Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
IOP Conference Series Materials Science and Engineering
OPEN ACCESS
Investigation of surface roughness in micro-electrodischarge machining of nonconductive ZrO2 forMEMS applicationTo cite this article A Sabur et al 2013 IOP Conf Ser Mater Sci Eng 53 012090
View the article online for updates and enhancements
You may also likeSurface modification and functionalizationby electrical discharge coating acomprehensive reviewPay Jun Liew Ching Yee Yap JingsiWang et al
-
Effect of external magnetic field on thermalconductivity and viscosity of magneticnanofluids a reviewSerkan Doganay Rahime Alsangur andAlpaslan Turgut
-
Exploration of government policy structurewhich support and block energy transitionprocess in indonesia using systemdynamics modelA R Destyanto T D Silalahi and AHidayatno
-
This content was downloaded from IP address 826675160 on 14022022 at 0750
Investigation of surface roughness in micro-electro discharge
machining of nonconductive ZrO2 for MEMS application
A Sabur1 A Moudood
2 M Y Ali
3 M A Maleque
4
Department of Manufacturing and Materials Engineering Faculty of Engineering
International Islamic University Malaysia PO Box 10 50728 Kuala Lumpur
Malaysia
Email1 asabur72yahoocom email
2 mamoudoodgmailcom email
3
mmyaliiiumedumy email4 malequeiiumedumy
Abstract Micro-electro discharge machining technique a noncontact machining
process is applied for drilling blind hole on nonconductive ZrO2 ceramic for MEMS
application A conductive layer of adhesive copper is applied on the workpiece surface
to initiate the sparks Kerosene is used as dielectric for creation of continuous
conductive pyrolytic carbon layer on the machined surface Experiments are
conducted by varying the voltage (V) capacitance (C) and rotational speed (N)
Correlating these variables a mathematical model for surface roughness (SR) is
developed using Taguchi method The results showed that the V and C are the
significant parameters of SR in micro-EDM for nonconductive ZrO2 ceramic The
model also showed that SR increases with the increase of V and C
1 Introduction
Microelectromechanical systems (MEMS) are developed in accordance with the advancement in
modern technologies MEMS or MEMS-based devices can be used for many engineering applications
In telecom or consumer electronics MEMS-based devices may be used in huge volume potentially
MEMS may also be used in niche markets in small scale where it can be the key enabling factor [1]
Structuring various types of micro holes and micro channels are needed in MEMS devices MEMS are
produced mainly by lithography and silicon micromachining processes which are applicable for
specific and limited materials Advanced ceramic materials have been used for a variety of biomedical
and implant devices These ceramics are considered very important material that has high potential to
deliver significant contributions for solving the challenges of our future especially in MEMS
application such as microfluidics reactors and electromechanical generators [2] But advanced
ceramics is difficult to be processed by lithography and silicon micromachining techniques Micro-
electro-discharge machining (micro-EDM) is considered as a suitable machining technique for
microstructuring which can fulfil the gap between the diversity of engineering ceramics and the ability
to use them in MEMS Micro-EDM provides excellent opportunities for research development and
manufacturing of such products It allows leveraging of non-traditional high-performance engineering
materials with various features such as plasticity robustness chemical inertness and biocompatibility
that cannot be achieved through conventional MEMS fabrication processes and their compatible
materials This ability also promotes proper choice of materials that are compatible with particular
environments for MEMS fabrication [3] Micro-EDM is an electro-thermal material removal process
which is a derived form of EDM for manufacturing micro-components It is a known process for
1 To whom any correspondence should be addressed
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
Content from this work may be used under the terms of the Creative Commons Attribution 30 licence Any further distributionof this work must maintain attribution to the author(s) and the title of the work journal citation and DOI
Published under licence by IOP Publishing Ltd 1
structuring and shaping of hard and brittle materials In micro-EDM a series of electrical sparks or
discharges occur rapidly in a short span of time within a constant spark gap between tool electrode and
workpiece and materials are removed due to the thermal energy of the spark The material to be
machined by micro-EDM requires a minimal electrical conductivity of 01 Scm-1
Most of the
