i

EXPERIMENTAL STUDY OF ELECTROCHEMICAL DEBURRING

OF DIE-STEEL WORKPIECES

BY

SIBSUNDAR DAS B.TECH (Mechanical)

Jalpaiguri Govt. Engg. College

Jalpaiguri, W.B.

2008

EXAMINATION ROLL NO.-M4PRD10-03

THESIS

SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR

THE DEGREE OF MASTER OF PRODUCTION ENGINEERING IN

THE FACULTY OF ENGINEERIG & TECHNOLOGY

JADAVPUR UNIVERSITY

2010

DEPARTMENT OF PRODUCTION ENGINEERING

JADAVPUR UNIVERSITY

KOLKATA-700 032

INDIA

ii

JADAVPUR UNIVERSITY

FACULTY OF ENGINEERING & TECHNOLOGY

I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY

SUPERVISION BY SIBSUNDAR DAS ENTITLED EXPERIMENTAL STUDY OF

ELECTROCHEMICAL DEBURRING OF DIE-STEEL WORKPIECES BE

ACCEPTED IN PARTIAL FULFILMENT OF THE REQUIRMENT FOR THE

DEGREE OF MASTER OF PRODUCTION ENGINEERING.

COUNTERSIGNED

……………………..………………………………………

(DR. SOUREN MITRA)

HEAD

DEPARTMENT OF PRODUCTION ENGG.

…………………..…………………………………

(DR. SOUREN MITRA)

THESIS ADVISOR

DEPARTMENT OF PRODUCTION ENGG.

………………………..……………………………………

(PROF. NILADRI CHAKRABORTY)

DEAN,

FACULTY OF ENGINEERING & TECHNOLOGY

.

iii

JADAVPUR UNIVERSITY

FACULTY OF ENGINEERING & TECHNOLOGY

CERTICATE OF APPROVAL*

The forgoing thesis is hereby approved as a creditable study of an

engineering subject carried out and presented in a manner

satisfactory to warrant its acceptance as a pre-requisite to the degree

for which it has been submitted. It is understood that by this approval

the undersigned do not necessarily endorse or approve any

statement made, opinion expressed or conclusion drawn therein but

approve the thesis only for the purpose for which it is submitted.

COMMITTEE ON FINAL EXAMINATION _________________________

FOR EVALUTION OF THE THESIS

_________________________

*Only in case the recommendation is concurred in

iv

ACKNOWLEDGEMENT

The author takes the opportunity to express immense gratitude to respected thesis

advisor Dr. Souren Mitra Head of Production Engineering Department, Jadavpur

University for his guidance, encouragement and motivation towards real-time research

work right from the beginning to the completion of the dissertation.

I express deep respect to all the faculty member of the department for their

inspiration and help during the entire period of this thesis work.

I am also thankful to departmental technical staffs specially Sri Biswanath Das

and Sri Biswajit Pathak and all non-teaching staff of production engineering department

who in some way or other helped and encouraged me during the thesis work.

I express my heartiest thanks to Manoj Singha, Mukander Sekh, Goutam Pal,

Biplab kanti haldar, Suman Samanta, Bijan Mallick for their co-operation during the

work. I would like to thank the person whose name could not figure here, once again for

their valuable guidance, support and kind attention given to me throughout the project

work.

Finally I bow to my parents, my all-family member, well-wisher for their blessing

and inspiration without which it was next to impossible to achieve my goal.

__________________________

(SIBSUNDAR DAS)

Examination Roll No.-M4PRD10-03

v

TABLE OF CONTENTS

CHAPTER PAGE NO

TITLE SHEET i

FORWARDING CERTIFICATE ii

CERTIFICATE OF APPROVAL iii

ACKNOWLEDGEMENT iv

CONTENTS v

1. INTRODUCTION 1

1.1 Burr Formation Mechanism 3

1.2 Definition of Deburring 4

1.3 Various Deburring Processes 4

1.4 Principle of Electrochemical Deburring 6

1.4.1 Fundamental features of electrochemical deburring 6

1.4.2 Mechanism of burr removal in electrochemical deburring 7

1.4.3 Electrochemistry of electrochemical deburring 10

1.4.4 Various electrolytes used in electrochemical deburring 12

1.5 Review of Past Research Works 14

1.6 Objective of the Present Research 24

2 MODELLING OF ELECTROCHEMICAL DEBURRING

PROCESS

26

2.1 Faraday’s Laws of Electrolysis 27

2.2 Material Removal Rate in ECD 28

vi

2.3 Voltage Drop During ECD 30

2.4 Modeling for Evaluation of Change in Burr Height & Base

Material Removal

31

2.4.1 Evaluation of change in burr height & base material removal

at zero feed rate

33

2.4.2 Determination of change in burr height at constant feed rate. 36

3 EXPERIMENTAL SETUP FOR ELECTROCHEMICAL

DEBURRING

3.1 General Features of the Electrochemical Deburring Set-up 38

3.2 Electrolyte Flow Supply Unit 40

3.3 Tool Holding Device 42

3.4 Workpiece Holding Device 42

4 EXPERIMENTAL ANALYSIS OF ELECTROCHEMICAL

DEBURRING PROCESS

4.1 Plan of Experimentation 48

4.1.1 Taguchi’s approach to parameter design 48

4.2 Experimental Procedure 53

4.3 Evaluation of Change in Burr Height and Amount of Base

Material Removal

55

4.4 Analysis and Discussion of Experimental Results 59

4.4.1 ANOVA Test for change in burr height 59

4.4.2 ANOVA Test for base material removal 59

4.5 Parametric Analysis Based on Taguchi Methodology 60

4.5.1 Analysis of the effect of process parameters on change in burr

height

60

vii

4.5.2 Analysis of the effect of process parameters on base material

removal

61

4.6 Confirmation Test 62

5 STUDY OF THE EFFECT OF ELECTROLYTE ON CHANGE

IN BURR HEIGHT & BASE MATERIAL REMOVAL

64

5.1 Investigation on the Effect of Electrolyte on Change in Burr

Height

67

5.1.1 Effect of voltage on change in burr height at different

electrolyte concentrations

68

5.1.2 Influence of electrolyte concentration on change in burr height

at different voltage

70

5.1.3 Comparison of the effect of the type of electrolyte on change in

burr height

72

5.2 Study of The Effect of Electrolyte on Base Material Removal 73

5.2.1 Effect of voltage on base material removal at different

electrolyte concentrations

73

5.2.2 Influence of electrolyte concentration on base material

removal at different voltage

75

5.2.3 Comparison of the effect of the type of electrolyte on base

material removal

77

6 GENERAL CONCLUSION AND FUTURE SCOPE OF WORK

6.1 General Conclusions 80

6.2 Future Scope of Work 82

7 REFERENCES 83

1

1. INTRODUCTION

Demands for miniature components are rapidly increasing in various fields like

optics, electronics, medicine etc. These components, which have a variety of features

from a simple hole to complex three-dimensional (3D) freeform surfaces, can be

produced using a number of manufacturing methods, such as cutting, abrasion, and non-

traditional machining. In field of manufacturing many new materials and alloys are

developed for their specific uses and have a very low machinability. Different

conventional and non-conventional machining processes are developed to produce

different type of shape. Some materials are impossible to machine by conventional

machining processes because of low machinability of these materials. Sometime

producing complicated geometry of hard materials has become extremely difficult with

the traditional method machining.

Non-traditional machining processes are very useful to create complicated shape

in hard materials. Various type of micro-hole, mirror finishing, complex 3D shape can be

achieved by non-traditional machining very easily. Apart from the situation cited, higher

production rate and economic requirements may demand the use of non-traditional

machining processes.

A burr is defined as a projection of undesired material beyond the desired

machined features. Burrs are thin ridges, usually triangular in shape, that develop along

the edge of a work piece from various manufacturing operations, e.g. machining, shearing

of sheet materials, trimming, forging, casting, etc. Most of the conventional machining

processes and also some non-conventional machining process produce burrs. Shapes of

the burrs are generally triangular but sometime curly, wedge, circular may be appeared.

Elimination of burrs at the machining stage itself is not possible but it can only be

minimized by controlling the machining parameters and by selecting proper machining

method as far as possible.

Burrs formed during machining are the cause of many industrial problems.

Burrs can cause many problems during inspection, assembly and automated

manufacturing of precision components. They usually reduce the quality of machined

parts and can cause interference, jamming and misalignment of parts. Because of their

sharpness, they can be a safety hazard to personnel. Burrs may reduce the fatigue life of

2

components and can damage them. Burrs can lead to noisy, unsafe operation in

assembled machine parts, produce friction and wear in parts moving relative to each

other, short circuit in electrical component and may reduce fatigue life in components.

Production efficiency somehow reduces efficiency of production and also increased cost.

During heat treatment, an edge crack into the parts can lead to breakdown with

increasing tensile stress. Sharp burrs can be hazardous to the worker. Hence burrs are

totally undesirable portion of a workpiece and are required to remove in order to avoid

various disadvantages mentioned above. Deburring and edge finishing technology is

mostly required as a final process of machining operation in manufacturing of precise

components. But fitting a deburring process suitably into a FMS and full automation is an

extremely difficult problem. Burrs which are required to remove from the workpiece in

order to achieve desired surface finish are of various shapes, dimension and properties. It

is mainly because of this reason that there is no standardize procedure for removal of

burrs. The readily available possible solution to this problem is employed of manual

treatment for removal of burrs. In most of the industries, manual methods are commonly

used for removal of burrs. Manual methods of removal of burrs demand skilled workers

so that the surface finish desired can be fully achieved. So burr removal by manual labour

will lead to lower productivity and increase cost. Also different internal burrs, which are

complicated in shape and not very easily accessible, are very much difficult to be treat

manually. To overcome this problem, electrochemical deburring has been developed.

The electrochemical deburring process can be automated and can also be effectively

fitted to any flexible manufacturing system.

3

1.1. Burr Formation Mechanism

Various manufacturing operations can produce burrs by different ways. But there

has not been much detailed study of their formation in machining. Burr formation

mechanism to some general conventional cutting processes is described below.

Conventional cutting operations are three dimensional in nature, orthogonal

cutting and oblique cutting are generally used to study. But in most cases orthogonal

cutting is used because of the geometrical simplicity. Studies of burr formation in oblique

cutting have exhibited the relationship between burr size, shape and cutting parameter

and generally over a narrow range of cutting condition.

Shape of the burr in both orthogonal and oblique cutting is shown in Fig-1.1. The

initial burr formation is characterized by the initial negative shear angle and the initial

tool distance from the end of the workpiece. Burr size depends on the initial negative

shear angle and the initial tool distance from the end of the workpiece at which the

transition to burr formation occurs. Increasing thickness of the undeformed chip and

decreasing tool rake angle lead to increasing burr size. During burr initiation, the pivoting

occurs on the exit surface and large deformation zone is around the primary shear zone

extends towards the pivot point. A negative shear zone is formed between the tool edge

and pivoting point. Separation of chip along the ideal cutting line stops as soon as a crack

initiates and grows along the negative shear zone.

On the other hand, in oblique cutting, burr initiation starts from the leading side of

the tool on the workpiece. The distance of the leading portion of the tool from the part

edge for burr initiation is smaller than that in orthogonal cutting. As the tool advances,

the chip starts to twist and the deformation zone expands towards the left-hand side. The

pivoting point formed moves along the exit surface towards the left-hand side.

4

Fig-1.1 General burr shapes in orthogonal and oblique cutting

1.2 Definition of Deburring

Deburring is a process by which burr or thin ridges are removed by some

machining process or manual process to improve surface finishing and also improving the

quality of the parts.

