towards sustainability using minimum quantity lubrication

Towards Sustainability Using

Minimum Quantity Lubrication

Technique and Nano-Cutting Fluids

in Metal-Machining Processes.

Author: Marta García Tierno

Publication type: Master thesis

Supervisor: Amir Rashid

University: KTH Royal Institute of Technology, Stockholm, Sweden

Department: Department of Production Engineering

Marta García I

ACKNOWLEDGEMENTS

First, I would like to thank professor Amir Rashid, for giving me this opportunity and for his

support. Also, I would like to thank Javier Echavarri, for supervising my thesis from Spain, thanks

for all your comments and corrections given.

Secondly, I want to express my gratitude to LetsNano AB team. Professor Muhammet Toprak,

Bernhard Hirschauer, Tafazzul Mahmood and Nader Nikkam. This project and my work at KTH

couldn’t be possible without their effort and support. I would also like to thank to the people

working at the laboratory at IIP-KTH, specially Anton Kviberg, Jan Stamer and Mats Bejhem for

sharing with me his endless knowledge and wisdom.

Finally, I would like to mention my family, always supporting me in all the aspects of my life,

specially my father and my aunt, Pascual and Rosa. And to my friends, both the ones living in Spain

and the ones in Stockholm, for helping me every day and making me happy.

For those of you who helped me directly or indirectly and I may have forgotten, many thanks.

Marta García II

ABSTRACT

Sustainable manufacturing is making products from processes which have minimal environmental

impact, energy and resource efficient, economically viable and safe for consumers and society as

whole. Achieving sustainability in manufacturing would mean infusing sustainability methods on

product process and system level. On the process level, machining technology is one of the most

widely extended processes in the industry. One way to attain sustainability in this technology is by

adopting efficient management of Metal Working Fluids (MWF). In this purpose to reduce the

amount of MWF starts Minimum Quantity Lubrication (MQL), where very small quantity of fluid

is applied to the cutting zone with maximum precision. Moreover, addition of nanoparticles to

these ´minimum quantity lubricants´ further enhances its tribological properties leading to higher

reduction in friction and temperature in the machining process.

The main objective of this thesis is to study the performance of cooling-lubricating fluids and these

fluids modified with nanoparticles, how the use of this new lubricants improves the results obtained

in material process technologies, particularly in turning. This project is being supported by the

company LetsNano AB, providing the lubricants enhanced with nanoparticles and the funding,

and Accu-Svenska AB, providing base oil and MQL technology.

The experiments are carried out at Kungliga Tekniska Högskolan (KTH), at Institutionen för

Industriell Produktion (IIP) laboratory. The turning process was tested with two different

workipiece materials: hardened steel (Toolox® 44) provided by SSAB, and grey cast iron (Scania

case study material). Two different tooling systems, due to the different materials. One provided

by Mircona AB, and the other given directly by Scania, provided by Sandvik AB and Cermatec AB.

The MQL system is a high-performance booster provided by Acuu-Svenska AB. The lubricant is

a vegetable oil that will also be the base for the Nanofluids (NF). This Nanofluids and produced

and developed by LetsNanoAB.

The study revealed an encouraging potential of moving from conventional (dry) cooling techniques

to the vegetable oil based MQL. Machining performance of MQL was encouraging as in most of

the cases the systematic reduction in tool wear reveals a better machinability. The contribution of

this work for Scania could help them to take the decision and move to more sustainable machining

processes. To prove the potential of the nanotechnology in this kind of processes further study is

needed, and it is going to be tested at IIP facilities in near future. The implementation of this

technology brings more challenges that should considered a study of the hazards of the technology

(emissions, fire and explosion, noise, skin…) necessary safety measures (cleaning, operator

instruction, skin protection…) and modifications in the machine tools system beyond the process

only. This could also be a next step in the further study of this research.

Keywords: Manufacturing, Machining, Turning, Minimum Quantity Lubrication, Nanoparticles.

UNESCO Codes: 3316.07; 2210.30.

Marta García III

SAMMANFATTNING

Hållbar tillverkning gör produkter från processer som har minimal miljöpåverkan, energi och

resurseffektiv, ekonomiskt genomförbar och säker för konsumenterna och samhället som helhet.

Att uppnå hållbarhet i tillverkningen skulle innebära infusion av hållbarhetsmetoder på

produktprocess och systemnivå. På processnivå är bearbetningsteknologi en av de mest utbredda

processerna inom branschen. Ett sätt att uppnå hållbarhet i denna teknik är genom att anta effektiv

hantering av metallbearbetningsvätsko (MWF). I detta syfte för att minska mängden MWF startas

Minimalsmörjning (MQL), där mycket liten mängd vätska appliceras på skärzonen med maximal

precision. Dessutom ökar tillsatsen av nanopartiklar till dessa "minimala smörjmedel" ytterligare

sina tribologiska egenskaper vilket leder till högre minskning av friktion och temperatur i

bearbetningsprocessen.

Huvudsyftet med denna avhandling är att studera prestanda av kylsmörjande vätskor och dessa

vätskor modifierade med nanopartiklar, hur användningen av de här nya smörjmedlen förbättrar

resultaten som erhållits i materialteknik, särskilt vid vridning. Projektet stöds av företaget LetsNano

AB, vilket ger smörjmedlen förbättrad med nanopartiklar och finansieringen, och Accu-Svenska

AB, som erbjuder basolja och MQL-teknik.

Experimenten utförs vid Kungliga Tekniska Högskolan (KTH) vid Institutionen för Industriell

Produktion (IIP). Vridprocessen testades med två olika material: Härdat stål (Toolox® 44) som

SSAB levererade och grått gjutjärn (Scanias fallstudiematerial). Två olika verktygssystem, på grund

av olika material. En som tillhandahålls av Mircona AB och den andra som ges direkt av Scania,

tillhandahållen av Sandvik AB och Cermatec AB. MQL-systemet är en högpresterande booster

som tillhandahålls av Acuu-Svenska AB. Smörjmedlet är en vegetabilisk olja som också kommer

att vara basen för Nanofluiderna (NF). Dessa Nanofluider och produceras och utvecklas av

LetsNanoAB.

Studien avslöjade en uppmuntrande potential att flytta från konventionell (torr) kylningsteknik till

den vegetabiliska oljebaserade MQL. Maskinens bearbetningsförmåga var uppmuntrande,

eftersom i de flesta fallen den systematiska minskningen av verktygsslitaget visar bättre bearbetning.

Arbetet med detta arbete för Scania kan hjälpa dem att fatta beslut och flytta till mer hållbara

bearbetningsprocesser. För att bevisa nanoteknikens potential i denna typ av processer krävs

ytterligare studier, och det kommer att bli testat vid IIP-anläggningar inom en snar framtid.

Genomförandet av denna teknik ger fler utmaningar som bör övervägas en studie av farorna med

tekniken (utsläpp, brand och explosion, buller, hud ...) nödvändiga säkerhetsåtgärder (rengöring,

operatörsinstruktion, skydd mot huden ...) och modifikationer i verktygsmaskinerna system utöver

processen bara. Detta kan också vara nästa steg i den fortsatta studien av denna forskning.

Marta García IV

TABLE OF CONTENTS

LIST OF FIGURES .................................................................................................................................................. VI

LIST OF TABLES ..................................................................................................................................................... IX

LIST OF ABBREVIATIONS ................................................................................................................................. XI

LIST OF NOMENCLATURE ............................................................................................................................. XII

1 INTRODUCTION ............................................................................................................................................1

1.1 Background ................................................................................................................................................1

1.2 Objectives ...................................................................................................................................................2

1.3 Thesis structure ..........................................................................................................................................3

1.4 Collaborators ..............................................................................................................................................4

1.4.1 LetsNano AB ........................................................................................................................................4

1.4.2 Accu-Svenska AB .................................................................................................................................4

1.4.3 Scania: Case study .................................................................................................................................5

1.5 Time planning ............................................................................................................................................6

2 STATE OF THE ART ......................................................................................................................................8

2.1 Sustainable manufacturing in machining ...............................................................................................8

2.2 Tribology of metal cutting .......................................................................................................................9

2.3 Minimum Quantity Lubrication Technique (MQL) ......................................................................... 12

2.3.1 Characteristics .................................................................................................................................... 13

2.3.2 Advantages ......................................................................................................................................... 15

2.3.3 Heat management in MQL .............................................................................................................. 17

2.4 Minimum Quantity Lubrication (MQL) using Nano-cutting Cooling Fluids .............................. 18

2.5 Previous work at KTH-IIP ................................................................................................................... 27

3 EXPERIMENTAL METHODOLOGY .................................................................................................... 28

3.1 Planning of the experiments ................................................................................................................. 28

3.2 Experimental set-up ............................................................................................................................... 29

3.2.1 CNC turning-lathe machine ............................................................................................................. 29

Marta García V

3.2.2 Workpiece material ............................................................................................................................ 31

3.2.3 Tooling system ................................................................................................................................... 34

3.3 Description of the MQL system .......................................................................................................... 38

3.4 Collection of the machining variables ................................................................................................. 40

3.4.1 Measurement of tool wear mechanisms and tool life .................................................................. 40

3.4.2 Measurement of Temperature in the cutting zone ....................................................................... 44

3.4.3 Measurement of the Surface Roughness ....................................................................................... 45

4 RESULTS AND DISCUSSION: TOOLOX® 44 ...................................................................................... 49

4.1 Preliminary results .................................................................................................................................. 49

4.2 Comparison between different lubrication techniques .................................................................... 51

4.2.1 1 mm of depth of cut ........................................................................................................................ 51

4.2.2 0.5 mm of depth of cut ..................................................................................................................... 57

5 RESULTS AND DISCUSSION: SCANIA CASE STUDY .................................................................... 60

5.1 Comparison between different lubrication techniques .................................................................... 61

5.1.1 Tool wear and tool life ..................................................................................................................... 61

5.1.2 Surface roughness .............................................................................................................................. 65

5.1.3 Temperature ....................................................................................................................................... 67

6 CONCLUSIONS AND FUTURE WORK ................................................................................................ 69

6.1 Recommendations for future work ..................................................................................................... 70

REFERENCES .......................................................................................................................................................... 71

APPENDIX A. CODES .......................................................................................................................................... 76

APPENDIX B. FLANK WEAR EVOLUTION ................................................................................................ 82

APPENDIX C. SURFACE ROUGHNESS MEASUREMENTS ................................................................... 85

APPENDIX D. POSTER PVC ANNUAL CONFERENCE .......................................................................... 86

Marta García VI

LIST OF FIGURES

Figure 1. Structure of the master thesis. .................................................................................................. 3

Figure 2. LetsNano AB [3]. ........................................................................................................................ 4

Figure 3. Accu-Svenska AB [4].................................................................................................................. 4

Figure 4. Scania AB [6]. .............................................................................................................................. 5

Figure 5. Gantt diagram of the master thesis. ......................................................................................... 7

Figure 6. Basic elements of sustainable machining [8]. .......................................................................... 8

Figure 7. Cutting process as a tribological system [10]. ....................................................................... 10

Figure 8. Flood cooling with Emulsion [15]. ........................................................................................ 12

Figure 9. Minimum Quantity Lubrication System (MQL) [17]. ......................................................... 13

Figure 10. Metal working fluid costs in metal machining [20]. ........................................................... 15

Figure 11. Percentage of energy consumption in wet machining [18]. ............................................. 16

Figure 12. Comparison of emission during machining between wet and MQL turning [22]. ....... 16

Figure 13. Heat generation in metal cutting [19]. ................................................................................. 17

Figure 14. Possible lubrication mechanisms by the application of Nano-oil between the frictional

surface [25]. ................................................................................................................................................. 18

Figure 15. Variation of flank wear and nodal temperature with machining time [27]. ................... 19

Figure 16. Flank wear vs. machining time 4 cooling techniques and two Nanofluids 1. Al2O3

and 2. TiO2[30, 31]. ................................................................................................................................... 20

Figure 18. Specific energy and power reduction for both lubrication mode [35]. ........................... 21

Figure 17. Variation of surface roughness with cutting condition [34]. ............................................ 21

Figure 19. Tool wear vs. number of cuts [2]. ........................................................................................ 27

Figure 20. Schemetic and picture SMT Swedturn 300 [41]. ................................................................ 29

Figure 21. Schematic diagram of turning operation and cutting parameters [43]. ........................... 30

Figure 22. Workpiece material groups [44]............................................................................................ 31

Figure 23. Cemented carbide inserts, DCMT 11 T3 08-PM7. ........................................................... 34

Marta García VII

Figure 24. Tool holder design for MQL, Mircona AB [8]. ................................................................. 35

Figure 25. Tool holder for MQL, Mircona AB. ................................................................................... 35

Figure 26. Oxide ceramic inserts, DNMX 15 T07 12. ......................................................................... 36

Figure 27. MQL external supplier designed at KTH-IIP. ................................................................... 37

Figure 28. Clamping system for Scania Set-up...................................................................................... 37

Figure 29. Ecolubric MQL booster and Ecolubric E200L vegetable oil. ......................................... 38

Figure 30. MQL booster drawing and components list. ..................................................................... 39

Figure 31. Microscope NIKON Optiphot 150. .................................................................................. 40

Figure 32. DeltaPix Insigtht software..................................................................................................... 40

Figure 33. Types of tool wear (a. Flank wear, b. Crater wear, c. Built-up edge, d. Notch wear, e.

Plastic deformation, f. Thermal cracks, g. Edge breakage) [55]. ......................................................... 42

Figure 34. Cutting profile for grey cast iron machining experiments. ............................................... 43

Figure 35. Thermal infrared camera FLIR SC 640 [55]. ...................................................................... 44

Figure 36. ThermaCAM Researcher Professional 2.10. Software. ..................................................... 45

Figure 37. Mitutoyo SJ-210 Surface Roughness Tester. ...................................................................... 46

Figure 38. Surface roughness profile and values, Ra, Rz and Rq for JIS 2001 standard [57] ........ 47

Figure 39. Effect of geometric factors in determining the theoretical finish on a work surface for

single-point tools: (a) effect of nose radius, (b) effect of feed, and (c) effect of end cutting-edge

angle [57]. ..................................................................................................................................................... 48

Figure 40. Flank wear vs. Machining time, first experiments Toolox® 44, dry machining. ........... 50

Figure 41. Flank wear vs. Machining time, first unsuccessful experiments Toolox® 44, three

lubrication techniques. ............................................................................................................................... 50

Figure 42. Damaged and broken chip breaker, crater images x10, 1mm of depth of cut, dry

machining. ................................................................................................................................................... 51

Figure 43. Crater images x10, 0,5 mm of depth of cut. ....................................................................... 52

Figure 44. Flank wear vs. machining time for dry and MQL, 1 mm of depth of cut, Toolox 44. 52

Figure 45. Comparison of tool life, dry and MQL, 1 mm of depth of cut, Toolox 44. ................. 53

Marta García VIII

Figure 46. Flank wear measurement, 1 mm of depth of cut, dry,MQL with vegetable oil and

compressed air. ........................................................................................................................................... 53

Figure 47. Flank and Crater images x10, 13,3 mins of machining, 1 mm, Toolox 44 (a)Dry

machining (b)Compressed air (c)MQL. .................................................................................................. 54

Figure 48. Temperature graphs 1 mm, dry, air and MQL, Toolox 44(a)Average temperature vs.

machining time (b)Evolution of T during 90 s of machining (c) Evolution of T last 15 s of one

machining step. ........................................................................................................................................... 55

Figure 49. Instantaneous Temperatures IR image, compressed air, 1 mm, Toolox 44. ................. 56

Figure 50. Chips samples for Dry, Compressed air and MQL, 0.5 mm, Toolox 44. ...................... 57

Figure 51. Flank wear vs. machining time for dry, air and MQL, 0.5 mm of depth of cut, Toolox

44. ................................................................................................................................................................. 58

Figure 52. Flank images, 15 mins of machining, 0.5mm of depth of cut, Toolox 44. .................... 58

Figure 53. Average temperature vs. machining time, 0,5 and 1 mm, Toolox 44. ............................ 59

Figure 54. Flank and crater images x5, new ceramic insert. ................................................................ 61

Figure 55. Flank and crater images x5, broken ceramic inserts, Scania sample. .............................. 61

Figure 56. Orientation of nozzles, Scania case study tool holder. ..................................................... 63

Figure 57. Flank wear vs. N of test specimen, Dry 1, MQL 1 and MQL 2 Scania case study. ..... 63

Figure 58. Flank wear vs. N of test specimen, three techniques, Scania case study. ....................... 64

