HEIDENHAIN TNC 122 User Manual - Manual (Page 12)

1 Fundamentals of Positioning
12 TNC 122
Datums and positions
Setting the datum
The workpiece drawing identifies a certain point on the workpiece
(usually a corner) as the “absolute datum” and perhaps one or
more other points as relative datums. The datum setting procedure
establishes these points as the origin of the absolute or relative co-
ordinate systems: The workpiece, which is aligned with the ma-
chine axes, is moved to a certain position relative to the tool and
the display is set either to zero or to another appropriate value
(e.g., to compensate the tool radius).
Y
X
Z
Y
X
Z
1
10
5
Fig. 1.3: The workpiece datum represents the
origin of the Cartesian coordinate
system
Fig. 1.4: Hole defines the coordinate system
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Example: Coordinates of hole :
X = 10 mm
Y = 5 mm
Z = 0 mm (hole depth: Z = – 5 mm)
The datum of the Cartesian coordinate system
is located 10 mm from hole on the X axis and
5 mm from it in the Y axis (in negative direction).
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