2014. 04. 25.
International Scientific Conference “Development in Machining”
DIM 2014, 24-25 April 2014 Cracow Poland
Study on surface quality and
electrode wear in EDM
technology
MIKÓ Balázs; DRÉGELYI-KISS Ágota; POÓR Attila
Óbuda University
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
EDM – Electric discharge machining
The thermal energy of the electric spark remove
the material
Electrically conductive materials
Independent from the hardness of the workpiece
No mechanical load and deformation
Electrode material: copper, graphite, other
Aim of the research
Study
The surface quality and the Electrode wear.
In case of different
Electrode material and Process parameters.
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Test part and tools
1.2343 (x38CrMoV5-1)
52-54 HRC
pocket size 15x7.5 mm
Cu
3
Copper (Cu 99.9%)
Graphite (Gr Meusburger Q60)
Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Test devices
Ingersoll Gantry 400
Mitutoyo SJ-301 surface roughness
measurement unit
Mitutoyo PJ-H3000F measuring projector
Minitab v14
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
DOE
Four parameters
Electrode material (MAT):
Required surface quality based on VDI 3400 (VDI_r):
18, 21, 24, 27, 30,
Spark distance (SD):
copper (Cu 99.9%) or
graphite (Gr Meusburger Q60),
0.20 mm, 0.25 mm, 0.30 mm,
Depth of cavity (DC):
1 m, 2 mm, 3 mm.
23-1 DOE plan was used with two centrum points
32 sets
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
DOE
The measured and calculated parameters are the next:
Surface roughness parameters: Ra, Rz,
Machining time (MT),
Material removal rate (MRR),
MRR =
]
Electrode wear rate (EW).
EW =
6
[
volume _ of _ material _ removed _ from _ workpiece
mm3 / min
time _ of _ machining
volume _ of _ material _ removed _ from _ electrode
[%]
volume _ of _ material _ removed _ from _ workpiece
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Ra
VDI/Ra
DC
?
SD
Rz
MT
E MAT
MRR
EW
Main effect
analysis
Regression
analysis
Statistical
analysis
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…
ANN
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Results #1 - Ra
Cu
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Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Results #2 – Ra / Rz
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Results #3 – MRR / Machining time
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2014. 04. 25.
Results #4 – Electrode wear rate
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Results #5 – Main effect plots
!
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!
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Results #6 – Regression analysis
ln T = 3.44 - 0.629 ln Ra + 0.769 ln VRWp - 0.668 MAT
Predictor
Coef SE Coef
T
P
Constant
3.4364
0.3414
10.06 0.000
ln_Ra
-0.62856 0.05854 -10.74 0.000
ln_VRWp
0.76864 0.06317
12.17 0.000
MAT
-0.66842 0.05556 -12.03 0.000
S = 0.157145
R-Sq = 93.5%
R-Sq(adj) = 92.9%
Ra
- required surface roughness
VRWp - removed volume of the workpiece
MAT – 0 – Copper electrode
1 – Graphite electrode
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Cu
Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Results #6 – Regression analysis
ln Ra_m = - 0.364 +
VRWp + 0.597 MAT
Predictor
Coef
Constant
-0.3644
ln_Ra
0.7635
ln_SD
0.6140
ln_VRWp
0.2714
MAT
0.59672
S = 0.269086
R-Sq
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0.764 ln Ra + 0.614 ln SD + 0.271 ln
SE Coef
0.7262
0.1002
0.2963
0.1082
0.09514
= 80.1%
T
P
-0.50 0.620
7.62 0.000
2.07 0.048
2.51 0.018
6.27 0.000
R-Sq(adj) = 77.1%
Cu
Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Results #6 – Regression analysis
MRR = - 13.3 + 4.72 RA_d + 42.3 SD + 0.0179 VRWp + 9.57 MAT
Predictor
Coef
SE Coef
T
P
Constant
-13.286
2.473 -5.37 0.000
RA
4.7178
0.4122 11.44 0.000
SD
42.349
8.649
4.90 0.000
VRWp
0.017902 0.003745
4.78 0.000
MAT
9.5746
0.6836 14.01 0.000
S = 1.93356
R-Sq = 93.3%
R-Sq(adj) = 92.3%
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Cu
Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Results #6 – Regression analysis
ln EW = 1.64 - 0.334 ln VRWp - 0.143 ln Ra + 0.687 MAT
Predictor
Coef SE Coef
T
P
Constant
1.6428
0.5607
2.93 0.007
ln_VRWp
-0.3342
0.1037 -3.22 0.003
ln_Ra
-0.14278 0.09613 -1.49 0.149
MAT
0.68729 0.09124
7.53 0.000
S = 0.258066
R-Sq = 71.3%
R-Sq(adj) = 68.2%
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Cu
Gr
DIM 2014 - miko.balazs@bgk.uni-obuda.hu
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2014. 04. 25.
Conclusion
The electric discharge machining has a very wide range of
application and perspective in booth die and mould
manufacturing and part manufacturing. The accuracy, productivity
and the cost control there are the centre of developments.
Based on our research the EDM process with copper
electrode shown
Good capability for produce accurate surface roughness,
Small and constant wear but
Long machining time.
The graphite electrode has
Higher material removal rate (short machining time),
Higher wear speed and wear rate and
Produce higher surface roughness.
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DIM 2014 - miko.balazs@bgk.uni-obuda.hu
Thank You for Your Attention
Dr MIKÓ Balázs
PhD, Associate professor,
Deputy-head of the Institute
Óbudai University
Bánki Donát Faculty of Mechanical and Safety Engineering
Institute of Material Science and Manufacturing
Engineering
Add.:
Tel.:
Fax:
E-mail:
H-1081 Budapest Népszínáz u. 8.
+36-1-666-5408
+36-1-666-5480
miko.balazs@gbk.uni-obuda.hu
The authors appreciate the company Koop 55 LtD and Jozsef Poór, Hungary, for enabling this work and for providing
workpieces, electrodes and testing.
CIII-SK-0067-09-1314
ADVANCES IN MACHINING - innovation trends for joint education and research - part 2
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