Figure 59. Flank wear images at the end of tool life Dry 1 x10, NF 2 x5, MQL 3 x10, Scania case

study. ............................................................................................................................................................ 64

Figure 60. Comparison of tool life, three cooling techniques, Scania case study. ........................... 65

Figure 61. Average arithmetical mean surface roughness Ra (µm), Scania case study. ................... 65

Figure 62. Surface roughness profile 1. Scania test specimen sample, 2. MQL + NF, 3. MQL +

Vegetable oil, 4. Dry machining. .............................................................................................................. 66

Figure 63. Scania set-up image. ............................................................................................................... 67

Figure 64. Temperature in the cutting zone vs. machining time, Scania case study. ...................... 67

Figure 65. Instantaneous Temperature IR image, Scania case study. ................................................ 68

Figure 67. Flank wear vs. machining time, 0.5 mm Toolox 44. ......................................................... 84

Figure 68. Flank images, evolution of tool wear................................................................................... 84

Marta García IX

LIST OF TABLES

Table 1. Work packages decomposition. .................................................................................................. 6

Table 2. Lubrication strategies and its functions [10]. .......................................................................... 10

Table 3. Summary of MQL with NF with different nanoparticles literature for turning process. . 23

Table 4. Summary of MQL with NF with different nanoparticles literature for milling process. . 25

Table 5. General technical data SMT Swedturn 300 [41]. .................................................................... 29

Table 6. Turning parameters. .................................................................................................................... 30

Table 7. Chemical composition Toolox 44 [46]..................................................................................... 32

Table 8. Mechanical and phyical properties of Toolox® 44 [46]. ....................................................... 32

Table 9. Chemical composition of grey cast iron. ................................................................................. 33

Table 10. Hardness and microstructure of grey cast iron..................................................................... 33

Table 11. Geometrical properties of the carbide inserts. ..................................................................... 34

Table 12. Benefits of insert coatings [54]. ............................................................................................... 35

Table 13. Geometrical properties of the ceramic inserts. ..................................................................... 36

Table 14. General properties of Ecolubric E200L [11]. ....................................................................... 38

Table 15. Test specimen equivalent cutting parameters. ...................................................................... 43

Table 16. General specification on thermal infrared camera FLIR SC 640 [12]. .............................. 44

Table 17. Specifications of Surface Roughness Tester Mitutoyo SJ-210 [56]. .................................. 45

Table 18. Surface roughness JIS 2001 standard parameters. ............................................................... 46

Table 19. Cutting parameters, first experiments Toolox® 44. ............................................................. 49

Table 20. Cutting parameters, Toolox 44 experiments. ........................................................................ 51

Table 21. Tool life, dry and MQL, 1 mm, Toolox 44. .......................................................................... 53

Table 22. Average temperature values, 0,5 and 1 mm, Toolox 44. ..................................................... 59

Table 23. Cutting parameters, Scania Case Study. ................................................................................. 60

Marta García X

Table 24. Flank wear, Scania used inserts, 120 test specimens. ........................................................... 62

Table 25. Tool life for different techniques, Scania case study. .......................................................... 64

Marta García XI

LIST OF ABBREVIATIONS

Al2O3 Aluminium oxide

BUE Built up edge

CFD Computational Fluid Dynamics

CLF Cooling Lubricating Fluids

CNC Computer Numerical Control

CVD Chemical Vapour Deposition

ECEA Cutting edge angle

ENP Engineered NanoParticles

FE Finite Element.

FOV Field of View

GDP Gross Domestic Product

ICP -MS Inductively coupled plasma mass spectrometry

IR Infrared

MoS2 Molibdenum Disulfide

MWF Metal Working Fluid

MQL Minimum Quantity Lubrication

MWF Molibdenum Disulfide

nCLF Nano-Cooling Lubricating Fluids

NF NanoFluid

PVD Physical Vapour Deposition

TiC Titanium Carbide

TiN Titanium Nitrate

TiO2 Titanium dioxide

Marta García XII

LIST OF NOMENCLATURE

Symbol Parameter Units

µ Vicosity cP

Ap Cutting depth mm

d Insert size/Cutting edge length mm

Fc Cutting force N

fc Feed mm/rev

fr Feed rate mm/min

lc Length of cut mm

n Spindle speed rpm

NR Nose radius/ Corner radius mm

Pc Flank wear µm

Ra Arithmetical mean surface roughness µm

Rai Theoretical mean surface roughness µm

Rq Root mean square surface roughness µm

Rz Ten points mean surface roughness µm

tc Machining time s

Tc Cutting temperature ºC

VB Flank wear µm

Vc Cutting speed m/min

ρ Density g/cm3

KTH Royal Institute of Technology Introduction

Marta García Tierno 1 of 88

1 INTRODUCTION

1.1 Background

The concept of sustainability directly affects to all the stages in the production chain. Nowadays

the corporative strategy of a company should be developed integrating sustainability as a major

concept. Sustainable manufacturing is defined as making products and pieces from processes,

which have minimal environmental impact, safe for consumers, energy and resource efficient and

economically feasible. Sustainable manufacturing should involve both the process and the system

level. The material processing technologies are included in the process level and a fundamental part

of them is the need of cooling and lubricating.

Cutting fluids have several functions in material processing technologies, such as lubrication,

cooling and chip removal. Usually the cutting fluids, also known as cooling-lubricating fluids (CLF)

are toxic and dangerous for the nature and the human health. The disposal of these fluids also

needs a special attention and there is strict environmental legislation in this regard. In order to

reduce the quantity of CLF used in machining processes it is desirable to machine in dry or near

dry environments. Minimum Quantity Lubrication (MQL) is a lubrication technique in which a

very small quantity of lubricant is applied on the cutting zone with high precision. It goes from

flow rates of litres per minute with conventional flood cooling methods to 2-100 millilitres per

hour flow rates with MQL systems. The benefits of the method could be synthetizing in [1]:

• Reduction of friction.

• Improvement of surface finish.

• Better removal of heat and its consequent reduction of temperature.

• Tool wear reduction and increase of tool life.

Of course, a reduction of flow of lubricant is also considered a positive impact of MQL.

In recent years nanoparticle-based cooling-lubricating fluid (nCLF) have been designed and

produced by suspending engineered nanoparticles (ENP) in conventional lubricants, for example

vegetable-based oils. These vegetable oils are biodegradable and not hazardous for the nature and

the human health, but the influence of the nanoparticles suspended on should be considered.

The usage of ENP increases both the heat transfer capabilities and the tribological properties of

the lubricants. Previous research in using nanotechnology to improve the lubricants’ properties has

been developed in KTH in the department of Production Engineering (IIP). The results of this

experiments and research have been published in the form of papers in prestigious publications

[2].



1.2 Objectives

The main objective of this project is to study the performance of the MQL technology using

vegetable base oil and using cooling-lubricating fluids modified with nanoparticles for two different

set-ups and case studies. How the use of this new coolants improves the results obtained in material

processing level.

For this aim, a scientific analysis between three different lubrication techniques will be employed:

• MQL using vegetable-based oil.

• MQL using nCLF, also called in this project NanoFluids, NF.

• Dry machining.

Some of these techniques are widely known and developed but will be used due to the need to

compare the results obtained with the new nanofluids.

The nanoparticle-based cooling-lubricating fluid selected for the experiments must be

economically and environmentally sustainable, which means that it should not be harmful to health

and the environment and must be economically feasible and produced.

The MQL technique can efficiently reduce the associated environmental impact produced by the

disposal of the lubricants. Due to the development of nanoparticles suspended in the CLF the

results can be greatly improved.

The literature review presented in the next chapter shows that the benefits of introducing this kind

of fluids in machining processes, especially in turning, are significant. In most of these articles three

different cooling-lubricating techniques are compared, sometimes including also flood cooling.

Mostly, empirical models have been developed to predict the tool wear evolution and tool life,

usually utilizing home-made MQL systems. The potential of this research resides also in the fact

that the utilized booster is a high-performance booster available in the market. This makes the

project more interesting from the side of the companies involved.

The second part of the project is focused on experimental work for a well-known automotive

Swedish company. This fact gives the opportunity to test the potential of this technology in an

industrial process that it is being used for production, and how this process can be improved and

make it more sustainable.

The scope of this master thesis has a time limitation. It is restricted to the experimental work of

turning two different materials for two case studies that will be explained in detail in the following

sections.



1.3 Thesis structure

The master thesis consists in 6 chapters. The project is structured separating two big groups of

results: Pre-hardened steel experiments and Scania case study. Common material and information

is presented in previous chapter: State of art and Experimental methodology. Four Appendix, A

to D, are added at the end of the document to extend and complete the information about some

relevant topics.

• Background of the problem

• Thesis scope and objectives

• Calendar of the project (Gantt)

Chapter 1. Introduction

• Explain the following, based on published literature:

• Minimum Quantity Lubrication Technique, its main characteristics, advantages and restrictions.

• Nano-cutting fluids development and advantages.

Chapter 2.State of art

• Planning of the experimental work.

• Explain the process followed to conduct the research, facilities and set-up.

• Collection of relevant variables and MQL system description.

Chapter 3. Experimental methodology

• The results from the experimental study to evaluate the potental of MQL technology for machining pre-hardened steel Toolox 44.

• Tool wear and tool life, temperature and chips.

Chapter 4. Results and discussion.

Toolox® 44

• The results from experimental study to evaluate the potential of MQL technology and Nano-cutting fluids for machining grey cast iron, Scania case study.

• Tool wear and too life, temperature and surface roughness.

Chapter 5. Results and discussion.

Scania case study

• Conclusions and future work in the topic. Chapter 6.

Conclusion and future work

Figure 1. Structure of the master thesis.



1.4 Collaborators

This project is being supported by the company LetsNano AB and it is done in collaboration with

Accu-Svenska AB. Scania AB is in close contact with KTH, and they understood the potential of

this technology, thus a case study to test the system in one of their processes was proposed.

1.4.1 LetsNano AB

LetsNano AB is a start-up grown at KTH. Their occupation is focused on the developing and

production of Nanofluids for lubrication, heat transfer and energy storage. This Nanofluids that

they produce provide several benefits, such as reduced down time from change events, reduced

thermal deformation of workpiece, better surface finish, reduced consumption of CLF, improve

tool life by reducing tool wear rate or absence of toxic additives giving a healthier working

environment [3].

1.4.2 Accu-Svenska AB

Accu-Svenska AB is a supplier of products and services for MQL systems to industrial applications

of all kinds. Their entire offerings include an ecological profile; and lubricants are brought to

customers directly from the nature with no additives. MQL System is completely designed and

produced in Sweden. The system meets the entire EU standards through the reach directive in

order to be an exempt from the restrictions. The system is completely sustainable; and it does not

expose any environmental or personal health risks [4].

Accu-Svenska AB has been active in industrial lubrication and cooling technology since 1996.

During the first ten years, the company was an agent of the Accu-Lube GmbH, one of the world’s

leading company in production of MQL systems. To meet today’ demands and needs of Swedish

industry for quality health and environment, Accu-Svenska AB developed its unique MQL system

n that is a competent Programmable Logic Controlled, PLC, application system. The system is

exclusively used in conjunction with Accu-Svenska’s self-produced vegetable-based oil. The system

launched to the market in 2006; and it is offered with performance guarantee. It is the only MQL

system that employs Accu-Svenska’s special-processed vegetable-based oil that contains no

additives of any kind [5].

Figure 3. Accu-Svenska AB [4].

Figure 2. LetsNano AB [3].



1.4.3 Scania: Case study

Scania AB is a major Swedish automotive industry manufacturer of commercial vehicles –

specifically heavy trucks and buses. It also manufactures diesel engines for heavy vehicles as well

as marine and general industrial applications. Scania AB was formed in 1911 through the merger

of Södertälje-based Vabis and Malmö-based Maskinfabriks-aktiebolaget Scania. The company's

head office has been in Södertälje since 1912. Today, Scania has production facilities in Sweden,

France, Netherlands, India, Argentina, Brazil, Poland, and Russia. In addition, there are assembly

plants in ten countries in Africa, Asia and Europe. Scania's sales and service organization and

finance companies are worldwide [6].

Figure 4. Scania AB [6].



1.5 Time planning

In this section, the temporary planning of the thesis is presented. Firstly, Table 1 shows the

decomposition of the work packages, including start and end days of the tasks. Once the

decomposition in work packages is done, the Gantt diagram is made with the help of Microsoft

Project software. The diagram is shown in Figure 5. During the development of the project the

progress was presented in various presentations. These presentations have been set in the time

planning as milestones.

Table 1. Work packages decomposition.



Fig

ure

5. G

antt

dia

gram

of th

e m

aste

r th

esis

.

KTH Royal Institute of Technology State of the Art


2 STATE OF THE ART

2.1 Sustainable manufacturing in machining

Machining is the most widely extended industrial process, especially machining of metal products.

In the last years, sustainability in manufacturing is becoming a key issue due to strict environmental

legislation and the necessity of reuse and recycle materials. But for the companies adopting

sustainable strategies would suppose a big effort and investment for the first years. Achieving

sustainability in manufacturing should consider aspects in all levels: system, process and product

levels, trying to find a general view of all them. Concretely the main objective of the sustainable

manufacturing is to change from the classical ideology of manufacturing based on increase the

productivity to a new vision focus on the concept of global value. There is not an official definition,

but the recent work describes it as a process that leads to [7, 8]:

• Environmental friendliness.

• Reduced cost.

• Reduced power consumption.

• Reduced wastes.

• Enhanced operational safety.

• Improved personnel health.

Sustainable manufacturing

Enviromental Friendliness

Machining cost

Power Consumption

Waste Management

Operational Safety

Personnel Health

Figure 6. Basic elements of sustainable machining [8].



By changing usual practices in metal cutting sector to sustainable activities would benefit the

company economically, ecologically and socially. In the metal machining sector, a fundamental part

are the cutting fluids. These fluids have several functions, such as lubrication, cooling or chip

removal.

The usual cutting fluids,CLF, the ones that are used for flood cooling are an emulsion, made with

water and oil, usually up to 90% of water. This water must be recycled because it is hazardous for

both the environment and the human health. They can cause problems to human skin and pollute

the soil. These cutting fluids affect directly to some all the basic elements to achieve sustainable

manufacturing, shown in Figure 6.

Klocke and Eisenblätter [9] studied the influence of CLF emulsions in the total cost of the

machining process. The conclusion was that the 15% of the total cost of machining is due to the

CLF emulsions, while the cost fraction of tools is only 4%.

These are also important reasons, not only environmental but also economic reasons, for

developing new cooling and lubrication techniques such as dry or near dry machining or MQL.

The main drawback that the mentioned techniques must deal with is the quality of the results. This

problem is even harder machining difficult-to-cut materials, such as titanium and nickel base alloys

or hardened steels.

2.2 Tribology of metal cutting

The complexity of the machining processes makes very difficult to define systematic friction and

wear mechanisms. The detailed information of what happens in the interface between the tool and

the workpiece is particularly important to understand control and design the machining processes.

The optimization of the processes can be achieved by understanding the tribology of the contact

between tool and workpiece.

Tribological contacts are usually defined by pairs of bodies in contact. This contact is characterized

by a basic body, as an element subjected to the wear, and a counter body [10]. In any machining

process the basic body Is the tool and the counter body the machined workpiece. But apart from

the contact and interfacial element itself the cutting process needs to be understood as a whole and

keep all the parameters of the cutting process under control. All these variables have a direct

influence and impact in one of the main studies of the tribology: the wear (Figure 7). The main

wear mechanisms present in the cutting inserts are abrasion, adhesion, tribochemical reactions and

surface damage. This wear mechanisms of cutting tools often detrimentally limit the performance

of cutting processes. The complexity of a machining process makes it difficult to systematically

analyse the friction and wear mechanisms at the active areas of the tool [11].



Focusing on the interfacial element in the cutting process, three cooling-lubricating strategies can

be defined: flood-wet cooling (emulsion), MQL (vegetable oil) and Compressed air. The last two

strategies could be considered as a dry or near dry machining, with the benefits that this involves.

As it is said before, the primary functions of the cutting fluids are cooling, lubricating and chip

removing. In Table 2 shows a summary of the functions and how each lubrication strategy is fixing

them.

The conventional coolant, also known as emulsion has other functions such as transporting chips

or cleaning tools, fixtures and workpieces. If the coolant is removed from the process, these

secondary functions must be taken by other components.

Table 2. Lubrication strategies and its functions [10].

