12.93 12 Functional Descriptions
12.18.13 Start-up
General optimization of axes and spindles
• Axes:
You must set all axes in the GI grouping according to the optimization instructions in the
Start-up Guide (section headed "Drive optimization"). It is particularly important that the
set servo gain factor corresponds to the actual servo gain factor occurring on the machine
(check via following error in the service display). Set the acceleration of the following axis
to approximately 20 % higher than that of the leading axis to ensure correct operation. If
link factors of > 1 are expected, then you must raise the following drive acceleration by a
corresponding amount.
You can install a second measuring system for axes. If you wish to do so, set the
appropriate machine data in the MD 1204* to MD 1388* range.
Caution:
If the following axis is an endlessly turning rotary axis, you must not activate your software
limit switches since the axis will otherwise reach the working area limitation as a result of
the modulo motion and come to an abrupt halt in the middle of a cut. If the following axis is
a rotary axis, you must enter the modulo value of the axis in NC MD 344*.
• Spindle:
Spindles must also be set according to the instructions under section headings GENERAL
RESET and STANDARD START-UP.
Setting the feedforward control
When the dynamic feedforward control function is active, the part setpoint is multiplied by the
feedforward control factor and applied directly to the speed controller input. The setpoint is
injected at the position controller input via a PT1 element with a delay defined by the time
constant set in the machine data.
Please refer to section heading Functional Description, Feedforward
Control, for a description of how to set the feedforward control.
Matching the dynamic response of the drives
The following drive and all leading drives connected to it in a setpoint link must have the same
dynamic control response. The same dynamic response means that the following errors of all
drives are equal when measured at the same velocity (check required).
• If the dynamic response of all the drives involved is virtually the same, you should enter
exactly the same values for the servo gain and feedforward control; these should be the
lowest possible value in each case (referred to the axis with the worst dynamic response).
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12–159
SINUMERIK 840C (IA)