Page 137 - Module DMV20173

7.0 NON CONVENTIONAL PROCESSES

Example 7.1:

A typical alloy whose melting point = 900 °C is to be machined using EDM process.
If the discharge current used is 20 amps, what is the approximate value for the
material removal rate in the process?

Solution:

Using equation (7.1), an approximate material removal rate is

4
MRR = 4 x 10 ITw -1.23
MRR = (4 x 10 )(20)(900 -1.23 )
4

3
MRR = 185.94 mm /min

The typical parameters used in an EDM process are:
i) Spark gap 0.0125 – 0.125 mm
ii) Current 0.1 – 500 A
iii) Voltage (DC) 40 – 300 V
iv) Pulse duration 2 – 2000 µs
v) Dielectric pressure < 0.2 Mpa
vi) Surface finish 3 – 10 µm Rough

0.8 – 3 µm Finish

EXERCISE 7.1

A typical alloy whose melting point = 500 °C is to be machined using EDM process.
If the MRR is 574.709 mm /min, what is the approximate value for the discharged
3
current used in the process?

Describe some advantages of electrical-discharge machining.

BPLK 169 DMV 20173