Siemens SINUMERIK 840D sl Programming Manual page 372

Path traversing behavior
9.1 Tangential control (TANG, TANGON, TANGOF, TANGDEL)
Insert intermediate block at contour corners, TLIFT
At one corner of the contour the tangent changes and thus the setpoint position of the
following axis. The axis normally tries to compensate this step change at its maximum
possible velocity. However, this causes a deviation from the desired tangential position over
a certain distance on the contour after the corner. If such a deviation is unacceptable for
technological reasons, the instruction TLIFT can be used to force the control to stop at the
corner and to turn the following axis to the new tangent direction in an automatically
generated intermediate block.
The path axis is used for turning if the following axis has been used once as the path axis.
A maximum axis velocity of the following axis can be achieved with function
TFGREF[ax] = 0.001.
If the follow-up axis was not previously traversed as a path axis it is now traversed as a
positioning axis. The velocity is then dependent on the positioning velocity in the machine
data.
The axis is rotated at its maximum possible velocity.
Optimization possibility
Velocity jumps of the following axis caused by jumps in the leading axis contour are rounded
and smoothed with (Dist and Angletol).
The following axis is controlled with look-ahead (see diagram) to keep deviations as small as
possible.
9-6
Programming Manual, 03/2006 Edition, 6FC5398-2BP10-1BA0
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