1.3. Various Deburring Processes

Different techniques generally available for external and internal deburring are as

follows:

A) Conventional deburring processes

a) Manual post processing:

High skilled operators are required in this process. It is useful for external

deburring and not suitable for precession jobs. As it takes more time, therefore

productivity is low and also manufacturing cost is high.

b) Robotic deburring:

Industrial robots are generally used for performing deburring operation. Robotic

deburring can be performed in two ways. If the part is relatively lightweight, the robot

can handle the part and hold it against a tool that performs the actual deburring. If the part

is heavy, the robot can hold the deburring tool and control its motion around the

stationary part. In both ways, the relative motion between the tool and the part is of a

5

continuous-path (CP) type with high repeatability and accuracy. Hence, sensing the

contact forces that develop between the end-effectors of the manipulator and its interface

is very important and provides vital feedback information in the servo control for guiding

and controlling the robot in completing its task. . In both ways, deburring operation has

done automatically. However the cost for fixture and clamping and for on line

programming of the robot largely exceeds the potential savings of using robot for small

series of workparts. So, robotic deburring is mainly limited to deburring of large series of

parts with small burrs.

B) Non conventional deburring processes:

a) Abrasive jet deburring:

This is based on the principal of abrasive jet machining (AJM). In the AJM

process, when accelerating abrasive particles carried by air are directed onto the target

surface, the high velocity particles strike the target surface and remove the material by

erosion. But this process is suitable for high alloy and small burrs. Internal deburring

cannot be done by this process.

b) Thermal deburring:

It removes burr by the application of heat. This process is suitable for component

of large thickness. The physical properties may get affected due to the application of heat

in this process.

c) Vibratory deburring:

Ultrasonic vibration is used in this process and is useful for ductile materials only.

It can be applied for external deburring only. A very cost of the vibration unit is

encountered in this process.

d) Electrochemical deburring:

This is based on the principle of electrochemical machining. Electrochemical

deburring process overcomes many of the drawbacks experienced in case of other

deburring processes and is found to have the potential to become a highly effective and

efficient process.

6

1.4. Principle of Electrochemical Deburring

In electrochemical deburring, burrs are removed by concentrating electrolytic

dissolution on the desired spot in the material, as in the application of electrochemical

machining. Here electrode (tool) is placed close to the work-piece (generally 0.1mm to

0.5mm away). When an electrolyte flows and an electric current passes through the gap,

the burr near to the electrode gets dissolved due to the electrochemical action.

When a grater current density is induced into the gap between work-piece and

electrode, then the dissolution rate of work-piece becomes higher. The dissolution rate is

independent of the hardness and other characteristics of the workpiece material.

Deburring rate is being proportional to the current density.

The machining rate can be kept constant irrespective of hardness and the

toughness of the workpiece material. In electrochemical deburring, the hardness of the

machined surface is not changed after the deburring process. However, careful treatment

against electrolytic erosion is needed.

1.4.1. Fundamental features of electrochemical deburring

Electrochemical deburring has some distinct features which are as follows:

a) Electrochemical deburring does not apply any mechanical force or thermal effects

because of the non-contact nature of the process.

b) In electrochemical deburring, machining rate can kept constant irrespective of

hardness and toughness of the material.

c) In electrochemical deburring, the hardness of the machined surface is not changed

after the machining process. However careful treatment against tool movement and

electrolyte erosion is essential.

d) It can be applied for both external and internal deburring.

e) It relatively economical process for burr removal.

7

f) It is effective on all conductive materials irrespective of their hardness, toughness and

other properties.

g) This being a non contact type of process, the tool does not experience any force and

as a result there is no tool wear.

h) The physical properties of the workpiece do not get affected because very low

temperature is generated at the time of electrochemical deburring process.

i) Electrochemical deburring has the ability to machine materials with very low

machinability.

1.4.2. Mechanism of burr removal in electrochemical deburring

The mechanism of electrochemical deburring using NaNO3 as the electrolyte

fluid and metal including Fe as the work piece described in fig.1.2. Fe is dissolved at the

anode, the work piece, and hydrogen gas is generated at the cathode, resulting in Fe(OH)3

being precipitated. Unless the oxide formed between electrode and work piece is

removed quickly, it could insulate the work piece so that continuous machining is

disturbed. A fast flow of electrolyte through the small gap is acquired, controlled by a

pump for constant flow-rate. Also, the electrolyte transfers heat and sludge generated

during machining away from the working area, the electrolyte being re-used after

filtering.

Fig. 1.2 Mechanism of electrochemical deburring

8

Electrochemical deburring process is a process of material removal with the help

of electrochemical dissolution. It involves the principal of electrolytic anodic dissolution.

Initially certain amount gap is given in between the tool and workpiece. And tool acts as

a cathode, workpiece as the anode and gap filed with electrolyte. As a D.C. voltage is

usually applied across the two electrodes, a current passes through an electrolytic

solution. During this process, anodic dissolution of workpiece takes through

electrochemical dissolution reaction. The principal process parameter can control

machining rate and feed rate of tool should be given according to the machining rate. The

composition of workpiece material decides molecular weight. Different constituents may

have different valencies one element may exhibit more than one valency. Hence the

composition of work material is important in determining the actual machining rate.

Various process parameters are shown in fig-1.3.

The major advantages gained from electrochemical deburring process are

dependent upon the various process parameters such as machining voltage, current

density, feed rate, electrolyte and workpiece combination, flow rate of electrolyte,

conductivity of electrolyte, etc. For example, too much increase in voltage may cause a

rise in the generated gap pressure that throws the electrolyte out of the machining gap

decreasing the overall conductivity and thereby decreases the current density. It also

results in severe sparking which impair the surface finish, dimensional accuracy and

damages the work surface. So, from this point of view, the various process parameters of

electrochemical deburring process are very much important and should be controlled

properly in order to get full advantage from electrochemical deburring process.

9

Fig-1.3: Various process parameters of electrochemical deburring

Process parameter

Of

ECD

Work

Material Electro-

chemical

Equivalent

Electrical

Conductivity

Composition Chemical

Affinity

Working

Parameters

Electrolyte

Purity Concentration Feed

Rate

Voltage

Composition

& type Electrolyte

Flow rate

10

Fig-1.4: Schematic diagram of ECD

1.4.3. Electrochemistry of electrochemical deburring

ECD is based on the electrolysis. A typical arrangement of an electrolytic cell is

shown in the figure-2. When a potential difference is applied across the cathode and

anode, there are a number of possible reactions that can take place. The following are

some of that are relevant for ECD.

The reaction taking place at the anode is the dissolution of anode by the electrolyte.

Fe Fe++

+2e

Similarly, at cathode, hydrogen gas is released from the water contained in the

electrolyte.

H2O + 2e H2 +2OH

Combining the above two reactions, the iron and hydroxyl ions would combine form the

iron hydroxide as follows:

Fe++

+ OH Fe(OH)2

11

The net reaction of all the above three reactions can be shown as

Fe + 2H2O Fe(OH)2 + H2

It is further possible that the ion (ferrous) hydroxide may further react with water and

oxygen forming the ferric hydroxide as shown below:

4Fe(OH)2 + 2H2O + O2 4Fe(OH)3 + H2

It is interesting to note at this stage the net result is that iron gets dissolved from the

anode and forms the residue, consuming electricity and water only. The reaction products

are ferrite hydroxide and hydrogen gas. Based on this reaction, it is possible to make the

following observation.

• The metal from the anode is dissolve electro-chemically and hence the metal

removal rate based on the Faradays laws will depend upon atomic weight,

valancy, the current passed and the time for which the current is passed, and on no

other parameter.

• At the cathode, only hydrogen gas is evolved and no other reaction takes place, so

the shape of the cathode is unaffected.

Fig-1.5 Principal of electrolysis

12

1.4.4. Various electrolytes used in electrochemical deburring

Electrolytes play a key role in electrochemical deburring. It performs several

functions:

Completing the electrical circuit and allowing current to pass in between the electrodes.

ii) Sustaining the required electro-chemical reaction.

iii) Carrying away the heat generated.

iv) Carrying away the west products like sludge, debris, etc.

The first function required the electrolyte, ideally to have a large electrical

conductivity. The second function required the electrolyte to be such that at anode the

workpiece material is continuously dissolved, and a discharge of the metal ion on the

cathode should not occur.

The desired properties of an electrolyte required for an effective electrochemical

deburring operation are as follows:

i. High electro-chemical aggressiveness towards the material to be deburred.

ii. High electrical conductivity.

iii. Resistance to formation of passivating film on the work surface.

iv. Low viscosity and high specific heat.

v. Ability to suppress stray cutting.

vi. Should have chemical stability.

vii. Chemical inertness towards the conductive material and chemical inactiveness

towards the machine components.

viii. Non-corrosive, non-toxic, inexpensive and readily available.

Generally an aqueous solution of inorganic compounds is used as electrolyte. The

commonly used electrolytes for electrochemical deburring process are sodium chloride

(NaCl) solution in water, sodium nitrate (NaNO3) solution in water, permasol-60, etc.

The concentrations of the electrolyte are commonly kept between 15-25%. Specific

conductivity of the electrolyte depends upon the type of the electrolyte and its

concentration.

13

The viscosity determines the energy required to push it through the machining

gap. Conductivity and viscosity are again temperature dependent, the effect of which

must be considered to evaluate the deburring gap. In the present thesis work NaCl and

NaNO3 has been used to carry out the deburring operation, their composition shown in

table-1.1.

Electrolytes

Molar

mass

g/mol

Elemental composition

Symbol Element Atomic

weight

Number of

atoms

Mass

percent

(%)

NaNO3 84.9948

Na Sodium 22.98976 1 27.0484

N Nitrogen 14.00672 1 16.4795

O Oxygen 15.99943 3 56.4720

NaCl 58.4430 Na Sodium 22.98976 1 39.3371

Cl Chlorine 35.4532 1 60.6629

KCl 74.5515 K Potassium 39.09831 1 52.4447

Cl Chlorine 35.4532 1 47.5553

NaOH 39.9971

Na Sodium 22.9897 1 57.4785

O Oxygen 15.9994 1 40.0014

H Hydrogen 1.0079 1 2.5200

NaClO3 106.4413

Na Sodium 22.9897 1 21.5986

Cl Chlorine 35.4532 1 33.3078

O Oxygen 15.9994 3 45.0937

Table-1.1: Composition of different types of electrolytes.

14

1.5. Review of Past Research Works

A number of research works have been done on electrochemical deburring and

related field for studying the fundamental features and developing electrochemical

deburring system. Applied researchers are in progress to find out the parametric condition

required to enhanced edge quality and surface finish. Researchers are also progress to

working with very less time to removing burrs from different shape by different types of

tools. However most of the researchers are consider that surface finish is the main factor.

In this section the contribution of researchers on deburring are described.

Yuming Zhou, Jeffrey J. Derby [1] presented a new formulation for the cathode design

problem in electrochemical machining which is based on a finite element method for

solution of the direct problem of anode shape simulation and an optimization approach

for cathode shape determination. Analytical solutions of the inverse ECM problem are

quite limited in the classes of anode shapes which can be considered, while numerical

inverse formulations have been plagued by inaccuracy and convergence difficulties. By

posing the design problem as an optimization rather than an inverse problem, the

difficulties associated with the "ill-posedness" of the inverse formulation are

circumvented.

In-Hyu Choi, Jeong-Du Kim [2] studied about the characteristics of electrochemical

deburring, identified through experiments and the main factors, such as electrolytic gap

and electrolytic fluid, contributing to the elimination of a burr, were analyzed by the

height of the burr. Also the deburring efficiency and electrochemical performance for an

internal cross hole were examined for different electrolytic current and deburring

conditions. They describe the principle of electrochemical deburring using NaNO3 as the

electrolyte fluid and metal including Fe as the workpiece. And also find out the

equilibrium gap with various machining voltages and speed at the electrode. In

electrochemical deburring the equilibrium gap increases when the supply voltage

increases and decreases exponentially as the speed of feeding of the electrode increases.

The current contributing to electrochemical deburring decreases as electrolytic

15

dissolution proceeds owing to the prevention of electrochemical reaction by the

precipitation of sludge Fe(OH)3.

In-Hyu Choi, Jeong-Du Kim [3] developed a mechanism of electrochemical deburring

by using electroplated cubic boron nitride (CBN) wheels and its deburring performance is

investigated in an internal cross holes perpendicular to a small diameter and long length

pipe. The experimental technique used was based on the process of combination of a

rotation wheel (CBN) with an electrochemical dissolution involved in deburring inside

cross hole. Sintered carbide tool was used as deburring tool. Effective of different

parameter like abrasive material, current, electrolytic fluid, current density, cutting speed,

workpiece material, etc. were investigated to achieve the required surface finish and edge

quality. Deburring efficiency for internal cross hole was investigated with varying

electrolytic currents and other electrochemical condition. The others concluded that pulse

current was better than plain D.C. from the point of view of stability and performance of

deburring.

M. Abdel Mohsen Mahdy [4] investigated to find out the best combination of drilling

and enlarging as well as chamfering prior to enlarging, which minimizes the obtained

burr size. He developed a flowchart for the determination of the optimum conditions of

drilling with minimum manufacturing cost from the point of view of burr formation. It

enables also the evaluation of the ECD time to obtain the required deburring radius with

minimum cost for drilling followed by ECD, especially in case of drilling intersecting

holes. Burr can be reduced to a minimum value or approaches zero by proper selection of

predrilling and enlarging or chamfering/countersinking. A logic algorithm had been

established for the determination of the optimum values of cut for both predrilling and

enlarging, which gives maximum productivity and satisfies the imposed constraints and

leads to the minimum possible manufacturing cost of both drilling and ECD. The

minimum value of burr height to be deburred can be calculated using the optimum

conditions of drilling operations. The deburring time for a given fillet radius can be

estimated.

16

H. Hocheng, P.S. Kao, and Y.F. Chen [5] investigated the effects of the major

processing parameters on the anticorrosion performance and the surface roughness during

ECM. They had been reported a results of the experimental investigation on the effects of

the electrolyte temperature, electrical current density, water content, acid ratio, and

glycerin. The electrolyte temperature and current density show the major influence on the

corrosion resistance in their experiment. And the ideal passivation can be achieved at the

temperature over 70 0C and the electrical current nears the condition for a bright polished

surface. Good passivation is obtained at a temperature below 60 8C and a current density

of 2.5 A/cm2 or at a temperature higher than 75 0C and a current density of 0.75 to 1.0

A/cm2. When the temperature is below 60 8C, the passivation is mostly unsatisfactory

except that the current density is over 2.5 A/cm2. The water content of 10% is optimal for

passivation. Adding more water worsens the passivation.

Shuo-Jen Lee, Yu-Ming Lee, Ming-Feng Du [6] investigated about polishing

mechanism of electrochemical mechanical polishing (ECMP) technology for tooling steel

SKD11. The authors also evaluated the electrochemical process parameters and the

electrochemical characteristics of a material such as active, passive and trans-passive

(dissolution) can be revealed from its I–V curve. They analyzed experimental procedures

included qualitative, quantitative and surface quality. Qualitative analyses utilized

potentiostat to study the I–V curves of a specific specimen in various electrolytes and

electrolytic concentrations, and to find out the voltages at each electrochemical state. In

their quantitative analyses, the electrochemical polishing processes of the ECMP

technology were conducted. From the measured and theoretical weight losses, each

process state can be verified whether or not it followed the Faraday’s law. Finally, the

surface roughness was measured by a surface profiler. For good surface quality, it was

suggested to operate at the transient state. For better polishing efficiency, it may operate

at the trans-passive state. However, sufficient electrolyte may be needed to flush away

the reactant. Or, a mechanical polishing process with sufficient polishing pressure is

necessary to remove the re-depositary metallic hydroxide.

17

S. Sarkar, S. Mitra, B. Bhattacharyya [7] analyzed the characteristics of

electrochemical deburring through a developed mathematical model and main

influencing factors such as time, initial burr height, inter-electrode gap, voltage and base

material removal have been examined. The developed mathematical model is also used to

analyze and determine the deburring time as well as base material removal for a given

parametric combination. They also conclude that the rate of deburring is initially high and

it reduces gradually with respect to time, theoretically it would take an infinite time to

remove the burr completely. However a few minutes of deburring operation are sufficient

for all practical purpose. They were kept the gap between the workpiece and tool as small

as possible because it reduces the loss of base material as well as deburring time. And

also higher voltage should be used to reduce the deburring time. Loss of base material is

independent of electrolyte type, concentration, and voltage and workpiece material. It is

only function of inter-electrode gap setting, initial burr height and final desired burr

height.

H. Hocheng · P.S. Kao · S.C. Lin [8] analyzed that use the ECM process to erode a hole

of hundreds of micrometers on a thin metal sheet. The purpose of their study was to

predict the hole formation, particularly when boring through the hole. A theoretical

method is presented to illustrate how the machined profile evolves. Their analysis was

based on the fundamental law of electrolysis and the integral of the electrochemical

reaction over the finite width of the tool electrode. A concept of redistribution of electric

charge is adopted in the model when the hole is bored through. They observed at the

beginning of the ECM process, the percentage error of the model is larger with process

continues, the error is decreasing. The electrical current in the process is found to be the

same before and after boring through, hence the same amount of material removal with

the redistributed electric charges to the machined surface is adopted in the analysis. The

proper control of the initial gap and electrical voltage is essential in the electroboring

process.

18

P. S. Pa & H. Hocheng [9] analyzed the improvement of surface finish of medium or

large holes beyond traditional drilling, boring, rough turning, or extruding by

electrochemical smoothing using inserted rib-plate electrodes. In their experiment, six

types of electrode are completely inserted and connected to both continuous and pulsed

direct currents. The controlled factors include the chemical composition and the

concentration of the electrolyte, and the diameter of the electrode. The experimental

parameters are the current density, on/off period of pulsed current, rotational speed of

electrode, and the electrode geometry. The inserted electrodes with rib plates are suitable

for medium or large holes. The working time of the plate electrodes is short, provided the

power supply is sufficient. There exists an optimal rotational speed of electrode and

workpiece in the process. Various forms of electrode are developed and investigated. One

finds that the electrode with double lips performs better than the simple-plate electrode,

since the second lip provides a repolishing function. The electrode with a small wedge

angle towards the root of the rib provides a more sufficient discharge space, which

produces a better polishing effect. The use of a pulsed direct current only slightly

improves the effect of polishing, while it raises the machining cost due to the prolonged

cycle caused by the off time. The obtained surface roughness from either electrochemical

smoothing after drilling or electrobrightening after reaming is similar. Though the

polishing time of the electrochemical smoothing is longer, the total cycle time is shorter

by eliminating the preceding reaming process

Pai-Shan Pa [10] discussed about electrochemical smoothing and electrobrightening of

medium or large holes beyond traditional drilling, boring, turning, or extruding using

both inserted and feeding electrodes of borer-rib type for several common die materials.

In their experiment, six types of electrode are completely inserted and connected to both

continuous and pulsed direct current, while another six types of electrode are fed into

holes using continuous direct current. They conclude that higher flow rate of electrolyte

is advantageous, and there exists an optimal rotational speed of electrode and current

rating in the process. The use of pulsed direct current improves slightly the effect of

polishing, while it raises the machining cost due to the prolonged cycle time. For the

feeding electrodes, the electrode of one-side borer tip with half borer performs the best.

19

Though the polishing time of electrochemical smoothing is longer, the total cycle time is

shorter without the need of precision finishing process. The surface roughness obtained

from either electrochemical smoothing or electrobrightening is similar.

Joao Cirilo da Silva Neto, Evaldo Malaquias da Silva, Marcio Bacci da Silva [11]

studied about intervening variables in electrochemical machining (ECM) of SAE-XEV-F

Valve-Steel. They developed a prototype at the Federal University of Uberlandia, was

used for their experimental work. They studied about the material removal rate (MRR),

roughness and over-cut of ECM process. Feed rate, electrolyte, flow rate of the

electrolyte and voltage had the input parameter of their experiment. Two electrolytic

solutions i.e. sodium chloride (NaCl) and sodium nitrate (NaNO3) were used. They

showed that feed rate was the main parameter affecting the material removal rate. They

also concluded that the electrochemical machining with nitride sodium presented the best

results of surface roughness and over-cut.

P.S. Pa [12] investigated the geometry of electrodes and the advantages of low cost

equipments in electrochemical smoothing following end turning operation. An adequate

workpiece rotational speed associated with higher electrode rotation produces better

polishing. The effective design electrode with a small wedge angle and a small edge

rounding radius have an optimal value for higher current density and provides a larger

discharge space, which produces a smoother surface. The electrode of the partial curve

with a small line diameter performs the best for the electropolishing. Electrochemical

smoothing saves the need for precise turning, making the total process time less than the

electrobrightening. But the electrobrightening after precise turning only requires quite a

short time to make the workpiece bright. The use of ultrasonic in the electrochemical

smoothing and the electrobrightening is more evident than the pulsed current, since the

ultrasonic-aided process exempts off time and obtains a better polishing result. A smaller

wedge angle and smaller edge rounding radius are associated with higher current density

and provide a larger discharge space and better polishing. The electrode of the partial

curve with a small line diameter performs the best. The polishing effect of the ultrasonic

20

is superior to the pulsed current and the machining time needs quite short time by the off-

time. It was also found that electrobrightening after precise turning needs quite a short

time to make the workpiece smoothing and bright. The electrochemical smoothing saves

the need for precise turning, making the total process time less than the

electrobrightening.

Ramezanali Mahdavinejad, Mohammadreza Hatami [13] researched in a cartridge

house, inner surface electrochemical polishing of a gun pipe, with numerous serial

surface angles. They observed that the machined inner surface of the pipe via special

camera shows that, in most of them, there are refuses and non-uniformity patterns with

non-desirable surface quality in addition to the difficulties in gauge controlling

operations. They had solved this problem by filtering and heater installation in this

research. Besides, the polishing time has been optimized, so that, this time is nearly 30

times less than conventional polishing. Surface finishing in this research is 3.2µm before

polishing and it is 0.12µm after polishing. Their researched shows that the output

parameters of electrochemical polishing can be improved via set up conditions.

Kyeong Uk Lee, Sung Lim Ko [14] performed to analyze how deburring can be

efficiently carried out at intersecting holes. In case of inclined exit surface and

intersecting holes, deburring did not work so well. To simulate the surface at the

intersecting holes, a deburring experiment on inclined exit surface was carried out. Also

they performed an experiment to compare the deburring capability of each tool, namely

the burr-off tool and Beier tool. The burr-off tool is used for general burrs that were

formed on flat exit surfaces, whereas the Beier tool is special equipment for high-speed

deburring. They proposed a new efficient deburring method as well as a new deburring

tool design. Each parameter was analyzed to improve the deburring performance. Burr

geometry was analyzed using the burr measurement system, which was separately

developed.

