Siemens SINUMERIK 840D Function Manual page 233

● The value identifies the rotary axis target position in a range from 0° to 359.999° (modulo
360°). Alarm 16830, "Incorrect modulo position programmed", is output for values with a
negative sign or ≥ 360º.
● With DC (Direct Control), the rotary axis approaches the programmed absolute position
within one revolution along the shortest path (traversing movement max. ±180°).
● The control calculates the direction of rotation and the traverse path according to the current
actual position (in relation to modulo 360°). If the path to be traversed is the same in both
directions (180°), the positive direction of rotation has priority.
● DC application example: the rotary table is required to approach the changeover position in
the shortest time (and, therefore, via the shortest path) possible.
● If DC is programmed for a linear axis, alarm 16800, "DC traverse instruction cannot be used",
is output.
Example:
Programming
POS[C] = AC (7200)
POS[C] = DC (300)
POS[C] = AC (7000)
Note
In this example, it would be advisable to activate the modulo 360º display (MD30320
$MA_DISPLAY_IS_MODULO = 1).
Incremental programming (IC, G91)
Example for positioning axis: POS[axis name] = IC(+/- value)
When programming with incremental dimensions, the rotary axis traverses along the same
path as for the modulo axis. In this case, however, the traversing range is limited by the
software limit switches.
● The value identifies the rotary axis traversing distance.
The value can be negative and ≥ +/-360°.
● The sign of the value defines the rotary axis traversing direction.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
Effect
Rotary axis C traverses to position 7200°;
traversing direction depends on the starting position
Rotary axis C approaches "modulo" position 300°
along the shortest path
Thus, C traverses through 60° with a negative direction of rotation
and stops at absolute position 7140°.
Rotary axis C traverses to position 7000° absolute,
C traverses through 140° with a negative direction of rotation
R2: Rotary axes
7.3 Programming of rotary axes
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