Siemens SINUMERIK 840D sl Programming Manual page 455

FCUB
The feedrate is approached according to a cubic characteristic from the current feedrate
value to the programmed F value until the end of the block. The controller uses splines to
connect all the feedrate values programmed non-modally that have an active FCUB. The
feedrate values act here as interpolation points for calculation of the spline interpolation.
Example:
N50 F1400 FCUB X50
N60 F2000 X47
N70 F3800 X52
F=FPO(...,...,...)
The feedrate characteristic is programmed directly via a polynomial. The polynomial
coefficients are specified according to the same method used for polynomial interpolation.
Example:
F=FPO(endfeed, quadf, cubf)
endfeed, quadf and cubf are previously defined variables.
endfeed:
quadf:
cubf:
With an active
block beginning and block end.
Job Planning
Programming Manual, 03/2013, 6FC5398-2BP40-3BA1
10.2 Feedrate characteristic (FNORM, FLIN, FCUB, FPO)
Feedrate at block end
Quadratic polynomial coefficient
Cubic polynomial coefficient
, the spline is linked tangentially to the characteristic defined via
FCUB
Path traversing behavior
at the
FPO
455