Liang Liao, Fengfeng (Jeff) Xi, Kefu Liu [15] presented for modeling and control of an

automated polishing/ deburring process that utilizes a dual-purpose compliant toolhead.

21

This toolhead has a pneumatic spindle that can be extended and retracted by three

pneumatic actuators to provide tool compliance. By integrating a pressure sensor and a

linear encoder, this toolhead can be used for polishing and deburring. For the deburring

control, another PID controller is applied to regulate the tool length through tool

extension sensing. This control method have been tested and implemented on a

polishing/deburring robot, and the experiment results demonstrate the effectiveness of the

presented methods. Control scheme can effectively control the tool pressure to follow the

planned tool pressure under the constant contact stress condition. For the deburring

control, another PID controller is applied to maintain the desired tool length through tool

extension sensing. The experiment results show that this control scheme can effectively

control the tool length with or without the occurrence of burrs. The part profile

measurement has proven the uniform deburring along the part geometry with varying

burr geometry.

D. Shome, S. Mitra, S. Sarkar, [16] developed predictive models by studying the

influence of main process parameters of ECD process of SS304 stainless steel workpiece

on various deburring characteristics using Response Surface Methodology (RSM). High

values for coefficient of determination, obtained through Analysis of Variance

(ANOVA), ensure satisfactory fit of the developed models to the experimental data. They

analyzed the effect of different main influencing process parameters of ECD such as

concentration of the electrolyte, voltages, initial inter-electrode gap and machining time

on base metal removal and change in burr height were studied, using RSM. They

concluded that the experimental investigation is desirable to keep the gap between the

workpiece and the tool as small as possible, as it increases the burr removal rate, higher

voltage also should be used to enhance the removal height of the burr. Analysis of the

experimental results revealed that for the response ‘change in burr height’, the main

effects of deburring voltage, initial inter-electrode gap and deburring time and the

interaction effects of voltage-gap, voltage-time and gap-time and the quadratic effects of

voltage, gap and time, only, were significant. They had found the significance of the

effects of initial inter-electrode gap, deburring time and the interaction effects of gap-

time and the quadratic effects of gap and time on the base metal removal. They developed

22

second-order polynomial multiple regression model is quite powerful to analyze and

determine the change in burr height, as well as base metal removal amount, with good

accuracy for a given parametric combination.

M. Singha, S. Sarkar, S. Mitra [17] studied the influence of main process parameters of

ECD process of SS304 stainless steel workpiece on various deburring characteristics

using Response Surface Methodology (RSM). They developed a model for high values

for coefficient of determination, obtained through Analysis of Variance (ANOVA),

ensure satisfactory fit to the experimental data. They concluded that it is desirable to keep

the gap between the workpiece and the tool as small as possible, as it increases the burr

removal rate. Higher voltage should be used to enhance the removal height of the burr.

They developed a second order polynomial multiple regression model which is quite

powerful to analyse and determine the change in burr height, as well as base metal

removal amount, with good accuracy for a given parametric combination.

M. Singha, G.Paul, S. Sarkar and S. Mitra [18] presented a multi-objective

optimization technique for ECD of SS304 stainless steel. They modeled a process using

response surface methodology (RSM) in order to predict the response parameters i.e.

change in burr height and base metal removal as a function of different control

parameters i.e. concentration of the electrolyte, voltage, initial inter-electrode gap and

machining time. They applied grey relation analysis to compute grey relation grade. They

used grey relational grade that reduced the multi-objective problem to single response

problem, after obtaining the single response grey relational grade the model had

optimized to get the optimum level setting of the machining parameters. They got the

level setting which had been produces lowest base metal removal corresponding to

highest change in burr height.

M. Singha, A. S. Kuar, S. Sarkar and S. Mitra [19] presented a multi-objective

optimization technique for ECD. They applied a grey relational analysis on change in

burr height and base material removal. They used the grey relational grade to reducing

the multi objective problem to single response problem. After obtaining the single

23

response grey relational grade the model was optimized to get the optimum level setting

of the machining parameters. They used the central composite design (CCD) for their

experimental study. Finally they obtained a optimal solution for higher change in burr

height with less base metal removal.

24

Objective of the Present Research

Review of past research work revels that most of the researchers have performed

their experiments with deburring set-up for removing burrs of drilled holes and obtained

satisfactory indications for the possible industrial applications. Some of the researchers

were also concerned about surface finish and material removal rate. Most of the

researchers worked with the NaNO3 electrolyte. It is felt that further research is still

required on electrochemical deburring to analyze the effect of process parameters on

change in burr height and base material removal, on the basis of some planed

experimentation. This is required to minimize base material rate and maximize change in

burr height under various parametric settings. Moreover, the effect of electrolyte is

specially needed to be explored, as it is one of the most important parameter and very

little work has been done to highlight the role of electrolyte in ECD. Hence objective of

the present research has been planned as:

(i) to carry out an indepth study of burr removal mechanism in electrochemical

deburring and to identify the major process parameter and criteria of the process,

(ii) to investigate the change in burr height and base material removal with different

machining time, inter electrode gap, voltage and concentration on workpiece of same

initial burr height, on the basis of some planed experiment,

(iii)to carryout analysis of variance of the experimental results and to conduct verification

experiment for validation of the experimental design,

(iv) to plan for an experimental scheme to study the effect of electrolyte on change in burr

height and base material removal,

(v) to investigate the effect of the change of voltage and electrolyte concentration on

two types of electrolytes, i.e. NaNO3 and NaCl solutions , and in burr height and base

material removal,

(vi) to make a comparative analysis of the effect of NaNO3 and NaCl electrolytes on

change in burr height and also base material removal.

25

Composition of workpiece material (Die-steel):

Composition Symbol percentage

Carbon C 0.35%

Manganese Mn 0.4%

Silicon Si 1.0%

Chromium Cr 5.0%

Molybdenum Mo 1.5%

Vanadium V 1.0%

Table-1.2: Composition of die-steel

Mechanical properties of workpiece:

Property Values Unit

Density 7.8x10³ kg/m³

Modulus of elasticity 203 GPa

Thermal expansion (20 ºC) 12.6x10-6

ºC¯¹

Specific heat capacity 460 J/(kg K)

Thermal conductivity 24.6 W/(m K)

Hardness (annealed) 90 RB

Hardness (hardened) 60 RC

Hardening depth High

Resistivity to distortion Very high

Toughness Very high

Wear resistance Medium

Table-1.3: Mechanical properties of die-steel

26

2. MODELLING OF ELECTROCHEMICAL DEBURRING

PROCESS

In electrochemical deburring process gap between tool and workpiece influences

the machining speed and there exist a constant equilibrium gap when the electro-chemical

reactions taking place. When machining rate is same as theoretical one then inter

electrode gap may increase with zero tool feed rate. Initially a constant gap should

maintain called equilibrium gap. Machining rate can be controlled when concentration of

electrolyte, equilibrium gap, machining voltage are optimum, though tool feed is zero up

to the end of the machining. The equilibrium gap is determined by the supplied voltage

and feeding speed of the electrode when the workpiece material electrolyte are fixed,

which provides the effect of electrochemical in the machining process i.e. when the

machining distance between electrode and workpiece is smaller equilibrium gap, then the

dissolution of workpiece gets activated and when it is larger than equilibrium gap, then

the dissolution slow down. Thus, electrochemical deburring is a self adjusting process to

provide a stable machining process. The overall material dissolution rate is governed by

Faraday’s Laws of electrolysis.

27

2.1. Faraday’s Laws of Electrolysis

There are many industrial processes which are based on the principle of Faraday’s

laws of electrolysis. ECD is one of them, it can be considered as the reverse of

electroplating process. In ECD process metal has removed from burr with a very less

removal of base. The magnitude of the current employed in ECD process is very high as

compare to that used in electroplating or electrolytic pickling.

During ECD, metal from the anode (or workpiece) is removed atom by atom by

removing negative electrical charges that bind the surface atom to their neighbours. The

ionized atoms are then positively charged and can be attracted away from the workpiece

by an electric field. In an electrolytic cell material removal is governed by Faraday’s laws

of electrolysis given below.

(i) The amount of chemical change produced by an electric current (or the amount of

substance deposited or dissolved) is proportional to the quantity of electricity

passed.

(ii) The amount of different substances deposited or dissolved by the same quantity of

electricity are proportional to their chemical equivalent weights.

These laws can be expressed in mathematical from as follows:

……………………………...2.1.1

Where

m = weight (in grams) of a material dissolved or deposited,

I = current (in amperes)

t = time (in seconds)

ε = gram equivalent weight of the metal.

28

Introducing the constant of proportionality F commonly called Faraday (=96500

coulombs) and the above equation (2.1.1) becomes.

…………………………….2.1.2

The gram equivalent weight of the metal is given by,

Where,

A= Atomic weight

Z= Valency of ions produced.

Hence the rate of mass removal can be expressed in the form,

…………………………….2.1.3

If the density of the anode material is ρ, the volumetric removal rate is given by,

....................................2.1.4

In the actual ECM process, there are many other factors which affect the removal rate

[20]. Also, the process is seldom as ideal as a result, the actual removal rate may differ

slightly from that obtained theoretically from equation 2.1.4.

2.2. Material Removal Rate in ECD

It is always desirable to have minimum possible gap (usually≤0.5 mm) between

the two electrodes (tool and work) mainly to get accurate reproduction of tool shape on

the workpiece. To simplify the analysis given in this section, the following assumptions

are made [21]:

29

(i) Electrical conductivity (k) of electrolyte in the IEG remains constant.

(ii) Electrical conductivities of tool and workpiece materials are very large (1,00,00

Ω-1

cm-1

) as compared to that of electrolyte (less than 1.0 Ω-1

cm-1

). Hence, surface

of the electrodes can be considered as equipotentials.

(iii) Effective voltage working across the electrode is (V-∆V), where ∆V is a small

fraction of V (discussed latter) and include electrode voltage, overvoltage, etc. It

is assumed to remain constant.

(iv) The anode dissolves at one fixed valancy of dissolution.

For the simplicity of mathematical modeling, a case of plane parallel electrode

normal to feed direction is considered. The equation derived in the following will be

applicable mainly for such cases. Electrolyte is assumed to flow in the direction of

increasing X across the gap between two electrodes. It is also assumed that the properties

of electrolyte remain unchanged in the Z direction.

..................................2.2.1

………………….…...2.2.2

Where, η is current efficiency.

In ECD tool (cathode) is usually fed towards the workpiece (anode) at a constant rate.

During equilibrium, feed rate (f) of the cathode is equal to the rate at which length of the

burr (anode) being reduced i.e. MRR1. It is given in the following equation.

……………………...2.2.3

Where, J=I/A (A/mm2), and ρa is density (g/mm

3) of the anode material. In ECD process,

tool concentrates electric current on those area of the workpiece (burrs) from which

preferential removal of the metal is desired. Metal removal rate (MRR) from the burr is

controlled by current density of the edge of burr. Current density during machining

30

process is a function of shape of the electrodes (work and tool), their distance apart,

voltage applied across them, and electrical conductivity of electrolyte flowing through the

gap.

2.3. Voltage Drop During ECD

The relationship between the voltage applied across the electrodes and the flow of

current is not very simple. The total potential profile (fig-2.1) consists of the following:

(i) Electrode potential.

(ii) Overvoltage due to activation polarization. The electrochemical changes at an

electrode are in equilibrium when no current flows. The electrode potential acts as

a barrier to a faster rate of reaction. So an additional energy has to be supplied to

get the required MRR.

