05.91 3 Directions of Movement, Dimensioning
3.2 Position data, preparatory functions
3.2 Position data, preparatory functions
The position data comprises an axis address and a numerical value, which describes the path
on the addressed axis. If a sign is specified, it is written between the address and the
numerical value.
In order to start the positioning procedure, the position data must be supplemented by the
preparatory function (G function) and the feedrate (F) data. The preparatory functions describe
the type of machine movements, the type of interpolation and the method of dimensioning.
The G functions are divided into groups (see program key). A program block may contain only
one function from each group (exception: G90/G91).
The G functions are either modal (stored) or effective for a single block. The G functions
which remain active until they are replaced by a new G function in the same group are said to
be modally active. The G functions which are only active in the block in which they are
contained are said to be active block-by-block.
The resets take effect after powering up the control, and after reset or program end. They
need not be programmed.
3.3 Dimension systems: absolute and incremental position data
G90/G91
The traversing movement to a particular point in the coordinate system can be described by
means of absolute or incremental position data. A ”zero offset” is allowed for in both absolute
and incremental programming.
Absolute position data input G90
If absolute position data input is selected, all dimensional inputs refer to a fixed zero, which is
normally the workpiece zero. The numerical value of the associated position data specifies the
target position in the coordinate system.
Example:
The tool is at position (P1) X = 20, Y = 10 and is to move to position (P2) X = 60, Y = 30.
The input is:
G90 X60 Y30
The tool moves to the programmed target position irrespective of its current position.
X=60
P2
W
X
604020
P1
Y
20
10
30
Y=30
© Siemens AG 1991 All Rights Reserved 6ZB5 410-0HD02 3–3
SINUMERIK 880, (PG)
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