Siemens SINUMERIK 840C - Manual (Page 819)

12 Functional Descriptions 06.93
12.7.2 Description of the spindle modes
Speed characteristic for case 2
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Creep speed for M19
Recognition of zero mark
The following applies when selecting the creep speed:
The drive must have sufficient acceleration reserves in the speed range below the creep
speed, corresponding to the programmed acceleration for position-controlled spindle operation.
The values in the preset range (100 rev/min to 500 rev/min) are generally suitable.
If the spindle leaves the target position when function M19 is selected (e.g. by being pushed
out of position when the closed loop control is switched off), it is returned to the target position
using interpolation when the servo enable is reactivated.
If the closed loop control is disabled while the position is being approached, the positioning
operation restarts when servo enable is restarted, if M19 is still selected.
• Incremental positioning
There are two preconditions to be fulfilled in this case:
– spindle stopped
– spindle synchronized with encoder
The specified angle in this case is not the position to be reached but the distance to be
traversed. The starting point for this distance is the last position to which the spindle was
driven (last M19 position). The direction of rotation is determined by the sign of the
programmed path.
If the spindle has not been driven to an absolute position before incremental positioning is
carried out for the first time, the starting point is assumed to be 0°.
It is possible, e.g. due to drift, that the actual position does not agree with the last M19
position. In this case the discrepancy is included in the distance to be traversed.
The actual position can be uniquely defined only within one revolution (0 ... 360°). Since
one assumes that the spindle has moved little since the last positioning, the difference is
defined in the range -180 to +180°.
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SINUMERIK 840C (IA)