(iii) Concentration polarization. The ions migrate towards the electrodes of opposite

polarities, causing a concentration of ions near the electrode surfaces. Each ion

must pass through this concentration barrier to release its charge at the electrode

surface. So, extra voltage is required for the migration of ions through the

concentration layers.

(iv) Ohmic overvoltage. The films of solid materials forming on the electrode surface

offer an extra resistance to the passage of current.

(v) Ohmic resistance of electrode. The ohmic voltage drop occurs across the bulk of

the electrolyte. This is the main voltage drop and is the only part of the circuit

within the electrolyte which obeys Ohm’s law.

If the total overvoltage at the anode and the cathode is ∆V and the voltage applied

is V, the current I is then given by

………………………2.3.1

where R is the ohmic resistance of the electrolyte.

31

The conductivities of the tool and the workpiece are much larger than the

conductivity of electrolyte. The typical conductivity is about 0.1-1.0 Ω-1

cm-1

, whereas

that of iron is 105Ω

-1cm

-1. Thus the surface of the tool and the workpiece may considered

as equipotential. The conductivity of the electrolyte is not really constant because of the

temperature variation and accumulation of bubbles. However, for simple calculations, it

may be treated as constant.

Anode potential

Activation polarization overvoltage Anode

Ohmic overvoltage overvoltage

Concentration polarization overvoltage

V V-∆V Ohmic voltage

Concentration polarization overvoltage

Cathode Ohmic overvoltage

overvoltage

Activation polarization overvoltage

Cathode potential

Fig-2.1: Voltage drops in the gap between electrodes.

2.4. Modeling for Evaluation of Change in Burr Height & Base Material

Removal

Fig-2.2 shows a set of electrodes with plane and with plane and parallel surface.

The work (the upper electrode) is being fed with a constant velocity f in the direction Y

(normal to the electrode surface). The problem is considered to be one dimensional and

the instantaneous distance of the work surface from the tool is taken to be y. Consider the

workpiece to be pure metal, the removal rate of the workpiece metal is given by equation

(2.2.3). If the over voltage is ∆V, the density of the current flow through the electrolyte is

given by

32

…………………………2.4.1

where ‘k’ is the conductivity of the electrolyte.

y

Electrolyte +

Flow with y V

Velocity, v x

Fig-2.2: Kinematic scheme of ECM

Now the removal of workpiece material causes the surface of the workpiece to recede (in

the Y direction) with respect to the original surface with a velocity given by MRR1.

MRR1 is nothing but penetration rate, or rate of change of IEG, i.e. dy/dt.

………………………….2.4.2

Now using equation (2.4.1), we find this equation becomes

…………………...2.4.3

Replacing the term within the square brackets by a constant parameter λ, and became

……………………………...2.4.4

This is the basic equation representing the dynamics of ECM process.

tool

work

33

Now consider a workpiece with burr shown in fig-2.3. A and B two points located

on the tip of the burr and on the base material just adjacent to the burr, respectively,

before deburring operation. After deburring operation for time‘t’ points A and B will be

shifted to points A1 and B

1, respectively. Initial burr height and inter electrode gap are h0

and y0, respectively. After deburring operation for time‘t’ the reduced burr height is ‘h’

and ∆y is the measure of removal of base material or stock material as shown in fig-2.3.

Now consider two cases for getting the rate of change of IEG are (i) at zero feed rates, (ii)

at constant feed rate.

∆

h B

h0 A1 Burr after Flowing

A deburring y0 y electrolyte.

ya ya1 Burr before

deburring

Tool electrode (-)

Fig-2.3 Mechanism of deburring operation.

2.4.1 Evaluation of change in burr height & base material removal at zero feed rate

Now for this case of electrochemical deburring, tool is stationary, i.e. for a

stationary tool, f=0. Hence the equation (2.4.4) becomes

……………………………2.4.5

And after integration

………………………...2.4.6

Workpiece (+)

∆y

B1

34

Now from fig-2.3 it is seen that

…………………………2.4.7

After substituting the value of y from equation (2.4.6) the expression becomes

……………………2.4.8

As exhibited in fig-2.3 ya1 is the distance of the point A

1 after deburring from tool

electrode surface and ya is the distance of the point A before deburring operation from the

tool electrode surface. Hence,

...........................................2.4.9

And

………………………..2.4.10

Substituting the value of ya in equation (2.4.10)

…………………..2.4.11

Again from fig-2.3 instantaneous burr height can be expressed as follows:

……………………………2.4.12

Combining equations (2.4.6), (2.4.11) and (2.4.12) following equation can be obtained:

………………….2.4.13

Squaring both sides of equation (2.4.13) and rearranging the following equation obtained:

…2.4.14

35

Again squaring both side of equation and simplifying, the following equation is obtained:

.............................................................2.4.15

After rearranging the above equation deburring time can be expressed as follows:

……………2.4.16

From the above expression it may be observed that when h=0 deburring time t becomes

infinite i.e. it would take an infinite time to remove the burr completely. It means it is not

possible to remove the burr completely. However in practical situation burr height

reaches the desired allowable limit within few minutes.

Combining equation (2.4.8) and (2.4.16) removal of base material can be expressed as

follows:

………2.4.17

From the above expression it is clear that for a specified final burr height, loss of base

material is independent of voltage, workpiece material and conductivity of the

electrolyte. This only depends on initial burr height final burr height final burr height and

inter electrode gap. The above set of equation will be utilized to determine the burr

height, deburring time and material for various parametric combinations in

electrochemical deburring [7].

36

2.4.2 Determination of change in burr height at constant feed rate

An even increasing gap is not desirable in an ECM process. So, in practice, the

electrode provided with a constant feed velocity of suitable magnitude. Thus, in equation

(2.4.4), f is constant. Obviously, when the feed rate f equals to the velocity of recession

of the electrode surface due to metal removal, the gap remains constant. This gap (which

depends on the feed velocity) is called the equilibrium gap (ye). Thus, for the equilibrium

gap, equation (2.4.4) yields

……………………………2.4.18

Using non dimensional quantities and equation obtained

………………..2.4.19

Now equation (2.4.4) takes the form

With the initial condition , the solution of this equation yields

…………………2.4.20

Figure 2.4 shows the plot of versus for different value of the initial gap. It is seen that

the gap always approaches the equilibrium value irrespective of the initial condition.

37

4

3

3

2

1.5 2

1

0.5

0

0

2 4 6

Fig-2.4 electrode gap characteristics in ECM

38

3. EXPERIMANTAL SETUP FOR ELECTROCHEMICAL

DEBURRING

To carry out the research work on the parametric effect on deburring

characteristics in electrochemical deburring, an electrochemical deburring system with

the provision of variation and proper control of process parameter i.e. voltage, inter-

electrode gap etc. is absolutely essential. Hence, an attempt has been made in the present

research to carry out the effective study of deburring characteristics and successfully

application of electrochemical deburring in the field of advanced machining technology,

an electrochemical machine (EC MAC-II) is used and some modification has been done

on holding the workpiece. Generally electrochemical machining set-up (EC MAC-II) has

been used to carry out experimental investigation, changes has made in electrolyte flow

system, work holding device and machining tool. Brief descriptions of operating systems

are as follows. Photo 3.1 shows an overall view of electrochemical machining system.

3.1. General Features of Electrochemical Deburring Set-up

Fig 3.1 shows a schematic view of electrochemical machining set up.

Electrical power supply for machining operation: Generally alternative current (AC)

current has been employed as an input. A rectifier circuit comprise of three phase step

down transformer, three phase bridge rectifier to convert AC into DC. The control panel

is a 3 Dia bridge type rectifier with manual control on the DC output current 0-300A at

any voltage between 0-26V DC. DC Ammeter and DC voltmeter monitor and increase-

decrease push button is used to control the current and voltage respectively.

Power supply for machine drive: Stepper motor is the key drive at different load

combination. A 4-phase sequence and suitable stepper motor drive has been used and

which should be able to rotate the stepper motor at required speed with adequate torque.

PMW MOSFET is also used as a power drive of stepper motor. Geared motor, coupling

and lead screw should be able to control the tool feed. Over all system is an open loop

control based system and micro-controller based electronic unit has maintained the tool

feed without the help of feedback.

39

Geared motor

coupling driving lead screw.

lock nut

Cathode(-) Electrolyte nipple

sliding

bush

electrolyte

collector

Drain belt

A= remove 6 Nos allen cap screws of M8 form bottom of the electrolyte collector for the

replacement of the belt of screw jack or for repairs of X-Y coordinate plate.

B= handle of table rising & lowering.

Fig-3.1: Schematic view of electrochemical machining set-up (EC MAC-II)

Tool post

Tool

Tool holder

Screw jack

Anode workpiece

A

B

40

Machining chamber: Machining chamber made of transparent perplex sheet. The

perplex material has enough rigidity and also have good corrosion resistant properly

against electrolytes generally used in electrochemical deburring. Machining chamber was

fixed to the electrolyte collector tank. Machining chamber as well as electrolyte tank was

fixed with a screw jack. With controlling the handle of screw jack Z-axis movement of

machining chamber is possible. Workpiece was fixed with machining chamber by the

fixing arrangement. Both tool and work holding devices are insulated from the main body

in order to prevent the main machine body from electric shock and also to focus an

electrochemical reaction between tool and workpiece only. Machining chamber also

worked as insulation during machining operation. Unwanted electrolyte flow can be

maintained by the chamber with closing the transparent hood. An illumination system

also used to see the machining chamber when transparent hood is closed. Photo-3.2 is the

photographic picture of the machining chamber.

3.2. Electrolyte Flow Supply Unit

A sufficient flow of electrolyte into the gap between tool and the workpiece is

necessary to carry away the heat and products of machining and to assist the machining

process at required feed, producing satisfactory deburring results. Cavitation, stagnation

and vortex formation should be avoided because these lead to bad and improper

deburring result.

Flow of electrolyte into the machining chamber is made with the help of Fisher

water pump as shown in Fig-3.2. The electrolyte from the reservoir is pumped to the

machining chamber by the single phase pump of induction type motor through strainer.

Specification of pump is shown in Table-3.1. Initially valve A, B, C is open and all other

valves must be closed. Valve D is a bypass valve is used controlled the flow. If valve D

has a large opening then flow of electrolyte in the machining chamber must reduce.

Valve E and F are used to cleaning purpose. Valve C is used for recirculation of

electrolyte.

41

A flow meter is used to measure the flow rate in m3/hr. Flow rate was measured at

the delivery pipe of pump outlet. Photographic picture of the flow meter is shown in

Photo-3.4.

Fig-3.2: Flow diagram of electrolyte supply

42

KW/H.P.-0.75/1.0

Voltage-240 V

Frequency-50 Hz

Phase-single

Current(I)-3.5 amp

Speed(N)-2800 rpm

Pipe (mm)-25*25

Q (max)=40 (L/mm)

Head (max)-40 m

Table-3.1: Specification of pump.

3.3. Tool Holding Device

Tool holding device is a tool post and a tool holder. Tool was attached with the

tool holder. Adjustable spanner is used to tightening the tool. A driving lead screw has

been providing the Z-axis movement of the tool post. A gear motor and coupling is the

main drive system of the lead screw. Electrical power supply has been employed in the

tool by this tool post, and it insulated from the main body of machine. Tool feed is

depends on the rotation of the lead screw. So in case of selection of the gap between tool

and workpiece movement of the tool post is very important.

3.4. Workpiece Holding Device

During deburring, the job holding unit plays a vital role in the outcome of

accuracy and finish, as any steps of job and misalignment could lead to variation in the

desired results. So a tight and proper gripping of the job is needed for better performance.

