Rounding And Repositioning (Repos) - Siemens SINUMERIK 840D sl Function Manual

Activation/deactivation
Continuous-path mode with rounding of tangential block transitions can be activated in any
NC part program block by the modal command G645.
Selecting the exact stop which works on a block-by-block basis enables rounding to be
interrupted (G9).
Continuous-path mode with rounding of tangential block transitions (G645) can be deactivated
by selecting:
● Modal exact stop (G60)
● Continuous-path mode G64, G641, G642, G643 or G644
Comparison between G642 and G645
When rounding with G642, the only block transitions rounded are those which form a corner,
i.e. the velocity of at least one axis jumps. However, if a block transition is tangential, but there
is a jump in the curvature, no rounding block is inserted with G642. If this block transition is
traversed with finite velocity, the axes experience some degree of jump in acceleration which
(with the jerk limit activated!) may not exceed the parameterized limit (MD32432
$MA_PATH_TRANS_JERK_LIM). Depending on the level of the limit, the path velocity at the
block transition may be greatly reduced as a result. This constraint is avoided by using G645
because the rounding motion is defined here in such a way that no jumps occur in acceleration.
Parameterization
The following machine data indicates the maximum permissible path deviation for each axis
during rounding with G645:
MD33120 $MA_PATH_TRANS_POS_TOL
This value is only of relevance to tangential block transitions with variable acceleration. When
angular, non-tangential block transitions are rounded, (as with G642) the tolerance from
MD33100 $MA_COMPRESS_POS_TOL becomes effective.
See also
Free-form surface mode: Basic functions (Page 224)
4.3.3.5

Rounding and repositioning (REPOS)

If the machining in the area of the rounding contour is interrupted, a REPOS operation
cannot be used to position again directly on the rounding contour. In this case, positioning can
be made only on the programmed contour.
Example
Programmed: Two traversing blocks N10 and N20 with programmed rounding G641.
The traversing motion is interrupted in the rounding area. The axes, e.g. manually, are then
traversed to the REPOS start point. Depending on the selected REPOS mode, the
repositioning on the contour is made at the points
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
B1: Continuous-path mode, Exact stop, Look Ahead
① ② ③
, or .
4.3 Continuous-path mode
199