Siemens SINUMERIK 840C - Manual (Page 711)

09.95 10 Axis and Spindle Installation
10.4.1 Drive optimization
10.4.1.2 Speed setpoint matching / tacho compensation
NC MD 256* Scaling factor maximum velocity [mm/min]
[inches/min]
[degrees/min]
NC MD 260* Scaling factor maximum speed setpoint [mV] (up to SW 2)
[0.01 % of max. setpoint
speed] (as from SW 3)
The quotient of MD 256* and MD 260* is used to match the controlled system to the servo
gain factor defined in MD 252*. The quotient serves as the multiplier for the entered servo gain
factor.
Procedure for standard installation
Basic setting: The maximum speed of the axis is entered in MD 256*. The unit is always
mm/min or inches/min for linear axes depending on the position control basic system (1800*)
(mm or inches). The unit for rotary axes is always degrees/min. The input value depends on
the resolution of the basic system.
The speed setpoint which will produce the maximum traversing velocity is entered in MD 260*
(the unit of the MD is mV). For analog drives a maximum speed setpoint voltage of 9V is
usually selected, i.e. 9000 is input.
On digital drives 100% is set, i.e. 10 000 is entered. The control margin is taken into account
in the drive machine data.
Tacho compensation (analog only)
This compensation is carried out in the tacho potentiometer in the drive. A traversing velocity
of 10% of the maximum velocity can be defined via the control. The speed setpoint service
display must be watched during the traversing operation. The tacho compensation at the drive
must be continued until the speed setpoint is approx. 0.9 V. The voltage 0.9 V corresponds to
a speed setpoint display of 737 VELOS or 900 [0.01 %].
Fine tacho compensation (analog only)
The axis must then be traversed at maximum velocity. A speed setpoint of approx. 9 V or 7373
VELOS or 900 [0.01 %] results. This displayed value must be converted and entered in MD
260*.
Conversion (analog only)
MD 260* =
mV
VELO
Speed setpoint VELO
0.8192 (until SW2)
”In the service display”...
After the compensation, the contour deviation at constant velocity must be nearly zero. The
following error value must correspond to the theoretical value which results from the defined
servo gain factor and the velocity.
Precision enhancement
For even more precision of the setpoint matching, MD 256* and MD 260* can be increased by
the same factor.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 10–21
SINUMERIK 840C (IA)