ANALYSIS OF SURFACE ROUGHNESS FOR END MILLING …

ANALYSIS OF SURFACE ROUGHNESS

FOR END MILLING OPERATIONS

by

EVELIO R. ARIAS, ING. MECANICO

A THESIS

IN

INDUSTRIAL ENGINEERING

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

IN

INDUSTRIAL ENGINEERING

Approved

May, 1983

f.^

J ,-

ACKNOWLEDGMENTS

I am deeply indebted to Dr. Brian K. Lambert for his direction of

this thesis. I express my gratitude to Dr. Lee Alley and Dr. James Smith

for their helpful criticism.

11

TABLE OF CONTENTS

PAGE

ACKNOWLEDGMENTS i i

LIST OF TABLES vi

LIST OF FIGURES vii

CHAPTER I. INTRODUCTION 1

Purpose and Scope 1

Review of Past Research Studies 2

Peripheral Milling 3

Face Mi 11 i ng 3

End Milling 3

End Mi 11 i ng Cutters 4

Methods of Specifying Surface Roughness 8

Surface Roughness in Peripheral

Milling 12

Surface Roughness in Face Milling 15

Factors Affecting Surface Finish 15

Feed 18

Cutti ng Speed 18 Depth of Cut 23 Tool Material 23 Tool Wear 24 Cutter Di ameter 24 Number of Teeth on the Cutter 25 Helix Angle 25 Method of Milling 27 Workpiece Materi al 27 Chatter 27

m

PAGE

Cutting Speed and Feed Interaction

Cutting Speed-Depth of Cut Interaction

Depth of Cut-Feed Interaction

Purpose

CHAPTER II. METHODS AND PROCEDURES ,

Materials, Methods, Equipment, and Experimental Design

Workpi ece Materi al ,

Machine ,

Profi1ometer

Cutti ng Tool s ,

Cutting Conditions ,

Cutti ng Speed ,

Depth of Cut ,

Feed Rate ,

Cutter Di ameter ,

Experimental Design ,

Experimental Procedure

CHAPTER III. EXPERIMENTAL ANALYSIS AND DISCUSSION...,

Data Analysis for Tool 1: Diameter 5/8 Inch


Data Analysis for Tool 3:

Diameter 1 Inch

CHAPTER IV. CONCLUSIONS AND RECOMMENDATIONS

Tool 1: Diameter 5/8 Inch

28

28

29

29

31

31

31

31

33

33

33

36

37

37

38

38

41

42

42

47

53

65

65

TV

PAGE


Tool 3: Diameter 1 Inch

Performance of Cutter Diameters

Recommendations for Future Research

REFERENCES

APPENDIX ,

Surface Roughness Data for Tool 1: Diameter 5/8 Inch ,

Surface Roughness Data for Tool 2: Diameter 3/4 Inch ,

Surface Roughness Data for Tool 3: Diameter 1 Inch ,

67

68

69

70

71

74

75

78

81

LIST OF TABLES

PAGE

Table 1. Values of Cutting Speed Used in the

Experiment 37

Table 2. Independent Variables 38

Table 3. Experimental Design for Any Tool

Diameter 40

Table 4. Anova for Tool 1 43



Table 7. Results of the Effects in Each Tool 64

Table 8. Favorable Conditions for Each Tool 69

VI

LIST OF FIGURES

PAGE

Figure 1. Standard End Mill With Taper Shank 5

Figure 2. Multiple Tooth End Mill 5

Figure 3. Two-Lip End Mill 6

Figure 4. Shell End Mill 7

Figure 5. End Mill Geometry 7

Figure 6. Approximate Range of Roughness of Machine

Operations and Materi al s 9

Figure 7. Machined Surface Profile 11

Figure 8. Tooth Marks in Peripheral Milling 13

Figure 9. Surface Roughness in Face Milling 16

Figure 10. Feed Marks 17

Figure 11. Effect of Feed on Surface Roughness 19

Figure 12. Effect of Cutting Speed on Cutting Forces 21

Figure 13. Effect of Cutting Speed on Surface Roughness 22

Figure 14. Effect of Helix Angle on Surface Roughness

for Different Feed Rates 26

Figure 15. Workpi ece Material Used in the Research 32

Figure 16. Milling Machine Used in the Research 34

Figure 17. Profilometer Used in the Research 35

Figure 18. Cutting Speed-Feed Interaction for Tool 1: Diameter 5/8 Inch 45

Figure 19. Speed-Depth of Cut Interaction for Tool 1: Diameter 5/8 Inch 46

Figure 20. Feed-Depth of Cut Interaction for Tool 1: Diameter 5/8 Inch 48

v n

PAGE

Figure 21. Speed-Depth of Cut Interaction for Tool 2: Diameter 3/4 Inch 51

Figure 22. Feed-Depth of Cut Interaction for Tool 2: Diameter 3/4 Inch 52

Figure 23. Cutting Speed-Depth of Cut Interaction for Tool 3: Diameter 1 Inch 55

Figure 24. Feed-Depth of Cut Interaction for Tool 3: Diameter 1 Inch 57

Figure 25. Surface Roughness Average Versus Cutting Speed 58

Figure 26. Surface Roughness Average Versus Feed Rate 59

Figure 27. Surface Roughness Average Versus Depth of Cut 61

Figure 28. Surface Roughness Average Versus Cutting Speed for Different Cutter Di ameters 62

Figure 29. Surface Roughness Versus Cross-Secti onal Area 63

vm

CHAPTER I

INTRODUCTION

Purpose and Scope

Milling operations are one of the most widely used processes in the

machining of metals. Many parts are designed such that they must be

processed on milling machines in at least one stage of their fabrication

(12). Part design and specification, along with economical and quality

reasons, make the study of the finish of a milled surface important.

The process of generating a milled surface is affected by several

factors, some of them, namely the cutting conditions and tool geometry,

are of primary importance in determining the quality of a milled surface.

An important tool variable in milling operations is cutter diameter,

since it has been demonstrated that better surface finish is produced

when the cutter diameter is increased (25). Therefore, cutter diameter

and cutting conditions should be investigated in any surface finish

study.

Past research studies on milling and similar operations have focused

on the different aspects of tool performance, forces involved in the

process, and on the resulting surface roughness (9, 11, 15, 16, 17, 19,

29). But, so far no investigation has been made to analyze the charac

teristics of surface roughness in milling operations considering various

factors simultaneously in order to evaluate their main effects, as well

as their interactions.

In this research, a study of the surface roughness produced in end

milling of AISI 4140 cold rolled steel, using high speed steel tools, was

undertaken. This study assesses the process variability with respect to

surface roughness, using different cutting conditions with three

different tool diameters.

For this study a 4x4x3 factorial experiment was performed for each

tool (four levels of cutting speed, four levels of feed rate, and three

levels of depth of cut) with three replications for each combination,

resulting in a total of 144 experimental points for each tool and a total

of 432 trials for the three tools.

A statistical analysis was performed to assess and compare the ef

fects of the three independent variables for each tool. Center line aver

age (CLA) values of surface roughness were measured as the dependent

variable. After the analysis, conclusions were drawn and recommendations

are given. In addition, the practical significance of the findings were

evaluated.

Review of Past Research Studies

Milling is a machining operation through which a machined surface is

obtained by progressively removing a predetermined amount of material

from a workpiece, which is advanced at a relatively slow rate of movement

or feed, to a milling cutter which is rotating at a comparatively high

speed (1). Since milling operations are performed by using different

types of cutters and machine configurations, they have been grouped

according to two main operations: peripheral and face milling operations.

Peripheral Milling

Peripheral milling generates surfaces that are parallel to the cut

ter axis (1). When the peripheral velocity is in the opposite direction

to the feed, the process is called conventional, or up-milling. In this

case, the undeformed chip thickness is zero at the start of the cut and

increases to maximum value just before the tooth disengages the

workpiece. When the cutter velocity and the feed are moving in the same

direction, the process is called climb, or down-milling; the chip

thickness will have a maximum value just after the cut is started, and

will drop to zero at the end of the cut (4).

Face Milling

Face milling is performed by cutting edges on the periphery and the

end of the cutter. The surface generated is usually at right angles to

the cutter axis. In face milling, the maximum chip thickness is obtained

at the center of travel and decreases toward the end of the tooth

engagement (4). Face milling is a very efficient operation because the

metal removal rate is high in comparison with single point tool cutting

(8).

End Milling

End milling can be considered as a combination of peripheral and

face milling where a multiple tooth cutter with straight or helical teeth

is used (1).

End Milling Cutters

End milling cutters are tools with teeth on the circumferential

surface and on one end. End milling cutters are made in three general

types:

1. Multiple Tooth End Mill

With straight or helical teeth, these cutters are used for

light operations such as the milling of slots and profiling and

facing of narrow surfaces. This type of cutter is shown in

Figures 1 and 2.

2. Two-Lip End Mill

This type of milling cutter is also known as a slotting

mill and has two straight, or helical, teeth on the circumfer

ential surface and end teeth cut to the center. In milling

grooves, this cutter can be sunk into the material like a drill,

and then fed lengthwise in the groove. This type of cutter is

shown in Figure 3.

