”, Journal of Materials Processing Technology, Vol. 120, pp. 327-334,

2002.

Kevin Chou, Y., “Hard Turning of M50 Steel with Different Microstructures in

Continuous and Intermittent Cutting”, 14th International Conference on Wear of

Materials, vol. 255(7-12), pp.1388-1394, 2003.

Khan M.M A., and Dhar N.R., “Performance Evaluation of Minimum Quantity

Lubrication by Vegetable Oil in term of Cutting Force, Cutting Zone

Temperature, Tool Wear, Job Dimension and Surface Finish in Turning AISI-

86

1060 Steel”, Journal of Zhejiang University Science and Technology, Vol. 7(11),

pp. 1790-1799, 2006.

Khan,, M. M. A., Mithu,, M. A. H. and Dhar N. R., “Effects of Minimum Quantity

Lubrication on Turning AISI 9310 Alloy Steel Using Vegetable Oil-Based

Cutting Fluid”, Journal of Materials Processing Technology, Vol. 209, pp. 5573-

5583, 2009.

Kitagawa, T., Kubo, A., and Maekawa, K., “Temperature and Wear of Cutting Tools in

High-Speed Machining of Inconel 718 and Ti-6Al-6V-2Sn”, Wear, Vol. 202, pp.

142-148, 1997.

Klocke, F., Gerschwiler, K., Fritsch, R., and Lung, D., “PVD-Coated Tools and Native

Ester-An Advanced System for Environmentally Friendly Machining”, Surface

Coatings Technol., Vol. 201, pp. 4389–4394, 2006.

Konig, W., “New Approaches to Characterize Cutting Tool Coatings”, Annals of the

CIRP, vol. 41(1), pp.49–52, 1993.

Kovacevic, R., “Apparatus and Method of High Pressure Water Jet Assisted

Cooling/Lubrication in Machining”, Patent No. 5,288,186, 22 February, 1994.

Krahenbuhl,, U., “Vegetable Oil-Based Coolants Improve Cutting Performance (Cutting

Fluids) Tool in Production”, Vol. 1, pp. 6.2011, December 2002.

Li,, K.-M., and Liang S.Y., “Performance Profiling of Minimum Quantity Lubrication in

Machining”, International Journal of Advanced Manufacturing Technology, Vol.

35, pp. 226-233, 2007.

Liu, Z.Q., Cai, X.J., Chen, M. and An, Q. L., “Investigation of Cutting force and Turning

of End-Milling Ti-6Al-4V with Different Minimum Quantity Lubrication (MQL)

87

Parameters”, Proceedings of the Institution of Mechanical Engineers, Part B:

Journal of Engineering Manufacture, Vol. 225, pp.1273-1279, 2011.

Machado, A. R., Diniz, A. E., “Advantages and Disadvantages of the Use of the Cutting

Fluids”, Machining Congress, São Paulo, SP, Brazil, 2001.

McCabe, J. and Ostaraff, M. A., “Performance Experience with Near-dry Machining of

Aluminum”, Lubrication Engineering, pp. 22-27, 2001.

Michael Jacobson, M., Dahlman, P. and Gunnberg., F, “Cutting Speed Influence on

Surface Integrity of Hard Turned Bainite Steel”, Journal of Materials Processing

Technology, vol.128, pp.318–323, 2002.

Noordin, M.Y., Kurniawan, D. and Sharif, S., 2007, “Hard Turning of Stainless Steel

Using Wiper Coated Carbide Tool”, International Journal Precision Technology,

vol.1, pp 75-84.

Novaski, O. and Do¨rr, J., “Usinagem Quase a Seco. Ma´quinas e Metais”, pp. 34-41,

1999.

Obikawa,, T., Kamata,, Y., Asano,, Y., Nakayama,, K. and Otieno,, A., “Micro-Liter

Lubrication Machining of Inconel 718”, International Journal of Machine Tools

and Manufacture, Vol. 48, pp. 1605-1612, 2008.

Paul, S., Dhar, N.R., and Chattopadhyay, A.B., “Beneficial Effects of Cryogenic Cooling

over Dry and Wet Machining on Tool Wear and Surface Finish in Turning AISI

1060 Steel”, Proc. of the ICAMT-2000, Malaysia, pp. 209-214, 2000.

Rahman, M., Kumar, A.S. and Salam. M.U., “Experimental Evaluation on The Effect of

Minimal Quantities of Lubricant in Millin”.. Int. J. Machine Tools & Manuf, 42

(5), 539–547, 2002.

88

Rahman, M., Kumar, A.S., and Salam, M. U., “Evaluation of Minimal Quantities of

Lubricant in End Milling”, Int. J. Adv. Manuf. Technol., Vol.18, pp.235–241,

2001.

