UMIES Paper Nadia 2

8/2/2019 UMIES Paper Nadia 2

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Investigation into New Development of Minimal Quantity

Lubricant (MQL) System in High Speed Milling of H13

I.N Yassin1*, M.Hamdi

2, M.Fadzil

3,M.Z Norhirni

4

1,2,3,4Dept. of Engineering Design and Manufacture,

Faculty of Engineering, University Malaya, 50603 Kuala Lumpur, Malaysia

Tel: 03-79677633 / Fax: 03-796752821Email: [email protected]

2Email: [email protected]: [email protected]

4Email: [email protected]

Abstract - The primary objective of this present work is to investigate the effect of high speed milling

machining towards the new development of minimal quantity lubricant (MQL) system using the Taguchi

Mehod. The most effective of MQL control system will be developed in which continues solid stream pressure

will be varied. The MQL is an alternative way to replacing the common method of applied the cutting fluid in

CNC machining process. The conventional method is not effective enough especially at the higher cutting

speed besides it is requiring a large amount of cutting fluid where it can lead to increment of total production

cost in terms of procurement storage, maintenance and disposal of the cutting fluid. It is also improving the

quality of surface finish and tool life. The successful of this study will benefit to the machining performance

especially for the improvement of the minimal cutting fluid application at the high speed end milling of

hardened steel where it can be commercialize as replacement of dry cutting and flood application.

Keywords: Minimal cutting fluid, CNC Coolant System, Micropulsed Jet System, Programmable Cooling

System, Integrated CNC System, Minimal quantity lubrication application

1. INTRODUCTION

Computer numerically controlled (CNC) machine

tools form the basis of flexible manufacturing systems and

computer integrated manufacturing systems. CNC

machines make the most important means for CAD/CAM

technologies today. However, improving the performance

of metal cutting operations in high speed machining is still

a major concern. In high speed machining, tool life and

surface finish are largely depend on cutting speed, tool

material, machine tool rigidity and also the existence of cutting fluid during machining process (Klocke F,

Eisenblatter (1997)).

During the cutting operation, the cutting fluid acts as a

lubricant as well as a coolant. This lubricant helps in

reducing the surface friction and temperature on the tool-

workpiece and tool-chip interfaces. The common method of

applied the cutting fluid, formally known as a flash flood.

However, this method is not effective especially at the

higher cutting speeds due to the large amount enquiry and

negative effect on the working environment.

Cutting fluid application gives the bad impact to the

environment especially when improperly handled. Dhar et.

Al (2006) mention that besides affecting worler’s helth

defectively, the amount of money spent on cutting fluids is

higher compared to the amount needed associated to cutting

tools. There are lots of MQL systems that have been

developed by researchers where it has its own mechanism

in delivering the cutting fluid. However, these mechanisms

are equal by a few factors that can be considered as MQL

system. Y. Su et al. (2007) states that MQL techniqueapplied a very small amount of cutting oil in the range of 6

– 100ml/h. Meanwhile, H.R Dhar et al. (2006) state that the

range of MQL flow rate is between 50-500ml/h.

Therefore, using the minimal quantity lubrication

(MQL) is an alternative way to overcome this problem.

Thanonsak Thepsonthi (2005) has concluded that the

minimal cutting fluid application in pulsed jet form during

the high speed end milling of hardened steel can be

regarded as the replacement of flood and dry cutting

application.



There is a great need to further improve the MQL

system. The successful of this present work will benefit to

the machining performance especially for the improvement

of the minimal cutting fluid application during the high

speed end milling of hardened steel and can be

commercialize as replacement of dry cutting and flashflood application.

2. EXPERIMENT PROCEDURE

Experiment have been carried out by plain turning a

block of AISI H13 Alloy Steel with dimension 150mm

width, 150 length and 150 high in a vertical machining

centre (Mitsui Seiki VT3A) at robust design parameter

combination under dry, air and minimum quantity

lubrication conditions to study the role of MQL specially

on the surface roughness effect. The experimental control

factors are given in Table 1.

Table 1: The control factor of experiment

FactorFactors

Control

Level

1

Level

2

Level

3

ASpindle

Speed (RPM)7,957 9,284 10,610

BDepth of cut

(mm)0.50 0.75 1.00

CFeed rate

(mm/tooth)0.05 0.10 0.15

D Type of cooling

MQL Air Dry

The values of the control factor of the experiment

were selected based on the brainstorming from the

manufacturer’s recommendation and industrial practices. In

this experiment with four factors and three levels each, the

fractional design used are L9(34 ) orthogonal array.