3. Shell End Mill

Shell end mills are solid, multiple-tooth cutters having

teeth on the face and periphery, and are made without a shank.

The teeth are generally helical, with either a right- or

left-hand helix. The teeth may also be cut parallel to the axis

of rotation. These cutters are used in face milling operations

requiring the milling of two surfaces at right angles to each

other. Figure 4 shows a milling cutter of this type. The geome

try of an end milling cutter is shown in Figure 5.

Figure 1. Standard End Mill With Taper Shank (D

Figure 2. Multiple Tooth End Mill (D

Figure 3. Two-Lip End Mill (1)

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Chamfer or Rounding

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Figure 4. Shell End Mill (1)

Radial Rake Angle

Radial Relief Angle

Corner

Helix Angle

Radial Relief Angle

Figure 5. End Mill Geometry (1)

8

Methods of Specifying Surface Roughness

The surface finish of a machined part is described, basically, by

waviness and roughness. Waviness refers to irregularities on the surface

produced by machine or workpiece deflections, vibrations, and other ir

regularities in the cutting process. Roughness is an ideal effect that

results from the geometry of the tool, feed, speed, feed-speed interac

tion, and the condition of the plastic flow of the material removed.

Roughness must be considered as superimposed feed marks on a wavy surface

(1, 2, 7, 11, 18, 20). The final surface roughness, obtained during a

practical machining operation, may be considered as the sum of the two

independent effects mentioned above.

The ideal surface roughness is the best possible finish obtainable

for a given set of tool geometry and cutting conditions, if a built-up

edge, chatter, inaccuracies in machine tool movements, and other factors

were completely eliminated.

Surface finish quality is a relative term since it varies from one

spot to another, even under the same operating conditions; therefore,

when surface finish quality is referred to, it must be specified in a

certain range of performance. Figure 6 shows some approximate ranges of

roughness of machining operations and materials (22). Readings of surface

roughness also vary with a change in direction of the stylus of the

measuring instruments. Waviness varies from one machine to another, even

of the same kind, due to different levels of dynamic stability (8).

Surface finish of machined surfaces follow different patterns ac

cording to the operations performed; thus, differences within machining

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operations are found when using single point tools, as in turning opera

tions, and multiple tooth tools, as in milling operations. In addition,

in milling operations, differences exist within operations because of the

tool geometry or the way the material is fed.

There are several methods of specifying the surface roughness of a

machined surface; one is the root mean square (RMS), which is the root

mean square average of the surface variations above and below a

hypothetical nominal or mean surface line. It is expressed in microinches

or micrometers. If a cross-section were made of a typical surface, the

irregularities would appear somewhat as illustrated in Figure 7. Since an

average of the extreme heights and depths of the roughness would not

represent a true average of the irregularities, a root mean square aver

age of all the individual irregularities is used as a basis for roughness

measurement. In Figure 7, if a horizontal line, A-B, is drawn represent

ing the center line of the surface generated, and a, b, c, d, e, etc.,

represent the distances of the irregularities from the center line, then

the root mean square is obtained as follows:

RMS = a^ + b^ + c^ + d^ + e^ ... (1)

n

where: a, b, c, ..., are irregular values measured from the center line

n = number of values used

The root mean square is also expressed as:

RMS = -; L

1 r ..2 y dx (2)

11

B

Figure 7. Machined Surface Profile (23, 24)

12

where: L = the length of the surface measured, which depends on the kind

of machining operation

y = irregularities

dx = distance along L

Another method used to specify surface roughness is the center line

average (CLA) or arithmetical average (AA), which is expressed in micro-

inches or micrometers as follows:

CLA or AA = 1

L n .

dx (3)

Other practical methods less frequently used are:

a) the maximum peak-to-valley height, which is the root-to-crest

value of roughness,

b) visual comparison,

c) single parameter methods, and

d) profile graphing.

Surface Roughness in Peripheral Milling

In peripheral milling, tooth feed marks are found superimposed on

waviness; they are approximately parallel to the axis of the cutter,

spaced at a distance equal to the feed per tooth. Figure 8 shows surface

roughness in peripheral milling. Since in milling, more than one cutting

edge is removing material, a milled surface is the result of the combina

tion of several surfaces generated by individual teeth.

13

Tooth Marks

One Revolution

Figure 8. Tooth Marks in Peripheral Milling

When the trochoidal tooth path is considered, Martellotti (8'

peak-to-valley height to be given by:

" - ^ (4) f. N.

where: f. = feed per tooth

R = radius of the cutter

N. = number of teeth

h = peak-to-valley height as defined above.

The positive sign is used for up-milling and the negative sign for

down-milling. If a circular path is considered, the peak-to-valley height

is:

(f ' ) ^ h = -^ (5)

8R

where: f.' = true feed per tooth = f. cos X

X = helix angle

Rewriting Equation (5), we obtain:

(f. cos X)^ h = — ^ (6)

8R

This equation shows the relationship between the peak-to-valley

height, feed per tooth, helix angle, and the cutter radius. Also, it can

be observed that the peak-to-valley height increases with an increase of

the feed per tooth and helix angle, and decreases with an increase of the

cutter radius.

t "t X

8(R + "~r~)

Thus,

h = 5 (8) tan 0^ - cot 9^ c s

where: h, f. is as mentioned above

9 is the corner angle (degrees)

9 is the rake angle (degrees).

If a corner radius exists, the theoretical surface roughness is given as

a function of the nose radius.

Factors Affecting Surface Finish

As mentioned before, surface roughness occurs from tooth marks left

when machining a surface. The tool marks are affected by the different

factors that are present in the cutting operation. Some of these factors

are: tool geometry, workpiece material, and cutting conditions. The qual

ity of the surface finish in milling operations has been related to:

15

Surface Roughness in Face Milling

In face milling, feed marks are similar to those in a turning opera-

tion since tool geometries are comparable. In face milling, the tooth j

must traverse the finished surface before it begins the next cut so that 5 m

further interference (and feed marks) may result (4, 7). Figure 9 •

schematically illustrates surface roughness in face milling. Figure 10

shows the theoretical feed marks generated in face milling. The

peak-to-valley height equation is obtained from the geometry on Figure 10

as follows:

h - tan 9^ - h cot 9^ = f . (7) c St

>

16

e f<:\ 9

..Lv i 1 '^t Interfering Feed Marks

Section X

Figure 9. Surface Roughness in Face Milling (2)

17

n

Feed

Figure 10. Feed Marks (2)

tooth spacing, feed per tooth, diameter of the cutter, method of milling,

difference in teeth heights of the cutter, chatter conditions, favorable

conditions for the formation of built-up edge, and arbour deflections.

The effect of these variables on surface roughness, as stated by various

researchers, are discussed in the following sections.

Feed

It has been observed that, in general, surface finish deteriorates

when feed rate is increased. The effect of feed on surface roughness, for

two different cutting speeds, in a turning operation is shown in Figure

11. Martellotti (8) showed the relationship between the feed per tooth

and the peak-to-valley height when a surface is machined in face and

peripheral milling operations. Galloway (28), in his study of the effect

of feed on surface roughness, observed that there was a lower limit of

feed at which any further decrease in feed would not improve the surface

roughness.

Cutting Speed

Cutting speed is another factor of great importance in the cutting

process. It takes direct action on chip formation, forces, and tempera

ture; therefore, the kind of chip obtained depends on the cutting speed,

and the kind of chip formed affects surface finish.

Cutting forces first increase with increasing cutting speed up to a

maximum value, then decrease with a further increase in cutting speed,

tending to become constant at high cutting speeds. The high forces at low

cutting speeds are attributed to the welding occurring between the tool

and the chip, thus forming a built-up edge. At high cutting speeds.

19

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Figure 11. Effect of Feed on Surface Roughness (27)

20

forces decrease due to a continuous reduction in the size of the built-up

edge, thus causing an improvement in the surface finish obtained (5, 7,

10, 26). Figure 12 shows how cutting forces are affected by cutting

speed.

Chandiramani and Cook (20) found that changes in the cutting speed

during orthogonal cutting operations cause the formation of three types

of chips; these are: continuous chip, continuous chip with a built-up

edge, and discontinuous chip. They also showed, that at low cutting

speeds, chips are discontinuous and surface finish is poor due to the

successive cracking of formed chips caused by the variation in forces.

The effect of cutting speed on surface finish is shown in Figure 13.

The response of surface roughness with increased cutting speed can be

described by three zones. Zone A represents an increase in speed which

causes improvement in surface finish. Zone B represents a range where, if I —

speed is increased, surface finish deteriorates due to the formation of

chips with a built-up edge^This is called the transition zone. After the

transition zone, any increase in speed causes improvement in surface

finish, represented by Zone C in Figure 13.

It has been proposed (15) that all welds between tool and chip occur

because of high pressure at low speed. Thus, it seems that by increasing

cutting speed a better surface finish is obtained. However, as speed

increases there occurs an increase in temperature which facilitates the

formation of a built-up edge. The possibility of built-up edge occurrence

is increased as the ductility of the workpiece material increases since

friction is increased and continuous chips are retarded; hence, poor

surface finish is obtained. Often, this effect is lessened by using a

21

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1 n z

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o i-o c

2 '3

Cutting Speed

Figure 12. Effect of Cutting Speed on Cutting Forces (26)

n X

Cutting speed

Figure 13. Effect of Cutting Speed on Surface Roughness (20)

large rake angle or cutting fluids that facilitate chip flew or decrease

friction (31).