Strategy/Function Cooling Lubrication Chip Removal

Emulsion-Flood Excellent Good Excellent

Oil-MQL Good Excellent Good

Compressed air Little No Little

• None

• Comp. air

• Coolant

• MQL

•Properties

•Coating

•Surface

•Cutting speed

•Feed

•Depth of cut

•Hardness

•Toughness

•Structure

WorkpieceCutting

parameters

Interfacial element

Tool

Contact conditions

• Direct stress

• Shear stress

• Temperature

Wear mechanisms

• Tribo. reactions

• Abrasion

• Adhesion

• Fatigue

Figure 7. Cutting process as a tribological system [10].



In following subchapters, the lubrication technique that is the focus of this project will be deeply

developed. In addition, a review of the published literature on a new technology is presented,

Nano-cutting fluids and MQL Technique. Nevertheless, to understand the process properly wear

mechanisms should be explained, as an important study field of the tribology.

Tribology is defined as the science that studies the interaction between surfaces in relative motion.

This study includes not only lubrication, but also friction and wear. In tribological contacts wear

occurs due to the interaction between surfaces in contact and implies gradual removal of the surface

materials. The wear mechanisms are abrasive, adhesive, fatigue and tribo chemical wear. Usually an

interrelationship between these types of wear is what occurs in the contacts [12]. To understand

what it is happening in the interface between cutting tool and workpiece material it is important to

explain the wear mechanisms [13].

Adhesive wear

Adhesive wear has its origin from the shearing contact between the asperities of two solid in relative

motion. During sliding elastic and plastic deformation of the asperities occur resulting in a contact

area where the boding forces give the adherence and the surfaces get welded [14].

Abrasive wear

Abrasive wear occurs when one of the surfaces in contact is significantly harder than the other.

Abrasion can also occur when harder particles are introduced in the tribo contact. Abrasive wear

causes high plastic deformation. Harder material of the contact will scratch the softer in a ploughing

action, resulting wear, scratches and grooves in the soft material [14].

Fatigue wear

Fatigue wear is caused by periodical loads. Repeated loads generate microcracks, usually below the

surface, at a point of weakness such an inclusion. On the subsequent loading and unloading, the

microcrack is propagating and voids coalesce. When the crack reaches a critical size, it changes

direction to emerge the surface and a flat sheet-like particle is detached. This wear mechanism does

not usually occur in metal cutting, it is more common in rolls and dies [12].

Tribo chemical wear

Tribo chemical wear is mainly dominated by chemical reactions in the contact and the material is

therefore consumed. The environmental conditions in combination with the mechanical stresses

have great important. The chemical action, such as diffusion or solution, is not a wear mechanism

on its own, but it is in combination with other wear mechanisms. So, it is better to consider

chemical effects as an additional influence parameter which could change the material properties

of the surfaces in contact [12].



2.3 Minimum Quantity Lubrication Technique (MQL)

If a fluid is applied in the cutting zone, the main lubrication techniques regarding to application

method in machining can be summarized in two groups:

• Flood-cooling. It is the most common lubrication method, but also the most hazardous

and expensive one. It guarantees a very good level of lubrication, cooling and chip

removing. Applying this method of lubrication, it is also possible to orientate the nozzle to

the clearance tool surface, reducing the flank wear, especially when the cutting speed is

slow [15].

• Minimal quantity lubrication (MQL). in MQL very small lubricant flow (ml/h instead

of l/min) is used. In this case, the lubricant is directly sprayed on the cutting area. It

guarantees a good level of lubrication, but the cooling action is very small, and the chip

removal mechanism is obtained by the air flow used to spread the lubricant.

In recent years several researchers have tried to reduce the quantity of lubricant using different

cooling strategies. The most successful technique is the near dry machining or MQL technique,

which is implemented in the market.

MQL [16] is a recent technique introduced in machining obtains safe, environmental and economic

benefits, reducing the use of coolant lubricant fluids in metal cutting. In these methods, high-speed

air jet is introduced with micro-drops of vegetable oil in suspension to lubricate the cutting zone.

In these techniques, lubricate flow rate is limited to millilitres/ hour instead of litre/ min like in

flood cooling environment. This mist or suspension made from air and lubricant should be

delivered accurately into the cutting zone.

First, the lubricant must be mixed with the air to achieve the mist that is being introduced into the

interface of the cutting insert and the workpiece. For this purpose, there are different types of

systems, but in this project a high-performance booster provided by Accu-Svenska AB is the one

chosen. The characteristics of this system will be explained in the following chapter.

Apart from the reduction of temperature and tool wear there are other advantages that MQL

technique can offer [16]:

Figure 8. Flood cooling with Emulsion [15].



• Chip, workpiece and tool holder have a low residue of lubricant: their cleaning is easier and

cheaper.

• During machining the working area is not flooded so, if necessary, the cutting operation

can be readily observed.

The successful application of MQL technique in machining processes involves good understanding

of different variables such as feed technology, parameters settings, fluids properties [17]… All the

relevant and parameters that are important for the MQL technique are summarized in the Figure

9. All the components in the MQL system must be very carefully coordinated in order to achieve

the desired outcome, which is optimal, both technologically, economically and environmentally

[10].

2.3.1 Characteristics

The main characteristics of MQL can be described in these points:

• Small amount of fluid. The German DIN specification fix the maximum flow for MQL

up to 50 mL/hour of lubricant and in exceptional cases up to 150 mL/hour. But generally,

the amount is subjective and depends on the material, process and the selected tools [18].

• Lubricant. Since very good lubrication properties are required for the MQL technique,

usually the fluid utilized for this technology is pure oil. It could be from mineral or

vegetable oil to synthetic oils.

• Generation of the mist. The oil in MQL technique is applied in form of a mist. This

mist is formed by compressed air, at a medium pressure, from 2 to 10 bars and the

lubricant itself. The mist should be as much uniform as it is possible. The size of the

droplets depends on the equipment used and the characteristics of the selected oil.

MQL

Equipment

• High performance booster

Fluids

• Vegetable oil

• NF

Machine tool

• Upgradability

Settings

• Oil flow

• Air flow

Tools

• Internal feed

• External feed

Figure 9. Minimum Quantity Lubrication System (MQL) [17].



• Accurate application. The oil in MQL must be applied accurately into the cutting zone

to achieve good machining products. It is particularly important to control all the

parameters to ensure that the oil reaches properly the cutting point.

So, the goal of the MQL is simple, apply just enough fluid to fully lubricate the cutting zone using

the least amount of oil as possible. But in this technology, there are also some general factors that

should be considered to obtain good outcomes related to the lubricants, oils, tools, materials and

removal of the chips.

Oils

There are some types of oils that are not the suitable for MQL. Water-miscible metalworking fluids

don not have good enough lubricity properties. On the other hand, their flash point is too low for

the temperatures that could be reach in cutting with MQL.

Lubricants with organic additives or zinc are not the best option since these additives can react at

MQL machining temperatures and cause hazard products. Mineral oil-based products with high

aromatic compound content could also change in relatively short time [18].

Workpiece material

Not all the materials are appropriated to be cut using MQL technology. This decision of selecting

or switching to MQL system depends on mechanical, physical and chemical properties of the

materials.

Grey cast iron works very well with MQL since the graphite liberated during machining acts as an

additional lubricant. Cutting these kind of materials, a significant amount of dust is generated. In

flood cooling this dust is easily removed by the cutting fluid, so if MQL is selected this dust removal

must be considered.

Non-ferrous materials, like some aluminium alloys and steel up to 800MPa of tensile strength are

easy to cut, and therefor suitable for MQL cooling technique. Even difficult-to-cut material, such

as titanium alloys, can be machined with MQL if the system is properly designed.

But also, some materials have demonstrated that they are not suitable for this technology, such as

copper in heavy cutting dur to the heat generation in this process [18].

Tools

In the implementation of MQL technology in a cutting process, the selection of an appropriated

tool can help to minimize the drawbacks and extend the tool life. Tools designed for dry cutting

usually work well with MQL, because they are designed to resist thermal shocks. One example of

this type of tools could be ceramic inserts.

In the machining of high strength steels multi-layer coating tools are recommended. These coatings

help the tool to resist to high temperatures without breaking. Tools can be designed for MQL, with

special chip breakers. Although, these tools may be more expensive, using them might allow

reaching the proper tolerances, cutting faster and obtaining longer tool life [19].



Chips

Chips removal in MQL is completely different from chip removal in flood cooling. The main

mechanisms to remove the chips in MQL are gravity and compressed air. In the work space it is

important to remove the chips as soon as possible because they can damage the process in different

aspects (e.g. workpiece and machining equipment).

The design of the workspace can help removing the chips in MQL technique. The gravity is the

simplest method, designing an inclined metal sliding into a collector or onto a conveyor [18]. The

position of the workpiece also helps in the chips removal. Compressed air also can be used to

remove the chips. But the mist for lubricating and the air should go in separate nozzles [20].

2.3.2 Advantages

Related to the application of this technology into the industry, there are many known advantages

that the MQL technology could provide. MQL has demonstrated in multiple worldwide plants

with better quality, higher productivity, minimal environmental impact, lower operation health

issues, reduced water and greenhouse gas emission, and reduced energy consumption, which result

in lower overall cost [21]. The main advantages that MQL could provide to the industry can be

summarized in five points:

Costs

The MWF associated costs are in the range of 10-20% of total manufacturing cost. By changing

this type of flood cooling method to MQL most of the costs associated to MWF can be reduced

or eliminated [19].

In Figure 10 the costs analysis in metal machining re shown in detail. This 16% of costs would be

reduced, because the MQL energy consumption is very small, the disposal is zero, the investment

for the system itself is much cheaper compared to the system of wet machining, and MQL does

not need extra work from the employers.

16%

4%

80%

MWF costs Tools Other costs

14%7%

10%

40%

22%

7%

WF system

Energy

Employees

System

Disposal

Others

Figure 10. Metal working fluid costs in metal machining [20].



Energy consumption

The largest energy consumption in CNC machines with traditional flood cooling are:

• 25% in the cutting process itself.

• 30-40% in the MWF system.

• 15-20% to obtain the necessary compressed air for flood cooling.

In traditional flood or wet machining, the energy consumption is mostly fixed and difficult to

reduce, it can only be reduce improving the tooling and cutting efficiency. Using MQL technology

this energy related to MWF system and compressed air no longer exists (≈50% of the total energy

consumption), which results in savings in energy.

Environment and safety

MQL is considered as a low-emission process due to a considerable reduction of MWF inhaled

and skin compared to flood machining. A study by a German association shows that turning under

MQL and wet conditions has confirmed that the concentration of oil is less than the half in MQL

and always below the inhalable fraction for a human (10 mg/m3) as it is shown in this figure, in

which are presented the results of measuring the concentration of oil in the air in three different

points of the turning process [22].

25%

25%

15%

35%

0,00%

20,00%

40,00%

60,00%

80,00%

100,00%

ENERGY CONSUMPTION WET MACHINING

MWF System

Compressed air

Cutting process

Others

Figure 11. Percentage of energy consumption in wet machining [18].

0

2

4

6

8

10

12

14

16

18

Person Control Panel Extracted air

EM

ISSIO

N [M

G/

M3 A

IR]

MEASUREMENT POINT

MQL

Wet

Figure 12. Comparison of emission during machining between wet

and MQL turning [22].



Chips recycling

Revenue from chips re-melting is often a significant component in plant’s operating budget. Drying

and cleaning the chips produced after wet machining requires floor space, energy and it is

expensive. In the use of MQL the chips are nearly dry and virtually clean, that is why there is not

necessary to dry them [21].

Nano-cutting fluids

Addition of Engineered Nano Particles (ENP) to base fluid enhance tribological and thermal

properties, so the quality of the product obtained after the process could also be enhanced. This

technology is very new, and it is being developed continuously. In the next subchapter the main

advantages and literature published in this technology will be discussed.

2.3.3 Heat management in MQL

One of the main objectives of the cooling-lubrication technologies in metal cutting is to absorb

the heat generated in the cutting zone, which could be translated in reduction in temperature.

In metal cutting there exist to main zones in where the heat generation is occurring: Primary and

secondary shear zones (Figure 13).

The primary heat is difficult to reduce, and the only possible solution is to try to reduce its effects.

That is the main function of the conventional cutting fluids, to go into the effect instead of looking

to the source of the heat. This rapid cooling achieved by conventional cutting fluids has also some

drawbacks. If the tool is cooled down too fast, it can cause a sudden breakage due to thermal cracks

in the tool. This rapid heating and cooling phenomena in the tools is called thermal cycles.

On the other hand, MQL technology focuses on the elimination of the heat generated by the

friction, in the secondary shear zone, between the tool and the chip interface. The heat generated

in this zone is one of the main reasons for premature tool wear [18]. In this case the major part of

the generated is taken by the chips. The temperature is reduced both in the workpiece and in the

cutting insert. Improving the thermal properties of the MQL lubricants could also help reducing

the temperature in the cutting point.

Figure 13. Heat generation in metal cutting [19].



2.4 Minimum Quantity Lubrication (MQL) using Nano-cutting

Cooling Fluids

One of the main objectives of the cutting fluids is cooling the interface of the cutting tool and the

workpiece. A Nanofluid (NF) is designed and fabricated by suspending engineered nanoparticles

(ENPs) in biodegradable vegetable-based fluids. The addition of this Nanoparticles into

conventional oils improves its thermal properties, which means and improvement of cooling

capabilities. These Nano-cutting fluids are expensive to produce, so they are not advisable for wet

or flood machining. But the small amount of flow that MQL provides can make Nanofluids a

viable alternative [23].

Several parameters affect directly to the machining process: cutting forces, type of cutting tool,

temperatures… But it is found that the most influential one is the temperature[24]. One of the

main functions of the cutting fluids is the control of the temperature during the process. The

cooling fluid prevents the rise of temperature, preventing also the thermal expansion of the

workpiece. Consequently, the cutting fluids enhance the tool life and the quality of the machined

piece. Using MQL techniques instead of traditional flood-cooling high cooling is needed to be

achieve with very small quantity of lubricant. Thermal conductivity increases introducing

nanoparticles into conventional oils, which improves its cooling capabilities.

But this improvement of the thermal properties of the cutting fluid is not the only advantage of

adding nanoparticles into the oil. There is also a reduction in the friction recorded due to the

addition of ENP. This phenomenon could be explained by the following mechanisms [25].

Ball-bearing effect. The nanoparticles suspended in the oil play the role of a ball between the two

lubricated surfaces, reducing the friction between them.

• Protective film. The nanoparticles protect the surface by coating the rough surfaces.

• Mending effect. The ENP can help reducing the loss of mass in the surfaces. This effect

also reduces the surface roughness or the workpiece.

• Polishing effect. The nanoparticles help in the abrasion of the surface, which is known as

a polishing effect. This effect is very important and one of the main reason of using ENP

in metal machining processes.

Figure 14. Possible lubrication mechanisms by the application of Nano-oil between the frictional surface [25].



The literature written and published about cutting fluids enhanced with Nanoparticles is wide and

varied, trying to prove the potential that this new technology has in metal machining. Researchers

used different MQL techniques for their experiments, but the flow of oil that they supply is always

limited to millilitres per hour, instead of the litres per minute of the traditional flood cooling. In

this chapter the literature and papers found in this topic will be summarize.

Krishna et al. [26] performed a study to prove the potential of nanoboric acid suspensions in two

different base oils, SAE-40 and coconut oil. The material turned was AISI 1040 stainless steel with

carbide tools. They tried with different concentrations of Nanoparticles as well, obtaining the best

performance in terms of cutting temperatures, tool wear and surface roughness at 0.5% nanoboric

acid suspensions in coconut oil.

Rao et al. [27] studied the behaviour of different concentrations, from 0,5 to 1% of carbon

nanotube (CNT) inclusions in the oil turning of AISI 1040 stainless steel and cemented carbides.

The obtained results in terms of nodal temperatures and tool wear showed and reduction in

temperature and flank wear comparing with traditional cutting fluid. The results in both

temperature and wear remain constant at concentrations of more than 2%. Variation of

temperature and flank wear are shown in Figure 15.

Khandekar et al. [28] run a comparative study of tool wear, cutting force, surface roughness and

chip thickness among dry turning, conventional cutting fluid as well as Nano-cutting fluid (1%

weight of Al2O3). The material was AISI 4340 steel, machined with uncoated cemented carbide

inserts. Machining with Nano-cutting fluid shows a significant reduction in the surface roughness

of 54.5% and 28.5% compared to dry machining and traditional cutting fluid.

Amrita et al. [29] utilized three types of Nano-cutting fluids in turning AISI 1040 hardened steel.