Rahman,, M. M. Khan,, M.M.A and Dhar,, N.R., “An Experimental Investigation into the

Effect of Minimum Quality Lubricant on Cutting Temperature for Machinability

of AISI 9310 Steel Alloy”, European Journal of Scientific Research, Vol. 29(4),

pp. 502-508, 2009.

Shaw, M. C., “Metal Cutting Principle”, 2nd Edition, Oxford University Press, pp. 479-

498, 2005.

Silva, L. R., Bianchi, E. C., Catai, R.E., Fusse, R. Y., França T. V., and Aguiar, P. R.,

“Study on the behavior of the Minimum Quantity Lubricant-MQL Technique

Under Different Lubricating and Cooling Conditions When Grinding ABNT 4340

Steel”, Journal of the Brazilian Society of Mechanical Sciences and Engineering,

Vol. 27(2), pp. 192-199, 2005.

Sokovic, M., Mijanovic, K., “Ecological Aspects of the Cutting Fluids and its Influence

on Quantifiable Parameters of the Cutting Processes”, Journal of Materials

Processing Technology, Vol. 109(1-2), pp. 181-189, 2001.

Sreejith,, P.S., “Machining of 6061 Aluminium Alloy with MQL, Dry and Flooded

Lubricant Conditions”, Materials Letter, Vol. 62, pp, 276-278, 2008.

Su,, Y., He,, N., Li,, L., Iqbal,, A., Xiao,, M. H., Xu,, S. and Qiu,, B.G., “ Refrigerated

Cooling Air Cutting of Difficult-To-Cut Materials”, International Journal of

Machine Tools and Manufacture, Vol. 47, pp. 927-933, 2007.

89

Suda, S.,Wakabayashi, T., Inasaki, I.,and Yolota, H., “Multifunctional Application of a

Synthetic Ester to Machina Tool Lubrication Base on MQL Machining

Lubricants”, Annals of CIRP, Vol. 53 (1), pp. 61-64, 2004.

Sutherland,, J.W., Kulur V.N., and King N.C., “An Experimental Investigation of Air

Quality in Wet and Dry Turning”, Annals of the CIRP, Vol. 49/1, pp. 61-64,

2000.

Tasdelen,, B., Thordenberg,, H. and Olofsson,, D., “An Experimental Investigation on

Contact Length During Minimum Quantity Lubrication (MQL) Machining”,

Journal of Materials Processing Technology, Vol. 203, pp. 221-231, 2008.

Varadarajan, A.S. Philip, P. K. and Ramamoorthy, B., “Investigations on Hard Turning

with Minimal Cutting Fluid Application (HTMF) and its Comparison with Dry

and Wet Turning”, International Journal of Machine tools and Manufacture, Vol.

42, pp.132-200, 2002.

Vieira, O.V., Botelho, R.J., Rameh, L., Brachmann, S.M., Matsuo, T., Davidson, H.W.,

Schreiber, A., Backer, J.M., Cantley, L.C. and Grinstein, S., “Distinct Roles of

Class I And III Phosphatidylinositol 3-Kinases in Phagosome Formation and

Maturation”, J. Cell Biol. Vol. 155, pp. 19–25, 2001.

Wakabayashi, T., Sato, H., Inasaki, I., “Turning Using Extremely Small Amounts of

Cutting Fluids”, JSME International J. (Series C), Vol. 41/1, pp.143-148, 1998.

Wakabayashi,, T., Inasaki,, I. and Suda,, S., “Tribological Action and Optimal

Performance: Research Activities Regarding MQL Machining Fluids”, Machining

Science and Technology, Vol. 10, pp. 59-85, 2006.

90

Wang,, Z.G., Rahman,, M., Wong,, Y.S.,Neo,, K.S., Sun,, J., Tan,, C.H. and Onozuka,,

H., “Study on Orthogonal Turning of Titanium Alloys with Different Coolant

Supply Strategies”, International Journal of Advanced Manufacturing

Technology, Vol. 42, pp. 621-632, 2009.

Weinert, K., Inasaki, I., and Sutherland, J. W., Wakabayashi, T., “Dry Machining and

Minimum Quantity Lubrication”, Keynote Paper, Annals of the CIRP, Vol. 53/2,

pp.511-537, 2004.

Zhang P, Wang L and Nie X., “Tribological Properties of a-C/Cr(N) Coatings in Micro-

and Nano-Scales”, Surface & Coatings Technology, Vol. 201, pp. 5176-5181,

2007.

Zhong,, W., Zhao,, D. and Wang,, X., “A Comparative Study on Dry Milling and Little

Quantity Lubricant Milling Based on Vibration Signals”, International Journal of

Machine Tools & Manufacture, Vol. 50, pp. 1057–1064, 2010.

turning machinability assessment of hardened steel …

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