Siemens SINUMERIK 840Di sl Programming Manual page 296

Feedrate Control and Spindle Motion
7.7 Feedrate with handwheel override (FD, FDA)
The feedrate is accelerated to 700 mm/min in block N50. The path velocity can be increased
or reduced according to the direction of rotation on the handwheel.
Note
It is not possible to traverse in the opposite direction.
Handwheel travel with path default for positioning axes, FDA[axis]=0
In NC blocks with programmed FDA[axis]=0, the feed is set to zero in order that the program
does not generate any travel movement. The programmed travel movement to the target
position is now controlled exclusively by the operator rotating the handwheel.
Example: N20 POS[V]=90 FDA[V]=0
The automatic travel movement is stopped in block N20. The operator can now move the
axis manually using the handwheel.
Direction of movement, travel velocity
The axes accurately follow the path set by the handwheel in the direction of the leading sign.
Depending on the direction of rotation, you can travel forwards or backwards – the faster you
turn the handwheel, the higher the travel velocity.
Traversing range
The traversing range is limited by the starting position and the end point programmed with
the positioning command.
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Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Fundamentals