Fgroup And Fgref - Siemens SINUMERIK 828D Function Manual

Note
The INCH/METRIC operation is only generated if the compatibility machine data:
MD10260 $MN_CONVERT_SCALING_SYSTEM
is set.
Rounding machine data
All length-related machine data are rounded to the nearest 1 pm when writing in the inch measuring system
(MD10240 $MN_SCALING_SYSTEM_IS_METRIC=0 and MD10260 $MN_CONVERT_SCALING_SYSTEM=1),
in order to avoid rounding problems.
The disturbing loss of accuracy, which occurs as a result of conversion to ASCII when reading out a data backup
in the inch system of measurement, is corrected by this procedure when the data is read back into the system.
7.3.3

FGROUP and FGREF

Programming
It should be possible to program the effective machining feedrate in the usual way as a path feedrate via the F
value in processing procedures where the tool, the workpiece or both are moved by a rotary axis (e.g., laser
machining of rotating tubes).
In order to achieve this, it is necessary to specify an effective radius (reference radius) for each of the rotary axes
involved. You can do this by programming the modal NC address:
FGREF[<rotary axis>]=<reference radius>
The unit of the reference radius depends on the G70/G71/G700/G710 setting.
In order to include the axes in the calculation of the path feedrate, they must all be specified in the FGROUP
command.
In order to ensure compatibility with the behavior with no FGREF programming, the evaluation 1 degree = 1 mm is
activated on system power­up and RESET.
This corresponds to a reference radius of:
FGREF = 360 mm/(2π) = 57.296 mm
This default is independent of the active basic system (MD10240 $MN_SCALING_SYSTEM_IS_METRIC) and
the currently active G70/G71/G700/G710 setting.
Special features of the feedrate weighting for rotary axes in FGROUP:
Program code
N100 FGROUP(X,Y,Z,A)
N110 G1 G91 A10 F100
N120 G1 G91 A10 X0.0001 F100
The programmed F value in block N110 is evaluated as a rotary axis feedrate in degrees/min, while the feedrate
weighting in block N120 is either 100 inch/min or 100 mm/min, depending on the current inch/metric setting.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
G2: Velocities, setpoint / actual value systems, closed-loop control
7.3 Metric/inch measuring system
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