the study on milling machining for aluminum alloy

THE STUDY ON

MILLING MACHINING FOR

ALUMINUM ALLOY

GOHHANWEI

This project is submitted in partial fulfillment of

the requirements for the degree of Bachelor of Engineering with Honors

(Engineering in Mechanical and Manufacturing Systems)

Faculty of Engineering

UNIVERSITI MALAYSIA SARAWAK

2004

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

ACKNOWLEDGEMENT

The author would like to acknowledge several people who contributed significantly their

undisputed support during the author final year project.

Special thanks are due to author respectful supervisor, Mr. Abdullah Bin Haji Yassin that

guides him thoroughly within his thesis report. Without his supreme guidance, this thesis

would not have been produce.

Deep thanks to all dedicated mechanical lab assistants that willing to share their precious

experience on machining method and troubleshooting.

The author is grateful to all Faculty of Engineering staff that is so supportive and helpful.

Appreciation to author course-mates and especially his housemate that is not hesitating to

give their precious advice on the author final year project.

Finally, to author beloved family that always backs him up. Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

ABSTRAK

Kajian ini mengkaji kesan kelajuan putaran, kadar suapan dan kedalaman pemotongan

keatas kemasan permukaan pada aluminium aloi. Eksperimen ini dijalankan melalui

operasi pengisaran berlandaskan pembolehubah seperti diatas dengan menggunakan mesin

pengisar CNC. Kemasan permukaan telah diguna secara meluas di sektor industri dan

pad a umumnya untuk mengkuantitikan kelicinan permukaan. Kualiti permukaaan

memainkan peranan penting dalam meningkatkan daya fatig dan daya ketahanan produk

terhadap kakisan. Secara am, kekemasan permukaan operasi mengisar adalah dipengaruhi

oleh faktor seperti kelajuan putaran, kadar suapan, kedalaman pemotongan, criteria bahan

kerja, pinggir terbina, kehausan mata alat dan kestabilan mata alat, bahan kerja. Jenis

sepihan dihasilkan juga mempengaruhi kemasan permukaan hasil kerja dan operasi

permotongan (sebagai contoh hayat mata alat, dan getaran mesin). Jadi, kajian terhadap

sepihan besi juga menjadi amat penting. Akhimya, spesimen eksperimen tersebut

diperiksa dan nilai purate kemasan (Ra) diperolehi melalui mesin Stylus.

II

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

ABSTRACT

This research investigates the effect of the spindle speed, feed rate and depth of cut on

surface finish of aluminum alloy. The experiment is done by carrying out several milling

operation based on above parameters using CNC milling machine. Surface roughness is

widely used in industry and is generally to quantify the smoothness of a surface finish.

The quality of the surface plays a very important role in improving fatigue strength,

corrosion resistance, or creep life of product. Basically, surface finish in milling operation

is influenced by a number of factors, such as spindle speed, feed rate, depth of cut,

workpiece material characteristic, built up edge (BU£), tool wear and rigidity of the

machine tool, work piece set up. Type of chip produced will influences the surface finish

of the workpiece and the overall cutting operation (for instant tool life, vibration and

chatter). Thus, study on the chips produces is also important. Finally, specimen was

inspected and the value of average height roughness (Ra) for the surface is obtained using

Stylus Device.

111

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

,.

