Siemens SINUMERIK 840D sl Function Manual page 332

G2: Velocities, setpoint / actual value systems, closed-loop control
7.3 Metric/inch measuring system
Input resolution and computational resolution
The input and calculation resolution is defined as an internal number of increments per
millimeter.
MD10200 $MN_INT_INCR_PER_MM
The precision of entry of linear positions is limited to the calculation resolution. The product of
the programmed position value and the calculation resolution is rounded up to the next integer.
To make the rounding clear, powers of 10 should be used for the calculation resolution.
Example
1 inch = 25.4 mm ⇒ 0.0001 inch = 0.00254 mm = 2.54 μm = 2540 nm
To be able to program and display the last 40 nm, a value of 100,000 must be parameterized
for the input and calculation resolution.
Only with this identical setting for both systems of units is it possible to change the system of
units without a significant loss of accuracy. Once MD10200 has been set to this value, it will
not need to be changed each time the system of units is switched over.
JOG and handwheel factor
The machine data:
MD31090 $MA_JOG_INCR_WEIGHT
consists of two values containing axis-specific increment weighting factors for each of the two
systems of units.
Depending on the actual setting in machine data:
MD10240 $MN_SCALING_SYSTEM_IS_METRIC
the controller automatically sets the appropriate value.
The user defines the two increment factors, e.g. for the first axis, during the installation and
startup phase:
● Metric:
MD31090 $MA_JOG_INCR_WEIGHT[0;AX1]=0.001 mm
● Inch:
MD31090 $MA_JOG_INCR_WEIGHT[1;AX1]=0.00254 mm ≙ 0.0001 Inch
In this way, MD31090 does not have to be written on every inch/metric switchover.
Remaining distances are not accumulated during incremental traversing with JOG when the
system of units is changed, since all internal positions always refer to mm.
Data backup
Individual data sets that are read from the control 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
332
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions