Siemens SINUMERIK 840Di Function Manual page 159

2.3.3 Rounding according to path criterion
Blending
Rounding means that an angular block transition is changed to a tangential block transition
by a local change to the programmed feedrate.
Rounding replaces the area in the vicinity of the original angular block transition (including
transitions between blocks inserted by the CNC) by a continuous contour. In this case, it is
not only the geometry axes that are taken into account, but all machine axes, which are
traversing synchronously. The rounding function therefore smoothes the traversing path of
orientation axes as well as general velocity step changes in synchronized axes.
Note
Rounding cannot and should not replace the functions for defined smoothing: RND, RNDM,
ASPLINE, BSPLINE, CSPLINE.
If a rounding movement initiated by G641, G642, G643, G644 is interrupted, the corner point
of the original contour will be used for subsequent repositioning, rather than the interruption
point.
Rounding is initiated by shortening discontinuously adjoining blocks and inserting one or two
intermediate blocks at this point. The original block boundary is removed and can no longer
be used for synchronization conditions (e.g., auxiliary function output parallel to motion, stop
at end of block).
With rounding, all synchronization conditions are best referred to the end of the shortened
first block and not to the end of the intermediate rounding block. The following block is thus
not started and with a stop at end of block, the contour of the following block can still be
changed.
Rounding is only performed if the block transition is to be traveled with finite velocity. The
maximum path speed is influenced by the curvature. The maximum acceleration values of
the axes are not exceeded. A block without traverse information for the path axes requires
velocity "zero" and therefore no rounding.
Rounding is also used if the traversal of the block transition requires a velocity that lies below
the permissible velocity at the end of the block according to G64 (see overload factor). This
means that very small knees in the contour (e.g., 0.5 degrees) can be overtraveled directly.
Continuous-Path Mode, Exact Stop, LookAhead (B1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed Description
2.3 Continuous-path mode
2-11