The effect of chip type on surface finish is described as follows: a S

continuous chip with no built-up edge is desirable because it indicates J

that steady cutting conditions exist, hence better surface finish is j *

obtained. Discontinuous chips create force fluctuations which would 8

originate greater marks on the machined surface. The least desirable type

is a continuous chip with built-up edge.

Depth of Cut

Previous investigations on the effect of depth of cut on surface

finish indicate that as depth of cut increases, surface roughness also

increases when operating at low speeds; the contrary occurs when opera

ting at higher speeds (14). The reason for this effect has not been com

pletely established, although some authors believe that it is caused by

temperature conditions at high speed (28).

Tool Material

It has been observed that surface roughness varies with tool mate

rial (3, 4, 20). The key to producing better surface finish with any tool

is the wear resistance at high cutting speed. High speed steel produces

good surface finish when moderate cutting speeds are used. Cemented

carbide tools are manufactured in various grades for machining cast iron,

steel, and steel alloys. These grades are divided into light, medium, and

heavy duty applications by increasing the toughness with a decrease in

hardness. Light duty carbide grades have high hardness and low toughness.

This grade is used for finish machining operations, permitting the use of

n X

high cutting speeds, which in turn produce good surface finish,

carbide cutting tools are made by depositing a very thin layer of a

resistant material on a cemented carbide substrate, resulting in improved

wear resistance of the tool and improved surface finish when compared to

cemented carbide. Ceramic coated tools have a high wear resistance at

elevated temperature and high resistance to chemical reaction, thus >

permitting much higher cutting speeds under otherwise identical condi

tions than do uncoated tools. Such cutting speeds produce considerable

improvement in surface finish. Superior surface finish is produced with

ceramic tools, which permit extremely high cutting speeds without loss of

tool life (23, 33).

Tool Wear

For a fixed set of conditions, surface roughness changes more or

less proportionally to the cutting time. Flank wear changes the tool

form, resulting in changes in the expected surface finish and dimensional

accuracy of the workpiece. Tool wear increases with cutting time, with a

pronounced accelerated rate at the beginning. Following this "break-in"

period, tool wear increases in a linear manner. The two most important

types of wear that behave in this manner are flank wear and crater wear.

These two types of wear are taken as the tool life criterion by specify

ing a certain amount of acceptable wear (13). The amount of wear permit

ted can also be specified by the required surface finish.

Cutter Diameter

From the geometry of the cutting process in milling operations, it

has been established (8) that surface roughness is related to the cutter

25

diameter, as indicated in Equation (5). The general observation is that

as cutter diameter increases the surface finish improves.

Number of Teeth on the Cutter

One important factor, affecting cutting conditions in milling opera- -' r

tions, is the number of teeth on the cutter. Kuljanic (3) investigated • n

tool life as a function of the number of teeth on the cutter. The tool

life of the cutter was found to decrease as the number of teeth on the

cutter increases. The temperature on the cutter body, and on the work-

piece, increases as the number of teeth on the cutter increases (34).

Nee, Wong, and Chan (9) found that in face milling, a cutter with more

teeth produces a better finish, and for peripheral milling, better sur

face finish is obtained with a greater number of teeth with a large helix

angle.

Helix Angle

Figure 14 illustrates how surface roughness varies with helix angle

for different feed rates (9). Some improvement in surface finish is ob

tained by increasing the helix angle at lower feed rates. At higher feed

rates, better finish is obtained when a large helix angle is used.

Other causes of variation in surface finish, related to the tool in

milling operations are:

1. Variation in tooth spacing, which is determined by the manufac

turer of the tool.

2. Variation in the distance of the cutting edge of the teeth from

the center of the cutter rotation. It produces high and low

teeth in the cutter, due to inaccuracies in cutter sharpening.

26

0.50

cr* 0,40

0.30

0,20

0.10

n

Helix Angle o 25*' X 35^

A 55®

L ._ !

n X

10 20 30

S (mm/min)

Feed Rate

40 50

Figure 14. Effect of Helix Angle on Surface Roughness for Different Feed Rates (9)

27

Method of Milling

The method of milling influences the peak-to-valley height. Martel

lotti (8) showed that improved surface finish is obtained in peripheral

milling with up-milling, which is indicated by the positive sign in the

denominator of Equation (4). In down-milling, the negative sign in the

denominator indicates that the peak-to-valley height is greater than for

up-milling. Sabberwal (24) showed that in down-milling, the cutting

forces are generally higher than in up-milling. He also showed that in

down-milling, the specific and mean cutting pressures are higher than in

up-milling. It is possible that these increases in force and pressure

deteriorate surface finish in down-milling.

Workpiece Material

The relation between the Brinell hardness number and roughness has

been investigated using steel (6, 21). In general, roughness decreases as

the Brinell hardness number increases (6). Very little attention has been

devoted to the effect of workpiece material in milling operations using

surface finish as the response.

Chatter

Chip formation is also affected by vibration produced in machining

operations. In milling operations, chatter is a condition of resonant

vibration in which the cutter and the workpiece move with respect to each

other at a frequency of one or more elements of the machine. When this

condition has been established, the interaction of cutter and workpiece

sustains the vibration at this frequency (1).

X

28

Chatter conditions can vary with the number of teeth on the cutter.

Chatter is one cause of poor surface finish. Its occurrence can be mini

mized by locating the cutter and workpiece as close as possible to the ^^

spindle, or by variation of the cutting conditions. Cutting conditions H n X

may be varied by: increasing the feed per tooth, reducing the cutting r s

speed, reducing the length of the cutting edge in contact with the work, |

reducing the clearance angle, or providing negative rake angles which

reduce, or eliminate, chatter conditions (1, 19, 32).

Cutting Speed and Feed Interaction

Often, the combined effect of two or more factors is different from

that of each factor alone. Therefore, the consideration of two or more

factor interactions can be important in determining cutting conditions

that allow the best surface finish.

The combined effect of cutting speed and feed on surface finish has

been investigated for fine turning and the results indicate that better

surface finish is obtained with a combination of large cutting speed and

low feed (4, 10). However, no investigation has been done on the combined

effect of cutting speed and feed on surface roughness in the case of end

milling operations.

Cutting Speed-Depth of Cut Interaction

It was stated that for a turning operation, an increase in both the

cutting speed, as well as depth of cut, improves the surface finish (35).

However, a combined increase of both of these variables beyond certain

limits may cause poor surface finish due to vibration. At higher cutting

speeds, and at smaller feeds, if the depth of cut is increased, an

29

increase in cutting force will occur (35). For end milling operations,

the combined effect of cutting speed and depth of cut on surface finish

has not been investigated. < 9 tt

H Depth of Cut-Feed Interaction

r

An increase in depth of cut has been found to improve the surface • i

finish in the case of turning operations, but an increase in feed would ^

deteriorate the surface finish. The size of the chip cross-sectional area

has a dominating effect on surface roughness (36). For larger chips, the

surface roughness is increased, due to higher friction, at the tool-chip

interface; the contrary occurs for smaller chips (19). For best results,

with respect to surface finish, a combination of a relatively large depth

of cut and a small feed should be used for turning operations. No

investigation has been reported to date to demonstrate the combined

effect of depth of cut-feed rate on surface finish, in the case of

milling operations.

Purpose

The specific purposes of this research were as follows:

1. To determine the main effect of cutting speed, feed, and depth

of cut on surface roughness in finish milling.

2. To determine the interacting effect of these variables on sur

face roughness in finish milling.

3. To compare the performance of three cutter diameters, with re

spect to surface roughness, for different levels of cutting

speed.

30

4. To establish a set of conditions at which favorable surface

roughness is attained for each tool diameter.

From the present study, it is possible to obtain a considerable t <

amount of information about the milling process that can be an aid for 1

the following: ! 5 s

1. Tool failure time may be recognized since the surface roughness S

will show an increase from the desired value if the tool begins

to show excessive wear.

2. Catastrophic tool failure can be avoided by detecting the reason

for the variation in the surface roughness.

3. The set of conditions determined from this study can be used as

a starting point to improve metal removal rate without sacri

ficing the quality of the machined surface.

The scope of this research was confined to the analysis of surface

roughness in finish end milling operations since it is one of the most

widely used machining processes in industry. In this study cutter dia

meters that are widely utilized were selected. To accomplish the proposed

objectives, a 4x4x3 factorial experiment was designed for each tool with

three replications per cell. A description of the experimental design and

procedure is presented in Chapter II. Chapter III is devoted to the

analysis of the experimental data. Chapter IV deals with the results,

conclusions, and recommendations for further research. The collected data

is presented in the Appendix.

CHAPTER II

METHODS AND PROCEDURES

Material, Methods, Equipment, and Experimental Design •:,

Workpiece Material '

i The workpiece material selected was AISI 4140 cold rolled steel. The

test specimens were taken from a 7 inch diameter bar and cut into

sections 4 inches thick. Two opposite sides of each specimen were

machined flat to insure rigidity of the mounted piece on the machine

table, as shown in Figure 15. The chemical composition of this material,

as supplied by the producer, is:

Carbon .40%

Manganese .99%

Chromium 1.02%

Silicon .29%

This material was selected for study due to its extensive use in the

manufacturing industry, such as aircraft parts, auto parts, and small

engine parts.