LIST OF FIGURES

Items Page

Figure 1.1 Vertical spindle knee and column type milling machine 3

Figure 1.2 Horizontal milling machine equip with automatic tool changer 4

Figure 1.3 Basic milling cutters and operation 5

Figure 1.4 Slab milling cutter 6

Figure 1.5 Up milling 6

Figure 1.6 Down milling 7

Figure 1.7 Face Milling Tools 8

Figure 1.8 End Milling Tools 8

Figure 2.1 The DOC and DOl of end milling cutting by vertical spindle 13

machine

Figure 2.2 Cutting force in peripheral milling 14

Figure 2.3 Cutting force in face milling 15

Figure 2.4 Surface finish ofmilling 18

Figure 2.5 Standard terminology and symbols 19

Figure 2.6 Categories of chip types 23

Figure 2.7 Cutter geometry 25

Figure 2.8 Form milling cutters 27

Figure 2.9 Vertical-milling cutter variety 28

Figure 2.10 PVD (TiN) 30

Figure 2.11 Cutting tool BUE 35

Figure 2.12 Cutting tool Plastic Deformation 35

IV

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

Items Page

Figure 2.13

Figure 2.14

Figure 2.15

Figure 2.16

Figure 2.17

Figure 2.18

Figure 2.19

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Figure 4.8

The typical wear pattern of a wedge-shape cutting tool 35

Force effect on tlank wear of machining hardened steel 36

Photographs of fractured teeth, nonnal; minor fracture; severe 37

fracture

Taylor Tool Life Theory 27

The graph plots the effect of cutting speed on tool pertonnance 38

when machining alloy steel

Chip predicted with simulation 41

Procedure and Step of Taguchi Parameter Design 42

Machine Description 48

Machine Clamping 49

2-tlute semi-finish end mill for preparing dimension 49

4-tlute finishing end mill for experiment cutting 50

6-tlute face mill for experiment cutting 50

Surfpak Device 51

Specimen at 4000 rpm, 100 mm/min and 1 mm depth of cut 53


Specimen at 500 rpm, 100 mm/min and 1 mm depth ofcut 55






v

~______I

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

Items Page

Figure 4.9 Specimen at 500 rpm, 100 mm/min and 5 mm depth of cut 59



Figure 4.12 Specimen at 4000 & 3500 rpm, 100 mm/min and 1 mm depth of 61

cut



Figure 4.15 Workpiece crack when tool breakage (left), tool breakage (right), 67

when machining under low spindle speed (500 rpm) and high

feed rate (250 mm/min).

Figure 4.] 6 Tool Clogging when cutting workpiece under low spindle speed 68

and high feed.

Figure 4.17 Graph ofRa (/lm) vs. spindle speed (rpm) for 1 mm depth of cut 70



Figure 4.20 Graph ofRa (/lm) vs. spindle speed (rpm) for 400 mm/min feed 75

rate


Figure 4.22 Graph ofRa (/lm) versus depth of cut (mm) at 100 mm/min 80

Figure 4.23 Specimen with 4000 rpm, 400 mm/min and 1 mm depth of cut 81

Figure 4.24 Specimen with 500 rpm, 400 mm/min and 1 mm depth ofcut 81

Figure 4.25 Specimen with 500 rpm, ] 00 mm/min and 3 mm depth of cut 82


VI

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

Items Page



Figure 4.29 Specimen with 100 mm/min and 1 mm depth ofcut with end 84

milling and face milling operation.

Figure 4.30 Specimen with 3500 rpm, 100 mm/min and 1 mm depth of cut at 85

both side but with different milling method, up milling (left),

down milling (right).

Vll

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

---~...-.~---------------------

LIST OF TABLES

Items Page

Table 2.1 General Recommendations for milling operations 13

Table 2.2 Outlines of factors that influence a cutting process 16

Table 2.3 Typical Properties of Tool Materials 32

rate

rate with I mm, 2 mm and 3 mm depth of cut respectively.

