Module
9
Non conventional
Machining
Version 2 ME, IIT Kharagpur
Lesson
38
Electro Chemical
Machining
Version 2 ME, IIT Kharagpur
Instructional Objectives
(i)
Identify electro-chemical machining (ECM) as a particular type of
non-tradition processes
(ii)
Describe the basic working principle of ECM process
(iii)
Draw schematically the basics of ECM
(iv)
Draw the tool potential drop
(v)
Describe material removal mechanism in ECM
(vi)
Identify the process parameters in ECM
(vii)
Develop models for material removal rate in ECM
(viii)
Analyse the dynamics of ECM process
(ix)
Identify different modules of ECM equipment
(x)
List four application of ECM
(xi)
Draw schematics of four such ECM applications
1. Introduction
Electrochemical Machining (ECM) is a non-traditional machining (NTM) process
belonging to Electrochemical category. ECM is opposite of electrochemical or
galvanic coating or deposition process. Thus ECM can be thought of a controlled
anodic dissolution at atomic level of the work piece that is electrically conductive by a
shaped tool due to flow of high current at relatively low potential difference through
an electrolyte which is quite often water based neutral salt solution.
Fig. 1 schematically shows the basic principle of ECM.
In ECM, the workpiece is connected to the positive terminal of a low voltage high
current DC generator or power source. The tool is shaped and shape of the tool is
transferred to the workpiece. The tool is connected to the negative terminal.
Machining takes place due to anodic dissolution at atomic level of the work material
due to electrochemical reaction. A gap between the tool and the workpiece is
required to be maintained to proceed with steady state machining.
W
O
R
K
T
O
O
L
W
O
R
K
T
O
O
L
electrolyte
Initial stage of
ECM
Steady state of
ECM
Fig. 1 Schematic principle of Electro Chemical Machining (ECM)
2. Process
During ECM,