Machine

The machine used in this experiment was a general purpose, universal

milling machine, manufactured by Cincinnati Milling Maching Co., with a

15 H.P. motor. The table length was 79 inches and the width was 16

inches; the knee had a traverse movement capacity of up to 40 inches, and

the vertical movement capacity was up to 20 inches. The RPM range on this

31

32

<

t

I

Figure 15. Workpiece Mater ial Used in the Research

33

machine was from 18 to 1300 with 21 levels and the feed rate range was

from 5/16 to 60 inches per minute with 24 levels.

The head, mounted for this study, was a high speed universal milling

attachment which increased the RPM by a ratio of 1.66, transforming the

above speeds to a 30-2158 RPM range on the spindle. The milling machine

employed is shown in Figure 16.

Profilometer

The surface finish values were measured with a profilometer pilotor,

Bendix type VEG, model 26, 115 volt. This profilometer provided a digital

readout of surface finish in microinches, AA (Arithmetic Average). The

standard value of cutoff width of 0.03 inch was used. Figure 17 shows the

profilometer used in the experiment.

Cutting Tools

The tools employed in this study were general purpose, high speed,

steel end mills manufactured by Cleveland Twist Drill with the following

characteristics:

CUHER DIAMETER

5/8 inch

3/4 inch

1 inch

SHANK DIAMETER

5/8 inch

5/8 inch

5/8 inch

CUTTER LENGTH

1-1/2 inch

1-1/2 inch

1-1/2 inch

NO. OF FLUTES

2

2

2

Cutting Conditions

To determine a feasible range of cutting conditions, based on the

workpiece and tool materials, a total of 45 pilot tests were conducted.

34

Figure 16. Milling Machine Used in the Research

35

Figure 17. Profilometer Used in the Research

36

The pilot study resulted in a feasible range of 30 to 175 fpm for cutting

speed, 1 to 3-1/4 ipm for feed rate, and 0.01 to 0.03 inch for depth of

cut. The tests were conducted using the three cutter diameters of 5/8,

3/4 and 1 inch.

The experiments were conducted without using cutting fluid. The four

independent variables were: cutting speed, feed rate, depth of cut, and

cutter diameter. Details pertaining to the selection of the levels of

these variables are presented in the following sections.

Cutting Speed

It was not possible to select equal levels of speed for each tool

due to the limited spindle speeds on the machine. Thus, it was necessary

to select levels of cutting speed for each tool separately. From the

pilot tests performed, it was observed that cutting speeds lower than 30

fpm are not recommended since the quality of surface finish obtained was

very poor at levels of feed and depth of cut associated with finish

milling. At the same time, speeds larger than 175 fpm could not be used

since the tool wear tends to increase at a rapid rate, thus making it

impossible to use the same tool for the entire experiment. In addition,

large values of cutting speed, combined with relatively large depths of

cut and/or feed rates, can cause breakage of the entering teeth.

The different levels of speeds were selected in such a way that

approximately the same cutting speeds, in feet per minute, were obtained

for all three tools. The speed levels selected were values within the

range 30 fpm and 175 fpm. Also, these levels were the ones which are most

widely used in industry. The number of levels of cutting speed was

37

limited to four in order to minimize the cost of experimentation, without

sacrificing information regarding the effect of cutting speed on surface

finish.

Table 1 shows the levels of cutting speed in fpm selected for each

tool.

Table 1

Values of Cutting Speed Used in the Experiment

TOOL 1 TOOL 2 TOOL 3

VI 33.05 fpm VI 39.60 fpm VI 33.17 fpm

V2 62.50 fpm V2 61.30 fpm V2 66.00 fpm

V3 97.70 fpm V3 93.20 fpm V3 81.70 fpm

V4 149.30 fpm V4 145.00 fpm V4 155.00 fpm

Depth of Cut

Considering the material strength and tool material, the recommended

values of depth of cut for finish milling are up to 0.02 inch. However,

in the pilot tests, depths of cut up to 0.05 inch were used. The results

indicated that, for high speed and/or high feed rates, 0.05 inch or larg

er values of depth of cut should not be used because no improvement in

surface finish was obtained and there is an increased risk of tool break

age. Therefore, from the above test results it was decided to use three

levels of depth of cut: 0.01, 0.02, and 0.03 inch.

Feed Rate

Several values of feed rate were tested in the pilot study. The

results indicated that a feasible range of feed rate is between 1 and

38

3-1/4 ipm. From the values of feed rate available on the machine, the

selected feed rate levels were: 1-1/4, 2, 2-1/2, and 3-1/4 ipm, respec

tively. I •

Cutter Diameter \ • t

m m

Three cutter diameters were employed in the present research. They ;

were used to compare the influence of cutter diameter on surface rough- I

ness at different levels of cutting speed. These cutter diameters are

commonly used in finish end milling operations. The use of three cutter

diameters allowed sufficient experimental data to be obtained to enable

determination of the effect of this variable on surface finish, under

several sets of cutting conditions. The available cutter diameters were

5/8, 3/4, and 1 inch, respectively.

Experimental Design

Given the above conditions, all other conditions were maintained

fixed and constant during the experiment. Tool diameters were considered

(as blocks in the experimental design. For each tool diameter a 4x4x3

factorial experiment was designed (four levels of cutting speed, four

levels of feed rate and three levels of depth of cut). Table 2 shows the

code levels of the independent variables.

Table 2

Independent Variables

VARIABLE LEVELS CODE

Tool 3 Tl T2 T3 Cutting Speed 4 VI V2 V3 V4 Feed Rate 4 Fl F2 F3 F4 Depth of Cut 3 DI D2 D3

39

The dependent variable was surface roughness, CLA (or AA), values in

microinches. A total of 48 observations for each tool was taken and three

replications per cell were performed, representing a total of 144 |

o^^rvations for each tool diameter, employed with a total of 432 obser- \

vations for the three blocks. Table 3 shows the experimental design for \

each tool employed_^ j

The observations for each tool were taken in a random order to aver

age out effects of uncontrolled variables which could be present in the

experiment.

The observations for each experiment may be described by the statis

tical model (30), given as follows:

^ i j k i ^^^ -^ i ^ ^j ^^k ^ ^^^Nj ^ - ^Nk ^ ^^^^-k ^ ^^e^Njk ^ ^ i j k i ^

with: i 1, 2, ..., 4

J l , C , ..., *r

l\ l , c , ..., O

I l , b , ..., O

and Y...-, = the response surface roughness

p = the overall mean

T . = the effect of ith level of cutting speed

3. = the true effect of the jth level of feed rate

y. = the true effect of the kth level of depth of cut

de),-,- = the effect of the interaction between i. and 6,-

(TY)^I^ " ^^^ interaction between T. and Y|^

40

CO

CO ' : ! •

^-'

CO ^ ' ~

CO ^ ' ~

CO « * CVJ

CO ^ CVi

CO 'd-CVJ

CO ^ CO

CO ^ CO

CO ^ CO

CO CO ^

CO CO ^

CO CO ^

oc T3 <V 

<u E

o o

c <

o

•r-co O) O

c E

•r-i-<u Q. X

CVJ

Q.

o

CO

(U

oc

CVJ

a;

a:

<U

CO

CVJ CVJ CVJ CVJ CVJ CM CVJ

^ ^ ^

I— I— I— C V J C V J C S J c o c o c o ^ ^ ^

CVJ CO

41

(BY ) b = the interaction between 6- and y,

(TBY)4 4I. = the interaction between T. , 3-, and y.

(e). ..1 = a random error component since there are n = 3 replicates of

each experiment, there are a total of abcn = 4x4x3x3 = 144

observations for each tool.

Experimental Procedure

The test specimen was mounted in a vise clamped on the milling

machine work table. The end mill was placed in the tool holder, which was

previously mounted in the milling head. The specimen was set to the

starting position. The required speed, feed rate and depth of cut were

adjusted on the machine controls to perform the first cut. The entire

cutter diameter was used in each cut, and the length of each cut was

approximately 1 inch. After each cut the spindle was stopped and the next

set of conditions was selected. Each cut was marked with the cor

responding trial number to identify the conditions used.

The profilometer was placed on the machine table to measure surface

roughness after several cuts were done. After the measurement process,

the work surface was remachined using another tool different from that

employed in the experiment. These steps were repeated until the whole

experiment was complete for each tool.

CHAPTER III

EXPERIMENTAL ANALYSIS AND DISCUSSION

In this chapter, the experimental data for each tool is analyzed

statistically using the analysis of variance (ANOVA) procedure to deter

mine the effect of the independent variables of cutting speed, feed rate,

and depth of cut (DOC) on the dependent variable, surface roughness.

The statistical model used for this experiment was described in

Chapter II. In addition to the statistical analysis, graphs of the aver

age responses for each treatment combination, are presented to show the

interactions of the independent variables. Also, a graph of surface

roughness versus cutting speed for the three tools is constructed to

illustrate the effect of cutter diameter effect on surface roughness.