advanced ceramics such as ZrO2 Al2O3 Si3N4 are electrically nonconductive Therefore EDM cannot
be directly applicable to the nonconductive ceramics [4] A basic process is introduced to apply EDM
for processing the nonconductive ceramic in which an assisting electrode (AE) layer of electrically
conductive material is applied The sparks initially occur between the tool electrode and the AE layer
After finishing the temporary external layer a layer of pyrolytic carbon is deposited on the substrate
surface disassociating the carbonic dielectric in appropriate conditions [5 6] Micro-EDM of advanced
ceramics for MEMS structuring is considered as an important technique However surface roughness
is the significant characteristics that can limit the micro-EDM of advanced ceramics for production of
MEMS [7] The empirical modelling of the process is an effective way of selecting the best parameters
to get optimum outputs and to increase production rate significantly Precise surface roughness is
essential to fabricate intricate and micro products This study aims to investigate the effect of input
parameters on the continuous machining of nonconductive ceramics and to develop model of SR using
Taguchi method in micro-EDM of ZrO2 ceramic
2 Experiments
The schematic diagram of the experimental setup of micro-EDM for nonconductive ceramic with the
AE is shown in figure 1 The machining has been conducted using micro-EDM machine (Mikrotool
Singapore) In the present study 92 pure ZrO2 ceramic plate is used as workpiece material The
properties of the workpiece material are listed in the Table 1 The copper tool electrode of ϕ1 mm is
used The workpiece and the tool electrode were cleaned by acetone before machining Since the
workpiece is electrically nonconductive its surface is covered by an adhesive copper layer to occur the
sparks After the removal of this external layer a new conductive layer is created instantaneously on
the machined surface using cracked carbon combined with the debris of tool electrode material This
layer acts further as an AE Cu foil has excellent electrical conductivity and easy to remove after
machining without any damage After machining the workpiece is cleaned again by acetone
Figure1 Schematic diagram of micro-EDM set up for
machining of ZrO2
Table 1 Physical properties of ZrO2
Property [unit] Value
Hardness [Hv] 1270 Melting temperature [
0C] 2720
Specific heat capacity
[JKg0C]
540
Specific gravity [Kgm3] 610
Electrical resistivity [Ω-cm] 1010
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
2
The machining parameters used in the experiments are listed in the Table 2 After machining the
workpiece is cleaned by acetone for investigation of surface textures WYKO NT1100 optical
profiling system is used to measure the SR and machined surface is inspected by scanning electron
microscope (SEM) (JEOL JSM-5600) To find the optimum SR experiments are done varying the
parameters such as V C and S keeping other parameters constant In the present study L9 orthogonal
array (3 factors x 3 levels) based on Taguchi method is used to design of the experiments and
subsequent analysis of the data collected
3 Results and discussions
The ZrO2 ceramic workpiece machined by micro-EDM is shown in figure 2 and SEM image of
machined surface is shown in figure 3 Holes of 100 microm depth are created on the ZrO2 workpiece The
pyrolytic carbon layer on the machined surface is produced continuously from kerosene dielectric
fluid and adhesive Cu foil as initial assisting electrode Figure 3 shows the SR in different micro-EDM
conditions on the ZrO2 ceramics Table 3 shows the SR in different EDM conditions on the ZrO2
ceramics according to L9 orthogonal array (3 factors x 3 levels) based on the Taguchi design
ANOVA and F test results are given in Table 4 to show the significant parameters associated with
each machining conditions F-value of model implies the significance of the model There is only
about 005 chances that a ldquoModel F - Valuerdquo of this large could occur due to noise From this
analysis a model for the estimation of SR has been developed as the function of V C and N as shown
in equation (1)
079-00015V+86610
-4C-49310
-5N-36710
-6VC -17110
-6CN (1)
Figure 2 Micro-holes of ϕ1mm on ZrO2 substrate
machined by micro-EDM using adhesive Cu foil as
AE and Cu tool electrode with ndashve polarity
Figure 3 SEM image of surface texture of
micro-hole as (window A figure 2) in micro-
EDMed ZrO2 surface with SR=15 microm at C =
100 pF V = 90 V and N = 350 rpm
Table 2 Machining parameters
Parameters [unit] Values
Voltage [V] 80 90 100
Capacitance [pF] 10 100 1000
Speed (rpm) 250 300 350
Threshold () 27
Tool polarity -ve
Dielectric Kerosene
Assisting
Electrode Adhesive copper foil
Table 3 SR for micro-hole drilling by micro-EDM
designed according to Taguchi method
