Siemens SINUMERIK 840C Installation Instructions Manual page 726

10 Axis and Spindle Installation
10.4.4 Reference point approach
1st case: Axis is ahead of the reference point cam
Speed
MD 296*
MD 284*
0
Reference point cam
Axis is ahead of reference point cam
When the direction key is pressed, the reference point for the axis is approached in the
0
specified direction (MD 564* bit 0) at the speed defined in MD 296*.
When the reference point cam is reached, the "Deceleration" interface signal reduces
1
the axis speed to the value defined in MD 284*.
After the axis has left the reference point cam, the next reference point pulse is
2
evaluated and the axis decelerated.
To prevent backlash on the machine during reference point approach, an additional path
3
of 2000 units is travelled from the reference point pulse to the actual reference point.
Because point is in different places for different speeds, the distance still to be
traversed ( ) must be determined before the actual reference point is
approached. The axis decelerates down to zero speed.
Reference point reached.
4
Note:
The NC's approach path from to after reaching the zero mark depends on the position
control resolution entered in NC MD 18000. If the specified position control resolution is 1/2 -
-3
10 mm, the NC will travel another 2 mm after reaching the zero mark, whereas it will travel
20 mm if the position control resolution is 1/2 x 10
of NC MD 244* ("Reference point offset") by entering 2000 in NC MD 244* and a position
control resolution of 1/2 x 10
During reference point approach, the axis would then travel to and then back to .
10–36
1
Reference point pulse
-2
. This could be compensated with the aid
-3
.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50
2000 units
3 4
2
Reference point
SINUMERIK 840C (IA)
11.92
Path