Table 2.4 General characteristic of Cutting Tool Material 33

Table 2.5 Operating Characteristics of Cutting Tool Material 33

Table 2.6 Allowable Wear Land 38

Table 2.7 Effect of fced rate on surface finish 39

Table 3.1 Chip Fonnation 64

Table 3.2 Ra (in Ilm) result table for experiment under 1 mm depth of cut 69



Table 3.5 Ra (in Ilm) result table for experiment under 400 mm/min feed 75

Table 3.6 Ra (in Ilm) result table for experiment under I mm depth of cut 77

Table 3.7 Ra (in Ilm) result table for experiment under 100 mm/min feed 79

Vlll

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

TABLE OF CONTENTS

ACKNOWLEDGEMENT

ABSTRAK

ABSTRACT

LIST OF FIGURES

LIST OF TABLES

CHAPTER 1 INTRODUCTION

1.1 Introduction

1.2 Machining Processes Used to Produce Various Shapes

1.2.1 Classification of Milling Machine

1.2.2 Type of Milling Machine

1.2.3 Milling Operations

1.3 Problem statement

1.4 Objective

1.5 Scope

1.6 Outcome

CHAPTER 2 LITERATURE REVIEW

2.1 Milling parameter

2.1.1 General Recommendations for milling operations

2.1.2 Cutting Force

2.2 Factor in milling process

2.3 Surface Integrity and Surface Finish

IX

ii

iii

iv

v

1

2

2

4

5

9

9

10

10

11

13

14

16

17

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

2.3.1 Surface Finish Parameters 19

2.4 The Mechanics Of Chip Formation 21

2.5 Cutting Tools 25

2.5.1 Milling Cutter Geometry 25

2.5.2 Milling Tool and Cutters Variety 26

2.5.3 Tool Selection 28

2.5.4 Tools Wear 34

2.5.5 Tools life 37

2.5.6 Allowable Wear Land 38

2.5.7 Optimum Cutting Speed 38

2.6 Workpiece 39

2.7 The Effects Of Temperature And Friction 40

2.8 Effects of Cutting Fluids 40

2.9 Thermal Fatigue Wear And Residual Coolant Effects 40

2.10 Current Trend 41

CHAPTER 3 METHODOLOGY

3.1 Introduction 44

3.2 Experimental Procedure 45

3.3 Working Procedures 45

3.4 Experiment Result Table 46

3.5 Safety Precautions 47

3.6 Experiment Apparatus 47

3.6.1 Machine 47

x

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

3.6.2 Clamp (Vice) 49

3.6.3 Tool 49

3.7 Equipment for Analysis 50

3.8 Expected Outcome 51

CHAPTER 4 RESULT AND DISCUSSION

4.1 Introduction 52

4.2 Discussion on result from visual inspection 53

4.2.1 End Milling 53

4.2.1.1 Type Of Surface texture And Chip Produce At High 53

Spindle Speed

4.2.1.2 Type Of Surface texture And Chip Produce At Low 55

Spindle Speed

4.2.2 Face Milling 61

4.2.2.1 Type Of Surface texture And Chip Produce At Different 61

Spindle Speed

4.2.2.2 Tool Mark Effect 63

4.3 Analysis 64

4.3.1 Chip Analysis 64

4.3.1.1 End Milling 64

4.3.1.2 Face Milling 66

4.3.2 Tool Analysis 67

4.3.2.1 Tool Breakage 67

4.3.2.1 Tool Clogging 68

Xl

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

4.4 Discussion on result from Roughness Average (Ra) test 69

4.4.1 End Milling 69

69 4.4.1.1 The Effect Of Different Spindle Speed And Feed Rate On

Ra Value

4.4.1.2 The Effect Of Different Depth Of Cut On Ra Value 75

4.4.2 Face Milling 77

77 4.4.2.1 The Effect Of Different Spindle Speed And Feed Rate On

Ra Value

4.4.2.2 The Effect Of Different Depth Of Cut On Ra Value 79

4.5 Discussion On Factor Affecting Surface Roughness 81

4.5.1 Spindle Speed 81

4.5.2 Feed Rate 82

4.5.3 Depth Of Cut 83

4.5.4 Cutting Operation 84

4.5.5 Cutting Method 85

CHAPTER 5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 87

5.2 Recommendations 88

REFERENCES 89

APPENDIX 92

Part A-E

XlI

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

- .....p----.......--~~

CHAPTER 1

INTRODUCTION

1.1 Introduction:

Human beings have been using tools to cut metal for hundreds of years without

really understand how the metal was cut or what was occurring where the cutting tool met

the metal. Machining is a process of removing unwanted material from a work piece in the

form of chips. [18]

Milling is one of the most versatile processes in metal removing. Milling uses a

multitooth cutter that rotates along various axes with respect to the work piece. Milling

includes a number of versatile machining operations, which are capable of producing a

variety of configurations using a milling cutter. [4]

Milling machining of aluminum has becoming a challenge for manufacturing

engineers in all fields since aluminum has rapidly growth in some exclusive industries

especially in aerospace and recently in automobile industry.

Much research and development work has been carried out in the area of milling

machining of aluminium alloys, titanium alloys, steels and superalloys regarding the effect

of cutting speeds on type of chips produced, cutting forces and power, temperature

generated, tool wear, surface finish and the process economics.

Surface roughness of a machined product could affect product's functional

attributes, such as contact causing surface friction, wearing, light reflection, heat

transmission, ability of distributing and holding a lubricant, coating, and resisting fatigue.

[27] This research will seek the parameter for better machining of aluminium alloys to

optimise tool life, reduce tools cost and better surface finish product quality.

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

1.2 Machining Processes Used to Produce Various Shapes (Milling)

In addition to producing various external or internal round profiles, cutting operations can

produce many other parts with more complex shapes. Several cutting processes and

machine tools are capable of producing these shapes using multitooth and single-point

cutting tooth. [1]

Milling is the process to generating machined surface by removing a predetermined

amount material progressively from the work piece. The milling process employs relative

motion between the work piece and the rotating cutting tool to generate required surfaces.

[6]

1.2.1 Classification of Milling Machine

Milling machines are generally identified by the types of construction and the

orientation of the spindle. Machines may be classes as 'knee and column' or as 'bed'

type, and the spindle may be horizontal or vertical. The main datum features of the

machine must be correctly aligned to ensure accurate machining.

Additional features may include swivel tables, swivel heads and slotting attachments.

