Siemens SINUMERIK 840D sl, Function Manual

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Detailed description
2.3 Continuous -path mode
Basic logic functions: Continuouspath Mode, Exact Stop, LookAhead (B1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
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Acknowledgment outside of travel time
The path velocity for the block ahead is reduced to the point that the block duration
corresponds to the specified time if the traversing time is less than the time specified in the
machine data MD10110 based on the programmed path length and velocity of the block with
auxiliary function output.
If acknowledgment is not received within the time, the following prepared block cannot be
processed and the axes are braked to standstill with setpoint = 0 without considering the
acceleration limits.
Acknowledgment not received by end of block
If the acknowledgment is not received by the end of the block in long blocks in which the
velocity has not needed to be reduced on account of the PLC acknowledgment time, the
velocity is maintained until the end of the block and then reduced as described above.
Acknowledgment during braking
If the acknowledgment arrives while the axis is decelerating, the axis is not accelerated back
up to the requested velocity.
MD10110
The machine data is not evaluated:
MD10110 $MN_PLC_CYCLE_TIME_AVERAGE (average PLC acknowledgement time)
2.3.2 Velocity reduction according to overload factor
Velocity reduction according to overload factor
The function lowers the path velocity in continuouspath mode until the nontangential block
transition can be traversed in one interpolation cycle while respecting the deceleration limit
and taking and overload factor into account.
With the reduced velocity, axial jumps in velocity are produced with a nontangential contour
at the block transition. These jumps in velocity are also performed by the coupled motion
synchronized axes. The jump in velocity prevents the path velocity dropping to zero.
This jump is performed if the axial velocity was reduced with the axial acceleration to a
velocity from which the new setpoint can be reached with the jump. The magnitude of the
setpoint jump can be limited using an overload factor. Because the magnitude of the jump is
axial, the minimum jump of the path axes which are active during the block change is
considered during block transition. With a practically tangential block transition, the path
velocity is not reduced if the permissible axial accelerations are not exceeded. In this way,
very small angular changes in the contour can be overtraveled directly.