Run Voltage
[V]
Capacitance
[C]
Speed
[rpm]
SR
[microm]
1 100 10 350 164
2 80 10 250 13
3 90 100 350 15
4 90 1000 250 078
5 80 100 300 138
6 100 1000 300 17
7 100 100 250 153
8 80 1000 350 156
9 90 10 300 14
A
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
3
Table 4 ANOVA for Response Surface Reduced 2FI Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob gt F
Model 0013946 5 0002789 3919819 00062 Significant
A 000492 1 000492 691356 00036
B 0001005 1 0001005 1412583 00329
C 0009036 1 0009036 1269864 00015
AB 0001296 1 0001296 1820647 00236
BC 0007002 1 0007002 983975 00022
Residual 0000213 3 712E-05
Cor Total 001416 8
Figure 4 SR graph in different micro-EDM conditions for ZrO2 ceramic
vs (a) voltage (b)
capacitance (c) speed (d) Interaction graph of voltage and capacitance
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = A Voltage
Actual FactorsB Capacitance = 50500C Speed = 30000
8000 8500 9000 9500 10000
0604
0641
0677
0713
0750
A Voltage
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = B Capacitance
Design Points
Actual FactorsA Voltage = 9000C Speed = 30000
1000 25750 50500 75250 100000
0609
0644
0679
0714
0750
B Capacitance
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = C Speed
Actual FactorsA Voltage = 9000B Capacitance = 50500
25000 27500 30000 32500 35000
0592
0632
0671
0710
0750
C Speed
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)Design Points
X = A VoltageY = B Capacitance
Actual FactorC Speed = 30000
10Sqrt(SR + 100)
A Voltage
B C
apac
itanc
e
8000 8500 9000 9500 10000
1000
25750
50500
75250
100000
0626215
0643489
0660762
0678035
0695308
Voltage (V) Capacitance (pF)
Speed (rpm) Voltage (V)
Cap
acit
ance
(p
F)
a b
c
d
50500
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
4
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5
Investigation of surface roughness in micro-electro discharge
machining of nonconductive ZrO2 for MEMS application
A Sabur1 A Moudood
2 M Y Ali
3 M A Maleque
4
Department of Manufacturing and Materials Engineering Faculty of Engineering
International Islamic University Malaysia PO Box 10 50728 Kuala Lumpur
Malaysia
Email1 asabur72yahoocom email
2 mamoudoodgmailcom email
3
mmyaliiiumedumy email4 malequeiiumedumy
Abstract Micro-electro discharge machining technique a noncontact machining
process is applied for drilling blind hole on nonconductive ZrO2 ceramic for MEMS
application A conductive layer of adhesive copper is applied on the workpiece surface
to initiate the sparks Kerosene is used as dielectric for creation of continuous
conductive pyrolytic carbon layer on the machined surface Experiments are
conducted by varying the voltage (V) capacitance (C) and rotational speed (N)
Correlating these variables a mathematical model for surface roughness (SR) is
developed using Taguchi method The results showed that the V and C are the
significant parameters of SR in micro-EDM for nonconductive ZrO2 ceramic The
model also showed that SR increases with the increase of V and C
1 Introduction
Microelectromechanical systems (MEMS) are developed in accordance with the advancement in
modern technologies MEMS or MEMS-based devices can be used for many engineering applications
In telecom or consumer electronics MEMS-based devices may be used in huge volume potentially
MEMS may also be used in niche markets in small scale where it can be the key enabling factor [1]
Structuring various types of micro holes and micro channels are needed in MEMS devices MEMS are
produced mainly by lithography and silicon micromachining processes which are applicable for
specific and limited materials Advanced ceramic materials have been used for a variety of biomedical
and implant devices These ceramics are considered very important material that has high potential to
deliver significant contributions for solving the challenges of our future especially in MEMS
application such as microfluidics reactors and electromechanical generators [2] But advanced
ceramics is difficult to be processed by lithography and silicon micromachining techniques Micro-
electro-discharge machining (micro-EDM) is considered as a suitable machining technique for
microstructuring which can fulfil the gap between the diversity of engineering ceramics and the ability
to use them in MEMS Micro-EDM provides excellent opportunities for research development and
manufacturing of such products It allows leveraging of non-traditional high-performance engineering
materials with various features such as plasticity robustness chemical inertness and biocompatibility
that cannot be achieved through conventional MEMS fabrication processes and their compatible
materials This ability also promotes proper choice of materials that are compatible with particular
environments for MEMS fabrication [3] Micro-EDM is an electro-thermal material removal process
