Siemens Sinumerik 840D sl Programming Manual page 473

FCUB
The feed is approached according to a cubic characteristic from the current feed value to the
programmed F value until the end of the block. The control uses splines to connect all the
feed values programmed non-modally that have an active FCUB. The feed 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 feed 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 FCUB, the spline is linked tangentially to the characteristic defined via FPO at
the block beginning and block end.
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
8.2 Feedrate response (FNORM, FLIN, FCUB, FPO)
Feed at block end
Quadratic polynomial coefficient
Cubic polynomial coefficient
Path traversing behavior
473