Siemens SINUMERIK 840C - Manual (Page 395)

6 NC Machine Data (NC MD), NC Setting Data (NC SD) 07.97
6.9.1 MDs for collision monitoring
The setpoint position of the following axis is checked in every IPO cycle to establish whether it
is in the reduction range. The system is designed such that several IPO cycles elapse before
changes to the setpoints of a leading axis are output to the setpoint controller of the following
axis. To compensate this deadtime, the setpoint position is corrected by the predicted path.
The deadtime and thus also the compensation value are dependent on the gear interpolation
link type. The deadtime is 2 IPO cycles (200 %) for the setpoint link. A deadtime of 5.5 IPO
cycles (550 %) is recommended for the actual value link.
Minimum reduction factor 1) 3936*
Default value Lower input limit Upper input limit Units
200 0 1 000
in 0.01% of the
max. speed
Active on
Power On
The distance between the deadtime-compensated setpoint position and the active limitations is
calculated in this MD. The active limitations are the innermost limit values as defined by the
working field boundary and the selected SW limit switch. If the distance d is smaller than the
reduction range, the braking operation must be initiated. For this purpose, a permissible
velocity value Vperm is calculated from the distance d to the SW limit switch and the max.
acceleration value Amax.
2 * d * A
max
V
perm
=
A reduction factor is calculated from V
perm
and V
max
and transmitted to the mode group
channels. In a similar way to an override, the reduction factor is included in the path velocity
calculation in all mode group channels.
Reduction factor = V
perm
/V
max
* 100
Denominator gear encoder/load 3940*
Default value Lower input limit Upper input limit Units
0 0 5 000 000 –
Active on
Power On
This MD must be parameterized for rotary axes if MD 1808*, bit 7, is set. The value of gear
encoder/load must be entered.
Common divisors of numerators and denominators of the gear can be reduced.
Example: Gear 35/56 Common divisor 7 exists.
56 can thus be parameterized as the denominator, however value 8 is also permissible
(reduced by the common divisor) and is recommended.
Rough encoder position 3944*
Default value Lower input limit Upper input limit Units
0 -99 999 999 99 999 999 –
Active on
NC Stop
This MD is only used to secure the data of the absolute position against unforeseen data loss
in the SRAM of the NC-CPU.
This MD is only updated during power up and when all NC MDs are backed up. Further details
are given in the description of the function ”Range extension with ENDAT absolute encoder”.
Coordinate assignment (as from SW 6) 3948*
Default value Lower input limit Upper input limit Units
–
1 =Abscissa =X coordinate
2 =Ordinate
=Y coordinate
3 =Applicate =Z coordinate
_______
1) as from SW 5.6
6–210 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)