This oil includes 0.3 wt.% of graphite, nanoboric acid and MoS2. In general terms the better

properties were shown by the Nano-cutting fluid made with MoS2.

Figure 15. Variation of flank wear and nodal temperature with machining time [27].



Sharma et al. [30] examined the machining performance of a Nano cutting fluid prepared with

Al2O3 1 wt.% in turning a workpiece of AISI 1040 steel, using also MQL technique. The study

reveals clear reduction in tool wear and surface roughness compared to dry, conventional oil MQL

and wet machining. MQL shows the machining performance comparable to wet machining. In

other study performed by Sharma et al. [31] tried with TiO2 analysing forces, tool wear, surface

roughness and chip morphology. The obtained results are comparable in quality to the ones

obtained with Al2O3. The results obtained in tool wear for both types of Nanoparticles are shown

in Figure 16.

Su et al. [32] investigated the effect of Nanofluid with Nano-graphite using ester oil as base fluid

in turning of AISI 1045 medium carbon steel. Two different cutting speeds (55 m/min and 96

m/min) were tried finding a decrease in main cutting force with respect to dry cutting of 11 and

26% respectively, with the oil improved with 0.5 wt.% of Nano-graphite. On the other hand, the

maximum percentage of reduction in cutting temperature relatively to dry cutting was 11,9% and

21%, with 0.5 wt.% of Nano-graphite as well.

Chetan et al. [33] conducted an experimental study using MQL technique with Nanofluids

produced with commercially available powder of alumina (Al2O3) and colloidal solution of silver

(Ag) in sunflower oil in turning of Nickel based alloy. The lowest magnitude of cutting force and

flank wear were found with alumina NF and a flow rate of 125 ml/h.

The potential of the fluids enhanced with Nanoparticles and MQL technique is also tried to be

prove in other cutting processes such as milling or grinding, not only in turning, the case study of

this project. Uysal and Furkan Demiren [34] performed a research of milling Martensitic stainless

steel AISI 420 by using vegetable oil reinforced with 1wt.% of MoS2. Surface roughness and tool

wear results were analysed. These experimental results showed that the use of nanoparticles of

MoS2 gave the minimum tool wear and surface roughness due to the lubrication effect of the

nanoparticles. In Figure 17 Surface roughness is shown for Dry cutting, MQL with conventional

oil MQL with MoS2 nanofluid.

Figure 16. Flank wear vs. machining time 4 cooling techniques and two Nanofluids 1. Al2O3 and 2. TiO2[30, 31].



Sarhan et al. [35] studied the behaviour SiO2 nanoparticles with MQL technology in milling

aluminium alloy AL6061-T, commonly used in the aircraft and automotive industries for its

extraordinary mechanical properties. The main objective of this research is to reduce the power

consumption and pollution, so power and specific energy were also measured. In Figure 17,

evolution of specific energy and power reduction are shown vs. cutting time. The power reduction

in percentage is 30% during in all the cutting measured steps. The results show that the cutting

forces, specific energy, and the power required at the cutting tool are reduced considerably using

the lubricant made out SiO2 and vegetable oil. Sayuti et al. [36] investigated the machining

performance of Aluminium AL6061-T6 alloy also, under MQL cooling technique and Nanofluids

with SiO2 nanoparticles. This study was focused on the machined surface in the end milling of this

aluminium alloy. The results show that the machined surface contain a thin protective film of SiO2,

and this helps to reduce the friction and thermal deformation between the tool and the workpiece.

Sayuti et al. [37] an experimental study in milling aerospace duralumin AL-2017-T4 using carbon

onion nanofluid. The highest carbon onion concentration (1.5 wt.%) produces the lowest cutting

force and the best surface quality. A reduction of 21,99% in cutting forces and 46.32% in surface

roughness are recorded.

Figure 17. Specific energy and power reduction for both lubrication mode [35].

Figure 18. Variation of surface roughness with cutting condition [34].



Rahmati et al. [38] investigated the effects of MoS2 on the machined surface morphology after

milling aluminium alloy AL6061-T6 workpiece. The best machined surface quality was found with

0.5% of MoS2. The same researches in another investigation with aluminium alloy AL6061-T6 [39]

investigated with different concentration of MoS2, pressures and nozzle orientation angle. One of

the main conclusion that could be extracted from this research is that the minimum cutting force,

cutting temperature and the best surface roughness were achieved with an air pressure of 4 bars.

Mao et al. [40] performed experiments with different types of nanoparticles and base oils in

grinding process of hardened AISI 52100 steel. The results in surface roughness and cutting forces

showed with oil-based nanofluid in comparison with water-based nanofluid, but not cutting

temperatures. This shows that the oil has better lubrication properties, but the water-based NF has

a better cooling effect. The size of the nanoparticles only affects to the forces, decreasing with the

size of them, and to the surface finish, that is deteriorated at the larger diameter nanoparticles.



Table 3. Summary of MQL with NF with different nanoparticles literature for turning process.

No. Strategy/ Authors

Cooling methods

Workpìece/ Tooling

Cutting Parameters

Findings

1 Krishna et al., (2010) [26]

MQL+NF SAE 40 and coconut oil, 0.25-1 wt.% nanoboric acid NP (50nm)

AISI 1040 steel Cemented carbide tools MQL Tool holder

Vc=100m/min f=0,2mm/rev d=1mm

Thermal conductivity increased, and specific heat decreased with the concentration of NP. Best performance in surface roughness and temperatures at 0,5 wt.% of NP.

2 Rao et al., (2011) [27]

Dry, MQL and MQL+NF CNT (Carbon nanotube) nanoparticles 0.5-5 wt.%

AISI 1040 steel Cemented carbide tools

Vc=102m/min f=0,44mm/rev d=0,5mm

The decrease of tool wear and nodal temperature is limited to 2 wt.% of nanoparticles in the oil

3 Khandekar et al., (2012) [28]

Dry, MQL and MQL+NF 1 wt.% Al2O3

AISI 4340 steel Uncoated carbide tools

Vc=350m/min f=0,1mm/rev d=1mm

Great reduction in crater and flank wear. Reduction of 50% and 30% in cutting force and 54,5% and 28,5% in Ra compared to dry and machining with conventional cutting fluid.

4 Amrita et al., (2014) [29]

Dry, Wet, MQL and MQL+NF NanoGraphite, Nanoboric acid and MoS2 NP 0.3 wt%

AISI 1040 steel Uncoated cemented carbide tools

Vc=65m/min f=0,14mm/rev d=0,75mm

Oil with MoS2 shows better performance in cutting forces. NanoFluids, starting with MoS2 showed better results in terms of tool wear, even better than wet machining.

5 Sharma et al., (2016) [30]

Dry, Wet, MQL and MQL+NF 1 wt.% Al2O3


Vc=96,7m/min f=0,1mm/rev d=1mm

NF reduced cutting force up to 59.1%, 29.2% and 28.6% compared to dry, conventional mist and wet machining, respectively. Tool wear up to 63.9%, 44.9% and 5.27%. The machining performance is comparable to wet machining.



6 Sharma et al., (2016) [31]

Dry, Wet, MQL and MQL+NF 1 wt.% TiO2


Vc=96,7m/min f=0,1mm/rev d=1mm

NF reduced cutting force up to 62.67%, 34.88% and 35.85% compared to dry, conventional mist and wet machining, respectively. Tool wear up to 58.1% and 35.85%, compared to dry and conventional oil. The machining performance is comparable to wet machining.

7 Su et al., (2015) [32]

Dry, MQL and MQL+NF 0.1-0.5 wt% NanoGraphite

AISI 1045 steel Uncoated carbide tools

Vc=55/96mm/min f=0,1mm/rev d=1mm

The main cutting force with respect to dry cutting was 11 and 26 %, for the two selected cutting speeds. The maximum reduction of cutting temperature relative to dry cutting was 11.9 and 21% respectively for the different speeds.

8 Chetan et al., (2016) [33]

Dry, MQL and MQL+NF 0,1-10 wt.%Al2O3 and Ag

Nimonic 90 Nickel based alloy Multilayered carbide inserts

Vc=60 mm/min f=0,12mm/rev d=0,5mm

The smallest flank wear obtained was with the lowest flow and Al2O3 NF. Best surface quality also with Al2O3 in sunflower base oil.



Table 4. Summary of MQL with NF with different nanoparticles literature for milling process.

No.

Strategy/ Authors

Cooling methods

Workpìece/ Tooling

Cutting Parameters

Findings

1 Uysal and Furkan Demiren, (2015) [34]

Dry, MQL and MQL+NF 1 wt% MoS2

AISI 420 martensitic steel Uncoated WC cutting tools

n=995 1/min f=180mm/min d=0,5mm

Two flows were tested (20-40mL/h), not seeing a big difference. The reductions of the surface roughness were determined as 36,3% and 39,2% at 20 ml/h and 40 ml/ flow rates in nano MQL. The nano MQL method could reduce the tool wear by 16,8% and 19,9% at 20 ml/h and 40 ml/h flow

2 Sarhan et al., (2012) [35]

MQL and MQL+NF 0.2 wt% SiO2

Al 6061-T6 Aluminium alloy HSS with 2 flutes and 10 mm diameter

n=5000 1/min f=100mm/min d=5mm

The range of cutting force reduction is 40.22–42.13% compared to conventional oil. Power consumption analysis was also done obtaining a range of reduction of 40.22-42.13%.

3 Sayuti et al., (2014) [36]

MQL and MQL+NF 0.2-1 wt% SiO2

Al 6061-T6 Aluminium alloy HSS with 2 flutes and 10 mm diameter


Protective thin films were developed on the feed marks of the machined surface providing much less friction and thermal deformation. Drastic reduction of cutting oil consumption using MQL+NF was recorded.

4 Sayuti et al., (2013) [37]

MQL and MQL+NF 0.5-1.5 wt% Carbon onions

Duralumin AL2017-T4 Aluminium alloy SEC-ALHEM2S8 end mill, 8 mm diameter

n=5000 1/min f=75,408-100mm/min d=5mm

The highest carbon onion concentration (1.5 %wt) produces the lowest cutting force and best surface quality. The cutting force and surface roughness reduction percentage are found to be 21.99 and 46.32 %.

5 Rahmati et al., (2014) [38]

MQL and MQL+NF 0.2-1 wt% MoS2

Al 6061-T6 Aluminium alloy Tungsten


Machined surface quality was superior when NP of 0.5 wt% concentration. NP in the tool-workpiece



carbide, 2 flutes and 10 mm diameter

interface enhanced the machined surface due tothe rolling, filling and polishing actions.

6 Rahmati et al., (2014) [39]

MQL and MQL+NF 0.2-1 wt% MoS2

Al 6061-T6 Aluminium alloy Tungsten carbide, 2 flutes and 10 mm diameter


Minimum cutting force with 1 wt.% and 30º nozzle angle. Minimum temperature with 0.5 wt.% and 30º nozzle angle. Best surface roughness with 0.5 wt.% and 60º nozzle angle. The best performance is found with air pressure of 4 bars.

7 Mao et al., (2013) [40]

MQL and MQL+NF (Grinding) 0.2-1 wt% MoS2

AISI 52100 Vc=31,4m/s f=0,05m/s d=0,01mm

The lubricating and cooling performance in the grinding zone are improved with the increase of the NP concentration. Not significant influence on the diameter of the NP.



2.5 Previous work at KTH-IIP

Krajnik et al. [2] performed in 2016 experimental work at KTH-IIP laboratory, machining

experiments of MoS2 based nCLF in turning of hardened steel. Three cooling-lubricating

techniques were compared: flood cooling, MQL using vegetable-based soya bean oil and this base

oil enhanced with NP, 1% wt. MoS2, 10 nm co-axial nanotubes. The workpiece material is Toolox®

44, pre-hardened steel. The properties of this material will be explained in detail in experimental

methodology chapter, since it is the material selected for the current work

The machining experiments were carried out on a Swedturn 300 (SMT) CNC lathe machine.

Characteristics of metal-working process kept into consideration were tool wear evolution, tool

life, chip formation and temperature evolution (only for MQL and nCLF). Figure 19 shows the

evolution of tool wear vs. number of cuts for one measurement and three cooling techniques. It

can be observed that there is systematic reduction in evolution of flank wear each step of all three

measurements, for three lubrication methods. Also, there is apparent increase in tool life in nCLF

based lubrication method when compared with flood and MQL lubrication.

Figure 19. Tool wear vs. number of cuts [2].

KTH Royal Institute of Technology Experimental methodology


3 EXPERIMENTAL METHODOLOGY

3.1 Planning of the experiments

The experiments were focused in turning under dry, vegetable base oil for MQL and new

developed Nano-cutting fluids in CNC turning machine. The steps for running these experiments

are the following:

1. Problem statement. to investigate the potential of MQL technique and specially MQL

technique using Nano-cutting fluids in turning of two different materials, pre-hardened

steel (Toolox® 44) and grey cast iron (Scania case study).

2. Objectives. The main aim of this project is to measure different variables in the machining

process to prove the potential of this technology in different conditions. The secondary

aim could be study if this technology could be used as an alternative cooling technology in

industrial machining process.

3. Selection of the measurable variables. Considering which facilities were available in

KTH-IIP laboratory the influencing measurement variables were selected. Tool wear

mechanisms and tool life, surface roughness and cutting temperature will be measured.

4. Selection of the cutting parameters. This step of the planning was particularly important

since it affects directly to the succeed of the experimental work.

5. Experimental work. Execution of the experimental work, following the planned steps

and decisions.

6. Results and analysis. Analyse the collected variables and interpret the results. The

experiments were repeated to validate them and find repeatability.



3.2 Experimental set-up

3.2.1 CNC turning-lathe machine

Turning experiments were conducted in CNC lathe turning machine SMT Swedturn 300 [41]. Each

experiment was repeated at least two times to avoid possible errors.

Table 5. General technical data SMT Swedturn 300 [41].

Some general definitions and formulas should be defined in order to understand the turning

process properly. Turning generates cylindrical and rounded forms with a singlepoint tool. The

tool is stationary with the workpiece rotating. Turning is the most common process for metal

cutting and is a highly optimized process, requiring thorough consideration of the various factors

in the turning application [42].

Some equations should be presented to comprehend turning process and to calculate subsequently

the cutting parameters [43]:

Max distance

spindlenose - ref.plane

Machine weight

(approx)

Spindle

drive

Number of

spindle speeds

1295 mm 8000 kg 40 kW Stepless

Figure 20. Schemetic and picture SMT Swedturn 300 [41].



Cutting speed vc (m/min) 𝑣𝑐 =𝐷2×𝜋×𝑛

1000

Spindle speed n (rpm) 𝑛 =𝑣𝑐×1000

𝜋×𝐷2

Metal removal rate Q (cm3/min) 𝑄 = 𝑣𝑐 × 𝑎𝑝 × 𝑓𝑛

Machining time Tc (min) 𝑇𝑐 =𝑙𝑚

𝑓𝑛×𝑛

Cutting depth ap (mm) 𝑎𝑝 =𝐷1−𝐷2

2

Net power Pc (kW) 𝑃𝑐 =𝑣𝑐×𝑎𝑝×𝑓𝑛×𝑘𝑐

60×103

Table 6. Turning parameters.

Symbol Designation Unit

D1 Initial diameter mm

D2 Machining diameter mm

fn Feed per revolution mm/rev

ap Cutting depth mm

n Spindle speed rpm

Pc Net power kW

Q, MRR Metal removal rate cm3/min

Tc Machining time min

lm Machining length mm

ap

n

fn

Vc

Figure 21. Schematic diagram of turning operation and cutting parameters [43].



3.2.2 Workpiece material

The metal cutting industry produces an extremely wide variety of components machined from

different materials. Each material has its own characteristics that are influenced by heat treatments,

alloying elements…

Therefore, workpiece materials have been divided into six groups according to ISO-standard.

Toolox® 44 is pre-hardened steel and its hardness value is 45 HRC. Regarding to the ISO-standard

this material should be part of two groups: ISO H and ISO P. Its hardness is 45 HRC, which is the

limit between hardened steel and usual steel.

• ISO H. Hardened steel is the smallest group of steels from a machining point of view.

This group contains hardened and tempered steels with hardness between 45 and 65 HRC.

The hardness makes them all difficult to machine. The material generates heat during

cutting and it is very abrasive for the cutting tool.

• ISO P. It is the largest of all the workpiece material groups. This group includes unalloyed

to high-alloyed materials, martensitic and ferritic stainless steel… The machinability of

these steels differs a lot depending of the properties of the material: hardness, carbon

content etc. [44].