This control factors has been design from the design

of experiment using the Taguchi Robust Design Method in

order to optimize the machining parameter in different

cutting mode with focusing on investigation of surface

roughness and chip formation. The Taguchi method

proposed to reach characteristic data by using orthogonal

arrays (OA), and to analyze the performance measure from

the data to decide the optimal process parameters by

utilized analysis of variance (ANOVA).

Orthogonal arrays employed to study the whole

parameter space with a small number of experiments only.

The standardized Taguchi-based experimental design was

used in this experiment and is shown in Table 2. In

determines the quality characteristic implemented in

engineering problem, ‘the smaller the better’ signal-to-

noise (S/N) ratio is used.

Table 2: The L9(34) orthogonal array table

Exp.

No

Factors Control

TPMA

(Spindle

Speed)

B

(Dept

of cut)

C

(Feed

rate)

D

(Type of

cooling)

1 L1 L1 L1 L1

2 L1 L2 L2 L2

3 L1 L3 L3 L3

4 L2 L1 L2 L3

5 L2 L2 L3 L1

6 L2 L3 L1 L2

7 L3 L1 L3 L2

8 L3 L2 L1 L39 L3 L3 L2 L1

The experimental conditions are given in Table 3. The

value of depth of cut and feed rate was selected based on

the tool manufacturer’s recommendation while cutting

velocity was chosen after increasing three times value from

the conventional machining parameter to achieve the high

speed milling criterion.

Table 3: The Experimental Conditions

Experimental Conditions

Machine Tools Mitsui Seiki VT3A

Type of operations Slot milling

Work Specimen

Materials

AISI H13 Alloy steel with

hardness 50HRC±3

Size (mm) = 150 x 50 x 50

Tool Diameter 12mm

Cutting tool (insert)TiAlN coated carbide

inserts

MQL supply

Lubricant pressure of 10

bar, and delivery rate of 150 ml/min.

The dry cutting was performed without any air blow

meanwhile the air cutting was performed with air blow. For

the minimal cutting fluid application, the parameter of

application was set at the lubricant pressure of 10bar and

delivery rate of 150ml/min. The cutting fluid used was neat

cutting oil ECOCUT SSN 322 from FUCHS®. The

direction of application was set against the feed direction.



The MQL needs to be supply at high pressure through

the nozzle at the cutting zone. Considering the conditions

required for the present research work and uninterrupted

supply of MQL at constant pressure over a reasonably long

cut, a MQL delivery system has been designed, fabricated

and used. The schematic view of the MQL system is shownin Figure 1.

Continues solid stream of MQL was projected from a

nozzle along the cutting edge of the insert to be sure that

the coolant reaches as close to the chip-tool and the work-

tool interfaces as possible. The photographic view of the

experimental set-up is shown in Figure 2.

The MQL is expected to effects mainly in the cutting

temperature during machining. The effectiveness,

efficiency and overall economy of machining any work

material depend largely only on the machinabilitycharacteristics of the tool-work material under the

recommended condition. The machining performance

usually judged by factors (i) cutting temperature and

cutting tool performance, (ii) pattern and chip formation,

(iii) surface finish, and (iv) tool wear and tool life.

The present work the factor that considered is tool

wear, surface roughness and chip formation in order to

study the role and affect of minimum quantity lubrication

on machining performance. The surface roughness of the

machined surface after each cut was measured by aMarh

perthometer using a sampling five specific points along the

first 150mm of cutting distance.

At the end of full cut, the chip formation are collected

and observed under scanning tool maker microscope

(Sometech) along with the cutting inserts.

3. EXPERIMENTAL RESULTS ANDDISCUSSION

The influence of cutting condition towards surface

roughness and chip formation in term of different cutting

speed, feed rate, axial depth of cut and different lubricant

can be investigate through a series of experiment. The

evaluation of the effectiveness of all cutting condition is

based upon the comparison of surface roughness and chip

formation.

Surface roughness is one of the important physical

variables that embody relevant process information inmachining. It was an important index of machinability

because performance and service life of the machined

component are often affected by its surface finish, nature

and extent of residual stresses and presence of surface.

