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Programming of Traversing Blocks
Usually, the definitions according to the DIN standard 66025 apply. If the axis is traversed
towards the workpiece, the actual value must decrease, i.e the traversing direction is negative.
When traversing from the workpiece the actual value increases and the axes executes a
positive movement. The reference point definitions are different for every machine tool, but, in
most cases, the reference point is the zero point of the workpiece. The programming of the
traversing blocks of the WF axis also refers to the zero point. Furthermore, the following
coordinate-specific machine data refer to the zero point:
•
Reference point coordinate (MD 3)
•
Reference point traversing direction (MD 5)
•
Limit switch (MD 20, MD 21)
4.2
Dimensions G90, G91
The traversing direction to a specified point can be defined by the
•
absolute dimension G90 or
•
incremental dimension G91
The user can switch between absolute and incremental dimensions as desired. When
switching the machine on, the programming status refers to absolute dimensioning G90. G90
and G91 are modal. Thus, G90 or G91 only have to be entered when switching over to the
other dimension.
4.2.1
Linear axis
Absolute dimension G90
Absolute dimensions refer, in most cases,
to the workpiece zero point W or
machine zero point M.
W
Programmed
position
0
10
20
30
Programming:
N10 G90 X20.000 FX100.00
4 – 2
Incremental dimension G91
Incremental dimensions refer to the
last actual position.
W
Actual
position
40
50 mm
0
Programming:
N10 G91 X-30.000 FX100.00
©
Siemens AG 1997 All Rights Reserved
Programmed
Actual
position
position
10
20
30
40
6ZB5 440-0VU02
WF 723 C (Programming Guide)
04.97
50 mm
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