Siemens SINUMERIK 840D sl Function Manual page 742

R2: Rotary axes
13.3 Programming rotary axes
● 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 receives preference.
● 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 with 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 across the same
path as with 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 value's sign unequivocally defines the rotary-axis traversing direction.
742
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 about 60° with a negative direction of rotation
and stops at absolute position 7140°.
Rotary axis C traverses to position 7000° absolutely,
so C traverses about 140° with a negative direction of rotation
Function Manual, 10/2015, 6FC5397-1BP40-5BA3
Extended Functions