Different type of work holding device has been designed for specific use in the

field of material processing and machining technology. In the present thesis, a flat job has

43

been used for the suitable deburring operation. In case of flat job, normally jigs and

fixtures are used in many cases. In this present research work, fixture is used to hold the

flat workpiece tightly and with a proper accuracy for better performance. Work holding

device also connect the workpiece with the electric supply and a perplex sheet is used to

prevent current flow through the machine body.

A strap clamp, a square block and a stud with nut used as a work holding device.

This strap clamp and stud are based on the lever principle to amplify the clamping force

required. Overall setup of work holding device is shown in Fig-3.3. By tightening the

stud, clamping force is transferred to the workpiece. Square block work as a fulcrum

about which the lever acts while the clamping force is applied at the stud by tightening

the bolt. The actual force applied to the workpiece at the end of the strap as shown in Fig-

3.3.

The strap design is shown in Fig-3.4. The strap is made of titanium material to

avoid anodic attack. The metals in contact have been chosen in such a way that they do

not differ much in their electrochemical behaviour. The stud and nut are made of

conductive material. Studs connect the workpiece with the electric supply connection

with the help of nuts.

44

Stud

Nut

Strap

Workpiece clamp here

Fig-3.3: Workpiece holding setup.

Fig-3.4: Strap design used for clamping.

Perplex sheet

Square block

45

Photo-3.1: Overall view of electrochemical machine

Photo-3.2: Machining chamber.

46

Photo-3.3: Control panel.

Photo-3.4: Flow meter.

47

Photo-3.5: Pump.

48

4. EXPERIMENTAL ANALYSIS OF ELECTROCHEMICAL

DEBURRING PROCESS.

4.1 Plan of Experimentation

Based on literature survey and preliminary investigations the following four

parameters i.e. voltage, electrolyte concentration, gap between tool and workpiece and

time were chosen as input. Response parameters were change in burr height and base

material removal. Responses are verified after the analysis with some verification

experiment. Table 4.1 shows different levels of these control parameters considered for

conducting the experimental work. An orthogonal array L9 has been employed according

to the Taguchi method based robust design philosophy to evaluate the main influencing

factor that affect the change in burr height and base material removal. Electrochemical

machine has been used for experimental observation.

4.1.1 Taguchi’s approach to parameter design

Taguchi’s approach provides the designer with a systematic and efficient approach

for conducting experimentation to determine near optimum settings of design parameters

for performance and cost. The method emphasizes passing quality back to the design

stage, seeking to design a product/process, which is insensitive to quality problems. The

Taguchi method utilizes orthogonal arrays to study a large number of variables with a

small number of experiments. Using orthogonal arrays significantly reduces the number

of experimental configuration to be studied. The conclusion drawn from small-scale

experiments are valid over the entire experimental resign spanned by the control factors

and their settings. This method can reduce research and developmental cost by

simultaneously studying a large number of parameters. In order to analyze the results,

the Taguchi method uses a statistical measure of performance called singal-to-noice

(S/N) ratio. The S/N ratio takes both the mean and the variability into account. The S/N

equation depends on the criterion for the quality characteristics to be optimized. After

performing the statistical analysis of S/N ratio, an analysis of variance (ANOVA) needs

to be employed for estimating error variance and for determining the relative importance

of various factors. Using the Taguchi method for parameter design, the predicted

49

optimum setting need not corresponds to one of the rows of the matrix experiments.

Therefore, an experimental confirmation is run using the predicted optimum levels for the

control parameters being studied. The purpose is to verify that the optimum conditions

suggested by matrix experiments do indeed lead to the projected improvement. If the

observed and the projected improvements match, the suggested optimum conditions will

be adopted. The corrective actions include finding better quality characteristics, or S/N

ratios, or different control factors and levels, or studying a few specific interactions

among the control factors. An efficient way to study the effect of several control factors

simultaneously I to plan a matrix experiments using orthogonal arrays. Orthogonal

arrays offer many benefits. First, the conclusion arrive from such experiments are valid

over the entire experimental region by the control factor and their settings. Second, there

is a large saving in the experimental effort. Third, the data analysis is very easy.

Finally, it can detect departure from the additive model. An orthogonal array for a

particular robust design project can be constructed from the knowledge of the number of

control factors, their levels, and the desire to study specific interactions. In the present

research, experiment based on L9 orthogonal array has been performed to investigate the

effect of the process parameters on change in burr height and base material removal rate.

The key features of this approach are as follows:

L9 Orthogonal Array:

In L9 array 9 rows represent the 9 experiment to be conducted with 4 columns at,

3 levels of the corresponding factors. The matrix forms of these arrays are shown in

Table 4.2.

Determination of S/N Ratio Curve:

S/N ratio is a mathematically transformed form for quality/performance

characteristics, the maximization of which minimizes quality loss and also improves

(Statistically) the additively of control factor effect.

From the each experimental result S/N value can be calculated as

50

η 10 log 1ny

…………………………………………………………………… .4.1.1

For smaller the better type problem and

η 10log 1n 1y

……………………………………………………………………4.1.2

For larger the better type problem.

Where η denotes the S/N ratio calculated from the observed or experimental value yi

represents the experimental observed value of the ith

experiment, and n is the number of

times each experiment is repeated.

Calculation for mean value of η:

m 1nη

…………………………………………………………………………………4.1.3

The effect of the factor level is defined as the division it causes from the overall

mean. The average S/N ratio at any level suppose A3 for experiments 5, 6 and 7 which is

denoted by mA3 is given by

m 13 η η η ……………………………………………………………………4.1.4

Thus the effect of that parameter at level A3 is given by (mA3-m).

By taking the numerical values of η, the average numerical value mAi for each level of

the factors can be obtained. These averages are obtained graphically which is known as

S/N ratio curve

51

Determination of Analysis of Variance (ANOVA):

A better feel for the relative effect of the different factors can be obtained by the

decomposition of the variance, which is commonly known as analysis of variance

(ANOVA). The purpose in conducting ANOVA is to determine the relative magnitude of

the of each factor on the objective function η and to estimate the error variance. In

Robust Design, ANOVA also used to choose from among many alternatives the most

appropriate quality characteristics and S/N ratio for a specific problem. ANOVA used to

investigate which machining parameters affected the observed values significantly. In the

present investigation, ANOVA and the F-test applied to analyze the experimental data.

The related meaning and equations are as follows:

S" #∑η %q , S) η S" ………………………………………………4.1.5

S+ ∑η N S", S- S. S/ ………………………………………………4.1.6

V Sf , F4 VV- ………………………………………………………4.1.7

Where,

Sm is the sum of square, based on the mean,

ST is the sum of square, based on total variation,

SA is the sum of square, based on parameter A,

SE is the sum of square, based on error

q is no of experiment

ηi is the mean value of each experiment (i=1,….,q)

ηAi is the sum of ith

level of parameter A (i=1,2 or i=1,2,3),

N is the repeating number of each parameter A level,

fA is the freedom degree of parameter A

52

VA is the variation of parameter A,

FAB is the F-test value of parameter A,

F0.05 , n1, n2 is as quoted from the “Table for Statisticians”. The contribution of the input

parameter is defined as significant if the calculated values exceed F0.05, n1, n2 [22].

Change in burr height:

Change in burr height is the main observing parameter throughout the experiment.

Machining rate also depends on this parameter, so larger of this parameter can decided

the machining rate is higher. However, according to Taguchi based methodology, when a

larger value represents the better machining performance, such as change in burr height,

is called larger-the-better type problem. Burr height was measured before the experiment

with the digital micrometer and also measured after the experiment and the difference

was computed as change in burr height.

Base material removal:

Base material removal was another observing parameter. Machining accuracy can

be increased with reduction of this parameter, so it is better to get smaller of this

parameter. According to Taguchi based methodology, when a smaller value represents

the better machining performance, such as base material removal, is called smaller-the-

better type problem Base material removal was measured with a digital micrometer.

Table-4.1: Factor and their levels.

Symbol Control factor Level

Unit 1 2 3

A Voltage 18 22 26 volts

B Concentration 15 20 25 gm/lit

C Gap between

tool and burr tip 0.2 0.3 0.4 mm

D Time 3 4 5 min

53

Expt. No. Voltage

(volts)

Concentration

(gm/lit)

Gap

(mm)

Time

(min)

1 18 15 0.2 3

2 22 20 0.3 3

3 26 25 0.4 3

4 18 20 0.4 4

5 22 25 0.2 4

6 26 15 0.3 4

7 18 25 0.3 5

8 22 15 0.4 5

9 26 20 0.2 5

Table 4.2:L9 Orthogonal Array.

4.2 Experimental Procedure

In order to carry out the experimental studies, a total of 9 workpieces were cut

from a square bar of Die-steel for conducting 9 experimental runs. The electrolyte was

pumped into the inter-electrode gap with the help of a centrifugal pump. The flow rate of

the electrolyte (NaNO3) which was kept constant at 16.40 m3/hr for all the experimental

runs, was measured using an online flow measuring device and was adjusted with the

help of flow control valves attached to the flow control unit of the developed ECD set up.

Electrolytes of different concentrations, for different experimental runs, were prepared by

adding appropriate proportions of NaNO3 salt to distilled water after weighing the salt.

Experimental sequence has been shown as below:

54

Switching on the machine with no load condition

Opening the transparent cover of machining chamber

Fiting the job on the machining chamber

Fiting the tool on the tool post by spanner

Checking the parallelism between job and tool

To adjust the electrolyte flow between the tool and job

Touching the job with tool face

Switching on the pump

Giving a reverse feed to tool to create a gap

Switching off the feeding controller after creating required gap

Switching on the start button

Setting a voltage and current for machining

Observing on timer

Switching off the start button

Closing the pump switch

Opening of the machining chamber and collect the machined workpiece.

55

4.3 Evaluation of Change in Burr Height and Amount of Base Material

Removal.

In the present thesis work digital micrometer is used to measure the job height.

First, the height from tip of the burr to bottom face of the workpiece was measured. Then

the height from base of the burr to bottom face of the workpiece was measured. The

difference was computed as the initial height of the burr. Final height of the burr i.e. the

height of the burr after the deburring operation was also measured in the same way and

the difference was computed as the change in burr height. In case of base metal removal

first, the height from base of the burr to bottom of the workpiece was measured and after

the experiment same type of experiment same type of measurement had been done and

the difference was computed as base material removal

Change in burr height was measured by a flat tip end to end measuring digital

micrometer. And base was measured by sharp tip digital micrometer. Least count of those

micrometers was 0.001mm. Photo 4.1 and photo 4.2 is shows two types of micrometer.

Photo-4.1: Flat tip end to end measuring digital micrometer.

56

Photo-4.2: Sharp tip end to end measuring digital micrometer.

Expt.

No.

Voltage

(volts)

Concentration

(gm/lit)

Gap

(mm)

Time

(min)

Change

in burr

height

(mm)

Base

material

removal

(mm)

1 18 15 0.2 3 0.409 0.0190

2 22 20 0.3 3 0.557 0.0300

3 26 25 0.4 3 0.569 0.0315

4 18 20 0.4 4 0.370 0.0150

5 22 25 0.2 4 0.645 0.0410

6 26 15 0.3 4 0.571 0.0345

7 18 25 0.3 5 0.547 0.0298

8 22 15 0.4 5 0.359 0.0145

9 26 20 0.2 5 0.760 0.0521

Table 4.3 Input and Response parameters for different experiment by NaNO3 electrolyte.

