Siemens SINUMERIK 840D sl Function Manual page 507

Response on follow-up
A difference must made between the following cases:
● Without intermediate block (TLIFT)
The path velocity of the leading axes is reduced to such an extent that the following axis
reaches its target position synchronously with the other axes.
● With intermediate block (TLIFT), rounding off without G641
The intermediate block generates the required turn of the tangentially following axis. It is
interpolated in such a way that the following axis travels at its limit velocity. The intermediate
block is not rounded. At the beginning of the intermediate block, the path velocity of the
leading axes is zero.
Special cases
● G641 rounding is possible between two blocks, both of which move at least one of the two
leading axes of the tangentially following axis.
● G641 rounding is possible between two blocks, both of which do not move either of the
leading axes of the tangentially following axis.
In both cases, an intermediate block for the tangentially following axis is not created. An
intermediate block is not required because in the preprocessing run the rounded contour is
detected and the limit values for the following axis are calculated.
● Hidden corner in area
A corner relevant for the tangential follow-up control can be hidden in space. (The projection
of the contour on the plane defined by the two leading axes is relevant).
If there is a hidden corner in space, an intermediate block is inserted before the block (here
N6) causing the tangential jump. This intermediate block moves the following axis to the
new position. The block transition is not rounded.
Programming
N1 TANG (C, X, Y, 1)
N2 TLIFT (C)
N3 G1 G641 X0 Y0 F1000
N4 TANGON (C)
N5 X10
N6 Y10
N7 M3001.97
Special functions
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
T3: Tangential control - 840D sl only
11.2 Characteristics of tangential follow-up control
Comment
; The rotary axis is repositioned before working
off this block.
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