which is a derived form of EDM for manufacturing micro-components It is a known process for
1 To whom any correspondence should be addressed
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
Content from this work may be used under the terms of the Creative Commons Attribution 30 licence Any further distributionof this work must maintain attribution to the author(s) and the title of the work journal citation and DOI
Published under licence by IOP Publishing Ltd 1
structuring and shaping of hard and brittle materials In micro-EDM a series of electrical sparks or
discharges occur rapidly in a short span of time within a constant spark gap between tool electrode and
workpiece and materials are removed due to the thermal energy of the spark The material to be
machined by micro-EDM requires a minimal electrical conductivity of 01 Scm-1
Most of the
advanced ceramics such as ZrO2 Al2O3 Si3N4 are electrically nonconductive Therefore EDM cannot
be directly applicable to the nonconductive ceramics [4] A basic process is introduced to apply EDM
for processing the nonconductive ceramic in which an assisting electrode (AE) layer of electrically
conductive material is applied The sparks initially occur between the tool electrode and the AE layer
After finishing the temporary external layer a layer of pyrolytic carbon is deposited on the substrate
surface disassociating the carbonic dielectric in appropriate conditions [5 6] Micro-EDM of advanced
ceramics for MEMS structuring is considered as an important technique However surface roughness
is the significant characteristics that can limit the micro-EDM of advanced ceramics for production of
MEMS [7] The empirical modelling of the process is an effective way of selecting the best parameters
to get optimum outputs and to increase production rate significantly Precise surface roughness is
essential to fabricate intricate and micro products This study aims to investigate the effect of input
parameters on the continuous machining of nonconductive ceramics and to develop model of SR using
Taguchi method in micro-EDM of ZrO2 ceramic
2 Experiments
The schematic diagram of the experimental setup of micro-EDM for nonconductive ceramic with the
AE is shown in figure 1 The machining has been conducted using micro-EDM machine (Mikrotool
Singapore) In the present study 92 pure ZrO2 ceramic plate is used as workpiece material The
properties of the workpiece material are listed in the Table 1 The copper tool electrode of ϕ1 mm is
used The workpiece and the tool electrode were cleaned by acetone before machining Since the
workpiece is electrically nonconductive its surface is covered by an adhesive copper layer to occur the
sparks After the removal of this external layer a new conductive layer is created instantaneously on
the machined surface using cracked carbon combined with the debris of tool electrode material This
layer acts further as an AE Cu foil has excellent electrical conductivity and easy to remove after
machining without any damage After machining the workpiece is cleaned again by acetone
Figure1 Schematic diagram of micro-EDM set up for
machining of ZrO2
Table 1 Physical properties of ZrO2
Property [unit] Value
Hardness [Hv] 1270 Melting temperature [
0C] 2720
Specific heat capacity
[JKg0C]
540
Specific gravity [Kgm3] 610
Electrical resistivity [Ω-cm] 1010
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
2
The machining parameters used in the experiments are listed in the Table 2 After machining the
workpiece is cleaned by acetone for investigation of surface textures WYKO NT1100 optical
profiling system is used to measure the SR and machined surface is inspected by scanning electron
microscope (SEM) (JEOL JSM-5600) To find the optimum SR experiments are done varying the
parameters such as V C and S keeping other parameters constant In the present study L9 orthogonal
array (3 factors x 3 levels) based on Taguchi method is used to design of the experiments and
subsequent analysis of the data collected
3 Results and discussions
The ZrO2 ceramic workpiece machined by micro-EDM is shown in figure 2 and SEM image of
machined surface is shown in figure 3 Holes of 100 microm depth are created on the ZrO2 workpiece The
pyrolytic carbon layer on the machined surface is produced continuously from kerosene dielectric
fluid and adhesive Cu foil as initial assisting electrode Figure 3 shows the SR in different micro-EDM
conditions on the ZrO2 ceramics Table 3 shows the SR in different EDM conditions on the ZrO2
ceramics according to L9 orthogonal array (3 factors x 3 levels) based on the Taguchi design
ANOVA and F test results are given in Table 4 to show the significant parameters associated with
each machining conditions F-value of model implies the significance of the model There is only