57

Fig. 4.1: S/N ratio curve for change in burr height (NaNo3).

Source DOF SS MS % of

contribution

F

Voltage 2 0.0555 0.278 39.69 1.36

Concentration 2 0.0339 0.0169 24.24 1.16

Gap between

tool and burr

tip

2 0.0475 0.0238 33.97 1.63

Time 2 0.0029 0.0015 2.04

Error 0 0

Total 8 0.1398

Error 8 0.1398 0.0175

Table-4.4: ANOVA Analysis for change in burr height (NaNO3).

58

Fig. 4.2: S/N ratio curve for Base material removal (NaNo3).

Source DOF SS MS % of

contribution

F

Voltage 2 0.0004980 0.000249 40.90 1.62

Concentration 2 0.0002278 0.0001139 18.71 0.74

Gap between

tool and burr

tip

2 0.0004485 0.0002243 36.84 1.46

Time 2 0.0000431 0.0000215 3.45 0.14

Error 0 - - - -

Total 8 0.0012174 - - -

Error 8 0.0012174 0.000153 - -

Table-4.5: ANOVA analysis for base material removal. (NaNO3)

59

4.4 Analysis and Discussion of Experimental Results

All the degree of freedom for estimating the factor effects have been used, here

four factors with three degrees of freedom each make up all the eight degrees of freedom

for the total sum of squares. Thus, there are eight degrees of freedom left for estimating

the error variance. An approximate estimate of the error variance can be obtained by

adding the sum of squares corresponding of the entire factor. Error variance computed in

this manner is indicated by parentheses in the ANOVA table, and the computation

method is called pooling.

The largeness of the factor effect relative to the error variance can be judge from

the F column. The larger the F value, larger the factor effect is compared to the error

variance. The larger contribution of a particular factor to the total sum of squares, the

larger the ability is of that factor to influence η.

4.4.1 ANOVA Test for change in burr height

From the sum of square column in Table-4.4 we can see that the voltage makes

the largest contribution to the total sum of squares (SS), namely, 39.69%. Gap between

the burr tip and tool makes the next largest contribution i.e. 33.97% to the total sum of

square. Concentration makes the third largest contribution, 24.24% and machining time

makes very small contribution, 2.07% to the total sum of square.

Therefore, voltage, gap between tool and burr tip and concentration of electrolyte

has effect on change in burr height. Because the F value of this three parameters is higher

and also this three parameters are most significant. So for getting the efficient deburring

operation we have to control of this three parameters very carefully.

4.4.2 ANOVA Test for base material removal

Referring to the sum of squares column in Table-4.5, notice that operating voltage

makes the largest contribution to the total sum of squares, namely, 40.90%. Gap between

tool and burr tip makes the next largest contribution, 36.84% to the total sum of squares.

Concentration and machining time have very small contribution 18.71% and 3.45%

respectively to the total sum of squares.

60

Therefore, voltage and gap between tool and burr tip has effect on change in base

material removal. Because the F value of this two parameters is higher and also this three

parameters are most significant. So for getting the efficient deburring operation we have

to control of this two parameters very carefully. Minimizing of these two parameters we

minimize the base material removal.

4.5 Parametric Analysis Based on Taguchi Methodology

Influence of machining parameter on change in burr height and base material

removal of the machined 1.5 mm burr has been investigated. Taguchi analysis has been

performed to determine the optimal setting of process parameters such as voltage,

concentration, gap, and machining time for removing the burr with minimum base

material removal by electrochemical deburring machine.

4.5.1. Analysis of the effect of process parameters on change in burr height

From S/N ratio curve for change in burr height as shown in Fig-4.1 it has been

found that machining rate is increase very sharply with increasing the voltage. In case of

concentration machining rate also increase but effect is slower than the voltage.

Machining rate or deburring rate will decrease with increasing the gap between tool and

the tip of burr. Machining time has a little effect on the deburring rate. Because of

increasing the voltage and concentration current flow will be increase in between the gap

of tool and workpiece so that the deburring rate will increase. But when the gap is

increase current flow will decrease so that machining rate should minimum. Form the

Fig-4.1 we can see that at 0.4 gap machining rate is very less and at 25 voltage machining

rate is very high.

It has been seen from table-4.3 that removal of burr is highest when voltages 26,

concentration 20, gap 0.2 and machining time is 4 min. And the value is 0.760. Lowest

machining has been seen on 22 voltages, 15 concentrations, 0.4 gap and 5 min. this value

is 0.359. From S/N ratio curve shown in Fig-4.1, optimal parameter setting has been

come for maximum change in burr height. Outcome of the experiment for optimal

parameter setting is shown in Table-4.6.

61

4.5.2. Analysis of the effect of process parameters on base material removal

From S/N ratio curve for base material removal as shown in Fig-4.2, it has been

found that base material removal have an increasing trend with the gap of ECD system.

Because of the current flowing area has been increased with increasing the gap. It has

been seen that base material removal rate decrease with the increasing of voltage and

concentration. With the increment of voltage deburring rate will increase so that

machining time became very less. Machining has a little effect on the deburring rate.

From S/N ratio curve of Fig-4.2 it has been found that the base material removal

rate is minimum when voltage 18, concentration 15, gap 0.4 and machining time 3.

Outcome of the experiment for optimal parameter setting to minimize base material

removal is shown in Table-4.6.

Out Comes of the Experiment

Table-4.6: Optimum Parametric Combination

Physical requirement Optimal combination

voltage Concentration Gap Time

Maximum change in burr

height 26 25 0.2 5

Minimum base material

removal 18 15 0.4 3

62

4.6 Confirmation Test

Conducting a verification experiment is a crucial, final and indispensable part of the

Taguchi method oriented robust design project. Its aim is to verify the optimum condition

suggested by the matrix experiment estimating how close the respective predictions with

the real ones are. The additive model was used to predict the response parameters i.e.

change in burr height and base material removal for all possible combination of level of

the input factors. However, if the observed S/N ratios under the optimum conditions

differ drastically from their respective predictions, the additive model proves to be a

failure eventually. The S/N values were predicted under the optimum condition for the

above case study. Also, S/N values were estimated from the machining results under

optimum parametric settings. To verify the proposed model another set of experiment has

been carried out as shown in Table-4.7. It is observed from Table-4.8 that prediction

based on additive model is quite close to the experimental observation. Prediction error

has been defined as follows:

Prediction Error % ?Exprimental result Predicted resultExperimental result ? E 100

It is clear that the data agree very well with the predictions. Therefore, the optimum

settings given in Table-4.7 may be adopted and implemented accordingly.

Expt.

No. Time Voltage Concentration Gap

Change

in burr

height

Base

material

removal

1 3 18 25 0.3 0.541 0.027

2 4 26 20 0.2 0.752 0.056

3 4 18 25 0.3 0.544 0.031

4 5 22 20 0.4 0.491 0.021

5 5 18 15 0.3 0.415 0.021

Table-4.7. Verification Experiment

63

Expt.

No.

Experimental value Predicted value Prediction error

(%)

Change

in burr

height

Base

material

removal

Change

in burr

height

Base

material

removal

Change

in burr

height

Base

material

removal

1 0.541 0.027 0.523 0.0259 3.32 4.07

2 0.752 0.056 0.737 0.0510 1.99 8.92

3 0.544 0.031 0.530 0.0292 2.57 5.80

4 0.491 0.021 0.442 0.0196 9.97 6.66

5 0.415 0.021 0.408 0.0187 1.18 10.95

Table-4.8: Comparison between Experimental Result and Additive Model Prediction

64

5. STUDY OF THE EFFECT OF ELECTROLYTE ON CHANGE

IN BURR HEIGHT AND BASE MATERIAL REMOVAL

Two types of electrolytes i.e. NaNO3 and NaCl have been selected for studying

the effect on change in burr height and base material removal. Same experiments have

done with both types of electrolytes. Input parameters and machining setup was same. In

the present thesis a comparison of electrochemical deburring has been done into change

in burr height and base material removal. Composition of two types of electrolyte is

shown in Table-5.1.

Another experimental design is used for machining with NaNO3 and NaCl

electrolyte. The set of experiment was planned in the form of a factorial design with two

parameters, voltage and concentration being selected as variables. Voltage having four

levels and electrolyte concentration is having three levels. The other parameters were

kept constant. Constant parameters are selected as per experimental trial methods [23].

Variable process parameters and their levels are shown in Table-5.2. Fixed

parameters and their selected values are shown in Table-5.3.

The overall planning or scheme for experimental investigations is shown in

Table-5.4.

Electrolytes Molar

mass

Elemental composition

Symbol Element Atomic

weight

Number

of atoms

Mass

percent

NaNO3 84.9948

g/mol

Na Sodium 22.98976 1 27.0484 %

N Nitrogen 14.00672 1 16.4795 %

O Oxygen 15.99943 3 56.4720 %

NaCl 58.4430

g/mol

Na Sodium 22.98976 1 39.3371 %

Cl Chlorine 35.4532 1 60.6629 %

Table-5.1: Composition of NaNO3 and NaCl.

65

Variable parameters

Level

Unit

1 2 3 4

Voltage (X1) 14 18 22 26 volts

Concentration (X2) 15 20 25 - gm/liter

Table-5.2: Factor and their levels

Fixed parameters Type/value

Workpiece material Die steel

Type of electrolytes NaNO3 and NaCl

Time 3 min.

Gap between tool and burr tip 0.4 mm

Tool feed rate zero

Tool material Copper

Electrolyte flow rate 16.40 m3/hr

Burr height 1.8 mm

Current 300 A

Table-5.3: Various fixed parameters

66

Experiment No. X1 X2

1 1 1

2 1 2

3 1 3

4 2 1

5 2 2

6 2 3

7 3 1

8 3 2

9 3 3

10 4 1

11 4 2

12 4 3

Table-5.4: Experimental plan

Experiment

No. X1 X2 X1(V)

X2

(gm/lit)

Change in

burr height

(mm)

Base material

removal rate

(mm)

1 1 1 14 15 0.178 0.006

2 1 2 14 20 0.242 0.009

3 1 3 14 25 0.334 0.019

4 2 1 18 15 0.269 0.009

5 2 2 18 20 0.396 0.011

6 2 3 18 25 0.488 0.024

7 3 1 22 15 0.329 0.010

8 3 2 22 20 0.431 0.023

9 3 3 22 25 0.509 0.029

10 4 1 26 15 0.390 0.018

11 4 2 26 20 0.491 0.024

12 4 3 26 25 0.569 0.031

Table-5.5: Input and response parameters of different experiments for NaNO3 electrolyte.

67

Experiment

No. X1 X2 X1(V)

X2

(gm/lit)

Change in burr

height (mm)

Base material

removal rate

(mm)

1 1 1 14 15 0.883 0.084

2 1 2 14 20 1.049 0.091

3 1 3 14 25 1.210 0.098

4 2 1 18 15 1.270 0.109

5 2 2 18 20 1.436 0.129

6 2 3 18 25 1.591 0.173

7 3 1 22 15 1.299 0.112

8 3 2 22 20 1.455 0.138

9 3 3 22 25 1.616 0.189

10 4 1 26 15 1.324 0.122

11 4 2 26 20 1.485 0.159

12 4 3 26 25 1.640 0.210

Table-5.6: Input and response parameters of different experiments for NaCl electrolyte.

5.1. Investigation on the Effect of Electrolyte on Change in Burr Height

From Table-5.5and Table-5.6, it has been seen that the change in burr height of

different experiments for NaNO3 and NaCl electrolyte respectively. From these different

values of change in burr height a comparison has been done with four values of voltage

and three values of concentration. So, total number of graph is 7 of changes in burr height

has been drown. First three is in between the change in burr height and voltage for three

type of electrolyte concentration. Another 4 is on change in burr height with respect to

concentration at different voltages.

