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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

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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

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