[2]

Smaller milling machines are generally of the 'knee and column' type. The knee is

wound up and down on an elevating screw while the column is fixed. Larger milling

machines may be of the 'bed' type.

2

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

The cutting tools rotate and have many cutting edges (multi-tooth cutters). The work

piece is feed past the cutter to produce the required machined form. On vertical spindle

machines, the tool and spindle may be fed vertically for holes production.

W.rh ...'bll

f)ue--~'"

Figure 1.1: Vertical spindle knee and column type milling machine. (Source by G. Boothroyd)

Milling produces the following work piece features:

1. Flat vertical surfaces

11. Flat horizontal surfaces

lll. Closed or open slots

IV. Grooves

v. Holes and bores

VI. Cylindrical surfaces [2]

3

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

r

1.2.2 Type of Milling Machine

i. The Horizontal Milling Machine

Tools may be mounted directly

into the spindle, which IS

horizontal, or mounted on an

arbor that is supported at its end

to provide rigidity against the

cutting forces.

This is a robust, production

machine. It is fairly versatile and

can machine a number of faces at

one pass, however it cannot Figure 1.2: Horizontal milling machine equip with automatic tool changer. (Source

machine holes in the tope surface by Cincinati Milacron Inc.)

of the work piece. [2]

11. The vertical milling machines

Tools are mounted directly into the spindle that is normally vertical. Straight shank

tools are held in collets in a toolholder and retained by a drawbolt or cam-type

clamp arrangement.

On some machines, the vertical spindle may be set at an angle for complex

machining requirements. Attachments such as slotting heads provide further

machining capability. This is a very versatile machine and has largely superseded

the older horizontal type machines. [2]

4

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

-r I I

iii. The universal milling machine

This is a horizontal milling machines on which the machine table can be swivelled

for spiral/helical milling. Normally it is used with accessories, such as the dividing

head, for the production of complex components or special operations. It is

generally of lighter construction than the production-type horizontal machine. [2]

1.2.3 Milling Operations

Milling includes a number of highly versatile machining operations capable of

producing a variety of configurations with the use of a milling cutter, a multitooth tool

that produces a number of chips in one revolution. Among the milling methods are;

i. Slab milling 11. Face milling

iii. End milling IV. Single-piece milling

v. String or "gang" milling VI. Slot milling

vii.Profile milling viii. Thread milling

ix. Form milling x. Gear milling

i8; SIQb Ini~ I.b rare mlJhttl;

CULtft' I ~r

~-, , ',_ i I \

Figure 1.3: Basic milling cutters and operation [I]

5

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

i. Slab Milling

In slab milling, also called peripheral milling, the axis of cutter rotation is parallel to

the work piece surface to be machined. The cutter generally made of high-speed steel,

as number of teeth along its circumference, each tooth acting as a single-point cutting

tool called a plain mill. Cutting tool for slab milling may have straight or helical teeth

resulting in, respectively orthogonal or oblique cutting action the helical teeth on the

cutter shown below are preferred over straight teeth because the load on the tooth is

lower, resu Iting in a smoother operation and reducing tool forces and chatter. [1]

.--..---.'

Figure 1.4: Slab milling cutter [15]

The conventional milling, also called up milling, the maximum chip thickness is at

the end of the cut. [1] It is good practice with hard or abrasive skinned materials like

cast iron castings. However, The cutter tries to lift the workpiece, so rigid clamping is

required. [2]

r. or .. •~f'''

Figure 1.5 Up milling

6

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

For cl.imb milling, also called down milling, the chip produce is at its thickest. [1] The

direction of workpiece movement is in the same direction as relative tooth movement.

[2] The advantage is the cutting force holds the workpiece in place. [1] This makes it

particularly suitable for thin parts or those that are difficult to hold securely. The cutter

is heavi Iy loaded at the start to the cut, but the progression of the cut produces a better

surface finish. [2]

Figure 1.5 Down milling [15]

ii. Face Milling

In face milling, the cutter is mounted on a spindle having an aXIs of rotation

perpendicular to the work piece surface. It removes material in the manner shown in

figure below. Face milling cutter leaves feed marks on the machined surface due to

relative motion between the cutting teeth and the work piece. Thus, the surface

roughness of the work piece depends on insert corner geometry and feed per tooth.