The analysis of variance of the data collected for Tool 1 is shown

in Table 4. Since all the main effects in the experiment are fixed ef

fects, the F statistic for the model, main effects, and the interaction

effects, were calculated by dividing the respective mean square by the

error mean square. The F test statistic was compared with the respective

F value from the F tables. Thus, to test the model effect, the test stat-

** istic F^ = 4.46 was compared with the critical value FQ Q^ ^ ^ = irk

1.79 from the F tables. Since F, > FQ Q^ ^y gg, it was concluded that

the model effect is significant at a level of a = 0.01. Using the same

procedure, the following results were obtained: the main effects of

cutting speed and depth of cut are nonsignificant at a level of a =

42

43

OC

to LO i n

in CVJ

CO CT»

en CO CO

in

lO

CVi

CO

O ( -

E 3 3 CT

( / ) t o

O O

3 L. O <0

t /1 >

1 ^ CO CO CVJ en <x> y£> 0 0 wo CO

cy»

in

0 0 o CVJ

o o

CVJ CVJ CVJ CVJ

00 vo

o o o o LO

i n

1 ^

o 00 00

00

o 0 0 CVJ vo in

0 0 CO o cy>

t n o lO

CVJ

00 o CVJ

0 0 0 0 CVJ

vo lO

• o o

• o

0) 0)

oo u. o a

o o o • o (U a; o. to

o o o I

"O <u

LL.

O O O

I • o a;

LL. I

"O d) <u o.

i-o i-

o

TO <u O <U

o

in o o

(Ol (O

u

t o t o

44

0.05. The feed rate effect is significant at a level of a = 0.05. The

second order interaction effects are all significant at a level of a =

0.01. The three factor interaction effect is also significant at a level

of a = 0.01. Significant main effects are discussed later in this chapter

to compare different tool diameters.

Figure 18 shows the cutting speed-feed rate interaction for Tool 1.

The significant interaction between cutting speed and feed rate is

indicated by the lack of parallelism of the lines for the different lev

els of feed rate. At the 33.05 fpm speed level, feed rates of 1-1/4 and 2

ipm both gave improved surface finish over feed rates of 2-1/2 and 3-1/4

ipm. At the 51 fpm speed level, better surface finish was obtained with

feed rates 1-1/4 and 3-1/4 ipm than with a feed rate 2-1/2 ipm. At the

91.70 fpm speed level, improved surface finish was obtained with a feed

rate 1-1/4 ipm. At the 149.3 fpm speed level there was only a small

difference (about 6 microinches) in the surface finish produced at the

four levels of feed rate. Gaps between lines at the lower levels of

cutting speed indicate the significant feed rate effect.

Figure .19 presents the speed-depth of cut interaction for Tool 1. At

the 33.05 fpm level of cutting speed, the best surface finish was

obtained with a 0.03 inch depth of cut. At this level of cutting speed,

the greatest value of surface roughness was obtained with a 0.01 inch

depth of cut. At the 62.50 fpm level of cutting speed, the difference in

surface roughness obtained at any level depth of cut was very small

(about 4 microinches). At the 97.70 fpm cutting speed level the lowest

value of surface roughness was obtained at 0.02 inch depth of cut. For

120

45

(J

c •r -O i-O

110

3 100 CO CO

a> c en 3 O

OC 

f3

f4 V

90

80

f l f2

Feed Rate: fl: 1-1/4 ipm f2: 2 ipm f3: 2-1/2

f4: 3-1/4 ipm

33.05 51.00 97.70

Cutting Speed (fpm)

149.30

Figure 18. Cutting Speed-Feed Interaction for Tool 1: Diameter 5/8 Inch

46

150

o c •f— o s-u

in CO

c .c Ol 3 o oc 

l i ^ O .

110 Depth of Cut DI = .01 inch D2 = .02 inch D3 = .03 inch

33.05 62.50 97.70

Cutting Speed (fpm)

li*9-30

Figure 19. Speed -Depth of Cut Interaction for Tool 1: Diameter 5/8 men

47

this cutting speed level, the lowest value of surface roughness was ob

tained at the 0.02 inch depth of cut and the greatest value of surface

roughness was produced with 0.03 inch depth of cut. At the 149.30 fpm

cutting speed level, only a small difference (about 5 microinches) in the

values of surface roughness occurred for all three levels of depth of

cut.

Figure 20 shows the feed-depth of cut interaction for Tool 1. It can

be observed that, at the 1-1/4 ipm level of feed rate, the best surface

finish was obtained with a depth of cut of 0.03 inch. With the 2 ipm

level of feed rate, better surface finish was obtained with 0.01 and 0.03

inch depth of cut than with 0.02 inch. At the 2-1/2 ipm level of feed

rate, the same value of surface roughness was obtained with 0.02 and 0.03

inch depth of cut, and the greatest value of surface roughness was

produced with 0.01 inch depth of cut. The best surface finish at the

3-1/4 level of feed rate, was obtained with a 0.02 inch depth of cut. In

geneneral, better surface finish was produced with a 0.02 inch depth of

cut at feed rate levels larger than 1-1/4 ipm.



in Table 5. The F statistic for the model, main effects, and the inter

action effects were calculated by dividing the respective mean square by

the error mean square. The F test statistic was compared with the

respective F value from the F tables.

The following results were obtained: the model effect was signifi

cant at a value of a = 0.01. The main effects of cutting speed, feed

48

o s-o

CO CO 

150.

1^0

130

120

110 V Depth of Cut DI = .01 inch D2 = .02 inch D3 = .03 inch

i - i / i f 2-1/2 3-1/^

Feed (ipm)

Figure 20. Feed-Depth of Cut Interaction for Tool 1: Diameter 5/8 Inch

49

cc

s f ^

i n '~

00 o

CVJ r^

LO ^

CO CVi

« * CO

CO i n

II II

a>

II

o I—

II II

LO

II

CO

11

CO

II

* * -K -Jc •K -K * -K

>— CVJ CO . ^

* ¥• ^

•K -K -K i n vn r>. 00

<0 3

21 tn

LO

(O

CVJ

o o

o

<:

o

CO E 0) O 0) -o

cn a>

o 0 0

i n CO

CVJ LO

LO LO

00 o i n

CVJ CO

o LO

C O CVJ CVJ CVi

CVJ i n CVJ

LO CO

0 0 CVi 5

LO in 00

in o o

• i n CVi

o s.

E 3 3 cr

i n to

CO CO CVi 0 ^ i n i n 00 i n CO

«4- C o o

•r-

u <a 1- ••-3 i -o <e

t o 5>

CVi CVJ

a\

CO CO 00 o

00 00 CO

i n LO LO o

CVJ CVJ

o o o LO vn i n

i n i n i n

00 00 CO i n

i n 00

LO CVJ

i n i n i n

i n i n CVJ LO

o

CO

vn 00 vn

CVJ O 00

i n LO

o CVJ l O C O CVJ

CVJ i n o CVJ

0) "O o

• o

Q . to

0) o o o

T3

a> LL.

I T3 o o I

-o

u .

o o a

I "O a;

Uu I

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i n

o

o

T3

+J u 

o o II

3

4J

c <o u

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to

50

rate, and depth of cut were significant at a level of a = 0.01. The ef

fect of cutting speed-feed rate interaction was nonsignificant at a =

0.05. The effects of cutting speed-depth of cut interaction and the three

factor interaction were significant at a level of a = 0.01.

Figure 21 presents the speed-depth of cut interaction for Tool 2. At

the 39.60 fpm cutting speed level, the lowest value of surface roughness

was obtained with 0.03 inch depth of cut; the results obtained with 0.01

and 0.02 inch depth of cut were very close (about 2 microinches in

difference). At the 61.30 fpm level of cutting speed, improved surface

finish was obtained with 0.02 inch of depth of cut; the largest value of

surface roughness was obtained with 0.01 inch depth of cut. The best

surface finish, at the 93.20 fpm level of cutting speed, was obtained

with 0.02 inch depth of cut. The 145 fpm level of cutting speed resulted

in surface roughness improvement for the three values of depth of cut,

but better finish was obtained with 0.02 inch depth of cut. In general,

for Tool 2, better surface finish was obtained with 0.02 inch depth of

cut at cutting speeds larger than 61.30 fpm.

Figure 22 shows the feed rate-depth of cut interaction for Tool 2.

The 1-1/4 ipm level of feed rate gave the best surface finish with 0.03

inch depth of cut; also, a big difference (about 35 microinches) in

surface roughness between 0.01 and 0.03 inch depth of cut was observed at

this level of feed rate. The best surface finish was obtained with 0.02

inch depth of cut, at the 2 ipm level of feed rate. At the 2-1/2 ipm

level of feed rate a lower value of surface roughness was produced with

0.02 inch than with other values of depth of cut. A deterioration in

surface finish was observed at the 3-1/4 ipm when 0.01 and 0.03 inch

51

39.60 61.30

cutting Speed (fpm)

u 4: rut Interaction for F1.-^- ^/r2-tUUlA inch

52

180

170

o •r-o s. o

3 O

OC

a> C3>

t .

>

160

150.

1 *0

A

X \.