All graphs has been drawn from the origin of (10,0) and at a constant time of 3

min. and at the gap between tool and burr tip of 0.4mm.. Input parameters are on X axis

and response parameter are on Y axis.

68

5.1.1. Effect of voltage on change in burr height at different electrolyte

concentrations

Fig-5.1: Voltage vs change in burr height graph

Fig-5.2: Voltage vs change in burr height graph

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Voltage

NaNo3

NaCl

t=3 min

gap=0.4 mm

concentration=25 gm/lit

0

0.2

0.4

0.6

0.8

1

1.2

1.4

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Voltage

NaNO3

NaCl

t=3 mim

gap=4 mm

concentration=15gm/lit

69

Fig-5.3: Voltage vs change in burr height graph

From the above graph of Fig-5.1, Fig-5.2 and Fig-5.3 it is clear that change in

burr height (removal of burr material) has been increase with voltage at different

electrolyte concentration for both types of electrolytes. In case of NaNO3 change of burr

erosion should not be more with the increase of voltage, at 25 and 20 concentrations rate

of change burr height is increase very rapidly up to the voltage of 18 V. After that burr

height changes very slowly. When NaCl is used, burr removal rate increase rapidly at

lower voltage i.e. 14 V to 18 V for three electrolyte concentrations. After 18 V increment

burr removal has not too high. As compare to the NaNO3, NaCl has a very high material

removal rate with the increase of voltage.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Voltage

NaNO3

NaCl

t=3 mim

gap=4 mm

concentration=20 gm/lit

70

5.1.2. Influence of electrolyte concentration on change in burr height at different

voltage

Fig-5.4: Electrolyte concentration vs change in burr height graph

Fig-5.5: Electrolyte concentration vs change in burr height graph

0

0.2

0.4

0.6

0.8

1

1.2

1.4

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage=14 V

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage=18 V

71

Fig-5.6: Electrolyte concentration vs change in burr height graph

Fig-5.7: Electrolyte concentration vs change in burr height graph

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mmvoltage=22 V

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

10 15 20 25 30

Chan

ge

in b

urr

hei

ght

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage =26 V

72

Effect of electrolyte concentration in change in burr height is shown in Fig-5.4,

Fig-5.5, Fig-5.5, and Fig-5.7. Change of burr is increase with the increase of voltage for

both types of electrolyte. Here it can seen that rate of change of burr height with the

change of concentration is near about to same at any voltage. Here also burr removal rate

is high for NaCl electrolyte compare to NaNO3. Maximum value of material removal

from burr is 1.640 for NaCl and 0.569 for NaNO3.

5.1.3. Comparison of the effect of the type electrolyte on change in burr height

According to the experimental result, voltage and concentration control the

change in burr height for both type of electrolyte. However it is observed that NaCl

resulted in higher change in burr height than NaNO3. This is shown in Fig-5.8.

Fig-5.8: Comparative study on change in burr height for NaCl and NaNO3 electrolyte

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 2 3 4 5 6 7 8 9 10 11 12

Chan

ge

in b

urr

hei

ght

Experiment No.

Comparison of change in burr height

NaCl

NaNO3

t=3 min

gap= 4 min

73

5.2. Study of the Effect of Electrolyte on Base Material Removal

From Table-5.5and Table-5.6, we can see the base material removal rate of

different experiments of NaNO3 and NaCl electrolytes respectively. From these different

values of different experiments of base material removal a comparison has been done

with four values of voltage and three values of concentration. So, total number of graph is

7 of base material removal can drawn. First three are base material removal rate and

voltage at three type of electrolyte concentration. Another 4 is on base material removal

with respect to concentration at different voltages.

All graphs has been drawn from the origin of (10, 0) and at a constant time of 3

min. and at the gap between tool and burr tip of 0.4mm. Input parameters are on X axis

and response parameter are on Y axis.

5.2.1. Influence of voltage on base material removal at different electrolyte

concentrations

Fig-5.9: Voltage vs base material removal graph

0

0.05

0.1

0.15

0.2

0.25

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Voltage

NaNO3

NaCl

t=3 mim

gap=4 mm

concentration=25 gm/lit

74

Fig-5.10: Voltage vs base material removal graph

Fig-5.11: Voltage vs base material removal graph

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Voltage

NaNO3

NaCl

t=3 mim

gap=4 mm

concentration=15 gm/lit

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Voltage

NaNO3

NaCl

t=3 mim

gap=4 mm

concentration=20 gm/lit

75

From the graph of Fig-5.9, Fig-5.10 and Fig-5.11 it is seen that base material

removal rate has been increase with increase of voltage. Base material removal rate is

very high and it also increases with voltage when NaCl electrolyte has been used. But in

case of NaNO3 base material removal rate has not very high as compare to NaCl. And

also increment of base material removal is not very high with the voltage at different

concentration.

5.2.2. Influence of electrolyte concentration on base material removal at different

voltage

Fig-5.12: Electrolyte concentration vs base material removal graph

0

0.02

0.04

0.06

0.08

0.1

0.12

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage=14 V

76

Fig-5.13: Electrolyte concentration vs base material removal graph

Fig-5.14: Electrolyte concentration vs base material removal graph

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage=18 V

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage =22 V

77

Fig-5.15: Electrolyte concentration vs base material removal graph

From the above graph of Fig-5.12, Fig-5.13, Fig-5.14, and Fig-5.15 we can see

that the change of base material removal with respect to the concentration at different

voltage. At lower voltage (14 V, Fig-5.12) increment of base material is not very high

with the increase of concentration. But at higher voltage (18, 22 and 26 V) base material

removal rate increase very rapidly with the concentration when NaCl electrolyte has been

used. There has a little effect on base material removal with concentration when NaNO3

electrolyte has been used.

5.2.3. Comparison of the effect of the type electrolyte on base material removal

A comparative study on base material removal for NaCl and NaNO3 electrolyte is

shown in Fig-5.16. From the figure it is seen that base material removal is very high for

NaCl compare to NaNO3. Base material removal rate is not more than 0.31 when NaNO3

electrolyte has been used. Base material removal rate is higher than 0.2 for NaCl

electrolyte.

0

0.05

0.1

0.15

0.2

0.25

10 15 20 25 30

Bas

e m

ater

ial

rem

oval

Electrolyte concentration

NaNO3

NaCl

t=3 min

gap=0.4mm

voltage=26 V

Fig-5.16: Comparative study on base material removal for NaCl and NaNO

From the Fig-5.8

NaCl electrolyte than NaNO

NaCl. Base material removal is very less for NaNO

5.18 we can see that the difference between

higher for NaNO3 electrolyte than NaCl electrolyte.

Base material removal is less for NaNO

Material removal rate is also less with NaNO

surface can produce with NaNO

Burr can be removed with less time with NaCl electrolyte but base material removal

very high.

0

0.05

0.1

0.15

0.2

0.25

1 2

Bas

e m

ater

ial

rem

oval

78

omparative study on base material removal for NaCl and NaNO

and Fig-5.16 it is clear that change in burr height is higher for

NaCl electrolyte than NaNO3 electrolyte and base material removal is also

NaCl. Base material removal is very less for NaNO3 electrolyte. From Fig

we can see that the difference between burr removal rate and base removal rate is

electrolyte than NaCl electrolyte.

Base material removal is less for NaNO3 electrolyte than NaCl electrolyte.

Material removal rate is also less with NaNO3 electrolyte. So it can say that, a better

surface can produce with NaNO3 electrolyte but more machining time should be

can be removed with less time with NaCl electrolyte but base material removal

3 4 5 6 7 8 9 10 11

Experiment No.

Comparison of base material removal

omparative study on base material removal for NaCl and NaNO3 electrolyte

it is clear that change in burr height is higher for

al removal is also higher for

electrolyte. From Fig-5.17 and Fig-

and base removal rate is

electrolyte than NaCl electrolyte.

electrolyte. So it can say that, a better

machining time should be required.

can be removed with less time with NaCl electrolyte but base material removal is

12

NaCl

NaNO3

t=3 min

gap= 4 min

79

Fig-5.17: Comparative study on change in burr height and base material removal for

NaNO3 electrolyte

Fig-5.18: Comparative study on change in burr height and base material removal for

NaCl electrolyte

0

0.1

0.2

0.3

0.4

0.5

0.6

1 2 3 4 5 6 7 8 9 10 11 12

Chan

ge

in b

urr

hei

ght

& b

ase

mat

eria

l

rem

oval

Experiment NO.

Change in burr height and base material removal for NaNO3

change in burr

height

base material

removal

t=3 min

gap=0.4 min

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 2 3 4 5 6 7 8 9 10 11 12

Chan

ge

in b

urr

hei

ght

& b

ase

mat

eria

l

rem

oval

Experiment NO.

Change in burr height and base material removal for NaCl

change in burr

height

base material

removal

t=3 min

gap=0.4 min

80

6. GENERAL CONCLUSION AND FUTURE SCOPE OF

WORK

6.1 General Conclusion

Based on the present study and experimental analysis of electrochemical

deburring (ECD) on die-steel material, the following general conclusions may be drawn:

i) Electrochemical deburring (ECD) is a very effective and useful process of deburring

which requires very less operation time and also causes no side effect as compared to

other deburring processes,

ii) From the fundamental study of Electrochemical deburring process it can be said that

burrs are removed by concentrating electrolytic dissolution on the desired spot on the

workpiece, as in the application of electrochemical machining,

iii) The effective utilization of electrochemical deburring in modern manufacturing

industry to achieve higher deburring rate with greater accuracy especially for the hard

to machine advanced materials such as die steel, etc, there is need of proper selection

of electrolyte and combination of different process parameters,

iv) An experimental analysis for change in burr height and base material removal based

on Taguchi method and subsequent ANOVA test has been successfully used to

optimize the process i.e. machining time and gap between tool and burr tip with

NaNO3 electrolyte,

v) Experimental investigation based on Taguchi method and analysis of the results

reveal that the machining parameters used in the present set of research i.e. voltage,

concentration, gap, and machining time with NaNO3 electrolyte have got main effects

on change in burr height and base material removal as exhibited through the graphical

representations. This investigation also can evaluate the gap and machining time

where burr removal rate is high with little base material removal,

81

vi) A 2k full factorial experimental design was used to the study of the effect of voltage,

and electrolyte types and concentration with NaNO3 and NaCl at the gap of 0.4mm

and machining time of 3 minute,

vii) Experimental investigation of to explore the effect of type of electrolyte reveals that,

rate of change of burr height is higher for NaCl electrolyte than NaNO3 at different

concentrations and voltages as exhibited through the different graphical

representations,

viii) Experimental results also highlighted that the base material removal is higher for

NaCl electrolyte than NaNO3 electrolyte,

ix) From the comparative study it can be concluded that deburring with NaNO3

electrolyte is better than NaCl electrolyte because, from accuracy point of view, the

latter causes has a higher base material removal rate than that with NaNO3 electrolyte

for removing equal height burrs.

82

6.2. Future Scope of Work

The future scope of work includes:

i) Experimental study on complicated ribs and surfaces i.e. deburring cylindrical

surface, internal cross-hole, cross-drilled holes etc.

ii) To carry out experimental investigation on long workpieces of advanced materials

like γ-titanium aluminide etc.

iii) More experimental study using different techniques like GA, ANN etc. to

optimize the process criteria yields.

83

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