HEIDENHAIN TNC 406 - Manual (Page 79)

58 4 Programming: Fundamentals, Files, Program Entry, Spark Erosion, Erosion Tables
4.5 F
u
ndamentals of Spar
k Er
osion
4.5 Fundamentals of Spark Erosion
Electrical discharge machining is an electrothermal process which
uses a spark to remove metal by melting and vaporizing (”eroding”)
the workpiece surface.
In contrast, cutting machine tools such as milling machines remove
metal by direct abrasive action.
The spark erosion process is described on the following pages.
The electrode (e) and the workpiece (w) are submerged in a dielectric
fluid (d).
A generator applies a voltage to the electrode and the workpiece (both
the electrode and the workpiece are then electrodes).
An electric field is then created in the gap between the electrode and
the workpiece.
The electric field is strongest where the gap is the smallest.
The electrically conductive particles in the dielectric fluid are
concentrated at this point.
A bridge of electrically conductive particles forms between the
electrode and the workpiece.
d
e
W
U
+
–
I
+
–
+
–