INGENIEUR
● ●
● ●
EWR shows a increasing trend when the
EWR
shows
a increasing
trend
when the
applied
nominal
capacitance
increases.
applied
nominal
capacitance
increases.
EWR first shows linear increase and
EWR
first by shows
increase
followed
linear linear
decrease
with and
an
followed
by
linear
decrease
with
an
increase in the feed rate.
increase in the feed rate.
In, micro-EDM, high degree temperatures
micro-EDM,
high the
degree
temperatures
are In produced
to melt
work-piece
and the
are
produced
to
melt
the
work-piece
and
the
electrode at the same time. Hence, brass work-
electrode
at
the
same
time.
Hence,
brass
work-
piece with lower melting point can achieve higher
piece
with exhibit
lower melting
point at can
higher
MRR but
higher EWR
the achieve
same time
as
MRR
but
exhibit
higher
EWR
at
the
same
time
as
well (Dhirendra et al., 2014). When the work-piece
well
(Dhirendra
et al., 2014).
the work-piece
thickness
is increased,
the When
machining
process
thickness
is
increased,
the
machining
process
takes longer time to complete a through hole.
The
takes
a longer
time to complete
a through
hole. EWR.
The
prolonged
machining
time leads
to higher
prolonged
time
leads to higher
EWR.
The smaller machining
the diameter
of electrode,
the sparking
The
smaller
the diameter
of electrode, on
the a sparking
effect
becomes
more concentrated
smaller
effect
becomes
more
concentrated
on
a smaller
surface during the EDM process. Hence,
smaller
surface
during
the EDM
process.
smaller
electrode
diameters
exhibit
higher Hence,
EWR. Electrical
electrode
diameters
exhibit
higher
EWR.
Electrical
sparking is stronger when the nominal capacitance
sparking
is higher.
stronger The
when
the nominal
applied is
higher
charge capacitance
energy from
applied
is
higher.
The
higher
charge
energy
from
the power generator gives higher thermal
erosion
the power generator gives higher thermal erosion
Figure 16:
Graph of
Circularity
against
Figure
16:
Graph
Workpiece Material
Workpiece Material
on both electrode tool and work-piece (Dhirendra
on
both
electrode
tool and
et al.,
2014).
Therefore,
EWR work-piece
increases (Dhirendra
with higher
et
al.,
2014).
Therefore,
EWR
increases
with the
higher
nominal capacitance. EWR increases when
feed
nominal
capacitance.
EWR
increases
when
the
feed
rate increases from 4mm/s to 12mm/s, however
rate
increases again
from 4mm/s
to 12mm/s,
however
it decreases
from 12mm/s
to 20mm/s.
it 20mm/s
decreases
again
from
12mm/s
to
20mm/s.
feed rate is considered fast and gives
20mm/s
rate is
considered
repeated feed
electrical
discharge
in a fast
short and
time. gives
The
repeated
electrical
discharge
in
a
short
time.
The
melted electrode is not flushed away and continues
melted
electrode
is not Hence,
flushed machining
away and continues
for another
discharge.
by micro-
for
another
discharge.
Hence,
machining
by micro-
EDM
gives
a
lower
EWR
for
the
fast
feed
rate.
Figure
EDM
gives 16:
a lower Graph
EWR for of the Circularity
fast feed rate. against
Workpiece Material
Figure 17:
Workpiece T
Figure 18:
Graph
of of Circularity
against
Electrode
18: 17:
Graph
Circularity
against
19: G
Graph
of Figure
Circularity
against of Figure
of Figure
Circularity
against
17: Electrode
Graph
Circularity
Diameter
Diameter
Capacitance
Workpiece Thickness
Workpiece Thickness
Figure
Graph
of of
Circularity
against
Workpiece
Figure
19:
Graph
of of Circularity
against
Nominal
Figure
20: Graph
Graph
of
Figure
16:
of
Circularity
against
Figure
17:
Graph
of Figure
Circularity
against
Figure 16:
18:
Graph Graph
Circularity
against
Electrode
Figure against
19:
Graph
Circularity
against
Nominal
Figure
18: Graph
of Circularity
Electrode
19:
of Circularity
Circularity against
agains
Material
Capacitance
Workpiece
Workpiece
Diameter Material
Capacitance Thickness
Diameter
Capacitance
Figure 17:
18:
Graph
Circularity
against
Electrode
Figure
19: Graph
Graph
of
Circularity
against
Nominal
20: Graph
of Circularity
Feed
Rate
Figure
20:
of
Circularity
against
Feed
Rate
Graph
of of Circularity
against
Workpiece
arity against Figure
Figure
17:
Graph
of Figure
Circularity
against
Figure against
20:
Graph
of
Circularity
against
Feed
Rate
Diameter Thickness
Capacitance
Thickness
Workpiece
6
54
VOL
2017
VOL 70
55 APRIL-JUNE
JUNE 2013