Siemens SINUMERIK 840Di sl Programming Manual page 277

Path reference factors for orientation axes with FGREF
With orientation axes the mode of operation of the FGREF[ ] factors is dependent on
whether the change in the orientation of the tool is implemented by rotary axis or vector
interpolation.
In the case of rotary axis interpolation, the relevant FGREF factors of the orientation axes
are calculated, as for rotary axes, individually as reference radius for the axis paths.
In the case of vector interpolation, an effective FGREF factor, which is calculated as the
geometric mean value of the individual FGREF factors, is applied.
FGREF[eff] = n-te root of:[(FGREF[A] * FGREF[B]...)]
They are:
A: Axis identifier of 1st orientation axis
B: Axis identifier of 2nd orientation axis
C: Axis identifier of 3rd orientation axis Number of orientation axes
Example: There are two orientation axes for a standard 5-axis transformation, and the
effective factor is thus the root of the product of the two axial factors:
FGREF[eff] = square root of:[(FGREF[A] * FGREF[B])]
Note
With the effective factor for orientation axes FGREF, it is therefore possible to define a
reference point on the tool, to which the programmed path feedrate refers.
Fundamentals
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Feedrate Control and Spindle Motion
7.1 Feedrate (G93, G94, G95 or F..., FGROUP, FGREF)
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