• ISO K. Machining cast is completely different from machining steel, and there many

difference as well between the types of cast irons. All cast irons contain SiC which is very

abrasive for the tool.

Figure 22. Workpiece material groups [44].



Toolox® 44

The first workpiece material used in this research is Toolox® 44 provided by the company SSAB.

Toolox® 44 is low-alloyed steel because its alloying elements are less than 5% in concentration,

around 3% indeed. (Table 7).

Toolox® is based on low-carbon concept, which provides low carbide concentration. The

inclusions (carbides in this case) make the steel difficult to machine. This is the reason why Toolox®

44 is easy to machine despite its hardness, and it has good stability during machining [45].

This material is delivered quenched and tempered at a minimum temperature of 590ºC. Toolox®

is not supposed to have more heat treatments, which could avoid expensive and risky heat

treatments. Toolox® is produced to rigorous quality standards, its potent mechanical properties are

measured and guaranteed [46]. The mechanical properties of this steel are summarized in Table 8.

Element C (%) Si (%) Mn (%) P (%) S (%) Cr (%) Mo (%) V (%) Ni (%)

% Wt. 0,32 0,6-1,1 0,8 max 0,001 max 0,003 1,35 0,8 0,14 max 1

Table 8. Mechanical and phyical properties of Toolox® 44 [46].

Mechanical properties at 20 ºC Physical properties at 20 ºC

Tensile strength (Rm) 1450 MPa Heat conductivity 34 W/mK

Yield strength Rp02 1300 MPa Thermal expansion coefficient 13,5 10-6/K

Elongation Ap 13 %

Compressive yield strength 1250 MPa

Impact toughness 30J

Hardness 45 HRC

Regarding to these properties, Toolox® has high toughness compared to other steels of similar

hardness (two or three times tougher). This high toughness ensures longer tool life and better

machinability [45]. Toolox® 44 is suitable for plastic moulding, rubber moulding and machine

components.

Department of Production Engineering at KTH have valuable experience in machining this pre-

hardened steel. Daghini and Nicolescu [47] have investigated the influence of inserts coating and

substrate on Toolox® 44 turning process. Tool life, tool wear, chips morphology and temperature

were measured using seven types of cutting inserts and different combinations of two coatings and

four substrates.

Table 7. Chemical composition Toolox 44 [46].



Grey cast iron (Scania Case study)

The second material that is being tested is a Grey Cast Iron. This material is widely used in

automotive industry because it has very good antivibration properties. The chemical composition

of the material is shown in Table 9.

Table 9. Chemical composition of grey cast iron.

A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1 to

3% silicon by weight. Graphite may occupy 6 to 10% of the volume of grey iron. The presence of

graphite flakes makes the Grey Iron easily machinable as they tend to crack easily across the

graphite flakes. Grey iron also has very good damping capacity and hence it is often used as the

base for machine tool mountings.

The machinability of the grey cast iron is affected by variation in the surface composition, such as

free ferrite residues, which affects directly to the cutting process. The ferrite generates harder zones

in the metal, located randomly, and the graphite instead generates softer areas. This variations in

hardness could influence in the machinability of grey cast iron. In the tested material, to ensure its

machinability, the concentration of ferrite must be below 5%. The microstructure of it and the

hardness, which also affects highly to the machining behaviour are shown in Table 10.

Table 10. Hardness and microstructure of grey cast iron.

Element C (%) Si (%) Mn (%) P (%) S (%) Cr (%)

% Wt. 3-3,5 2 0,6-1 0,4-0,8 0,12 0,4-0,7

Hardness (HB) Microstructure

240-290

Ferrite<5%

Cementite <1%

Graphite (flakes) >90%



3.2.3 Tooling system

Since in this project two different materials are being tested, also two tooling systems are necessary.

Toolox® 44

The tooling system chosen for this project is provided by the company Mircona AB, cutting inserts

and tool holder. Table 11 shows the ISO designation of these inserts. These cutting inserts are

designed for medium roughing to finishing of all types of steel and cast iron.

Table 11. Geometrical properties of the carbide inserts.

Regarding to the material, chosen inserts are cemented carbide inserts, with three coatings, coated

by the method of CVD (Chemical Vapour Deposition). Coated cemented carbides represent 80 to

90 % of the total of the cutting inserts [48]. These inserts are widely used because they give a good

combination of toughness and tool wear resistant.

The coatings are TIN, Al2O3 and TiCN. CVD coating process is more recommended for inserts

for turning, milling or drilling steels or grey-cast irons. The typical thickness of this type of coatings

is between 9 to 20 µm. The layers are generated by chemical reactions at temperatures between

700ºC to 1050ºC. PVD (Physical Vapour Deposition) process allows obtaining layers of 2-3 µm.

These coatings are used mainly in cutting difficult to machine materials, such as superalloys or

titanium alloys [49]. The benefits of the CVD-coatings types are summarized in Table 12. These

coatings are continuously being improved, trying to optimize the toughness, adhesion and wear

resistance.

Code DCMT 11 T3 08-PM7

D 55 º (Rhombic)

C Clearance angle 7º

M Tolerances

T Type of clamping

11 Insert size, d=9.52 mm

T3 Insert thickness, 3.18 mm

0.8 Corner radius 0,8mm

PM Medium pass

Figure 23. Cemented carbide inserts, DCMT 11 T3 08-PM7.



Table 12. Benefits of insert coatings [54].

On the other hand, for the present study a specially designed tool holder is used. This MQL holder,

also designed by Mircona AB, allows to apply the lubricant with precision in the cutting zone. This

tool holder applies the oil internally [50]. Figure 24 shows the design of the tool holder utilized.

TiN coatings TiC Coatings Al203 Coatings

• Excellent build-up edge resistance

• Excellent wear resistance

• Excellent crater resistance

• Excellent on gummy materials • Effective at medium speeds

• Effective at high speeds and high heat conditions

• Excellent for threading and cut off operations

• Excellent on abrasive materials

• Makes it easy to identify what insert corners have been used

• Effective at lower speeds

Figure 25. Tool holder for MQL, Mircona AB..

Figure 24. Tool holder design for MQL, Mircona AB [8].



Selected holder has two outlets to supply the oil. On top, 1 mm diameter hole, to supply oil to the

crater, and on the front relief, 1.5 mm one, to apply the oil in the cutting edge. The connection

between in hose and the tool holder in made with a tread of 1/8”, and a cylindrical hole of 5 mm

of diameter. To ensure that the system works properly in particularly important to seal all the

connections, to avoid oil and air leakage. It is also important to ensure that the oil is reaching the

cutting zone. For this purpose, the amount of oil supplied can be controlled.

Grey cast iron (Scania case study)

For the second part of the project, Scania case study, it was necessary to use a new tooling system.

This tooling system was provided directly by Scania, to reproduce the same process as it is being

carried out at their plant.

Cutting inserts used are oxide ceramics, a standard cutting material for turning cast iron and alloyed

cast iron with high standards for wear resistance [51]. These inserts were provided by Ceramtec

AB. Oxide ceramics are aluminium oxide based (Al2O3) with added zirconia (ZrO2) for crack

inhibition. The composition makes cutting inserts very resistance to tool wear but lacks of thermal

shock resistance [48].

Table 13. Geometrical properties of the ceramic inserts.

The tool holder suitable for these inserts is provided by Sandvik Coromant. This tool holder is

designed for machining under flood cooling conditions, or dry cutting, but it is not suitable for

MQL technology. Sandvik Coromant is already working with this technology, so they can

customize tool holders for MQL. But for running this second experimental part, instead of using

a fixed tool holder designed by Sandvik Coromant, a system designed at KTH-IIP was chosen.

Code DNMX 15 T07 12

D 55 º (Rhombic)

N Clearance angle 0º

M Tolerances

X Type of clamping

15 Insert size, d=12.7 mm

T07 Insert thickness, 7.94 mm

12 Corner radius 1.2mm

Figure 26. Oxide ceramic inserts, DNMX 15 T07 12.



This new design allows to control the direction of the oil flow. The design has two nozzles. These

nozzles are made of 2 mm of internal diameter copper hoses. The decision of choosing the copper

is because it is flexible enough to be adjusted, but on the other hand it is stiff and resistant. The

tool holder with the design attached is shown in Figure 27.

One of the nozzles supplies the oil to the flank and the cutting edge, and the other directly to the

nose. In results and analysis section, the influence of the control of the direction of the oil flow

will be explained in detail.

The second challenge that appears while designing the experimental set-up for Scania case study

was the clamping. The workpiece material provided by Scania comes in the form of cylinders,

which poses a difficulty when clamping. The pressure that the clampers of the turning machine.

The pressure that the clampers of the chuck exert in the cylinders can break them. For this purpose,

two solid cylinders or bars were machined. The first one is made of aluminium alloy, and it is

introduced inside the cylinder, in the side of the chunk, to clamp it without damaging it. The

reason for choosing this material is that it is tough enough to withstand the pressure of the

clampers. The second one, machined in steel, is designed to fix the tailstock. Figure 28 shows the

clamping system used for the experimental work.

Workpiece rotation

Cylinder 1

Cylinder 2

Clampers

Figure 28. Clamping system for Scania Set-up.

Figure 27. MQL external supplier designed at KTH-IIP.



3.3 Description of the MQL system

MQL is known a lubrication technique in which a small amount of oil is applied in form of mist

directly into the cutting zone. Actually, as it is explained in the state of art, this technique is

worldwide used in the metal working industry and it effectiveness is already proved.

There are many alternatives of MQL boosters available in the market, but the Swedish company

Accu-Svenska AB is a leader in this type of technology, offering in their catalogue high

performance MQL boosters, such as ECOLUBRIC® booster, that is the one chosen for this

project. The booster system provided by Accu-Svenska AB transports the lubricant-air mixture

through the machine tool, in order to reach the cutting edge of the tool [52].

The oil chosen for performing the first experiments is ECOLUBRIC® E200L, also provided by

Accu-Svenska AB. This lubricant is an economic and environment-friendly alternative for friction

reduction in industry. The lubricant is directly extracted from plants; this oil is pure vegetable-based

lubricant without any chemical modification. The properties of ECOLUBRIC® E200L are shown

in Table 14 [53].

Table 14. General properties of Ecolubric E200L [11].

Properties Description

Chemical description

Cold-pressed rapeseed oil without additives.

Health hazard The product is not harmful to health and involves no special hazards for humans or the environment

Appearance Liquid

Colour Yellowish

Smell Neutral

Melting point -18°C

Flash point 325°C

Density (20°C) 0,92g/cm3

Viscosity (20°C) 70 cP

Figure 29. Ecolubric MQL booster and Ecolubric E200L vegetable oil.



Figure 30. MQL booster drawing and components list.

Figure 30 shows the schematic of the MQL Ecolubric booster system used for this research project. All the components are presented in the table in the right of the image.

1 oil and air (mist) outlet

2 oil refill

3 oil gauge

4 oil deposit

5 electric switch

6 air cleaner

7 handle

8 pressure gauge

9 electric plug

10 air connection

11 electric switch

12 electric plug

13 solenoid

14 mounting plate

15 oil pump

16 terminal



3.4 Collection of the machining variables

The equipment available in the KTH-IIP laboratory used for this project will be described in the

following section.

3.4.1 Measurement of tool wear mechanisms and tool life

The wear in the cutting insert appears due to the friction between the tool and the workpiece. To

measure the evolution of the wear, optical microscope NIKON Optiphot 150 is used. The flank

wear and the crater wear are being measured.

DeltaPix Insight software has the option to calibrate the different magnifications and to create a

ruler and a scale to quantify the wear. Also, surfaces can be measured. The capture of the images

of the flank and the crater is done with a Delta Pix Invenio II microscope camera and analysed

with the DeltaPix InsIght proed by DeltaPix.

Figure 32. DeltaPix Insigtht software.

Figure 31. Microscope NIKON Optiphot 150.



Wear on cutting edges

To understand the cutting process properly it is particularly important to study the different wear

mechanisms that occur in the cutting inserts and its causes.

a. Flank wear

Flank wear is the most common type and most desirable and predictive. It could cause bad surface

finish and bad tolerances in the workpiece. The variable that affects more to the presence of this

wear is the high cutting speed. This type of wear can be measured and quantified. The maximum

flank wear can be used as a limit for the end of the tool life. Flank wear occurs due to abrasion,

caused by hard constituents in the workpiece material [54].

b. Crater wear

This type of wear is located in the rake side of the cutting insert. It is usually caused by chemical

reactions between the workpiece material and the insert. Extreme crater wear could cause insert

breakage. It can be reduced decreasing the relation between cutting speed and feed (vc/fn). It is due

to chemical reaction between the workpiece material and the cutting tool and is amplified by cutting

speed [54].

c. Built-up edge

Material from the workpiece is welded into the cutting insert due to the high pressure. It is very

common in machining sticky and soft materials such as low carbon steel or aluminium. Low

machining speed increases the possibility to appear build-up edge. It occurs due to adhesion

processes.

d. Notch wear

Notch wear it is characterized by excessive damage localized in both the rake and the flank. The

damage appears at the depth of cut line. It usually appears in machining stainless steels and HRSA.

Cermets or Al2O3 coated inserts help to reduce this type of wear. It is caused by adhesion, pressure

welding of chips, and a deformation hardened surface [54].

e. Plastic deformation

Plastic deformation appears when the tool material is softened. High cutting temperatures are the

main cause. Harder grades or thicker coatings might be a solution. It could lead to premature chip

breakage.

f. Thermal cracks

Thermal cracks appear when there is fast variation in temperature. These cracks are perpendicular

to the cutting edge. This type of wear is related to interrupted cuts, and commonly appears in

milling operation. It can be avoided by using a tougher grade or controlling the cooling, using

abundant coolant or none at all.



g. Insert breakage

It is usually the result of an overload mechanical tensile stresses. But it can also be due to many

other reasons such as wrong cutting parameters, inclusions in the workpiece material, vibrations,

built-up edge or excessive wear.

a b

c d

e f

g

Figure 33. Types of tool wear (a. Flank wear, b. Crater wear, c. Built-up edge, d. Notch wear, e. Plastic deformation, f. Thermal cracks, g.

Edge breakage) [55].



Machining processes

The flank tool wear was measured in the machining experiments fixing the cutting time steps. Two

different procedures were follow for the two experimental set-ups. The maximum values of the

flank tool wear were measured after these defined cutting steps.

It was estimated a tool life of 15 minutes for the experiments with Toolox® 44 hardened steel. The

time of each cutting step was 90 seconds, so the flank wear was observed and measured under the

microscope every 90 seconds of continuous machining. In order to achieve this 90 seconds, the

cutting length has been adjusted for the different diameters of the round steel bar that was available.

On the other hand, the machining process for the grey cast iron was partially different. In this case,

since the objective was to compare the obtained results with real machining parts an equivalent test

specimen was defined.

Table 15. Test specimen equivalent cutting parameters.

Cutting paramenters 1 test specimen

Feed (mm/r) 0,3

Depth of cut (mm) 0,5

Cutting speed (m/min) 520

Spindle speed (rpm) 1210-1260

MRR (cm3/min) 78

Length of cut (mm) 50

Time (s) 7,9

Material removed (cm3) 10,3

0,5mm x 50mm

Equivalent to 1 test specimen

Figure 34. Cutting profile for grey cast iron machining experiments.



3.4.2 Measurement of Temperature in the cutting zone

FLIR SC 640 supplies a combination of infrared and visible spectrum images of superior quality

and temperature measurement accuracy [55]. The purpose of the Infrared Camera in the Project is

to measure the evolution of the temperature in the cutting zone. The specification of the camera

FLIR SC 640 is shown in the Table 16.

Table 16. General specification on thermal infrared camera FLIR SC 640 [12].

The thermal camera FLIR SC 640 needs a software to analyse and collect the data. The software is

called ThermaCAM Researcher Professional. This software allows to extract temperature data in

and IR images and videos. Afterwards, to analyse and extract conclusions from the temperature

values, Matlab software is being utilized to filter and plot the results.

Specifications Thermal camera FLIR SC 640

Field of View (FOV) / minimum focus distance

24° x 18° / 0.3 m – 12° x 9° / 1.2 m – 45° x 34° / 0.2 m as an option

Spatial resolution 0.65 mrad for 24°lens – 0.33 mrad for 12° lens – 1.3 mrad for 45° lens

Thermal sensitivity 30 mK at 30°C

Electronic zoom 1-8x continuous including pan function

Electric and manual focus Auto and manual

Accuracy ± 2°C or ± 2% of reading

Temperature range -40°C to +1500°C (optional up to +2000°C)

Figure 35. Thermal infrared camera FLIR SC 640 [55].



