Siemens SINUMERIK 840D sl Programming Manual page 115

Unit for rotary and linear axes
For linear and rotary axes which are combined with FGROUP and traverse a path together, the
feedrate is interpreted in the unit of the linear axes (depending on the default with G94/G95, in
mm/min or inch/min and mm/rev or inch/rev).
The tangential velocity of the rotary axis in mm/min or inch/min is calculated according to the
following formula:
F[mm/min] = F'[degrees/min] * π * D[mm]/360[degrees]
where:
Traverse rotary axes with path velocity F (FGREF)
For machining operations, in which the tool or the workpiece or both are moved by a rotary
axis, the effective machining feedrate is to be interpreted as a path feed in the usual way by
reference to the F value. This requires the specification of an effective radius (reference
radius) for each of the rotary axes involved.
The unit of the reference radius depends on the G70/G71/G700/G710 setting.
All axes involved must be included in the FGROUP command to be taken into account in the
calculation of the path feedrate.
In order to ensure compatibility with the behavior with no FGREF programming, the factor 1
degree = 1 mm is activated on system power up and RESET. This corresponds to a reference
radius of FGREF= 360 mm/(2π) = 57.296 mm.
Note
This default is independent of the active basic system
(MD10240 $MN_SCALING_SYSTEM_IS_METRIC) and the currently active G70/G71/G700/
G710 setting.
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
F: Tangential velocity
F': Angular velocity
π: Circle constant
D: Diameter
F'
7.1 Feedrate (G93, G94, G95, F, FGROUP, FL, FGREF)
F
Feed control
115