about 005 chances that a ldquoModel F - Valuerdquo of this large could occur due to noise From this
analysis a model for the estimation of SR has been developed as the function of V C and N as shown
in equation (1)
079-00015V+86610
-4C-49310
-5N-36710
-6VC -17110
-6CN (1)
Figure 2 Micro-holes of ϕ1mm on ZrO2 substrate
machined by micro-EDM using adhesive Cu foil as
AE and Cu tool electrode with ndashve polarity
Figure 3 SEM image of surface texture of
micro-hole as (window A figure 2) in micro-
EDMed ZrO2 surface with SR=15 microm at C =
100 pF V = 90 V and N = 350 rpm
Table 2 Machining parameters
Parameters [unit] Values
Voltage [V] 80 90 100
Capacitance [pF] 10 100 1000
Speed (rpm) 250 300 350
Threshold () 27
Tool polarity -ve
Dielectric Kerosene
Assisting
Electrode Adhesive copper foil
Table 3 SR for micro-hole drilling by micro-EDM
designed according to Taguchi method
Run Voltage
[V]
Capacitance
[C]
Speed
[rpm]
SR
[microm]
1 100 10 350 164
2 80 10 250 13
3 90 100 350 15
4 90 1000 250 078
5 80 100 300 138
6 100 1000 300 17
7 100 100 250 153
8 80 1000 350 156
9 90 10 300 14
A
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
3
Table 4 ANOVA for Response Surface Reduced 2FI Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob gt F
Model 0013946 5 0002789 3919819 00062 Significant
A 000492 1 000492 691356 00036
B 0001005 1 0001005 1412583 00329
C 0009036 1 0009036 1269864 00015
AB 0001296 1 0001296 1820647 00236
BC 0007002 1 0007002 983975 00022
Residual 0000213 3 712E-05
Cor Total 001416 8
Figure 4 SR graph in different micro-EDM conditions for ZrO2 ceramic
vs (a) voltage (b)
capacitance (c) speed (d) Interaction graph of voltage and capacitance
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = A Voltage
Actual FactorsB Capacitance = 50500C Speed = 30000
8000 8500 9000 9500 10000
0604
0641
0677
0713
0750
A Voltage
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = B Capacitance
Design Points
Actual FactorsA Voltage = 9000C Speed = 30000
1000 25750 50500 75250 100000
0609
0644
0679
0714
0750
B Capacitance
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = C Speed
Actual FactorsA Voltage = 9000B Capacitance = 50500
25000 27500 30000 32500 35000
0592
0632
0671
0710
0750
C Speed
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)Design Points
X = A VoltageY = B Capacitance
Actual FactorC Speed = 30000
10Sqrt(SR + 100)
A Voltage
B C
apac
itanc
e
8000 8500 9000 9500 10000
1000
25750
50500
75250
100000
0626215
0643489
0660762
0678035
0695308
Voltage (V) Capacitance (pF)
Speed (rpm) Voltage (V)
Cap
acit
ance
(p
F)
a b
c
d
50500
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
4
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5
structuring and shaping of hard and brittle materials In micro-EDM a series of electrical sparks or
discharges occur rapidly in a short span of time within a constant spark gap between tool electrode and
workpiece and materials are removed due to the thermal energy of the spark The material to be
machined by micro-EDM requires a minimal electrical conductivity of 01 Scm-1
Most of the
advanced ceramics such as ZrO2 Al2O3 Si3N4 are electrically nonconductive Therefore EDM cannot
be directly applicable to the nonconductive ceramics [4] A basic process is introduced to apply EDM
for processing the nonconductive ceramic in which an assisting electrode (AE) layer of electrically
conductive material is applied The sparks initially occur between the tool electrode and the AE layer
After finishing the temporary external layer a layer of pyrolytic carbon is deposited on the substrate
surface disassociating the carbonic dielectric in appropriate conditions [5 6] Micro-EDM of advanced
ceramics for MEMS structuring is considered as an important technique However surface roughness
is the significant characteristics that can limit the micro-EDM of advanced ceramics for production of
MEMS [7] The empirical modelling of the process is an effective way of selecting the best parameters
to get optimum outputs and to increase production rate significantly Precise surface roughness is
essential to fabricate intricate and micro products This study aims to investigate the effect of input
parameters on the continuous machining of nonconductive ceramics and to develop model of SR using
Taguchi method in micro-EDM of ZrO2 ceramic
2 Experiments
The schematic diagram of the experimental setup of micro-EDM for nonconductive ceramic with the
AE is shown in figure 1 The machining has been conducted using micro-EDM machine (Mikrotool
Singapore) In the present study 92 pure ZrO2 ceramic plate is used as workpiece material The
properties of the workpiece material are listed in the Table 1 The copper tool electrode of ϕ1 mm is
used The workpiece and the tool electrode were cleaned by acetone before machining Since the