3.4.3 Measurement of the Surface Roughness

The surface roughness tester chosen for conducting the study is the Mitutoyo SJ-210 [56]. The

most significant value measured and analysed is Ra, arithmetical mean of the surface profile. The

surface roughness was measured three times in each workpiece after machining, and only the mean

values are presented in this report. The roughness standard selected was JIS’01.

Table 17. Specifications of Surface Roughness Tester Mitutoyo SJ-210 [56].

The surface roughness was measured for the Scania study case. In this case the workpieces were

removed every 21-equivalent test specimen, so the surface roughness was measured for different

machining steps.

Model Mitutoyo SJ210

Measuring range 17.5 mm

Measuring speed 0.25/0.5/0.75 mm/s Returning:1mm/s

Measuring force 4mN

Standards JIS'82/JIS'94/JIS'01/ISO'97/ANSI/VDA

Filters Gaussian, 2CR75, PC75

Sampling length 0.008/ 0.25/ 0.8/ 2.5 mm

Stylus profile 5 µm/ 90°

Figure 36. ThermaCAM Researcher Professional 2.10. Software.



For the experiments for the pre-hardened steel the material came in the size of round bars of 140

mm of diameter and 2 m length. These bars were cut into smaller bars of 0.5 m length. The same

bar was utilized for several experiments, so the surface roughness could not be measured.

Software provided by Mitutoyo was used to analyze the measured surface roughness results. The

selected standard for this purpose is JIS 2001. In Table 18 the specifications of selected standard

are shown.

Table 18. Surface roughness JIS 2001 standard parameters.

JIS 2001 standard gives three surface roughness values:

• Ra

• Rz

• Rq

Arithmetical mean surface roughness Ra is obtained from the following formula, when the surface

roughness is expressed by y=f(x), taking x-axis to the mean line direction and Y-axis the vertical

value of the surface roughness curve in a sample reference length “l”.

𝑅𝑎 =1

𝑙∫ |𝑓(𝑥)|𝑑𝑥𝑙

0

Standard JIS 2001

Profil R

λs 2.5 µm

N 5

Cut-Off 0.8 mm

Filter GAUSS

Figure 37. Mitutoyo SJ-210 Surface Roughness Tester.



Following JIS 2001 standard Rz value is ten points mean roughness. This value is obtained from

the total of the mean value of each distance between the mean line and 5 peaks, Yp, from the

highest one, and the mean value of each distance between the mean line and the 5 valleys, Yv, from

the lowest one, of the roughness curve in a sample reference length “l”.

𝑅𝑧 =∑ 𝑌𝑝𝑖 + ∑ 𝑌𝑣𝑖5

𝑖=15𝑖=1

5

Root mean square surface roughness, Rq, is referred to as the sum of the squares of the individual

heights and depths from the mean line in a sample reference length “l”.

𝑅𝑞 = √1

𝑙∫ 𝑓2(𝑥)𝑑𝑥𝑙

0

Machining is usually the manufacturing process that determines the final geometry and dimension

and surface finish. The surface roughness of a machined piece is determined by geometric factors,

work material factors and vibration and machine tool factors. Within geometric factors there are

different parameters that determined the surface finish of a machined part [57]. They include:

• Type of machining operations.

• Cutting tool geometry, most importantly nose radius.

• Feed

Ra

Rz

Rq

Figure 38. Surface roughness profile and values, Ra, Rz and Rq for JIS 2001 standard [57]



Type of machining operation refers to the process that generates the surface, turning in this case.

Tool geometry combined with feed from the surface geometry. The effects of the feed and

geometry of the cutting insert in surface finish can be seen in Figure 39.

The effect of the nose radius can be seen in Figure 39. (a). Keeping the feed constant, a larger nose

radius causes less pronounced feed marks, thus leading to a better surface roughness. If two feeds

are compared with the same nose radius, larger feed rate increase the separation between feed

marks, leading to an increase in the surface roughness Figure 39 (b). Higher end cutting edge angle

(ECEA) will also result in a higher surface roughness value Figure 39 (c).

The effects of nose radius and feed can be combined in an equation to predict the ideal average

roughness of a surface machined by a single point tool. This equation will be use in this project to

compare the theoretical value with the experimental one.

𝑅𝑎𝑖 =𝑓𝑛

2

32𝑁𝑅

Where Rai=theoretical arithmetic average surface roughness, (mm), fn=feed (mm/rev) and NR= nose radius

on the tool point (mm) [57].

Figure 39. Effect of geometric factors in determining the theoretical finish on a work surface for single-point tools: (a) effect of nose radius, (b) effect of

feed, and (c) effect of end cutting-edge angle [57].

KTH Royal Institute of Technology Results and Discussion: Toolox® 44


4 RESULTS AND DISCUSSION: TOOLOX® 44

The results and discussion section show the experimental values obtained after machining under

different cooling-lubrication techniques at KTH-IIP laboratory. As it was explained in the

experimental methodology section, while Toolox® 44 pre-hardened steel was machined, internal

MQL is being tested. The comparison was made under different conditions that will be explained

in detail in this chapter. At the beginning of the experimental work some troubles were found with

the experimental set-up that did not allow to extract any conclusion from the collected values.

After solving these problems, valuable results were obtained, and the performance revealed

encouraging potential of MQL technology for turning Toolox® 44. In order to show the potential

of MQL three machining variables are going to be measured: tool wear, temperature and tool life.

Chips shapes and colour is also analysed.

To analyse the tool wear properly the subsequent procedure was followed:

• Flank and crater picture were captured. The flank wear was measured using the software

mentioned in the experimental methodology section.

• Chips were collected for each cooling lubricating technique. The chips were analysed

visually, paying attention to the colour and the shape.

• Every insert was utilized twice, following the recommendations of the producer.

• The experiments under each cooling-lubrication strategy were repeated three times.

The most significant wear type that appears in coated carbide inserts is the flank wear. The criteria

selected to declare the end of the tool life is 0.3 mm of wear in the flank. During the experimental

work, other types of wear also appear and will be explained in this section.

4.1 Preliminary results

First experiments were carried out using various cooling strategies at a cutting speed of 110 m/min,

feed of 0.2 mm/rev and depth of cut of 0.5 mm, following the recommendations suggested for

the cutting inserts. The cutting parameters are shown in Table 19. The flow rate used for these

experiments was between 2 and 5 mL/h and 4 bars of air pressure. As it is explained in the previous

section, the machining time is fixed for these experiments, in this case 48 seconds of continuous

machining for each step.

Table 19. Cutting parameters, first experiments Toolox® 44.

Cutting parameters Value

Cutting speed 110 m/min

Feed 0.2 mm/rev

Depth of cut 0.5 mm

Machining time (1 step) 48 s

Flow rate 2-5 mL/h

Air pressure 4 bars



Figure 40 shows the evolution of the flank wear observed for dry machining in the steel that was

available in the laboratory. This material came from an old batch with an uncertain origin. The

repeatability in the dry machining results was quite high, after three experiments three tool lives

were recorded, 11.2, 10.4 and 12.8 mins. After these dry experiments, different lubrication

techniques started to be tested in the same Toolox® 44 round bar.

As soon as the second experimental work started the drawbacks begin to appear. The experiments

were repeated at least three times for each lubrication technique, but the dispersion that appeared

in the results was too high. Figure 41 shows some examples of tool wear evolution for the different

tested techniques. Some experimental work with a Nanofluid with wt. 1% of MoS2 nanoparticles

was also tried (MQL+NF in the graph). But as it is presented in Figure 41, the results were

unconcluded, because repeatability could not be extracted from the experimental outcomes.

After these troubling outcomes, the reasons to explain them began to be an objective. The first

idea was that the problem resided in the tooling system, that it was not appropriated for the material

and the selected cutting parameters. Mircona engineers were contacted and they came to IIP-KTH

laboratory to analyse the cutting parameters. They concluded that the cutting variables were

adequate for the experimental work. Secondly, the material was studied, looking for an explanation.

The hardness was measured, extracting the conclusion that there was a significant difference from

the outside of the piece to the core. This was the reason why new Toolox 44 round bar was bought,

4 m length and 160 mm of diameter. Once the new bar arrived, the second round of experiments

started. These results are presented in the following section.

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0 2 4 6 8 10 12

Fla

nk

wear

(mm

)

Machining time (min)

Dry 1

Dry 2

Dry 3

End of tool life

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0 5 10 15 20

To

ol

wear

(mm

)

Machining time (mm)

End of tool life

MQL+Veg oil

Dry

MQL + NF

Figure 40. Flank wear vs. Machining time, first experiments Toolox® 44, dry machining.

Figure 41. Flank wear vs. Machining time, first unsuccessful experiments Toolox® 44, three lubrication techniques.



4.2 Comparison between different lubrication techniques

Once new hardened steel bar arrived, the second round of experiments started. In this case, the

cutting parameters were selected to cut under extreme conditions, increasing the cutting speed up

to 120 m/min and extending the continuous machining time up to 100 seconds. Two depths of

cut were tested: 0.5 and 1 mm, finding significant differences between them that will be explicated.

The experiments for each cooling-lubricating technique were repeated three times to understand

the process completely and rely in the results. In Table 20 the cutting parameters are presented.

Table 20. Cutting parameters, Toolox 44 experiments.

4.2.1 1 mm of depth of cut

Initially, 1 mm of depth of cut was selected for the experimental work. The reason of selecting

bigger depth is that the design of the chip breaker of the inserts is suitable for this depth of cut, so

shorter chips are obtained. Instead of long continuous chips obtained initially, these chips are 5-10

mm long. But after 360 seconds of machining, the chips became long and continuous. The crater

was observed under the microscope and as Figure 42 shows, the chip breaker was worn away. On

the left side of the picture the crater is shown after one step and on the right after 4 steps of dry

machining, that it stopped working.

Cutting parameters Value


Feed 0.2 mm/rev

Depth of cut 0.5/1 mm

Machining time (1 step) 90-100 s

Flow rate 5-10 mL/h

Air pressure 4 bars

Figure 42. Damaged and broken chip breaker, crater images x10, 1mm of depth of cut, dry machining.

Chip breaker

Damage in the

chip breaker



On the other hand, when the depth of the cut is 0.5 mm, the chips are long and continuous, which

means that the chip breaker is not working properly. Figure 43 shows two images of the crater for

0,5 mm of depth of cut machining under MQL with vegetable oil, after 90 seconds of machining

and after 360 seconds. The wear in the chip breaker is irrelevant, which means that it is not working

properly. This conclusion can also be extracted from the fact that the chips are long and continuous

from the first machining step.

The problem of continuous blue long chips is common in machining high tensile strength material.

Chips must be controlled in order to avoid future problems that affect adversely the machining

process in the following ways: spoiling the cutting edge, raising temperature, poor surface finish or

hazardous to machine operator.

Figure 44 shows the plots of the flank wear under the mentioned cutting conditions for two cooling

strategies: MQL using vegetable oil (Ecolubric E200L) and dry machining. The observation shows

that MQL performance is relatively better than dry machining, obtaining smaller flank wear values

for all machining steps. Each tool life experiment was repeated three times, and these results are

plotted in the graph.

0

0,05

0,1

0,15

0,2

0,25

0,3

0 5 10 15 20

Fla

nk

wear

(mm

)

Machining time (mins)

MQL(Vegetableoil, Ecolubric200L)EndOfToolLife

Dry

Figure 43. Crater images x10, 0,5 mm of depth of cut.

Figure 44. Flank wear vs. machining time for dry and MQL, 1 mm of depth of cut, Toolox 44.



In terms of tool life an average improvement of 21.4% was found comparing MQL with dry

machining. Figure 45 shows the different tool lives values for three repeated experiments.

Numerical results are summarized in Table 23.

While the tool wear and tool life were measured the chips were collected and analysed. In the case

of dry machining, the colour of the chips was completely burnt blue. On the other hand, the MQL

chips were purple, between gold and blue. The expected colour of the chips machined under MQL

was completely light golden. This colour means that the friction is being reduced, and consequently

the temperature is also lower. The first conclusion extracted from this colour of the chips was that

the oil was not reaching properly the cutting zone. The difference in the colour of the chips

between dry and MQL was due to the cooling effect of the generated mist. In order to separate the

two functions of the cutting fluids, cooling and lubricating, only pressured air was introduced

through the system. The MQL booster gives the option to reduce the oil delivered to the cutting

zone. Figure 46 shows the flank wear for machining with compressed air compared also with dry

and MQL cooling strategies.

Tool life (min) MQL Dry

Experiment 1 18.33 15

Experiment 2 20 16.67

Experiment 3 18.33 15

Average 18.89 15.56

Improvement 21.4%

Table 21. Tool life, dry and MQL, 1 mm, Toolox 44.

Figure 45. Comparison of tool life, dry and MQL, 1 mm of depth of cut, Toolox 44.

0

5

10

15

20

25T

oo

l li

fe (

min

s)

MQL DRY

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,00 5,00 10,00 15,00 20,00

To

ol

wear

(mm

)


MQL

Dry

Air

End of tool life

Figure 46. Flank wear measurement, 1 mm of depth of cut, dry,MQL with vegetable oil and

compressed air.



When oil is provided to the tool, the flank wear should be apparently smaller due to the friction

reduction. In this case the relative difference was below 15% for all steps. Figure 46 shows flank

and crater images after 8 steps of machining, 13.3 mins for three cooling techniques. The flank

wear curve was built based on these pictures of the inserts taken under the microscope. Flank wear

measurement, 1 mm of depth of cut, dry and MQL with vegetable oil.

The chips were also analysed. There was not any difference between the chips after machining with

MQL technology and the ones obtained machining only with compressed air. The colour of both

chips was between blue and golden, purplish.

Cutting temperature was also measured for the first four machining steps. The reduction between

machining under dry and MQL with vegetable oil is significant, up to 30% of relative reduction for

all the machining steps. Figure 48 (a) shows the average temperature for each machining step.

Furthermore, Figure 48 (b) shows the evolution of the temperature for three cooling techniques in

one step of 90 seconds.

(a)

(b)

(c)

Figure 47. Flank and Crater images x10, 13,3 mins of machining, 1 mm, Toolox 44 (a)Dry machining (b)Compressed air (c)MQL.



Reduction up to 30 ºC can be observe between MQL and dry machining. The relative difference

between MQL and air in average temperature is less than 5%, as it can be observed in Figure 48

(a). In the case of one machining step, Figure 48 (b), the maximum difference in temperature is 4

ºC. The temperature results in addition to the analysis of the colour of the chips could lead to the

conclusion that the oil mist machining under this set-up is not reaching properly the cutting edge.

This is the main reason to move to smaller depth of cut, to ensure that the oil reaches the cutting

point properly.

On the other hand, other conclusions could be extracted from Figure 48 (b) and (c). Firstly, graph

(b) shows the evolution of temperature during 90 seconds of machining. The curve for MQL and

compressed air are flat, and the increase of temperature between the initial and the final time is

only 4ºC. Instead, in the dry machining temperature curve there is a significant slope. The increase

of temperature is 22ºC in 90 seconds. It can also be observed that the temperature in dry is 15ºC

higher than MQL or compressed air when the machining started. Finally, in graph (c) the cooling

down zone is plotted. This zone represents the temperature that remains in the workpiece after

machining. The difference between the cooling techniques is significant, up to 18ºC when dry

machining and MQL are compared.

40

60

80

100

120

0 1,5 3 4,5 6

Tem

pera

ture

(ºC

)


Dry MQL Air(a)

(b)

(c)

Figure 48. Temperature graphs 1 mm, dry, air and MQL, Toolox 44(a)Average temperature vs. machining time (b)Evolution of T during 90 s of

machining (c) Evolution of T last 15 s of one machining step.



Figure 49 shows an example of an Infrared Image captured with ThermaCam FLIR SC640. The

maximum temperature of the area inside the circle, that includes the cutting point, is represented

in the previous graphs. There are some high values that were removed in order to obtain a reliable

average. Matlab code utilized for this purpose can be found in Appendix A.

Figure 49. Instantaneous Temperatures IR image, compressed air, 1 mm, Toolox 44.



4.2.2 0.5 mm of depth of cut

The main conclusion extracted from 1 mm of depth of cut experimental work was that, even if the

chip breaker was working and the chips were under control, the mist was not reaching properly

the cutting point. These results motivated the decision to move to smaller depth of cut and 0,5

mm was chosen. The other cutting parameters were kept constant. The parameters are shown in

Table 20.

