Siemens SINUMERIK 840D sl Function Manual page 1763

If feedrates, a sparking out time (dwell) or retraction path are programmed for an axis on
account of an external input, this axis must not be programmed as a POSA axis in this block
(positioning axis beyond end of block).
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
• Switching from infeed to working feedrate via proximity switch
Basic logic functions: Feeds (V1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
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.
Detailed description
2.3 Feedrate control
47