/ Depth of Cut

/ DI = .01 inch / D2 = .02 inch

D3 = .03 inch

V Dl

/o3

02

1-1A 2 2 -1/2

Feed (ipm) 3-1/^

Figure 22. Feed-Depth of Cut Interaction for Tool 2: Diameter 3/4 Inch

53

depth of cut were used. For 0.02 inch depth of cut, the surface finish

obtained was almost the same as that for 2-1/2 ipm. In general, better

surface finish was obtained with 0.03 inch depth of cut at the lowest

value of feed rate (1-1/4 ipm), and better surface finish was obtained

with 0.02 inch depth of cut, for feed rates larger or equal to 2 ipm.

Data Analysis for Tool 3: Diameter 1 Inch


in Table 6.

The F statistic for the model, main effects, and interaction effects

were calculated by dividing the respective mean square by the error mean

square. The test statistic F was compared with the respective critical F

value from the F tables, giving the following results: model effect is

significant at a level of a = 0.01. The main effects of cutting speed and

depth of cut were also significant at a = 0.01. The feed rate main effect

was significant at a significance level of a = 0.05. The effect of

cutting speed-feed rate interaction was nonsignificant at a level of a =

0.05. However, the effects of cutting speed-depth of cut interaction,

feed rate-depth of cut interaction, and three factor interaction were

highly significant at an a level of 0.01.

Figure 23 shows the cutting speed-depth of cut interaction for Tool

3. For 33.77 fpm of cutting speed, better surface finish was obtained

with 0.02 and 0.03 inch depth of cut than with 0.01 inch. At 51.80 and

81.70 fpm levels of cutting speed, the best surface finish was obtained

with 0.02 inch depth of cut. Lower values of surface roughness were

obtained at the 155 fpm level of cutting speed with 0.01 and 0.03 inch

54

o in »— o ^

in r- CVJ i n 0 0 I—

CO

(O ac

vn

<o

CO

o o

o

<:

O

< :

CO

II

vn II

r— CVJ

CO

II

CO

"id- r -

II II

LO

II

LO

II

CO

•K -K -K •K -K •»<

LO i n r>^ 0 0

0 )

C ro (O 3 CD O" !£ t o

854

CVJ

CJ^ CO CVJ ^~'

i n LO

i n r—

o CVJ

r CVJ

'd-i n o

1 ^ r*..

a> 00 CO r—

r-«. •—

CO CVJ LO

cy>

o CVJ 0 0

<T> LO

CVJ

vn

o LO

LO r^

r_

LO o CO CT»

^

CO

^ E a> o <u -o i~ <u O) .

0 0 CO

LO •

r^ a> o

in LO

LO in o>

CO 0 0

o •

o m

CVJ

CO CO CO CO

• CO CO CVi

o CO

o o in r>.

• p^ * * 0 0 0 0

0) ••-> O ro J- - 1 -3 ( . O (O to >

^-a> • o o z

"O <l) 0) c^

to

• o QJ Qi a. t o

<_) o a 1 • o Qi 0)

l i .

O O Q

1 X J

o; o 0) L. S. o o

o •

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s 4J ro

can

t gn

i

to *

m o •

o II

3

• IJ ro

can

t

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gni

t o

55

160 u

o u

DI

^ 150

CO I/) O) c .c o> 3 O

OC

Q) o> (O

>

li*0

D3

D2 130

120

Depth of Cut

.01 inch

.02 inch

.03 inch

DI = D2 = D3 =

33.77 51.50 81.70

Cutting Speed (fpm)

Figure 23. Cutting Speed-Depth of Cut Interaction for Tool 3: Diameter 1 Inch

56

than with 0.02 inch depth of cut. In general, for the three values of

cutting speed (33.77, 51.80, and 81.70 fpm), better surface finish was

obtained with 0.02 inch depth of cut. However, the best surface finish

was obtained at the 155 fpm speed level using 0.01 inch depth of cut.

Figure 24 shows the feed rate-depth of cut interaction for Tool 3.

It can be observed that for the 1-1/4 ipm level of feed rate the best

surface finish was obtained with 0.01 inch depth of cut. At the 2 ipm

level of feed rate, a lower value of surface roughness was obtained with

0.02 inch depth of cut. For 2-1/2 ipm of feed rate, better surface finish

was obtained with 0.02 inch depth of cut. For this level of feed rate, an

increase in surface roughness was obtained with 0.01 inch depth of cut.

An improvement in surface finish was observed at the 3-1/4 ipm of feed

rate when 0.03 inch depth of cut was used.

The main effects of cutting speed for Tool 2 and Tool 3 are shown in

Figure 25. It can be seen that better surface finish was obtained with

Tool 2 than with Tool 3. The surface roughness, obtained with Tool 3,

decreases as cutting speed increases; however, the surface roughness,

obtained with Tool 2, first increases slightly with cutting speed and

then decreases as cutting speed is increased.

Figure 26 shows the main effects of feed rate for the three cutter

diameters employed. For each tool the best surface finish was obtained at

the lowest value of feed rate (1-1/4 ipm). A tendency of surface finish

to deteriorate as feed rate increases was observed for the three tools.

At any level of feed rate, the best surface finish was produced with Tool

2 (3/4 inch). Intermediate values of surface roughness were obtained with

57

- 150 o

•r-O

b 140

CO (/)

^ 130 xz a> 3 O

OC



<: 100

Depth of Cut

DI = .01 inch D2 = .02 inch D3 = .03 inch

i-l/i^ 2-1/2 3-1/a

Feed (ipm)

Figure 24. Feed-Depth of Cut Interaction for Tool 3: Diameter 1 Inch

o

58

150 .

o u

140 .

a> en ro s->

•a:

CO

3 o oc Qi O ro

«+-i-3

i n

130

120

110 -

Tool 3

r e e l 2

33.77 39.60 6 1 . 3 0 93.-13

Cutting Speed (fpm)

Figure 25. Surface Roughness Average Versus Cutting Speed

59

150

u c o i . (J

 <c lO CO Qi c o> 3 O

OC

Qi O ro

*•-S-3

in

140

130

120

110

3 (1 inch)

1 (5/8 inch)

2 (3/4 inch)

i-iA 2 2 -1/2

Feed Rate (ipm)

; - l /4

Figure 26. Surface Roughness Average Versus Feed Rate

60

Tool 1 (5/8 inch) and the poorest surface finish was produced with Tool 3

(1 inch).

Figure 27 shows the main effects of depth of cut for Tools 1 and 3.

It can be observed that the best surface finish was produced with Tool 2

at the 0.02 inch level of depth of cut. In general, the best surface

finish was produced with Tool 2. It can also be observed that the

greatest value of surface roughness was produced at 0.01 inch depth of

cut for each cutter diameter individually.

Figure 28 shows surface roughness plotted for the different cutter

diameters as a function of cutting speed. In general, better surface

finish was obtained with Tool 2 (3/4 inch) at any level of cutting speed.

For cutter diameters 3/4 and 1 inch, respectively, surface roughness de

creases as the cutting speed increases. For a tool diameter of 5/8 inch,

surface roughness decreases as cutting speed increases, up to about 90

fpm. After that, surface roughness increases with an increase in cutting

speed. Surface roughness versus the cross-sectional area of cut (feed

rate x depth of cut) is shown in Figure 29 for the three tool diameters

employed. In general, for the three tool diameters, poor surface finish

was obtained for values of the cross-sectional area between 0.02 and

0.04. With Tool 1 and Tool 3 better surface finish was obtained than with

Tool 2. The lowest value of surface roughness was obtained for Tool 3 2

with a 0.0125 in /min cross-sectional area.

A summary of the results obtained from the analysis is presented in

Table 7. The implications of the analysis of the experimental data, and

conclusions regarding the effects of cutting speed, feed rate and depth

of cut on surface finish, are presented in Chapter IV.

61

(J c

•r—

o u

Qi en lO i. Qi >

(/> (/) a>

o^ 3 O

OC Qi O ro

» • -

3 i n

140

130

120..

110

Tool 3 (1 inch)

Tool 2 (3/4 inch)

0 .01 0.02

Depth of Cut (inch)

Figure 27.. Surface Roughness Average Versus Depth of Cut

62

140

130

o

o (J

Qi ay ro t -(U > CO

2 120

o> 3 O

OC

S no ro

M-U 3

in

ch)

Tool 2 (3/4 inch)

100

ICO 1 c

Speed (fpm)

Figure 28. Surface Roughness Average Versus Cutting Speed for Different Cutter Diameters

63

o

o i-

CO CO Qi c

3 o OC

Qi O (O

<4-s -3

to

170

160

— 150

140

-30

120

o l 2

ol 3

1 s

100 ,02

Cross-section (in /min)

10

Figure 29. Surface Roughness Versus Cross-Sectional Area

64

CO

o o

<o o

c

i n

c ro (J

en CO

c ro (J

+J C ro O +J

• I - C M- «0 •»- O C - 1 -C7» M -

CO

ro O

C «o o

™ c c c o> c en en cj>

• t - O • ! - • ! - •!-i n ^ 0 0 0 0 i n

o o

CVJ

o o

(O u

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oo

c ro u

c en

•r— t o

<o

O )

i n

c ro U

CD

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ro O

ro

vo C C C C O ) O ) Q) O 'r— •!— .|—

z <n OO i n

r^

xn ro

o ro

o

(U

o o

4-> C (O o

• r -M-• r -C en CO

c o z

+J c ro O

• r" «4-

C en

•r— 0 0

+J C ro U

•r— M-• r -C en CO

c o z

• ! - >

c ro U

•r— ^-c o>

' ^ 0 0

• M c <o u

•^ M-

c CO

• r -in

•M c «o (J

•r-<4-

C O^

•t—

oo

•M c ro U

M-

c en

•^ oo

* 4 -O

in

3 CO

Z3

o

0) +J ro

OC

o v^. O 3

O

O . (U

Q I Qi

4-> ro

OC

U 0)

Qi Qi CL

i n

o> c

Q)

ro

"O Qi Q)

•t-> 3

O

M -O

• o a> Qi

u. I

• o a> Q) CL

to en

01 3 Q o

Qi O

I "O Qi Qi O .

t o

o>

3

O . Qi

I 0^

•M (O

• o

Qi u.