Surface finish influences not only the dimensional

accuracy of machined parts, but also their properties. This

factor is important to machining due to its ability to

produce good surface finish. This type of information not

only can assist in understanding surface finish but also in

critical machining attributed such as machinability, cutter

wear/ fracture, machine tool cutter, and machine accuracy.

Figure 1: The schematic view of the MQL system



Generally, good surface finish, if essential, is achievedby finishing process like grinding but sometimes it is left to

machining. Even if it is to be finally finished by grinding,

machining prior to that needs to be done with surface

roughness as low as possible to facilitate and economize

the grinding operation and reduce initial surface defects as

far as possible. (N.R Dhar et al. 1995). During machining,

the cutting tool travel in certain velocity as workpiece

increased. Thus, the chip formation can determined the

machining performances that are relevant to present work.

Therefore the most important parameters in present

work to investigate in order to get improvement of surface

roughness to get the good quality product even machining

using the high speed milling machining. Figure 3 shows the

graph of data distribution of experiment.

The target performance measure (TPM) for this

present work was the average or mean value for surface

roughness and chip formation where this value used to

identify control factors that largely affect the mean. These

factors are called target control factors that used to adjust

the mean response to target. ANOVA proposes that make to

target approach to manufacturing. In this approach there

will be always be manufacturer aims to meet the optimum

machining operating parameter. The present work aims arebetter product surface roughness and good cooler chips.

The type of quadratic loss function applied for this

purposes is smaller-the-better, which target value is zero

and the level that optimizes the mean has been chosen.

Percent contribution ρ (rho) determine thecontribution of a factor to an effect. Error refers to

unknown and uncontrolled factors. If the percent

contribution due to error is low (15% or less), then it can be

assumed that no important factors have been omitted from

the experiment. If the percent contribution due to error is

high (15% or more), then it can be assumed that some

important factor have been omitted, condition were not

well controlled or there was a large measurement error. The

optimum parameter for each performance analysis is

determined from response table as shown in Table 4. The

TPM Pareto ANOVA in percentage is shown in Figure 4.

The minimum value of TPM is chosen as the optimum

level for each factor.

Table 4: The response table of surface roughness

performance

TPM A B C D

Level 1 1.185 0.483 0.475 0.615

Level 2 0.822 1.047 0.676 0.758

Level 3 0.582 1.060 1.439 1.217

Range 0.703 0.398 0.480 0.444

SSQ 1.108 1.305 3.103 1.186

Rank 4 2 1 3

Opt A3 B1 C1 D1

Figure 2: The Photographic view of experiment setup



Figure 4 shows factor which most affects theperformance of surface roughness was feed rate (43.75%

contributed), follow by depth of cut (17.91%), and type of

cooling (16.02%) and lastly was cutting speed (15.08%).

Error of the test is below 15%, it can be assumed that the

condition is under controlled and the optimum parameter

selection as shown in table 4.

From the response table the optimum set of conditions

was then selected by choosing all factors levels with the

lowest percentage of defectives since the percentage of

defectives is a smaller-the-better quality characteristic. In

order of ranking, the optimum condition is therefore C1, B1,

and D1 and lastly is A3.

Figure 4: TPM Pareto ANOVA in percentage

Therefore the chosen level that can minimizes the

value of TPM, which is at cutting speed of 10610 rpm,

depth of cut of 0.5mm, feed rate of 0.05mm/tooth and for

cooling mode was MQL. Result from confirmation

experiment was 0.122µm as shown in Table 5. From the

Figure 3 the lowest depth of cut gives the most optimum

surface roughness value. The good combination with using

the lowest depth of cut, highest cutting speed and MQL

cooling system gives more influence to get the best result

for surface roughness. The result shows that the surfaceroughness increased with the lowest in cutting speed while

the feed rate give more effect to surface roughness which

contributed the highest ranking between the other factors.

Table 5: The value of surface roughness results during

confirmation experiment.

Exp. A B C D TPM

OP C1 10610 0.5 0.05 MQL 0.122

OP C2 10610 0.75 0.05 Air 0.2466

MQL appeared to be effective in reducing surface

roughness. However, it is evident that MQL improves

surface finish depending upon the work – tool materials and

mainly through controlling the deterioration of the auxiliary

cutting edge by abrasion, chipping and built-up edge

formation.

