Siemens Sinumerik 840D sl Programming Manual page 391

Programming the axis angle (TU=)
To be able to clearly approach axis angles < ± 360 degrees, this information must be
programmed using the command "TU=".
The axes traverse by the shortest path:
• when no TU is programmed for a position,
• with axes that have a traversing range > ±360 degrees.
Example:
The target position shown in the diagram can be approached in the negative or positive
direction. The direction is programmed under address A1.
A1=225°, TU=Bit 0, → positive direction
A1= − 135°, TU=Bit 1, → negative direction
Figure 6-7
Example of evaluation of TU for generic 5/6-axis transformation and target positions
Variable TU contains a bit, which indicates the traversing direction for every axis involved in
the transformation. The assignment of TU bits matches the channel axis view of the round
axes. The TU information is only evaluated for the up to 3 possible round axes which are
included in the transformation:
Bit0: Axis 1, TU bit = 0 : 0 degrees <= round axis angle < 360 degrees
Bit1: Axis 2, TU bit = 1 : –360 degrees < round axis angle < 0 degrees
The start position of a round axis is C = 0. By programming C = 270, the round axis travels to
the following target positions:
C = 270: TU bit 0, positive direction of rotation
C = –90: TU bit 1, negative direction of rotation
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
Transformations
6.9 Cartesian PTP travel
391