Firstly, chips were collected and analysed repeating the same machining process: measuring the

tool wear after 90 seconds of continuous machining under three different techniques: MQL with

vegetable oil, compressed air and dry machining. The chips were different for three cases from the

first machining step. The chips are continuous and long in all the experiments, due to the selected

cutting depth and the properties of the workpiece material. Under these cutting conditions the

design of the chip breaker of the cutting inserts is not the most suitable option. The chips are

shown in Figure 50.

Chips obtained from dry machining are completely blue, burnt and washer type or helical. Blue

intense in colour indicates high chip tool interface temperature. When oil is applied using MQL

booster, the chips are light golden and completely tubular. The chips obtained machining with

compressed air are a mix between the two previous chips. They are blue-golden, purplish, and

helical. Chips obtained machining under air and MQL and 1 mm of depth of cut are very similar

to these chips. Light golden chips indicate lower temperature, due to the reduction in the friction

that the oil is generating. The mentioned indications lead us to think that the oil was reaching the

cutting zone properly machining 0.5 mm of depth of cut.

Secondly, the tool wear curves were built. A tool life of 15 minutes was estimated from previous

experiment, so initially 10 steps of 90 seconds of continuous cutting were defined for each

lubrication technique. The results of the flank wear are plotted in Figure 51.

Figure 50. Chips samples for Dry, Compressed air and MQL, 0.5 mm, Toolox 44.

Dry

Air

MQL



Figure 52 shows the flank images after 15 of machining, last measured step, for three studied

lubrication techniques. The only significant wear that appears in under these cutting conditions is

flank wear, caused by abrasion processes. There are not adhesion or chemical wear found in the

microscopic images. The end of the tool life is set to flank wear of 0.3 mm.

Some conclusions can be extracted from Figure 51. There is a systematic reduction in flank wear

when MQL technique is used. The biggest difference comes after 15 minutes of machining, up to

100% of improvement when dry and MQL are compared. The cutting inserts are almost broken

for dry machining and cutting with compressed air, obtaining flank wear values close to the 0.3

mm limit.

On the other hand, the cutting inserts used for machining under MQL have an acceptable value of

tool wear after 15 minutes, giving the possibility to continue machining. The results of cutting with

compressed air showed slightly better performance than dry machining during the middle steps,

but in terms of tool life are comparable. This behavior was also found in the previous experiments

when the cutting depth was 1 mm. The air introduced in the cutting zone helps to reduce the

cutting temperature directly but has no affect in the friction. The small improvement in the tool

life is caused by this reduction in temperature. It is particularly important to ensure that the oil is

reaching properly the cutting zone to reduce the friction in the chip tool interface. This leads to

bigger reduction in temperature as well.

1 2 3

0

0,05

0,1

0,15

0,2

0,25

0,3

0 3 6 9 12 15

Fla

nk

wear

(mm

)


Dry

Dry

MQL

MQL

Air

Air

3

2

1

Figure 51. Flank wear vs. machining time for dry, air and MQL, 0.5 mm of depth of cut, Toolox 44.

Figure 52. Flank images, 15 mins of machining, 0.5mm of depth of cut, Toolox 44.



Finally, temperature was measured for first four cutting steps of 90 seconds. The results are plotted

in Figure 53. New conclusions can be extracted from this graph that demonstrate that the MQL

system is optimized for a cutting depth of 0.5 mm.

Figure 53 shows the average temperature for first four cutting steps and two cutting depths. The

temperature in the cutting zone are significantly lower when air or MQL is applied. An average

relative reduction of 15 % was found. This difference in temperature is appreciable from the first

90 seconds of machining, with a reduction of 10ºC. In contrast, when the cutting depth is 1 mm,

the relative difference in temperature is only 5%, 2ºC after the first machining step. These results

evidence the hypothesis that the oil is reaching the cutting zone and the friction is reduced.

Finally, Table 22 summarizes average temperature values for the three cooling-lubricating strategies

and two cutting depths. The biggest difference appears when MQL with 1 mm and 0.5 mm are

compared, a reduction of 21.2%, compared to the 5.3% of dry and 11% of air.

Table 22. Average temperature values, 0,5 and 1 mm, Toolox 44.

Cooling strategy/ Cutting depth 0,5 mm 1 mm

Dry 98.7ºC 103.9ºC

Air 74.7ºC 82.9ºC

MQL 65.4ºC 79.2ºC

Figure 53. Average temperature vs. machining time, 0,5 and 1 mm, Toolox 44.

40

50

60

70

80

90

100

110

120

0 1,5 3 4,5 6

Tem

pera

ture

(ºC

)


Air 0,5mm

Dry 0,5mm

MQL 0,5mm

Air 1mm

Dry 1mm

MQL 1mm

KTH Royal Institute of Technology Results and Discussion: Scania Case Study


5 RESULTS AND DISCUSSION: SCANIA CASE STUDY

This chapter presents the results and the main outcomes from the experimental work done for

Scania Case Study. As it was explained in Experimental Methodology chapter, the workpiece

material was provided directly by Scania. Cutting inserts and tool holders were also supplied by

Scania. Cutting parameters were selected in collaboration with the company to try to reproduce the

process as close as possible. The experimental set-up was revised by Scania employees to ensure

that the machining process was correct.

Table 23 summarizes the cutting parameters for Scania Case Study. These parameters could not be

modified even if the results could be optimized. The values are kept constant to reproduce the

process that it is carried out at Scania in Södertälje. One test specimen equivalent is defined, to

compare with the number Södertälje of production provided by Scania with one cutting insert. 120

test specimens are machined in with one side of one cutting inserts. The cutting tools are indexable

inserts, meaning that they can be rotated or flipped, so each cutting insert will be used four times.

Table 23. Cutting parameters, Scania Case Study.

To summarize, the subsequent procedure was followed to analyse the machining process:

• Flank and crater picture were captured. The flank wear was measured using the software

mentioned in the experimental methodology section. They were observed after machining

three test specimen equivalent.

• Every insert was utilized four times, following the recommendations of the producer.

• The experiments under each cooling-lubrication strategy were repeated two times. In this

case experiments cannot be replicated three times due to the limitation in material amount.

Cutting parameters 1 test specimen


Feed 0.3 mm/rev

Depth of cut 0.5 mm

Spindle speed 1210-1260 rpm

Machining time (1 specimen) 7.9s

Flow rate 5-10 mL/h

Air pressure 4 bars



5.1 Comparison between different lubrication techniques

Three different cooling techniques were compared for Scania case study:

• MQL using vegetable oil Ecolubric E200L.

• MQL using Nanofluid, Ecolubric E200L as base oil and 0.5% by weight of MoS2.

• Dry machining. Scania, at Södertälje plant, produces the parts that are the focus of this case

study using this technology.

The main objective of these results and discussion part is to compare dry machining technology

with other technologies that could improve the process and increase the productivity. Tool wear,

tool life and temperature are being measured to compare the techniques. Surface roughness is also

used to prove the potential of this new lubrication techniques. Scania has very strict rules in terms

of quality for finished parts. The average surface roughness Ra should be below 2.5 µm for the

finished pieces.

5.1.1 Tool wear and tool life

In Söderltälje, they can machine up to 120 test specimen equivalents without changing or flipping

the cuttings. This value will be used to compare and established as a goal. Used inserts brought

directly from Scania were analysed under the microscope. Figure 54 shows flank and crater images

of a new ceramic insert, and Figure 55 one side of one of the inserts provided by Scania.

Figure 54. Flank and crater images x5, new ceramic insert.

Figure 55. Flank and crater images x5, broken ceramic inserts, Scania sample.



Only 2 sides up to the 16 analyzed were completely worn away. In others, a significant wear was

found, up to 155 µm at worst. Table 24 shows the flank wear found in the cutting inserts received

from Scania. It can be observed that in most of the cases the inserts are not completely broken,

only 2 out of 16, 12.5%. But as it will be discussed in next section, the transition from this wear

values to a worn away flank is unpredictable.

Table 24. Flank wear, Scania used inserts, 120 test specimens.

Firstly, dry machining experiments were carried out, repeating the experiments two times. Tool life

results were recorded, obtaining 69 test specimen equivalents in the first experiment and 54 in the

second one. There are many reasons that could explain these difficulties to reproduce real

conditions and to obtain as good results as the ones obtain in Södertälje (120 parts):

• Higher cutting temperature. In the set up at KTH the same cylinder is machining

continuously, machining 7 times, and 0.5 mm depth. The temperature increases in each

machining, although we wait before starting a new machining.

• Clamping system. The clamping system that we are using, as it is explained, consists of two

cylinders, one fixed in the inner part of the cylinder and the other to fix the tail-stock. There

is always a small deviation, a misalignment when the cylinder is clamped, because this

process is done manually.

• Air suppliers. At Scania facilities, air suppliers are used to remove the chips easily. In the

case studied, more sparks appear, since the chips are not being removed properly. This

process could make the insert and the workpiece itself to suffer more.

After dry machining tests, MQL was tested. In this case study two different fluids were applied,

vegetable oil Ecolubric E200L and 0.5% w.t. MoS2 nCLF, with Ecolubric E200L as base oil. But

first, it was important to ensure that the angle of the nozzles designed at IIP-KTH were correctly

aligned to make the oil reach the cutting zone. These first experiments were carried out using only

vegetable oil.

The first MQL experiment gave a tool life of 81 test specimens. Relative increase in tool life of

31% comparing MQL with vegetable oil with dry machining was found. But it was expected to

obtain a better performance in terms of tool life and tool wear due to previous experience, so the

angle of the nozzle was change. The main objective of this change was to ensure that the oil was

reaching properly the cutting edge and the flank, instead of the crater. So finally, one of the nozzles

was orientated to the nose and the other to the flank and cutting edge, as it is shown in Figure 56.

Flank wear (µm) Insert 1 Insert 2 Insert 3 Insert 4

Side 1 89.23 91.5 109.8 86.9

Side 2 Broken 82.4 116.7 96.1

Side 3 Broken 155.6 112,11 105.3

Side 4 82.37 96.1 105.3 103



As soon as the nozzle was realigned the results started to improve. Tool life of 150 test specimens

was obtained in the second tool life experiment with MQL and vegetable oil. Figure 57 shows the

evolution of the tool wear for two different nozzles positioning. Also, first dry machining

experiment is plotted. The new value of tool life shows and improvement of 85% and 117%

compared to first nozzle orientation (MQL 1) and first dry machining experiment (Dry 1)

respectively.

In total, 7 tool life experiments were carried out, comparing three cooling-lubricating techniques:

dry machining, MQL with vegetable oil and MQL with NF. Table 25 summarizes the experimental

work and tool life results in terms of number of test specimen and time. The repeatability of the

results of the same technique is high, excluding the first MQL with vegetable oil experiment, as it

was explained recently. The relative difference is 22% in dry machining, 8% in MQL and 13%

machining with NF. This is reasonable because the material utilized for this experimental work is

provided directly by Scania, and its properties and quality are proved and constant for all the test

specimens. Figure 58 shows the flank wear evolution for best results for different cooling

techniques, Dry 1, MQL 3 and NF 2.

Figure 56. Orientation of nozzles, Scania case study tool holder.

Nozzle to the nose

Nozzle to the cutting edge Nose

Cutting edge

0

50

100

150

200

250

300

0 30 60 90 120 150

Fla

nk w

ear

(µm

)

N of test specimen

Dry 1 MQL1 MQL 2

Figure 57. Flank wear vs. N of test specimen, Dry 1, MQL 1 and MQL 2 Scania case study.



Table 25. Tool life for different techniques, Scania case study.

It can be observed that there is a main difference in the evolution of the tool wear between different

cooling-lubricating techniques. Machining in dry and applying the NF the tool breakage occurred

suddenly, on the other hand, applying vegetable oil Ecolubric E200L, the breakage occurs due to

extreme flank wear. Figure 59 shows the flank images for the last machining step for three studied

cases. It can be observed that looking to the first two images, dry and NF, that the flank is destroyed

and above the 0.3mm limit. The decision of stopping the machining in MQL was the obtained

results during the turning. When the flank exceeds 0.25 mm, too many sparks appeared, and it was

not advisable to continue the experimental work, so the end of the tool life was declared.

Experiment number Name

Cooling/ Lubricating Technique

N of test specimen

Time (mins)

1 Dry 1

Dry machining

69 9.1

2 Dry 2 54 7.1

3 MQL 1

MQL Ecolubric E200L

81 10.7

4 MQL 2 150 19.8

5 MQL 3 162 21.4

6 NF 1 MQL NF(0,5%wt

MoS2)

114 15.0

7 NF 2 129 17.0

0

50

100

150

200

250

300

0 50 100 150

Fla

mk w

ear

(µm

)

N of test specimen

Dry 1 NF 2 MQL 3

Figure 58. Flank wear vs. N of test specimen, three techniques, Scania case study.

Figure 59. Flank wear images at the end of tool life Dry 1 x10, NF 2 x5, MQL 3 x10, Scania case study.



To conclude with tool wear and tool life analysis, Figure 60 summarizes the tool life results for the

three techniques and two rounds of experiments. In terms of flank wear, the wear obtained under

dry machining is slightly higher than MQL and NF. There is a systematic reduction in tool wear

when vegetable oil or NF is applied. But in terms of tool life the best results are for MQL technique

with vegetable oil. There is a relative improvement of 20.4% and 135 % when NF and dry

machining are compared with vegetable oil. There are some reasons that could explain results when

NF is applied, but the main motivation lies in the fact that the particles are not coming out from

the system. The booster itself might be getting partially block due to the concentration of

Nanoparticles and less amount of oil is reaching the cutting zone. This might be the reason why

the results obtained for turning with MQL and NF showed a performance between dry and MQL

with vegetable oil Ecolubric E200L.

5.1.2 Surface roughness

In this case study surface roughness was also measured. This was possible due to the geometry of

the workpiece as it was described previously. The workpiece was removed after machining 21 test

specimens equivalent for dry machining and 15 for MQL with vegetable oil and NF. Every

measurement was repeated three times and the average was calculated. The most significant value

was the arithmetical mean surface roughness Ra (µm). Figure 61 graphs the average surface

roughness for all the measured values.

69

162

114

54

150

129

0

20

40

60

80

100

120

140

160

Dry MQL NF

Tool life

N o

f T

est

Sp

ecim

en

Figure 60. Comparison of tool life, three cooling techniques, Scania case study.

0

1

2

3

4

Aver

age

Ra

(µm

)

Dry 1 Dry 2 MQL 2 MQL 3 NF 1 NF 2Figure 61. Average arithmetical mean surface roughness Ra (µm), Scania case study.



The process that is being done at Scania facilities in Södertälje requires a maximum arithmetical

mean surface roughness Ra value of 2.5 µm. The limit of 2.5 µm is plotted in Figure 61 in dots.

Theoretical surface roughness value is calculated for turning with the cutting parameters, obtaining

a value of 2.34 µm. This value is achieved in all the measured steps when oil is introduced, both

vegetable oil and NF. In dry experiments this value is highly exceeded, above 3 µm in all the

measurements taken. This reduction for both cooling techniques compared with dry machining

could be due to the reduction in cutting temperatures. Figure 62 shows 4 surface profile examples,

measured after one of the middles steps of the experimental work:

1. Scania test specimen sample. Ra=2.343 µm.

2. Machining with MQL + NF. Ra=2.308 µm.

3. Machining with MQL + Vegetable oil Ecolubric E200L. Ra=2.202 µm.

4. Dry machining. Ra= 4.122 µm

Figure 62. Surface roughness profile 1. Scania test specimen sample, 2. MQL + NF, 3. MQL +

Vegetable oil, 4. Dry machining.

-20,0

-10,0

0,0

10,0

20,0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

[µm]

[mm]

-20,0

-10,0

0,0

10,0

20,0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

[µm]

[mm]

-20,0

-10,0

0,0

10,0

20,0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

[µm]

[mm]

-20,0

-10,0

0,0

10,0

20,0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

[µm]

[mm]

1

2

3

4



All the measurements done for three different cooling-lubricating techniques are presented detail

in Appendix C. These values were utilized to calculate the average values of the surface roughness

that are presented in Figure 61. The arithmetical average surface roughness for dry machining in

presented profile is 4.33 µm. These high values of roughness could be justified by the high cutting

temperatures achieved in dry machining. The nose radius of the selected cutting tool is bit enough

(1.2mm) to achieve good surface roughness results, but the high feed (0.3 mm/rev) utilized makes

more difficult to obtain good quality. Temperature, nose radius and feed are the parameters that

affect most in the surface roughness.