I "O c

T3 • P 3

O

CHAPTER IV

CONCLUSIONS AND RECOMMENDATIONS

A summary of the results and conclusions, as well as some recommen

dations for future research, are presented in this chapter.


Even though the effect of cutting speed on surface roughness was

nonsignificant, its interaction effects were significant. This means that

for the established conditions, the effect of cutting speed on surface

roughness was not independent of the other two factors. Thus, no

significant difference in surface roughness could be obtained by varying

cutting speed alone. Also to be noted, is that a small increase in sur

face roughness occurred when cutting speed was increased beyond 90 fpm.

It is suspected that this increase was due to the beginning of the forma

tion of a built-up edge.

The effect of feed rate on surface finish was found to be signifi

cant. In general, surface roughness increased with an increase in feed

rate, this was in accordance with earlier investigations.

The main effect of depth of cut on surface roughness was not signi

ficant, but its interaction effects with other factors were highly sig

nificant. This implies that for this tool diameter and the selected cut

ting conditions, the effect of depth of cut on surface roughness was not

independent from the other two factors, and a significant difference in

surface roughness could not be obtained by varying depth of cut alone.

65

66

The results of this study indicate that the combined effect of

cutting speed and feed rate on surface roughness was highly significant.

To achieve better surface finish a combined variation in both factors is

necessary. For this tool diameter, the influence of feed rate does not

permit the use of large values of cutting speed without deterioration in

surface finish. It was found that the two combinations of these variables

which allowed improved surface finish were:

a. Cutting speed of 51 fpm and feed rate at 1-1/4 ipm.

b. Cutting speed of 97.70 fpm and feed rate at 1-1/4 ipm.

For maximum metal removal rate, the best combination was 97.70 fpm and

1-1/4 ipm of cutting speed and feed rate, respectively.

The combined effect of cutting speed and depth of cut was highly

significant. Since the main effects of these two variables on surface

roughness were nonsignificant, it can be concluded that to produce a

significant change in surface roughness, cutting speed and depth of cut

must be varied simultaneously. It was found that an improved surface

finish was obtained with the combination of 97.7 fpm and 0.02 inch of

cutting speed and depth of cut, respectively.

The effect of feed rate-depth of cut interaction was also highly

significant for this tool diameter, indicating that no significant change

in surface roughness could be produced if depth of cut alone is varied.

The best surface finish was obtained with 2 ipm feed rate and 0.02 inch

depth of cut. However, to increase the metal removal rate, the same depth

of cut, with a 3-1/4 ipm feed rate, may be used with only a small

increase in surface roughness. Thus, for a metal removal rate of 0.0250

cubic inch per minute, the roughness obtained was 111 microinches while

67

for 0.0406 cubic inch per minute an increase of only 5 microinches was

obtained.

The three factor interaction effect was significant. For this cutter

diameter, the combination which produced the best surface finish was 97

fpm, 2 ipm, and 0.02 inch for cutting speed, feed rate, and depth of cut,

respectively.


From the analysis performed on the data collected for this cutter

diameter, the following conclusions can be drawn: the main effects of

cutting speed, feed rate, and depth of cut were found to be highly signi

ficant. Cutting speed and feed rate were independent of each other,

which means that significant changes in surface roughness values could be

produced by varying each factor individually. In general, better surface

finish was obtained as cutting speed increased. Some dependence between

cutting speed and depth of cut was observed by the interaction effect,

which was found to be significant, meaning that significant changes in

surface roughness were produced by varying cutting speed and depth of cut

simultaneously.

The feed rate-depth of cut interaction was found to be highly signi

ficant. This indicates that to produce a significant change in surface

roughness, depth of cut must be varied along with feed rate. Even though

the best combination found was 1-1/4 ipm and 0.03 inch feed rate and

depth of cut, respectively, there is some indication that 0.02 inch depth

of cut produces acceptable surface roughness for higher values of feed

rate.

68

Since the best results, with respect to surface roughness, were

obtained with this tool diameter, it is recommended to use this cutter

diameter for practical application with the following cutting conditions:

145 fpm cutting speed, 0.02 inch depth of cut, and intermediate values of

feed rate. If improvement in production is required, 3-1/4 ipm feed rate

may be used with 145 fpm and 0.02 inch cutting speed and depth of cut,

respectively.

Tool 3: Diameter 1 Inch

From the analysis performed on the collected data for this tool

diameter, the following conclusions can be drawn: the main effect of the

three factors on surface roughness are all significant. Cutting speed,

feed rate, and depth of cut are independent of each other with respect to

their effect on finish. Thus, with a variation in any of these

parameters, a significant variation in surface roughness is produced.

It was found that surface roughness in general decreases as cutting

speed increases, which agrees with earlier investigations. The best com

bination of cutting speed and depth of cut was found to be 155 fpm and

0.01 inch cutting speed and depth of cut, respectively. The best combina

tion of feed rate and depth of cut was found to be 1-1/4 ipm and 0.01

inch feed rate and depth of cut, respectively.

A general tendency of increasing surface roughness as feed rate

increases was observed, which is in accordance with earlier investiga

tions. In general, the values of surface roughness produced with this

tool diameter are larger than those produced with cutter diameters of 5/8

and 3/4 inch.

69

Performance of Cutter Diameters

For cutter diameters of 3/4 inch and 1 inch it seems that rapid

formation of a built-up edge did not occur, even at the largest values of

cutting speed employed in this research. While the cutter diameter of 5/8

inch reached the transition zone indicated by Chandiramani and Cook (20),

at a cutting speed slightly over 90 fpm; cutter diameters of 3/4 and 1

inch did not reach the transition zone even at a cutting speed of 150

fpm. Since Tools 2 and 3 have greater areas than Tool 1, they can

dissipate heat faster than Tool 1, thus not allowing an increase in

temperature which could be favorable for the formation of a built-up edge

at cutting speeds near 100 fpm. This could be the main reason for

deterioration of the surface finish at cutting speeds over 90 fpm when a

cutter diameter of 5/8 inch is employed.

In general, it was observed that the size of the chip cross-section

al area did not show a dominating effect on surface roughness. Thus, for

the three cutter diameters employed, better surface finish was obtained 2

for a chip cross-sectional area of about 0.04 in /min. Generally, Tool 1

produced better results than the two other tools. A summary of the

favorable conditions with respect to surface roughness for the three

cutter diameters employed in the experiment is presented in Table 8.

Table 8

Favorable Cutting Conditions for Each Tool

Cutter Diameter (in) 5/8 3/4 1 ^

Cutting Speed (fpm) 97.7 144 155

Feed Rate (ipm) 2 2-1/2 1-1/4

Depth of Cut (in) 0.02 0.02 0.02

70

Recommendations for Future Research

The following areas are recommended for future investigation:

1. A similar experimental procedure may be used with a machine with

continuous speed, to use the same cutting speed with different

cutter diameters. This will allow statistical comparison of the

effect of cutter diameter on surface roughness.

2. A similar experimental procedure may be used with cemented car

bide and coated carbide tools, using different workpiece mate

rial or other milling operation.

3. Tool wear should be included as an independent variable in a

similar experiment.

4. The effect of the number of teeth on the cutter on surface

roughness, using a similar experimental procedure, should be

investigated.

5. A different experimental procedure should be used to develop

mathematical models to predict surface roughness values, using

the same independent variables.

6. Optimization methods should be used to obtain the optimum ma

chining conditions for milling operations using surface rough

ness as a response.

REFERENCES

(1) The Cincinnati Milling Machine Co., A Treatise on Milling and Milling Machines, 3rd ed., pp. 910, Cincinnati, OH U951).

(2) Armarego, E. J. A., and R. H. Brown, The Machining of Metals, Prentice-Hall, Inc., pp. 437 (1969).

(3) Kuljanic, Elso, "An Investigation of Wear in Single Tooth and Multi-Tooth Milling," Int. J. Tool Pes. Res., Vol. 14, pp. 95-109, Pergamon Press Ltd. (1974).

(4) Sundaram, R. Meenakshi, A Statistical Analysis of Surface Finish in Fine Turning of Steel, a PhD Dissertation 1n Industrial Engineering, pp. 175, Texas Tech University (1976).

(5) Perotti, Giovanni, "An Investigation on the Face Milling Inserted-Tip Geometry and Its Effect on Workpiece Vibrations," Int. J. Mach. Tool Pes. Res., Vol. 7, pp. 55-61, Pergamon Press Ltd. U957J.

(6) Lambert, B., Manufacturing Analysis Lectures. Spring (1982)

(7) Department of Education of International Business Machines Corporation, Precision Measurement in the Metal Working Industry, Vol. 2, pp. 229, Syracuse University U944).

(8) Martelloti, M., "Analysis of the Milling Process," Transaction of the ASME 63, (1941), 667 and 67 (1945).

(9) Nee, A. Y. C, and others, "Surface Finish in Milling," Technical Report, SME, pp. 38 (1978).

(10) Olsen, K. V., "Surface Roughness as a Function of the Cutting Data When Fine Turning Steel," ASTM Technical Paper #655 (1964).

(11) Reddy, C. T., "A Note on Theoretical Surface Finish in Turning and Milling Operations," Int. J. Prod. Res., Vol. 19, No. 1, pp. 344-360 (1981).

(12) King, R. I. and J. G. MacDonald, "Product Design Implication of New High-Speed Milling Techniques," Transactions of the ASME Journal of Engineering for Industry, pp. 1170-117b, Nov. {1975).

(13) Petropoulos, Petros C , "Statistical Basis for Surface Roughness Assessment in Oblique Finish Turning of Steel Components," International J. Prop. Res., No. 27 pp. 345-360, Nov. (1972).

(14) Taraman, K. and B. Lambert, "A Surface Roughness Model for A Turning Operation, Int. J. Prod. Res., pp. 693-704 (1973).

71

72

(15) Rakhit, A. K. and others, "The Influence of Metal Cutting Forces on the Formation of Surface Texture in Turning," Int. J. Tool Des. Res., Vol. 16, pp. 281-292, Pergamon Press Ltd. [ 1975).

(16) Crawford, 0. H. and M. Eugene Merchant, "The Influence of Higher Rake Angles on Performance in Milling," Transaction of the ASME, pp. 561-566, May (1953).

(17) Levi, R., "Finish on Surface Ground Steel," Int. J. Tool Des. Res., Vol. 2, pp. 351-367, Pergamon Press (1962).

(18) Bailey, J. A. and others, "Surface Integrity in Machining AISI 4340 Steel," Journal of Engineering for Industry, Transactions of the ASME, pp. 999-1006, August (1976).

(19) Shaw, M. C , "Study of Machined Surfaces," Proceedings of the Seminar on Metal Cutting, Paris (1967).

(20) Chandiramani, K. L., and N. H. Cook, "Investigations on the Nature of Surface Finish and Its Variation With Cutting Speed," Journal of Engineering for Industry, Transaction of the ASME, pp. 134-140, May (1964).

(21) Olsen, K. V., "Surface Roughness as a Function of Cutting Conditions When Turning Steel," Machine Tool and Production Trends, paper presented on New Industrial Technologies at Pennsylvania State University, pp. 149-160 (1965).

(22) Taraman, Khalil S., "Development and Utilization of Mathematical Models for Metal Cutting Responses," a PhD Dissertation in Industrial Engineering, pp. 172, Texas Tech University (1972).

(23) General Electric, Milling Handbook of High-Efficiency Metal Cuting, CarboToy Systems Department G.E., pp. 59-/4.

(24) Sabberwal, A. J. P., "Cutting Forces in Down Milling," Int. J. Mach. Tool Des. Res., Vol. 2, pp. 27-41, Pergamon Press Ltd. (1962).

(25) Salah, M. Said, "The Stability of Horizontal Milling Machines," Int. J. Mach. Tool Des. Res., Vol. 5, pp. 245-264 (1973).

(26) Niedzwiedzki, A., Theory of Metal Cutting and Tool Wear, Maison d'Edition Couillet, Belgium (I9bb).

(27) Ansel, C. T., and J. Taylor, "The Surface Finishing Properties of a Carbide and Ceramic Cutting Tool," Advances in Machine Tool Design and Research, Oxford, pp. 225-243, Pergamon Kress Ltd. [1952).

73

(28

(29

(30

(31

(32

(33

(34

(35

(36

Galloway, D. F., "Recent Research in Metal Machining," Proc. of the Inst. Mech. Engrs., Vol. 153, pp. 133-127 (1945).

Jamar, L. G. and R. A. Dudek, "Cutting Fluid Lubricity and Surface Roughness in Turning," The International Journal of Production Research, Vol. 5, No. 4, pp. 3U/-3I/ uyb/). "

Montgomery, Douglas C , Design and Analysis of Experiments, John Wiley & Sons, New York, pp. 4I« [l9/5j.

Takeyama, H. T. Onn, "Basic Investigation of Built-up Edge," Trans-actions of the ASME, Journal of Engineering for Industry, pp. 335-842, May (1968).

Srdhar, R. R. Hohn and G. W. Long, "Contribution to Machine Tool Chatter," Transactions of the ASME, Journal of Engineering for Industry, pp. 317-334 (1958).

ASME, Manual on Cutting of Metals, The American Society of Mechanical Engineering [ 19bZj.

Wang, K. K., S. M. W. U. and K. Iwata, "Temperature and Experimental Errors for Multitooth Milling," Transactions of the ASME, Journal of Engineering for Industry, pp. 3b3-3b9 [ 1958).

Kronenberg, M., Machining science and Application, Pergamon Press (1966).

Wilson, F. v., Machining With Carbides and Oxides, McGraw-Hill Book Company, NY (19^2T:^

APPENDIX

74

75

SURFACE ROUGHNESS DATA FOR TOOL 1: DIAMETER 5/8 INCH

OBS SPEED FEED DOC

1 CVJ

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

90 108 127 99 100 101 138 126 144 123 134 141 91 108 127 91 103 123 102 124 100 125 127 139 86 168 170 190 182 118 93 120 110 106 188 190 170 108 118 93 113 113 106 93 108 92 106

1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 3

2 2 2 2 2 2 2 2 2 2 2 4 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 3

76

OBS SPEED FEED DOC

48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

153 146 119 140 145 125 100 113 92 129 126 125 136 124 99 99 113 98 111 117 108 114 121 102 142 118 100 123 133 115 105 132 125 125 142 136 99 108 102 130 96 102 98 120 123 91 121 102

1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2 4 2

77

OBS SPEED FEED DOC

96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144

124 118 101 93 123 93 183 144 137 118 100 100 103 137 133 128 129 106 125 145 123 116 139 141 152 134 140 128 120 109 111 118 m 118 145 109 109 104 93 113 144 114 130 150 123 150 143 152 137

1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 CVJ

2 2 3 3 3 4 4 4 2

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 3

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 1

78

SURFACE ROUGHNESS DATA FOR TOOL 2: DIAMETER 3/4 INCH

OBS SPEED FEED DOC

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

132 70 70 127 116 130 95 132 129 68 77 90 142 139 150 137 114 134 120 101 108 95 88 111 96 78 118 124 124 117 132 119 120 107 90 112 164 156 176 199 121 117 160 100 139 126 107

1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4

79

OBS

48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

Y

107 129 137 126 101 95 109 99 83 112 64 72 109 102 92 95 93 87 120 99 133 93 91 134 128 130 116 122 113 117 108 91 91 89 92 71 90 121 112 108 112 110 117 109 85 84 87 95

SPEED

4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4

FEED

4

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4

DOC

1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

80

OBS

96 97 98 99 100 101 102 103 104 105 106 107 108 109 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144

Y

101 99 90 92 114 143 125 73 78 100 96 85 84 110 111 141 108 100 119 109 129 99 110 127 87 95 101 105 100 100 121 127 149 94 126 123 109 78 110 112 99 107 140 148 120 101 130 139

SPEED

4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 2 2 2 3 3 3 4 4 4 1 1 1 4 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4

FEED

4

2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 3 4 4 4 4 4 4 4 4 4

DOC

2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 . 3 2 3 3 3 3 3 3 3 3 3

81

SURFACE ROUGHNESS DATA FOR TOOL 3: DIAMETER 1 INCH

OBS SPEED FEED DOC

1 CVJ

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

114 141 117 177 170 154 125 100 124 89 85 97 180 166 141 154 142 135 134 132 119 105 89 117 159 169 178 129 122 187 186 177 135 155 141 164 180 170 195 172 129 167 133 146 136 140 135

1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4

82

OBS SPEED FEED DOC

48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

159 153 147 153 130 150 154 116 125 149 127 196 131 112 134 133 122 123 133 94 127 129 152 116 146 137 120 137 138 121 160 99 115 130 182 114 144 126 123 129 133 115 105 91 132 137 156 160

4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 CVJ

3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4

1 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

83

OBS SPEED FEED DOC

96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144

146 186 149 149 98 130 94 148 129 125 108 110 128 127 118 125 184 199 145 92 112 121 129 150 148 133 125 135 190 149 168 137 161 133 105 124 108 105 130 141 149 131 124 105 172 120 123 145 132

4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4 1 1 1 2 2 2 3 3 3 4 4 4

2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4

2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

Documents

ANALYSIS OF SURFACE ROUGHNESS FOR END MILLING …