Siemens SINUMERIK 840C - Manual (Page 726)

10 Axis and Spindle Installation 11.92
10.4.4 Reference point approach
1st case: Axis is ahead of the reference point cam
Axis is ahead of reference point cam
Reference point pulse
MD 284*
MD 296*
2000 units
Speed
Path 1 3 4 2
Reference point cam Reference point
0
When the direction key is pressed, the reference point for the axis is approached in the
specified direction (MD 564* bit 0) at the speed defined in MD 296*.
0
When the reference point cam is reached, the "Deceleration" interface signal reduces
the axis speed to the value defined in MD 284*.
1
After the axis has left the reference point cam, the next reference point pulse is
evaluated and the axis decelerated.
2
To prevent backlash on the machine during reference point approach, an additional path
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.
3
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 -
10
-3 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 -2 . This could be compensated with the aid
of NC MD 244* ("Reference point offset") by entering 2000 in NC MD 244* and a position
control resolution of 1/2 x 10
-3 .
During reference point approach, the axis would then travel to and then back to .
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SINUMERIK 840C (IA)