12 Functional Descriptions 06.93
12.7.2 Description of the spindle modes
12.7.2.2 Oscillation mode
The oscillation mode can be used with gear ratio changing to facilitate engagement of the gear
by oscillating the spindle.
When switching from open-loop control to oscillation control, the speed setpoint is first
reduced to zero at the deceleration ramp defined by the active acceleration time constant. The
oscillation speed setpoint is then output.
Preconditions
The request for the oscillation mode comes from the PLC. The PLC user program sets the IS:
OSCILLATION SPEED. The following conditions must be satisfied:
• IS:PLC SPINDLE CONTROL set
Parameter assignment
• The motor setpoint for oscillation speed is issued by MD 450*. The sign of the setpoint,
and hence the direction of rotation, is determined by IS: SET ROTATION CW
• There is no acceleration or speed limitation in the oscillation mode.
Implementation
• The spindle is actually oscillated by the setpoint being output with an alternating sign. This
has to be implemented in the PLC user program by inverting IS:SET ROTATION CW.
12.7.2.3 Positioning mode (M19, M19 through several revolutions)
General
In the positioning mode, the spindle is driven to a preset position under position control and
stopped there. The position is reached either directly (M19) or through several revolutions
(M19tsr).
Position control and actual value acquisition
• Actual value acquisition is needed for position control. Therefore, an encoder must be
mounted directly on the spindle.
• The reference point for the angle measuring system is the zero mark of the encoder. A
permanent offset to the zero mark can be established by using the zero mark shift
(MD 459*).
Accuracy
• The position is entered with an accuracy of 0.01
o
. The positioning accuracy achieved by
the spindle depends on a number of factors:
– The resolution of the angle measuring system
– The gain factor of the active gear ratio
– The drift
– The interfacing to the drive system.
Restrictions
• Gear ratio changing cannot be employed in the positioning mode.
• M19 must not be activated or programmed when the G96 function is active.
12–38 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)