Siemens SINUMERIK 840C Installation Instructions Manual page 367

6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.7.1 Axis-specific MD bits 2 (axial bits 2)
The derived following error difference is always evaluated against the actual set
speed in order to derive a compensation value across the total velocity range of an
axis. Otherwise a compensation proportional to the velocity would not be possible
if constant velocity operation is revoked.
The compensation values are deleted when compensation is deselected (MD
1804*, bit 1 deleted). New compensation values have to be calculated if the
function is reactivated.
After POWER ON the compensation values are recalculated and the previous
values are deleted.
If the tacho compensation is also to be used for spindles, a C axis must be
assigned to each spindle in order to set the axis-specific MD bit. Tacho
compensation and feed forward control is only active for spindles in position
control mode (M19 absolute, M19 through several resolutions).
Bit 0 In order to obtain a symmetrical traversing range around the zero position for
finitely turning rotary axes, bit 0 must be set to 1 under MD 1804*. This will require
no modulo correction within the range between -180 degrees and +180 degrees
(if MD 1808*, bit 6=1) or between -8 revolutions and +8 revolutions (if MD 1808*
bit 6=0) (see Section 12.11.2.4)
NC MD 7
SIPOS
Range
single-turn
extension
absolute
1808*
ENDAT
encoder
absolute
available (as
encoder
from SW 2)
Bit 7=1 ENDAT absolute encoder overflows are stored in the SRAM of the NC-CPU and
then included in the calculation of the actual position.
This function is required in the following cases:
• Rotary axes with an encoder on the motor (indirect measuring system) and a
gear not equal to 1/2".
• Linear axes with an encoder on the motor (indirect measuring system) and a
traversing range that is greater than the traversing range of the absolute
encoder.
For a more detailed description see the description of the function "Range
extension with ENDAT absolute encoder".
Bit 7=0 ENDAT absolute encoder overflows are not stored and evaluated.
Bit 6=1 Single-turn absolute encoder present
General:
The function in "Single-turn absolute encoder available" is required for rotary axes
with a SIPOS or Endat absolute encoder which is connected directly and an
unlimited traversing range. This function is used to evaluate the absolute value
within one revolution only in order to avoid incorrect positioning should there be a
counter overflow (danger to machine).
6–182
Bit No.
6 5 4
2nd 1st
measuring measuring
system system
distance distance
coded coded
©
Siemens AG 1992 All Rights Reserved
3 2 1
Absolute
encoder Value range
Absolute
counting extension
offset MD
direction of absolute
396* valid
opposite offset
sense
6FC5197- AA50
SINUMERIK 840C (IA)
09.01
0
Axis with
absolute
encoder
system