The lead angle of the insert in face milling has a direct influence on the undeformed

chip thickness. As the lead angle increase, the undeformed chip thickness decreases (as

does chip thickness), and the length of contact increases. When lead angle decreases,

there is a smaller and smaller vertical force component. The relationship of cutter

7

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

diameter and insert angles and their position relati ve to the surface to mill is important

that it will determine the angle at which an insert enters and exits the work piece. [1]

Figure 1.7: Face Milling Tools [19]

iii. End Milling

Flat surface as well as various profiles can be produced by

end milling. From figure, the cutter has either straight of

tapered shanks for smaller and larger cutter sizes. The cutter

usually rotates on an axis perpendicular to the workpiece,

although it can be tilted to machine-tapered surfaces. End

mills are also available with hemispherical end (ball nose)

for the production of curved surfaces, such as die and

molds. Hollow end mills have internal cutting teeth and are

used to machine the cylindrical surface of solid round work Figure 1.8: End

pieces. Usually end mills are made of high speed steels or Milling Tools [19]

have carbide insert. [1]

8

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

r 1.3 Problem statement

In milling operation, the parameters such as spindle speed, feed rate and depth of cut play

an important role on the finishing product lead time, surface finish and tool life. Thus, as

an engineer, he is responsible to detect the optimum parameter of spindle speed, feed rate

and depth of cut for the intended use material. In this thesis, the material used is the

aluminum alloy that is stated to gain popularity among automobile and aircraft industry.

Due to aluminum has softer grades, it tend to form a built-up edge, resulting in poor

surface finish. High cutting speeds, high rake angles and high relief angles are

recommended. Wrought aluminum alloys with high silicon content and cast aluminum

alloy may be abrasive; they require harder tool materials. Dimensional tolerance control

may be a problem in machining aluminum since it has a high thermal coefficient of

expansion and relatively low elastic modulus. [1] A particular problem in the end milling

of aluminum is that of holding good surface finish on the sides of thin ribs, which tend to

deflect under cutter pressure. [4] Consequence, it is become crucial to distinguish the

effect of the spindle speed, feed rate and depth of cut in machining operations so that the

best approach can be identify.

1.4 Objective

To study the effect of spindle speed, feed rate and depth of cut on surface finish of milling

machining (face milling and end milling) for aluminum alloy. To study type of chips

produced and compare with the surface finish obtained. By identifying the obtained

surface finish result, future work will be easier by calculating the metal removal rate or

feed per tooth, the workpiece surface finish going to achieve become predictable.

9

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

~~-~----~~~~--------------

1.5 Scope

A total of 72 end-milling and 72 face milling experiments will be conducted using

different spindle speed, feed rate and depth of cut on aluminum alloy. The parameters used

are as below:

The range of spindle speed is from SOO to 4000 rpm

The range of feed rate from 100-400mm/min

The range of depth of cut from l-Smm

The depth of immersion is set at Smm.

Down milling method are used to enable better gripping of work piece and produce better

surface finish.

Machining factors such as work pIece material characteristics, tools wear, tools

temperature, cutting angles of the tool, rigidity of the machine tools and work piece set up

are neglected and assume to be constant.

The visual inspection is carried out to compare the cutting result. For achieving more

precise result, a detail analysis is conduct by using stylus device to determine surface

roughness (Ra) value.

1.6 Outcome

At the end of the experiment, effect of different spindle speed, feed rate and depth of cut

on the surface finish will be identified. In the same time, through graphical method, an

optimum set of spindle speed, feed and depth of cut on aluminum alloy will be achieve.

10

l

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

CHAPTER 2

LITERA TURE REVIEW

2.1 Milling parameter

The most important factors affecting the efficiency of a milling operation are cutting

speed, feed and depth of cut. [7]

1. The cutting speed, V, is the rate of material removal recommended by the tools

manufacturer and is given as metres of chip per minute. This is developed

experimentally and gives a good rate of cutting together with a reasonable tool life.

Exceeding the recommended cutting speed substantially shortens the tool life. [2]

Cutting speed, V = 7r DN

Where D is the cutter diameter and N is the rotational speed of the cutter. [1]

11. Spindle speed (rpm) (N)

= [Cutting speed (m/min) (V) x 1000] I [n x diameter of cutter]

Or

N= V x 1000 In x D [2]

Ill. The thickness of the chip in slab milling varies along its length because of the

relative longitudinal motion between cutter and work piece. For a straight-tooth

cutter, undeformed chip thickness (chip depth of cut), ie, by

tc = 2fdl D

where f is the feed per tooth of the cutter, measured along its work piece surface

and d is the depth of cut. As tc becomes greater, the force on the cutter tooth

Increases. [1]

11

Demo (

Visit h

ttp://

www.pdfsp

litmerg

er.co

m)

the study on milling machining for aluminum alloy

Documents