Siemens Sinumerik 840D sl Programming Manual page 300

Path action
12.2 Continuous-path mode (G64, G641, G642, G643, G644, G645, ADIS, ADISPOS)
LookAhead predictive velocity control
In continuous-path mode, the control automatically determines the velocity control for several
NC blocks in advance. This enables acceleration and deceleration across multiple blocks with
almost tangential transitions.
Look Ahead is particularly suitable for the machining of motion sequences comprising short
traverse paths with high path feedrates.
The number of NC blocks included in the Look Ahead calculation can be defined in machine
data.
Continuous-path mode with smoothing as per distance criterion (G641)
With G641, the control inserts transition elements at contour transitions. The rounding
clearance ADIS (or ADISPOS for G0) specifies the maximum extent to which the corners can
be rounded. Within this rounding clearance, the control is free to ignore the path construct and
replace it with a dynamically optimized distance.
Disadvantage: Only one ADIS value is available for all axes.
The effect of G641 is similar to RNDM; however, it is not restricted to the axes of the working
plane.
Like G64, G641 works with LookAhead predictive velocity control. Corner rounding blocks with
a high degree of curvature are approached at reduced velocity.
Example:
Program code
N10 G641 ADIS=0.5 G1 X... Y...
300
Comment
; The rounding block must begin no more than
0.5 mm before the programmed end of the block
and must finish 0.5 mm after the end of the
block. This setting remains modal.
Programming Manual, 01/2015, 6FC5398-1BP40-5BA2
Fundamentals