Siemens SINUMERIK 828D Function Manual page 1401

When the input for the sparking out time or retraction path is activated, the distance­to­go for the path axes or the
particular single axis is deleted and the dwell or retraction is started.
Note
The unit for the retraction path refers to the current valid unit of measurement (mm or inch).
The reverse stroke is always made in the opposite direction to the current motion. SR/SRA
always programs the value for the reverse stroke. No sign is programmed.
It is also possible to poll the status of an input for synchronous commands of various axes.
Look Ahead is also active for multiple feedrates in one block. In this way, the current feedrate
is restricted by the Look Ahead value.
Application
Typical applications include:
• Analog or digital calipers
Depending on whether the external inputs are analog or digital, various feedrate values, a dwell and a
retraction path can be activated. The limit values are defined via the setting data.
• Switching from infeed to working feedrate via proximity switch
Example
Internal grinding of a conical ring, where the actual diameter is determined using calipers and, depending on the
limits, the feedrate value required for roughing, finishing or fine finishing is activated. The position of the calipers
also provides the end position. Thus, the block end criterion is determined not only by the programmed axis
position of the infeed axis but also by the calipers.
Figure 17-6 Calipers
Part program
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
V1: Feedrates
17.4 Feedrate control
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