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Transcript of Acc. No. DC 18
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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