5.1.3 Temperature

In Scania Case study temperature around the cutting zone was also measured. It is important to

explain that the temperature was difficult to measure in this experimental set-up. The turning

experiments were done utilizing the second revolver of the machine tool. Due to the geometry of

the tool holder, it was very hard to access to the cutting point with the Thermal Camera. Figure 63

shows the set up. Furthermore, the cutting time of each test specimen is only 7.9 seconds. This

short cutting time does not let the temperature increase, so it is even more problematic to record

the reduction.

Selected tool holder

Revolver 2

Figure 63. Scania set-up image.

Figure 64. Temperature in the cutting zone vs. machining time, Scania case study.



Nevertheless, reduction of 8ºC were recorded for one machining step. The temperature plotted in

Figure 64 shows a reduction up to 10ºC after machining one test specimen equivalent. Although,

it is very difficult to extract any significant conclusions from these temperature measurements.

Finally, Figure 65 shows an example of an Infrared Image captured with ThermaCam FLIR SC640

after 7.9 seconds of turning.

29.4ºC

29

28

27

26

25

24.9ºC

Figure 65. Instantaneous Temperature IR image, Scania case study.

KTH Royal Institute of Technology Conclusions and Future Work


6 CONCLUSIONS AND FUTURE WORK

The work presented in this thesis focused on the investigation of the potential of MQL and further

MQL technique improved with oils enhanced with nanoparticles in two different workpiece

materials and set-ups: pre-hardened steel and Scania case study: grey cast iron. This was executed

by performing different turning experiments with both set-ups and proper cutting parameters and

variables. The general conclusions drawn from this research can be summarized in the following

points:

• The overall potential of MQL technology for the selected experimental set-up and cutting

parameters has been proved in terms of quality and tool life. The utilized cutting parameters

tried to reproduce real conditions as close as possible.

• The better performance of MQL with vegetable oil was proved for Toolox® 44 pre-hardened

steel case study. Three cooling-lubricating techniques were compared in this study obtaining

reductions in tool wear up to 50 % (0.5 mm of depth of cut). In terms of tool life an

improvement of 25% was recorded compared to dry machining.

• When cutting temperatures where measured turning pre-hardened steel, reductions of 31% (1

mm) and up to 51% (0.5 mm) were recorded when vegetable oil Ecolubric E200L was applied,

compared to dry machining.

• The study reveals that it is particularly important to ensure that the oil reaches the cutting

point properly. This conclusion was proved when two different cutting depths were compared.

The colour of the chips is a good indicator of the behaviour of the system itself, obtaining

better results in terms of temperature and tool wear when golden chips appeared.

• The designed system for Scania case study gives the opportunity to adjust the direction of the

flow, which helps to ensure that the oils reaches properly the cutting edge.

• In Scania case study three cooling techniques were compared, dry machining, MQL with

vegetable base oil and MQL with NF. The best performance was obtained using vegetable oil,

obtaining a systematic reduction in the tool wear of 25% compared to dry machining. Tool

life of the cutting inserts was increased in 87% and 135% utilizing MQL with NF and MQL

with vegetable oil respectively.

• In terms of quality, surface roughness and cutting temperatures were also improved with the

new cooling-lubricating technology. The experimental work shows improvements of 34% in

surface roughness and reductions up to 15% in cutting temperature. Regarding to the surface

roughness, using any of the two proposed cooling methods (MQL with vegetable and MQL

with NF), the quality standard asked by Scania (2,5 µm) was achieved for every machining

step.

KTH Royal Institute of Technology Conclusions and Future Work


6.1 Recommendations for future work

During the current work, many interrogates have appeared which can be studied further in future

research work. These questions are summarized in the following points:

• In both studied set-ups, vegetable oil MQL and NF MQL can be studied under different

combinations of oil flow rates and air pressures for new cutting speeds, cutting depths and

feed rates.

• In order to understand the cooling-lubricating process properly, tribological properties of

the fluids could be studied at different temperatures and conditions.

• In Scania case study, the results obtained in dry machining are not as good as expected and

compared to the process done at Scania, Södertälje. These difficulties are explained in the

results chapter and can be solved following some of the advices given. The quality of the

results could be enhanced by improving other aspects of the machining process in the IIP-

KTH laboratory.

• The study shows that the cutting temperature highly affects to the machining process. The

MQL system itself is not able to achieve lower temperatures in machining. One improvement

in the booster system could be to cool down the temperature of the mist before being applied

in the cutting zone. The company Accu-Svenska AB is actually working on this project. They

are working on a new system in which they can reduce the temperature of the mist using a

cryogenic close loop.

• The research reveals that it is particularly important to ensure that the oil is reaching the

cutting edge properly. For this purpose, a solution could be to analyse the actual MQL tool

holder and optimize the design of the holes and nozzles. The CFD modelling techniques can

be very useful to design and visualize the oil flow while customising the tool holder. CFD

technology can provide an optimal solution and save cost and time required for prototyping.

• The literature review shows an impressing potential of oil enhanced with nanoparticles.

Further experimental work should be done using Nanotechnology in pre-hardened steel.

This technology reveals several challenges, such as the design of the MQL booster that

should be solved during the execution of the further research. First step of this research

would be ICP-MS (Inductively coupled plasma mass spectrometry) tests. Some samples of

the oil enhanced with nanoparticles would be collected in the cutting zone and will be

analyzed to measure the concentration of Nanoparticles afterwards. These tests would give

information about what is happening with the fluids inside the MQL booster.

• The potential that MQL reveals for this particular process makes interesting to continue with

this study. In order to include this technology in an industrial process, like the one that is

carrying out at Scania, Södertälje, Further study on MQL system design and implementation,

including cost and life cycle analysis.

KTH Royal Institute of Technology References


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KTH Royal Institute of Technology Appendix A. Codes


APPENDIX A. CODES

1. CNC Codes for turning operations

Toolox® 44

Channel 1: File name: MQLTEST

;Testing Toolox 44

;Cutting parameter

;v120 f0,2 d0,5-1

;Starting the experiment at D=150 L1=500

DEF REAL L1=139 ;Final diameter: external-cutting depth

DEF REAL L2=500 ;Length of the workpiece

N10 G54 G18 DIAMON

N11 TRANS X0 Z=L2 ;Change the origin of the workpiece

N12 T9D1

N20 G0 X=L1+10 Z10

N21 G0 Z5 ;Moving to the starting point

N22 G0 X=L1+5

N23 G96 F0.2 S120 M4 LIMS=3000

N24 G1 X=L1

N25 G1 Z-50 ;Finishing Z

N26 G1=L4+5

N27 GO X=L4+50

N28 M5

N29 G0 Z50

N40 M2

Channel 2: File name: MQLTEST

;Machining the chamfer before testing

DEF REAL L1=150 ;External diameter

DEF REAL L2=500 ;Length of the workpiece

N101 G54 G18 DIAMON

N102 TRANS X0 Z=L2 ;Change the origin of the workpiece

N103 T22 D1

N104 G0 X=L1+20 Z10

N105 G96 F0.15 S100 M4 LIMS=1000

N110 G0 Z5

N120 G0 X=L1+5

N130 G0 X=L1-4 Z1

N131 G1 X=L1+4 Z-3 ;Linear movement

N140 G0 X200 Z20



N150 M5

N152 M2

Scania Case Study

Channel 2: File name: SCANIA2017

;Testing Scania cylinder liners

;Cutting parameter

;v550 f0,3 d0,5

;Definition of geometrical parameters

DEF REAL L1=306; Total length (longer than the cylinder itself)

DEF REAL L2=138; Machining diameter

;Moving to the starting position N100

N101 G54 G18 DIAMON

N102 TRANS X0 Z=L1

N103 T22 D1 ;Selection of tool number

N105 G0 Z-205

N106 G0 X=L2+5

;Start machining N110

N111 G6 F0.3 S550 M4 LIMS=1500

N112 G1 X=L2

N113 G1 Z-30

;Returning to initial position N200

N201 G1 X=L2+5

N202 G0 X=L2+80

N203 G0 Z20

N211 M5

M2

Channel 2: File name: SCANIA2017GROOVES


DEF REAL L1=306 ;Total length (longer than the cylinder itself)

DEF REAL L2=138 ;Diameter of the cylinder

DEF REAL L3=138 ;Diameter of the groove

;Machining grooves

N101 G54 G18 DIAMON

N102 TRANS X0 Z=L1


N104 G0 X=L2+20 Z10

N105 G0 Z-22 ;Starting Z

N106 GO X=L2+5

;First groove

N111 G96 F0.2 S300 M4 LIMS=1500

N112 G1 X=L2



N113 G1 X=L3 Z-24

N114 G1 Z-27

N115 G1 X=L2 Z-29

N116 G1 X=L2+7

;Second groove

N121 G0 Z-79

N122 G1 X=L2

N123 G1 X=L3 Z-81

N124 G1 Z-84

N125 G1 X=L2 Z-86

N126 G1 X=L2+7

;Third groove

N131 G0 Z-136

N132 G1 X=L2

N133 G1 X=L3 Z-138

N134 G1 Z-141

N135 G1 X=L2 Z-143

N136 G1 X=L2+7

;Fourth groove

N141 G0 Z-193

N142 G1 X=L2

N143 G1 X=L3 Z-195

N144 G1 Z-198

N145 G1 X=L2 Z-200

N146 G1 X=L2+7

;Returning to initial position

N201 GO X=L2+60

N212 G0 Z20

N213 M5

M2

Channel 2: File name: SCANIA2017FIRSTFACING

;First facing


DEF REAL L1=306 ;Total length (longer than the cylinder)

DEF REAL L2=139 ;Cutting diameter

N101 G54 G18 DIAMON

N102 TRANS X0 ZZ=L1


N104 G0 x=l2+20 z10

N105 G0 Z-18 ;Starting Z

;Machining

N111 G96 F0.2 S300 M4 LIMS=1500

N112 G1 X=L2



N113 G1 Z-205

N114 G1 X=L2

;Returning to initial position

N211 GO X=L2+20 Z20

N212 M5

2. Matlab Codes for Temperature Analysis

Extraction of one temperature measurement

clc clear all

%Extracting temperature data data=load('ImageMax10.irp'); a=size(data);

%Parameters x1=5;%Diference in temperature at the beginning of the machining x2=10; seg=8.5; %Number of seconds machining %Temperature vector T(:,1)=data(:,1)+0.001*data(:,2)-273.15;

%Time vector t=zeros(a(1),1); t(1)=0;

for i=2:(a(1)-1) aux=0.001*[data(i+1,4)-data(i,4)]; aux2=data(i+1,3)-data(i,3); t(i)=t(i-1)+aux+aux2; end

%Plotting all temperature values plot(t,T) grid on hold on xlabel('Time (s)') ylabel ('Temperature (ºC)')

%Extracting values for cutting time j=1; while([T(j+1)-T(j)]<x1) j=j+1; end aux3=j;

%Time from the raise of T lim=seg+t(aux3); aux4=lim/(t(2)-t(1));

aux4=round(aux4);



t2=t(aux3:aux4); T2=T(aux3:aux4); mean1=mean(T2);

%Smoothing the curve 1 b=size(T2); if rem(b(1),2)==0 T3=sgolayfilt(T2,2,(b(1)-1)); else T3=sgolayfilt(T2,2,b(1)); end

%Deleting strange values u=1; for p=1:(b(1)-1) if(T2(p)<(T3(p)+5)&&(T2(p)>(T3(p)-5))) T4(u)=T2(p); t4(u)=t2(p); u=u+1; end end

Tm(1:a(1))=mean1;

%Cutting time calculation tcut=t(b(1))-t(1)

xmax=t(a(1)-1); ymin=min(T)-20; ymax=max(T)+20;

%Smoothing T4 c=size(T4); if rem(c(2),2)==0 T5=sgolayfilt(T4,2,(c(2)-1)); else T5=sgolayfilt(T4,2,c(2)); end

%Plotting xlabel('Time (s)') ylabel ('Temperature (ºC)') scatter(t,T,3); grid on hold on plot(t4,T4); hold on plot(t4,T5,'linewidth',3); xlim([0 xmax])

mean2=mean(T4) hold on



Plotting multiple temperature curves %Plotting tool wear clc clear all

data=xlsread('data'); nc=data(:,1); DRY1=data(:,2); DRY2=data(:,3); MQL1=data(:,4); MQL2=data(:,5); MQL3=data(:,6); NF1=data(:,7); NF2=data(:,8); aux=size(nc);

scatter(nc, DRY1,18,[1,0.6,0.2],'filled'); hold on plot(nc,DRY1,'LineWidth',0.5,'Color', [1,0.6,0.2],'LineStyle', '- -'); hold on grid on scatter(nc, DRY2,18,[0,1,1],'filled'); hold on plot(nc,DRY2,'LineWidth',0.5,'Color', [0,1,1],'LineStyle', '- -'); hold on scatter (nc, MQL2,18,[0,1,0],'filled'); hold on plot(nc,MQL2,'LineWidth',0.5,'Color', [0,1,0],'LineStyle', '- -'); hold on scatter (nc, NF1,18,[0,0,1],'filled'); hold on plot(nc,NF1,'LineWidth',0.5,'Color', [0,0,1], 'LineStyle', '- -'); hold on scatter (nc, MQL3,18,[1,1,0],'filled'); hold on plot(nc,MQL3,'LineWidth',0.5,'Color', [1,1,0],'LineStyle', '- -'); hold on

max=zeros(aux(1),1); max(:,1)=300; plot(nc,max,'Color',[1,0,0]); hold on

xlabel('N of test specimen'); ylabel('Tool wear (um)'); legend('DRY1','DRY1','DRY2','DRY2','MQL','MQL','NF','NF'); ylim([0 300]);

KTH Royal Institute of Technology Appendix B. Flank Wear Evolution


APPENDIX B. FLANK WEAR EVOLUTION

Flank wear images x10: Toolox 44 Cemented carbide inserts

0

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Fla

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MQL

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Figure 66. Flank wear vs. machining time, 0.5 mm Toolox 44.

Figure 67. Flank images, evolution of tool wear.

KTH Royal Institute of Technology Appendix C. Surface Roughness Measurements


APPENDIX C. SURFACE ROUGHNESS MEASUREMENTS

Scania sample Dry 1

Ra (µm) Rz (µm) Rq (µm)

N of test specimen

Ra (µm)

Rz (µm)

Rq (µm)

3.73 16.67 4.42 21 3.73 16.67 4.42

42 3.37 16.77 4.68

63 3.75 21.45 4.52

Average (µm) 3.62 18.30 4.54 Table 26. Surface roughness values JIS 2001, Scania sample, dry machining.

MQL 2 NF 2

N of test specimen

Ra (µm)

Rz (µm)

Rq (µm)

N of test specimen

Ra (µm)

Rz (µm)

Rq (µm)

15 2.2 14.87 2.83 15 2.13 11.57 2.69

30 2.6 12 2.29 30 2.26 13.37 2.82

45 2.27 11.85 2.93 45 2.58 11.78 2.89

60 2.1 10.32 2.57 60 2.39 13.78 2.66

75 2.28 15.41 3.16 75 2.89 12.25 3.26

90 2.48 13.93 3.27 90 2.51 11.18 3.2

105 2.21 12.63 2.66 105 2.69 11.7 3.15

120 2.73 15.74 3.46 120 3 13.4 3.21

135 2.58 14.97 3.4 Average (µm) 2.56 12.38 2.99

150 2.52 15.41 3.4

Average (µm) 2.40 13.71 3.00 Table 27. Surface roughness vaules JIS 2001, MQL with vegetable oil, MQL with NF.

KTH Royal Institute of Technology Appendix D. Poster PVC Annual Conference


APPENDIX D. POSTER PVC ANNUAL CONFERENCE

The overall goal of PVC, Processvätskecentrum, (Process Fluid Center) is to enhance

competitiveness for Swedish machining with minimal environmental impact. This requires a

competence base that benefits both increased productivity and increased knowledge of process

fluids and its use.

The ambition of PVC is to bring together user and supplier companies in a network within the

framework of the center programs Chalmers MCRs and KTH DMMS operations. Structure for

this network will be based on established work methods within the centers of MCR as the main

coordinator.

The annual conference of PVC took place at KTH-IIP department the 22nd of November 2017.

This project was presented in that conference, in the poster session. The poster utilized for this

presentation is presented in this appendix.

KTH Royal Institute of Technology Appendix D. Poster PVC Annual Conference

Marta García

I

towards sustainability using minimum quantity lubrication

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