12 Functional Descriptions 10.94
12.20.7 Retraction
12.20.7.2 Retraction as autonomous drive function (611D)
On SW 4 and higher, axes with digital 611D drive systems can perform a retraction
autonomously if the control fails (sign of life detection) or if the DC link voltage drops below a
warning threshold.
The retraction motion is performed by the 611D autonomously. The retraction path and the
velocity can be set in the part program.
From the beginning of the retraction phase, the drive stops its enables autonomously at the
previously valid values. Emergency retraction is only performed if the pulse and interface
signal "enable ESR" were set , i.e. the drive was enabled.
If the control fails, it is enough that the pulse enable is set. In this case the 611D drive system
generates its own servo enable - if it is still functional. (Partial functionality for the "Retraction
with clamped axes").
The external safety logic of a control and drive system combination with drive emergency
retraction must be such that on failure of the control (i.e. PLC stop and NC READY failure) the
drive unit is still able to move (configuration of the relevant machine safety logic).
The drive system has no reference to the NC geometry system. On the NC-side, the unit
system of the motor measuring system is only known if it is used as the position measuring
system.
The retraction path for the drive is set through the SERVO level with the following geometry-
neutral data:
• Speed setpoint
• Travel time/deceleration time for braking
The drive system traverses the programmed "retraction path" with an internal time-controlled
set speed.
The actual "retraction path" travelled in the event of an error depends on the current actual
speed at the time the emergency retraction begins and can deviate slightly from the
programmed value because the drive system does not monitor for the resulting path (no
interpolation).
After this sequence of operations, a zero speed setpoint is specified for the retraction axes
which are then stopped along the current limit (see autonomous drive stop operation).
The retraction motion is defined by programming:
• incremental dimension value,
• direction of traversal and
• speed setpoint (F value)
Notes:
• The autonomous drive emergency retraction is operative only if the bit "pulse
suppression" is set to "off" in the drive MD 1612 and 1613.
• When emergency retraction is active, it is not possible parameterize the emergency
retraction. Although the data are transferred to the drive, they are not accepted. No
message is output to the user to indicate this status.
• See the SINUMERIK 840C Programming Guide for further information on programming.
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SINUMERIK 840C (IA)