Siemens SINUMERIK 840D Function Manual page 42

G2: Velocities, setpoint / actual value systems, closed-loop control
2.3 System of units, metric/inch
Conversion factor (NC-specific)
The factor for converting from metric into the inch system of units is set in machine data:
MD10250 $MN_SCALING_VALUE_INCH (conversion factor for inch)
Default value: 25.4
The conversion factor becomes active when selecting the non-metric basic system (MD10240
$MN_SCALING_SYSTEM_IS_METRIC = 0).
The following data are multiplied by the conversion factor:
● Length-related data for input/output (e.g. when uploading machine data, work offsets)
● Programmed F values for linear axes
● Programmed geometry of an axis (position, polynomial coefficients, radius for circle
programming, ...), if the system of units programmed with G70/G71 differs from the basic
system (MD10240 $MN_SCALING_SYSTEM_IS_METRIC).
Note
By changing the conversion factor, the control system can be adapted to customer-specific
systems of units.
Extended system of units functionality
The extended system of units functionality can be activated using the following compatibility
machine data:
MD10260 $MN_CONVERT_SCALING_SYSTEM
Value
0 (= FALSE)
1 (= TRUE)
When changing MD10240, Alarm 4070 "Normalizing machine data has been changed" is
output.
Data backup
Individual data sets that are read from the control system and contain data affected by the
system of units, are assigned an identifier during reading that indicates the current setting for
the system of units:
● MD10260 $MN_CONVERT_SCALING_SYSTEM
● MD10240 $MN_SCALING_SYSTEM_IS_METRIC
The identifier records in which system of units the data have been read out. This ensures that
no data sets are read into the control with a system of units other than that which is currently set.
Since the identifier is also evaluated in part programs, these can also be "protected" against
operator errors as described above. You can therefore prevent part programs containing, e.g.
only metric data, from running on an inch system of units.
Archive and machine data sets are downward-compatible with the following setting:
42
Meaning
Extended system of units functionality not active (default setting; compatibil‐
ity to previous software releases)
Extended system of units functionality active
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA