1
Introduction
b
1.2 Fundamentals of NC
Setting a pole at a circle center (CC)
The pole is defined by setting two Cartesian coordinates. These two
coordinates also determine the reference axis for the polar angle (PA).
XY +x
YZ +Y
zx
+z
i-
Fig. 1 .I 3: Polar coordinates and their associated reference axes
Setting the datum
The workpiece drawing identifies a certain prominent point on the
workpiece (usually a corner) as the “absolute datum” and perhaps one
or more other points as relative datums. The process of datum setting
establishes these points as the origin of the absolute or relative coordi-
nate systems: The workpiece, which is aligned with the machine axes, is
moved to a certain position relative to the tool and the display is set
either to zero or to another appropriate position value (e.g. to compen-
sate the tool radius).
*s
Fig. 1.14: The workpiece datum serves as
the origin of the Cartesian
coordinate system
L
TNC 370
1-21
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