1. Investigation on Electrochemical
Discharge Machining of Fibre
Composites
I. Gomes, B.R. Sarkar, Dr. B. Doloi & Dr. B. Bhattacharyya
Production Engineering Department
Jadavpur University
Kolkata-700032

2. INTRODUCTION
 Composite materials are gaining wide acceptance in applications
where high specific strength, good elevated temperature properties and
good wear resistance.
 Conventional cutting of composite has certain problems like surface
roughness, cutting of fibers.
 In case of drilling, reports of damage at the entrance and exit wall of
holes exist .
 Unconventional machining is an alternative to machining of
composites.
 Electrochemical discharge machining is a new and developing hybrid
method of machining of composites.
 Effective utilisation of such process holds the promises of good
surface finish, effective material removal rate and accuracy.

3.  The fundamental material removing process in ECDM is by combined
effect of electrochemical and electrical spark discharge action .
 The basic characteristic of material removal in ECDM is based on the
utilization of energy released by sparking which raises the temperature of
the work piece.
 Fractured related spalling may also help in material removal rate.

4.  To perform through hole drilling on GFRP composites using
Electrochemical Discharge Machining (ECDM) process.
 To study the effects of various process parameters on different
machining performances.
OBJECTIVES

5. EXPERIMENTAL PLANNING
 The ECDM set up has various
sub-systems such as pulsed
D.C. power supply, a work
piece holding arrangement, a
tool mounting unit, a gravity
feeding arrangement and a
machining chamber.
 A set of through hole was
drilled on glass fibre reinforced
plastics (GFRP) work-sample
procured commercially.
Fig.1. Schematic diagram of
experimental ECDM set-up for drilling

6.  GFRP composites or Glass Fibre Reinforced Plastics are the most
commonly used in mechanical joints in pipes and structures in industry,
military defence, marine and offshore application.
 Sodium hydroxide (NaOH) salt was used as the electrolyte.
 Voltages were set at 35V, 45V and 55V.
 Electrolyte concentrations were 10%, 20% and 30% by weight.
 Inter-electrode gap were fixed at 20mm, 30mm, 40mm.
 Machining time was noted until a through hole was produced and recorded
with the help of a stopwatch.
 The amount of work and tool material removal were measured by taking
the difference in weight of the specimen before and after machining with
the help of Mettler Toledo balance of LC 1×10-5gm.

7. RESULTS AND DISUSSIONS
Expt. Voltage Concentration IEG
M/Cing
Time MRR TWR
No. (volt) (wt.%) (mm) (min) (mg/min) (mg/min)
1 35 20 30 65 0.049 0.00044
2 45 20 30 70 0.424 0.00143
3 55 20 30 20 0.446 0.0046
4 45 10 30 21 0.128 0.00017
5 45 20 30 70 0.424 0.00143
6 45 30 30 35 0.295 0.00033
7 45 20 20 30 0.431 0.007
8 45 20 30 70 0.424 0.00143
9 45 20 40 30 0.01 0.0178
Table 1: Experimental Results
MRR = (Weight of W/P before M/Cing - Weight of W/P after M/Cing)
Time of M/Cing
TWR = (Weight of Tool before M/Cing - Weight of Tool after M/Cing)
Time of M/Cing

8. PARAMETRIC INFLUENCES ON MATERIAL
REMOVAL RATE
Voltage 45 V, IEG 30mm
0
0.1
0.2
0.3
0.4
0.5
10 20 30
Concentration of electrolyte( wt%)
MRR(mg/min)
Electrolyte concentration 20%, IEG 30mm
0
0.2
0.4
0.6
35 45 55
Applied voltage( volt)
MRR(mg/min)
Fig. 2. Effect of Applied voltages on MRR Fig. 3. Effect of Electrolytic concentration
on MRR
Electrolyte concentration 20%, voltage 45 V
0
0.1
0.2
0.3
0.4
0.5
20 30 40
Inter-electrode gap (mm)
MRR(mg/min)
Fig. 4. Effect of Inter-electrode gap on MRR

9. PARAMETRIC INFLUENCES ON TOOL WEAR RATE
Voltage 45 V, IEG 30 mm
0
0.0004
0.0008
0.0012
0.0016
10 20 30
Electrolyte concentration (wt%)
TWR(mg/min)
Electro lyte co ncentratio n 20%, IEG 30 mm
0
0.002
0.004
0.006
35 45 55
Applied voltage (volt)
TWR(mg/min)
Fig. 5. Effect of Applied voltage on TWR Fig. 6. Effect of Electrolyte concentration
on TWR
Electrolyte concentration 20%, voltage 45 V
0
0.002
0.004
0.006
0.008
20 30 40
Inter-electrode gap (mm)
TWR(mg/min)
Fig. 7. Effect of inter-electrode gap on TWR

10. Fig. 8. GFRP machined at
45V/ 20wt% / 30mm
Fig. 9. GFRP machined at
45V/ 20wt% / 30mm
Fig. 10. GFRP machined at
55V/ 20wt% / 30mm
ANALYSIS BASED ON PHOTOGRAPHS

11. Fig. 11. GFRP machined at
55V/ 20wt%/ 30mm
Fig. 12. GFRP machined at
45V/ 10wt% / 30mm
Fig. 13. GFRP machined at
45V/ 10wt% / 30mm

12. CONCLUSION
 ECDM process can effectively be utilized against machining of glass
fibre reinforced composite.
 an optimum voltage, concentration of electrolyte and inter electrode
gap exist, which leads to optimum material removal rate which is at
55V, 20% and 20mm.
 Deposition on tool during the machining process takes place due to
electrochemical reactions.
 High level of electrolyte results in heat-affected zone formation and
damages the work-sample.