workpiece is electrically nonconductive its surface is covered by an adhesive copper layer to occur the
sparks After the removal of this external layer a new conductive layer is created instantaneously on
the machined surface using cracked carbon combined with the debris of tool electrode material This
layer acts further as an AE Cu foil has excellent electrical conductivity and easy to remove after
machining without any damage After machining the workpiece is cleaned again by acetone
Figure1 Schematic diagram of micro-EDM set up for
machining of ZrO2
Table 1 Physical properties of ZrO2
Property [unit] Value
Hardness [Hv] 1270 Melting temperature [
0C] 2720
Specific heat capacity
[JKg0C]
540
Specific gravity [Kgm3] 610
Electrical resistivity [Ω-cm] 1010
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
2
The machining parameters used in the experiments are listed in the Table 2 After machining the
workpiece is cleaned by acetone for investigation of surface textures WYKO NT1100 optical
profiling system is used to measure the SR and machined surface is inspected by scanning electron
microscope (SEM) (JEOL JSM-5600) To find the optimum SR experiments are done varying the
parameters such as V C and S keeping other parameters constant In the present study L9 orthogonal
array (3 factors x 3 levels) based on Taguchi method is used to design of the experiments and
subsequent analysis of the data collected
3 Results and discussions
The ZrO2 ceramic workpiece machined by micro-EDM is shown in figure 2 and SEM image of
machined surface is shown in figure 3 Holes of 100 microm depth are created on the ZrO2 workpiece The
pyrolytic carbon layer on the machined surface is produced continuously from kerosene dielectric
fluid and adhesive Cu foil as initial assisting electrode Figure 3 shows the SR in different micro-EDM
conditions on the ZrO2 ceramics Table 3 shows the SR in different EDM conditions on the ZrO2
ceramics according to L9 orthogonal array (3 factors x 3 levels) based on the Taguchi design
ANOVA and F test results are given in Table 4 to show the significant parameters associated with
each machining conditions F-value of model implies the significance of the model There is only
about 005 chances that a ldquoModel F - Valuerdquo of this large could occur due to noise From this
analysis a model for the estimation of SR has been developed as the function of V C and N as shown
in equation (1)
079-00015V+86610
-4C-49310
-5N-36710
-6VC -17110
-6CN (1)
Figure 2 Micro-holes of ϕ1mm on ZrO2 substrate
machined by micro-EDM using adhesive Cu foil as
AE and Cu tool electrode with ndashve polarity
Figure 3 SEM image of surface texture of
micro-hole as (window A figure 2) in micro-
EDMed ZrO2 surface with SR=15 microm at C =
100 pF V = 90 V and N = 350 rpm
Table 2 Machining parameters
Parameters [unit] Values
Voltage [V] 80 90 100
Capacitance [pF] 10 100 1000
Speed (rpm) 250 300 350
Threshold () 27
Tool polarity -ve
Dielectric Kerosene
Assisting
Electrode Adhesive copper foil
Table 3 SR for micro-hole drilling by micro-EDM
designed according to Taguchi method
Run Voltage
[V]
Capacitance
[C]
Speed
[rpm]
SR
[microm]
1 100 10 350 164
2 80 10 250 13
3 90 100 350 15
4 90 1000 250 078
5 80 100 300 138
6 100 1000 300 17
7 100 100 250 153
8 80 1000 350 156
9 90 10 300 14
A
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
3
Table 4 ANOVA for Response Surface Reduced 2FI Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob gt F
Model 0013946 5 0002789 3919819 00062 Significant
A 000492 1 000492 691356 00036
B 0001005 1 0001005 1412583 00329
C 0009036 1 0009036 1269864 00015
AB 0001296 1 0001296 1820647 00236
BC 0007002 1 0007002 983975 00022
Residual 0000213 3 712E-05
Cor Total 001416 8
Figure 4 SR graph in different micro-EDM conditions for ZrO2 ceramic
vs (a) voltage (b)
capacitance (c) speed (d) Interaction graph of voltage and capacitance
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = A Voltage
Actual FactorsB Capacitance = 50500C Speed = 30000
8000 8500 9000 9500 10000
0604
0641
0677
0713
0750
A Voltage
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = B Capacitance
Design Points
Actual FactorsA Voltage = 9000C Speed = 30000
1000 25750 50500 75250 100000
0609
0644
0679
0714
0750
B Capacitance
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = C Speed
Actual FactorsA Voltage = 9000B Capacitance = 50500
25000 27500 30000 32500 35000
0592
0632
0671
0710
0750
C Speed
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)Design Points
X = A VoltageY = B Capacitance
Actual FactorC Speed = 30000
10Sqrt(SR + 100)
A Voltage
B C
apac
itanc
e
8000 8500 9000 9500 10000
1000
25750
50500
75250
100000
0626215
0643489
0660762
0678035
0695308
Voltage (V) Capacitance (pF)
Speed (rpm) Voltage (V)
Cap
acit
ance
(p
F)
a b
c
d
50500
