Siemens SINUMERIK 840DE sl Function Manual page 98

M1: Kinematics transformation
2.6 Cartesian PTP travel
Function
With the Cartesian PTP travel, in G0 and G1 sets it is possible to approach a point programmed
as a Cartesian destination point with a synchronous axis movement.
Regarding the traversing movement, the Cartesian PTP travel acts as though no
transformation is active The position data in the part program continue to be in the Cartesian
workpiece coordinate system. Programmed frames (coordinate movements and rotations)
remain valid. The display is also in the Cartesian workpiece coordinate system.
The movement in the Cartesian PTP travel is described by a starting and end position of the
axes. The path of the movement described by the individual axes from the starting to the end
position is not specified by the controller by means of path interpolation points and can
therefore not be predicted. The axes only have to reach their specified target position.
Interaction between the axis movements only exists in regard to time, i.e. all axis start
simultaneously and are stopped at the same time when the target position has been reached.
The slowest axis determines the total traverse time.
One sensible usage option is to travel by a singularity. If Cartesian positions are available,
which are provided by a CAD/CAM system for example, this has the benefit of not having to
convert them into machine axis values. Furthermore, direct traversing of the machine axes is
time-optimized compared to Cartesian traversing with active transformation and programmed
feed. The result of this would either be a corresponding reduction of the feedrate when
traversing through the singularity (speed planning in preprocessing) or an overload of the axis
if no speed planning is carried out in preprocessing.
Note
Cartesian PTP travel is only permissible in conjunction with the interpolation types G0 and G1.
Versions
Three versions are available for Cartesian PTP travel:
● PTP
The programmed Cartesian position in G0 and G1 blocks is approached with synchronous
axis motion.
● PTPG0
Only in G0 blocks is the programmed Cartesian position approached with synchronous axis
motion. In G1 blocks, it is switched to the type of motion CP (CP = Continuous Path) and the
position is approached with a Cartesian path motion.
● PTPWOC (only for orientation transformation)
Just the same as PTP, however, without any compensatory motion, which is caused by
motion of rotary axes and orientation axes.
Since the transformation, which compensates the movement of the tool tip (TCP) during
orientation changes, is not active, the position of the TCP in the workpiece coordinate
system must generally also be changed if no linear axes involved in the transformation are
programmed.
Programmed linear axis movements are carried out in the workpiece coordinate system that
applies at the beginning of the block and overlays the simultaneously programmed rotary
axis movements if applicable. The block end point that is reached in the workpiece
coordinate system is therefore generally not the same as the programmed end point.
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Function Manual, 06/2019, A5E47435470B AA
Transformations