Absolute And Incremental Workpiece Positions - HEIDENHAIN TNC 640 User Manual

Fundamentals, File Management | Fundamentals

Absolute and incremental workpiece positions

Absolute workpiece positions
Absolute coordinates are position coordinates that are referenced
to the datum of the coordinate system (origin). Each position on the
workpiece is unambiguously defined by its absolute coordinates.
Example 1: Holes dimensioned in absolute coordinates
Hole 1 Hole
X = 10 mm X = 30 mm
Y = 10 mm Y = 20 mm
Incremental workpiece positions
Incremental coordinates are referenced to the last programmed
nominal position of the tool, which serves as the relative
(imaginary) datum. When you write an NC program in incremental
coordinates, you thus program the tool to move by the distance
between the previous and the subsequent nominal positions. This
is why they are also referred to as chain dimensions.
To program a position in incremental coordinates, enter the G91
function before the axis.
Example 2: Holes dimensioned in incremental coordinates
Absolute coordinates of hole
X = 10 mm
Y = 10 mm
Hole 5, with respect to 4
G91 X = 20 mm
G91 Y = 10 mm
Absolute and incremental polar coordinates
Absolute coordinates always refer to the pole and the angle
reference axis.
Incremental polar coordinates always refer to the last programmed
nominal position of the tool.
HEIDENHAIN | TNC 640 | ISO Programming User's Manual | 10/2017
2 Hole 3
X = 50 mm
Y = 30 mm
4
Hole 6, with respect to
G91 X = 20 mm
G91 Y = 10 mm
5
4
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