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
4
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5
The machining parameters used in the experiments are listed in the Table 2 After machining the
workpiece is cleaned by acetone for investigation of surface textures WYKO NT1100 optical
profiling system is used to measure the SR and machined surface is inspected by scanning electron
microscope (SEM) (JEOL JSM-5600) To find the optimum SR experiments are done varying the
parameters such as V C and S keeping other parameters constant In the present study L9 orthogonal
array (3 factors x 3 levels) based on Taguchi method is used to design of the experiments and
subsequent analysis of the data collected
3 Results and discussions
The ZrO2 ceramic workpiece machined by micro-EDM is shown in figure 2 and SEM image of
machined surface is shown in figure 3 Holes of 100 microm depth are created on the ZrO2 workpiece The
pyrolytic carbon layer on the machined surface is produced continuously from kerosene dielectric
fluid and adhesive Cu foil as initial assisting electrode Figure 3 shows the SR in different micro-EDM
conditions on the ZrO2 ceramics Table 3 shows the SR in different EDM conditions on the ZrO2
ceramics according to L9 orthogonal array (3 factors x 3 levels) based on the Taguchi design
ANOVA and F test results are given in Table 4 to show the significant parameters associated with
each machining conditions F-value of model implies the significance of the model There is only
about 005 chances that a ldquoModel F - Valuerdquo of this large could occur due to noise From this
analysis a model for the estimation of SR has been developed as the function of V C and N as shown
in equation (1)
079-00015V+86610
-4C-49310
-5N-36710
-6VC -17110
-6CN (1)
Figure 2 Micro-holes of ϕ1mm on ZrO2 substrate
machined by micro-EDM using adhesive Cu foil as
AE and Cu tool electrode with ndashve polarity
Figure 3 SEM image of surface texture of
micro-hole as (window A figure 2) in micro-
EDMed ZrO2 surface with SR=15 microm at C =
100 pF V = 90 V and N = 350 rpm
Table 2 Machining parameters
Parameters [unit] Values
Voltage [V] 80 90 100
Capacitance [pF] 10 100 1000
Speed (rpm) 250 300 350
Threshold () 27
Tool polarity -ve
Dielectric Kerosene
Assisting
Electrode Adhesive copper foil
Table 3 SR for micro-hole drilling by micro-EDM
designed according to Taguchi method
Run Voltage
[V]
Capacitance
[C]
Speed
[rpm]
SR
[microm]
1 100 10 350 164
2 80 10 250 13
3 90 100 350 15
4 90 1000 250 078
5 80 100 300 138
6 100 1000 300 17
7 100 100 250 153
8 80 1000 350 156
9 90 10 300 14
A
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
3
Table 4 ANOVA for Response Surface Reduced 2FI Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob gt F
Model 0013946 5 0002789 3919819 00062 Significant
A 000492 1 000492 691356 00036
B 0001005 1 0001005 1412583 00329
C 0009036 1 0009036 1269864 00015
AB 0001296 1 0001296 1820647 00236
BC 0007002 1 0007002 983975 00022
Residual 0000213 3 712E-05
Cor Total 001416 8
Figure 4 SR graph in different micro-EDM conditions for ZrO2 ceramic
vs (a) voltage (b)
capacitance (c) speed (d) Interaction graph of voltage and capacitance
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = A Voltage
Actual FactorsB Capacitance = 50500C Speed = 30000
8000 8500 9000 9500 10000
0604
0641
0677
0713
0750
A Voltage
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = B Capacitance
Design Points
Actual FactorsA Voltage = 9000C Speed = 30000
1000 25750 50500 75250 100000
0609
0644
0679
0714
0750
B Capacitance
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = C Speed
Actual FactorsA Voltage = 9000B Capacitance = 50500
25000 27500 30000 32500 35000
0592
0632
0671
0710
0750
C Speed
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)Design Points
X = A VoltageY = B Capacitance
Actual FactorC Speed = 30000
10Sqrt(SR + 100)
A Voltage
B C
apac
itanc
e
8000 8500 9000 9500 10000
1000
25750
50500
75250
100000
0626215
0643489
0660762
0678035
0695308
Voltage (V) Capacitance (pF)
Speed (rpm) Voltage (V)
Cap
acit
ance
(p
F)
a b
c
d
50500
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
4
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5
Table 4 ANOVA for Response Surface Reduced 2FI Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob gt F
Model 0013946 5 0002789 3919819 00062 Significant
A 000492 1 000492 691356 00036
B 0001005 1 0001005 1412583 00329
C 0009036 1 0009036 1269864 00015
AB 0001296 1 0001296 1820647 00236
BC 0007002 1 0007002 983975 00022
Residual 0000213 3 712E-05
Cor Total 001416 8
Figure 4 SR graph in different micro-EDM conditions for ZrO2 ceramic
vs (a) voltage (b)
capacitance (c) speed (d) Interaction graph of voltage and capacitance
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = A Voltage
