Hirth Axis; Axis-Specific System Variables - Siemens SINUMERIK 840D Function Manual

8.3.2.2

Hirth axis

Function
For a "Hirth axis", using a special gearing (Hirth gearing) the rotary axis is interlocked when
reaching an indexing position. In this case, a locking bolt or a gearwheel is engaged using a
linear axis. In order that the mechanical system of the machine is not damaged, the interlock
can only be engaged at an indexing position. For a Hirth axis, all of the indexing positions must
have the same the distance between one another (equidistant indexing positions).
Requirements
● The "Hirth axis" must be a rotary axis.
● The "Hirth axis" must be an indexing axis. See Section "Commissioning (Page 242)"
● The active measuring system of the indexing axis must be synchronized or referenced:
DB31, ... DBX60.4/.5 == 1 (referenced/synchronized, encoder 1/2)
Further information
R1: Referencing (Page 291)
Commissioning
Machine data
● MD30300 $MA_IS_ROT_AX = 1 (rotary axis)
● MD30505 $MA_HIRTH_IS_ACTIVE[ <axis> ] = 1 (indexing axis with Hirth gearing)
● MD30500 $MA_INDEX_AX_ASSIGN_POS_TAB[ <axis> ] = 3 (indexing axis with
equidistant indexing positions)
8.3.3

Axis-specific system variables

$AA_PROG_INDEX_AX_POS_NO
Function
The system variable includes the number of the indexing position programmed for the indexing
axis.
Syntax
$AA_PROG_INDEX_AX_POS_NO[<axis>]
Meaning
$AA_PROG_INDEX_AX_POS_NO
> 0
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
0 The axis is not an indexing axis, or presently the indexing axis is not traversing to an indexing
position
Number of programmed indexing position
T1: Indexing axes
8.3 Commissioning
247