HEIDENHAIN PT 855 for Milling - Manual (Page 10)

I - 1 Fundamentals of Positioning
Fundamentals of Positioning
8 Operating Instructions POSITIP 855
Fig. 4: Hole defines the coordinate system
Fig. 3: The workpiece datum represents the
origin of the Cartesian coordinate
system
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).
Example:Drawing with several relative datums
(ISO 129 or DIN 406 Part 11, fig. 171)
Y
X
Z
0
325 450 700 900 950
0
320
750
1225
300±0,1
0
150
-150
0
0
216,5
250
-250
-125
-216,5
0 -125 -216,5
-250
250
125 216,5
125
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 in the X axis and
5 mm from it in the Y axis (in negative direction).
The KT Edge Finder from HEIDENHAIN, together with the
POSITIP'S edge finding functions, facilitates finding and setting
datums.
Y
X
Z
1
10
5
1
1
1