Actual FactorsB Capacitance = 50500C Speed = 30000
8000 8500 9000 9500 10000
0604
0641
0677
0713
0750
A Voltage
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = B Capacitance
Design Points
Actual FactorsA Voltage = 9000C Speed = 30000
1000 25750 50500 75250 100000
0609
0644
0679
0714
0750
B Capacitance
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)
X = C Speed
Actual FactorsA Voltage = 9000B Capacitance = 50500
25000 27500 30000 32500 35000
0592
0632
0671
0710
0750
C Speed
10
Sqr
t(SR
+ 1
00)
One Factor PlotWarning Factor involved in an interaction
DESIGN-EXPERT Plot
10Sqrt(SR + 100)Design Points
X = A VoltageY = B Capacitance
Actual FactorC Speed = 30000
10Sqrt(SR + 100)
A Voltage
B C
apac
itanc
e
8000 8500 9000 9500 10000
1000
25750
50500
75250
100000
0626215
0643489
0660762
0678035
0695308
Voltage (V) Capacitance (pF)
Speed (rpm) Voltage (V)
Cap
acit
ance
(p
F)
a b
c
d
50500
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
4
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5
Figure 4(a) illustrates that SR increases with the increase of V On the other hand figure 4(b) indicates
that the SR decreases as C increases Hence SR is significantly influenced by capacitance and the gap
voltage in micro-EDM of nonconductive ceramic materials At very low capacitance spark energy is
very low which leads to lower flushing efficiencies and debris remains inside the machined hole So
at lower capacitance (below 100 pF) SR is higher On the contrary at higher values of capacitance and
voltage the more energy produced debris are carried away rapidly with dielectric bubbles from the
gap resulting lower SR However at higher energy level the crater is bigger and the SR increases
From the interaction graph (figure 4(d)) it is evident that the optimum parameter ranges lies at voltage
90 capacitance 500 pF and speed 300 rpm The existing Mikrotool machine does not have the facility
to use 500 pF Therefore further experiments are needed for verification of the results modifying the
Mikrotool machine adding extra capacitances
4 Conclusions
Micro-holes were created on nonconductive ZrO2 substrate for MEMS application by micro-EDM
using assisting electrode method The effect of input parameters such as voltage capacitance and
rotational speed of tool on surface roughness is investigated The parameters are optimized based on
the Taguchi method Following conclusions can be drawn from this study
1 Using adhesive copper foil as assisting electrode and copper tool electrode with ndashve polarity in
kerosene dielectric micro-EDM of nonconductive ZrO2 ceramic is done effectively (figure 2)
2 Empirical model of SR correlating the voltage capacitance and rotational speed of tool is
developed using Taguchi method (equation 1)
3 In the micro-EDM of nonconductive ZrO2 ceramic the significant parameter of SR is
capacitance and voltage (figure 4)
4 External copper layer can be removed from the micro-EDMed ceramic surface without any
damage to the holes (figure 2)
5 Further experiments are needed to investigate the effect of parameters on SR in micro-EDM of
nonconductive ZrO2 ceramic at higher capacitance values (gt1000 pF)
6 Experiments for verification of optimum parameter values (V=90 C=500) is needed through the
modification of the Mikrotool with extra capacitances
5 Acknowledgements
The authors would like to thank the Ministry of Science Technology and Innovation (MOSTI)
Malaysia for financial support under Science Fund Research Project 03-01-08-SF0135
References
[1] Pieters P 2009 Versatile MEMS and mems integration technology platforms for cost effective
MEMS development In Microelectr and Packag Conf European pp 1-5 IEEE
[2] Roumldel J Kounga A B Weissenberger-Eibl M Koch D Bierwisch A Rossner W and Schneider
G 2009 Development of a roadmap for advanced ceramics 2010ndash2025 J European Ceramic
Society 29(9) pp 1549-1560
[3] Takahata K 2009 Micro-electro-discharge machining technologies for MEMS Microelectronic
and mechanical systems IN-TECH pp 143-164
[4] Houmlsel T Muumlller C and Reinecke H 2011 Spark erosive structuring of electrically
nonconductive zirconia with an assisting electrode CIRP J Manuf Sci and Tech 4(4)
pp 357-361
[5] Mohri N Fukuzawa Y Tani T Saito N and Furutani K 1996 Assisting electrode method for
machining insulating ceramics CIRP Annals Manuf Tech 45 pp 201-204
[6] Sabur A Ali M Y Maleque M A and Khan A A 2013 Investigation of Material Removal
Characteristics in EDM of Nonconductive ZrO2 Ceramic Procedia Eng 56 pp 696-701
[7] Williams J R and Clarke D R 2008 Strengthening gold thin films with zirconia nanoparticles
for MEMS electrical contacts Acta Materialia 56(8) pp 1813-1819
5th International Conference on Mechatronics (ICOMrsquo13) IOP PublishingIOP Conf Series Materials Science and Engineering 53 (2013) 012090 doi1010881757-899X531012090
5