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
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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 (
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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
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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.
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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
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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 4000 rpm, 100 mm/min and 5 mm depth of cut 54
Specimen at 500 rpm, 100 mm/min and 1 mm depth ofcut 55
Specimen at 500 rpm, 250 mm/min and 1 mm depth of cut 55
Specimen at 500 rpm, 400 mm/min and 1 mm depth of cut 55
Specimen at 500 rpm, 100 mm/min and 3 mm depth of cut 57
Specimen at 500 rpm, 250 mm/min and 3 mm depth of cut 57
Specimen at 500 rpm, 400 mm/min and 3 mm depth of cut 57
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Items Page
Figure 4.9 Specimen at 500 rpm, 100 mm/min and 5 mm depth of cut 59
Figure 4.10 Specimen at 500 rpm, 250 mm/min and 5 mm depth of cut 59
Figure 4.11 Specimen at 500 rpm, 400 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 4.13 Specimen at 500 rpm, 100 mm/min and 1 mm depth of cut 62
Figure 4.14 Specimen at 3500 rpm, 100 mm/min and 3 mm depth of cut 63
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 4.18 Graph ofRa (/lm) vs. spindle speed (rpm) for 3 mm depth of cut 71
Figure 4.19 Graph ofRa (/lm) vs. spindle speed (rpm) for 5 mm depth of cut 73
Figure 4.20 Graph ofRa (/lm) vs. spindle speed (rpm) for 400 mm/min feed 75
rate
Figure 4.21 Graph ofRa (/lm) vs. spindle speed (rpm) for 1 mm depth of cut 77
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
Figure 4.26 Specimen with 500 rpm, 400 mm/min and 3 mm depth of cut 82
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Items Page
Figure 4.27 Specimen with 500 rpm, 250 mm/min and 1 mm depth of cut 83
Figure 4.28 Specimen with 500 rpm, 250 mm/min and 5 mm depth of cut 83
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).
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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 3.3 Ra (in Ilm) result table for experiment under 3 mm depth of cut 71
Table 3.4 Ra (in Ilm) result table for experiment under 5 mm depth of cut 73
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
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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
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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
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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
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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
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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.
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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.
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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
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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]
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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]
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-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
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Figure 1.3: Basic milling cutters and operation [I]
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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
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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
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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]
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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.
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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.
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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]
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