The quality of the surface plays a very important role

in the performance of milling as a good-quality milled

surface significantly improves fatigue strength, corrosion

resistance, or creep life. Surface roughness also affects

several functional attributes of parts, such as contactcausing surface friction, wearing, light reflection, heat

transmission, ability of distributing and holding a lubricant,

coating, or resistant fatigue. Therefore, the desired finish

surface is usually specified and the appropriate parameters

are selected to reach the required quality. The chip deforms

when cutting tool travel at certain velocity as workpiece is

increased. Therefore with this chip formation determined

the machining performances can be determined where it is

relevant to this present work.

Figure 3: The graph of data distribution of experiment.



An appropriate combination of cutting speed, feed rate

and depth of cut will enhance the tool life as well as

maintain a good quality of machined surface. The chip

formation mechanism, during the machining is mainly

influenced by cutting speed. Increases in cutting speed

results in the decreases in saw toothed chip. At highercutting speed, the mechanism of deformation on shear

plane involves local weakening of material due to intense

heat generation. From figure 5 shows that the chip obtained

in the case of MQL are much smaller than those obtained

under different cutting conditions.

Chip produced in dry cutting modes is the longer and

bigger. It is because workpiece softening close to the

cutting zone, which makes easier, chip formation. However,

at increases cutting speed, chip formation is largest for air

cutting than dry cutting. It is because increase cutting speed

did not allow an increase efficiency of the fluid coolingeffect and so the workpiece became heated and lost some of

its strength and hardness, even with cutting fluid. Therefore,

MQL proved its ability between dry and air coolant.

Figure 5: Chip formation in experiment

4. CONCLUSION

Based on the results of the present experimental

investigation the following conclusions can be drawn:

i. The surface roughness is better when machining

using the MQL system compared with the dry and

air method because MQL provides the benefits

mainly by reducing the cutting temperature which

improves the tool-chip interaction. This is mainly

due to reduction in feed rate, axial depth of cut and

radial depth of cut and increasing the cutting speed.

ii. MQL continues solid stream provided reduced tool

wear, and better surface finish as compared to dry

and air machining of steel.

iii. From the Taguchi’s robust design method, smaller

depth of cut (0.5mm), lower feed rate

(0.05mm/tooth), and high cutting speed (10610rpm)

can produce smaller surface roughness in slot

milling of die steels.

iv. Surface roughness increased with the increase of the feed rate.

v. Chip formation depending on the cutting speed;

when machining with the cutting speed around

10610rpm or above, the chip formation produces

are much thinner compared with the chip produced

by machining with lower cutting speed slower.

ACKNOWLEDGMENT

The authors would like to thank University of Malaya, who

provided the research fund for this project, as well as a

scholarship.

REFERENCES

N.R. Dhar, M.T. Ahmed, S. Islam (2007). An

experimental investigation on effect of minimum quantity

lubrication in machining AISI 1040 steel. International

Journal of Machine Tools & Manufacture, volume 47, pp

748 – 753.

N.R. Dhar, S. Islam, Improvement in machinability

characteristics and working environment by minimum

quantity lubrication, CASR Project Report, BUET, Dhaka,

Bangladesh, 2005.

Klocke F, Eisenblatter G(1997) Dry cutting. Ann

CIRP 46(2):519 – 5267. Toenshoff HK, Arendt C, Ben

Amor R (2000) Cutting hardened steel.Ann CIRP 49(2)

Dural U. Braga, Anselmo E. Diniz, Gilberto W.A.

Miranda, Nivaldo L. Coppini, Using a minimum quantity

of lubricant (MQL) and a diamond coated tool in the

drilling of aluminum-silicon alloys, Journal of Material

Processing Technology, Vol. 122, 2002, pp. 127-138.

Thanonsak Thepsonthi, Investigation into minimal

cutting fluid application in high speed milling of hardened

steel using carbide mills, M. Eng. Dissertation, UM,Malaysia, 2005.

AUTHOR BIOGRAPHIES

First Author is a student at the Department of Engineering

Design and Manufacture, Faculty of EngineeringUniversity of Malaya, Kuala Lumpur, Malaysia. She can be

reached at <[email protected]>

mailto:[email protected]

mailto:[email protected]

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UMIES Paper Nadia 2