10 Axis and Spindle Installation 12.93
10.4.1 Drive optimization
10.4.1.3 Servo gain factor K
V
NC MD 252*
To achieve only negligible contour deviations with continuous path control, a high KV (servo
gain) factor (NC MD 252*) is required.
If the KV factor is too high, however, instability, overshoots and possibly excessive machine
loads result.
The maximum permissible KV factor depends on:
• the drive configuration
(rise time, acceleration and braking ability).
• the quality of the machine
The KV factor is defined as
KV = Speed
Following error
[m/min]
[mm]
m/min
mm is the unit of the KV factor according to VDI standard
If an empirical value for the KV factor is known for the machine, set this value and check for
overshooting or instability.

Good speed controller optimization is a precondition for

a correct K

V

factor setting.

KV factor adjustment
Reduce the acceleration (NC MD 276*). The overshoot behaviour is decisive for evaluating the
maximum KV factor. The acceleration must therefore be set at an accordingly low level to
ensure that the drive remains below its current threshold.
If the drive is intended to have acceleration of 1 m/s2, adopt a cautious approach and reduce
to one-half of the value
0.5 m/s2 ˆ=
input 50
10–24 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)