Siemens SINUMERIK 840Di Function Manual page 394

Detailed Description
2.2 Metric/inch measuring system
This information is intended to prevent data sets from being read into the control system with
a measuring system, which is different from the active system. In this case, alarm 15030 is
triggered and the write process is interrupted.
Since the language instruction is also evaluated in parts programs, these can also be
"protected" against operator errors as described above. You can, therefore, prevent parts
programs containing only metric data, for example, from running on an inch measuring
system.
Archives and machine data sets are downward compatible if:
MD11220 $MN_INI_FILE_MODE = 2.
Note
The INCH/METRIC instruction is only generated if 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.
2.2.4 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[
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.
2-20
<axis name>
] = reference radius
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0